u blox 1EIQN2NN LTE Data Module User Manual LARA R2 series

u-blox AG LTE Data Module LARA R2 series

System Integrators Manual

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Document DescriptionSystem Integrators Manual
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Date Submitted2016-10-17 00:00:00
Date Available2017-04-17 00:00:00
Creation Date2016-10-06 14:43:48
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Document TitleLARA-R2 series
Document CreatorMicrosoft® Office Word 2007

LARA-R2 series
LTE Cat 1 / EGPRS modules
System Integration Manual
Abstract
This document describes the features and the system integration of
LARA-R2 series multi-mode cellular modules.
These modules are a complete, cost efficient and performance
optimized LTE Cat 1 / 2G multi-mode solution covering up to three
LTE bands and up to two 2G GSM/EGPRS bands in the very small
and compact LARA form factor.
www.u-blox.com
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LARA-R2 series - System Integration Manual
Document Information
Title
LARA-R2 series
Subtitle
LTE Cat 1 / EGPRS modules
Document type
System Integration Manual
Document number
UBX-16010573
Revision, date
R02
Document status
Objective Specification
03-Oct-2016
Document status explanation
Objective Specification
Document contains target values. Revised and supplementary data will be published later.
Advance Information
Document contains data based on early testing. Revised and supplementary data will be published later.
Early Production Information
Document contains data from product verification. Revised and supplementary data may be published later.
Production Information
Document contains the final product specification.
This document applies to the following products:
Name
Type number
Modem version
Application version
SDN / IN / PCN
LARA-R204
LARA-R204-02B-00
TBD
TBD
TBD
LARA-R211
LARA-R211-02B-00
30.17
A01.00
UBX-16024242
u-blox reserves all rights to this document and the information contained herein. Products, names, logos and designs described herein may in
whole or in part be subject to intellectual property rights. Reproduction, use, modification or disclosure to third parties of this document or
any part thereof without the express permission of u-blox is strictly prohibited.
The information contained herein is provided “as is” and u-blox assumes no liability for the use of the information. No warranty, either
express or implied, is given, including but not limited, with respect to the accuracy, correctness, reliability and fitness for a particular purpose
of the information. This document may be revised by u-blox at any time. For most recent documents, please visit www.u-blox.com.
Copyright © 2016, u-blox AG
u-blox® is a registered trademark of u-blox Holding AG in the EU and other countries. Microsoft and Windows are either registered
trademarks or trademarks of Microsoft Corporation in the United States and/or other countries. All other registered trademarks or
trademarks mentioned in this document are property of their respective owners.
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LARA-R2 series - System Integration Manual
Preface
u-blox Technical Documentation
As part of our commitment to customer support, u-blox maintains an extensive volume of technical
documentation for our products. In addition to our product-specific technical data sheets, the following manuals
are available to assist u-blox customers in product design and development.

AT Commands Manual: This document provides the description of the AT commands supported by the
u-blox cellular modules.

System Integration Manual: This document provides the description of u-blox cellular modules’ system
from the hardware and the software point of view, it provides hardware design guidelines for the optimal
integration of the cellular modules in the application device and it provides information on how to set up
production and final product tests on application devices integrating the cellular modules.

Application Notes: These documents provide guidelines and information on specific hardware and/or
software topics on u-blox cellular modules. See Related documents for a list of application notes related to
your cellular module.
How to use this Manual
The LARA-R2 series System Integration Manual provides the necessary information to successfully design in and
configure these u-blox cellular modules.
This manual has a modular structure. It is not necessary to read it from the beginning to the end.
The following symbols are used to highlight important information within the manual:
An index finger points out key information pertaining to module integration and performance.
A warning symbol indicates actions that could negatively impact or damage the module.
Questions
If you have any questions about u-blox cellular Integration:

Read this manual carefully.

Contact our information service on the homepage http://www.u-blox.com
Technical Support
Worldwide Web
Our website (http://www.u-blox.com) is a rich pool of information. Product information and technical documents
can be accessed 24h a day.
By E-mail
If you have technical problems or cannot find the required information in the provided documents, contact the
closest Technical Support office. To ensure that we process your request as soon as possible, use our service pool
email addresses rather than personal staff email addresses. Contact details are at the end of the document.
Helpful Information when Contacting Technical Support
When contacting Technical Support, have the following information ready:

Module type (e.g. LARA-R204) and firmware version

Module configuration

Clear description of your question or the problem

A short description of the application

Your complete contact details
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Contents
Preface ................................................................................................................................ 3
Contents.............................................................................................................................. 4
System description ....................................................................................................... 7
1.1
1.2
Overview .............................................................................................................................................. 7
Architecture .......................................................................................................................................... 9
1.3
Pin-out ............................................................................................................................................... 11
1.4
1.5
Operating modes ................................................................................................................................ 16
Supply interfaces ................................................................................................................................ 18
1.5.1
Module supply input (VCC) ......................................................................................................... 18
1.5.2
1.5.3
RTC supply input/output (V_BCKP) .............................................................................................. 25
Generic digital interfaces supply output (V_INT) ........................................................................... 26
1.6
System function interfaces .................................................................................................................. 27
1.6.1
1.6.2
Module power-on ....................................................................................................................... 27
Module power-off ....................................................................................................................... 29
1.6.3
Module reset ............................................................................................................................... 31
1.6.4
Module / host configuration selection ......................................................................................... 31
1.7
Antenna interface ............................................................................................................................... 32
1.7.1
Antenna RF interfaces (ANT1 / ANT2) .......................................................................................... 32
1.7.2
Antenna detection interface (ANT_DET) ...................................................................................... 34
1.8
SIM interface ...................................................................................................................................... 34
1.8.1
SIM card interface ....................................................................................................................... 34
1.8.2
SIM card detection interface (SIM_DET) ....................................................................................... 34
1.9
Data communication interfaces .......................................................................................................... 35
1.9.1
UART interface ............................................................................................................................ 35
1.9.2
1.9.3
USB interface............................................................................................................................... 46
HSIC interface ............................................................................................................................. 49
1.9.4
DDC (I C) interface ...................................................................................................................... 50
1.9.5
SDIO interface ............................................................................................................................. 51
1.10
Audio interface ............................................................................................................................... 52
1.10.1
Digital audio interface ................................................................................................................. 52
1.11
1.12
Clock output ................................................................................................................................... 53
General Purpose Input/Output (GPIO) ............................................................................................. 53
1.13
Reserved pins (RSVD) ...................................................................................................................... 53
1.14
System features............................................................................................................................... 54
1.14.1 Network indication ...................................................................................................................... 54
1.14.2
Antenna detection ...................................................................................................................... 54
1.14.3
1.14.4
Jamming detection ...................................................................................................................... 54
Dual stack IPv4/IPv6 ..................................................................................................................... 55
1.14.5
TCP/IP and UDP/IP ....................................................................................................................... 55
1.14.6
1.14.7
FTP .............................................................................................................................................. 55
HTTP ........................................................................................................................................... 55
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1.14.8
1.14.9
SSL/TLS ........................................................................................................................................ 56
Bearer Independent Protocol ....................................................................................................... 57
1.14.10
AssistNow clients and GNSS integration ................................................................................... 57
1.14.11
1.14.12
Hybrid positioning and CellLocate .......................................................................................... 58
Wi-Fi integration ...................................................................................................................... 60
1.14.13
Firmware upgrade Over AT (FOAT) .......................................................................................... 60
1.14.14
1.14.15
Firmware update Over The Air (FOTA) ...................................................................................... 60
Smart temperature management ............................................................................................. 61
1.14.16
Power Saving ........................................................................................................................... 63
®
Design-in ..................................................................................................................... 64
2.1
Overview ............................................................................................................................................ 64
2.2
Supply interfaces ................................................................................................................................ 65
2.2.1
2.2.2
Module supply (VCC) .................................................................................................................. 65
RTC supply (V_BCKP) ................................................................................................................... 79
2.2.3
Interface supply (V_INT) ............................................................................................................... 81
2.3
System functions interfaces ................................................................................................................ 82
2.3.1
Module power-on (PWR_ON) ...................................................................................................... 82
2.3.2
Module reset (RESET_N) .............................................................................................................. 83
2.3.3
Module / host configuration selection ......................................................................................... 84
2.4
Antenna interface ............................................................................................................................... 85
2.4.1
Antenna RF interface (ANT1 / ANT2) ........................................................................................... 85
2.4.2
Antenna detection interface (ANT_DET) ...................................................................................... 92
2.5
SIM interface ...................................................................................................................................... 94
2.6
Data communication interfaces ........................................................................................................ 100
2.6.1
2.6.2
UART interface .......................................................................................................................... 100
USB interface............................................................................................................................. 105
2.6.3
HSIC interface ........................................................................................................................... 107
2.6.4
2.6.5
DDC (I C) interface .................................................................................................................... 109
SDIO interface ........................................................................................................................... 113
2.7
Audio interface ................................................................................................................................. 114
2.7.1
Digital audio interface ............................................................................................................... 114
2.8
General Purpose Input/Output (GPIO) ............................................................................................... 118
2.9
Reserved pins (RSVD) ........................................................................................................................ 119
2.10
2.11
Module placement ........................................................................................................................ 119
Module footprint and paste mask ................................................................................................. 120
2.12
Thermal guidelines ........................................................................................................................ 121
2.13
ESD guidelines .............................................................................................................................. 122
2.13.1 ESD immunity test overview ...................................................................................................... 122
2.14
Schematic for LARA-R2 series module integration ......................................................................... 123
2.15
Design-in checklist ........................................................................................................................ 124
2.15.1 Schematic checklist ................................................................................................................... 124
2.15.2
Layout checklist ......................................................................................................................... 125
2.15.3
Antenna checklist ...................................................................................................................... 125
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Handling and soldering ........................................................................................... 126
3.1
Packaging, shipping, storage and moisture preconditioning ............................................................. 126
3.2
Handling ........................................................................................................................................... 126
3.3
Soldering .......................................................................................................................................... 127
3.3.1
Soldering paste.......................................................................................................................... 127
3.3.2
Reflow soldering ....................................................................................................................... 127
3.3.3
3.3.4
Optical inspection ...................................................................................................................... 128
Cleaning.................................................................................................................................... 128
3.3.5
Repeated reflow soldering ......................................................................................................... 129
3.3.6
3.3.7
Wave soldering.......................................................................................................................... 129
Hand soldering .......................................................................................................................... 129
3.3.8
Rework...................................................................................................................................... 129
3.3.9
3.3.10
Conformal coating .................................................................................................................... 129
Casting...................................................................................................................................... 129
3.3.11
Grounding metal covers ............................................................................................................ 129
3.3.12
Use of ultrasonic processes ........................................................................................................ 129
Approvals.................................................................................................................. 130
4.1
4.2
Product certification approval overview ............................................................................................. 130
US Federal Communications Commission notice ............................................................................... 131
4.2.1
Safety warnings review the structure ......................................................................................... 131
4.2.2
4.2.3
Declaration of conformity .......................................................................................................... 131
Modifications ............................................................................................................................ 131
4.3
Industry Canada notice ..................................................................................................................... 132
4.3.1
4.3.2
4.4
Declaration of Conformity ......................................................................................................... 132
Modifications ............................................................................................................................ 132
R&TTED / RED and European Conformance CE mark ........................................................................ 134
Product testing ......................................................................................................... 135
5.1
u-blox in-series production test ......................................................................................................... 135
5.2
Test parameters for OEM manufacturer ............................................................................................ 136
5.2.1
5.2.2
“Go/No go” tests for integrated devices .................................................................................... 136
Functional tests providing RF operation ..................................................................................... 136
Appendix ........................................................................................................................ 138
A Migration between SARA-U2 and LARA-R2 ........................................................... 138
A.1
Overview .......................................................................................................................................... 138
A.2
Pin-out comparison between SARA-U2 and LARA-R2 ....................................................................... 141
A.3
Schematic for SARA-U2 and LARA-R2 integration ............................................................................. 143
Glossary .................................................................................................................... 144
Related documents......................................................................................................... 146
Revision history .............................................................................................................. 147
Contact ............................................................................................................................ 148
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1 System description
1.1
Overview
The LARA-R2 series comprises LTE Cat 1 / 2G multi-mode modules supporting up to three LTE bands and up to
two 2G GSM/(E)GPRS bands for voice and/or data transmission in the very small LARA LGA form-factor (26.0 x
24.0 mm), easy to integrate in compact designs:

LARA-R204 is designed primarily for operation in North America (on Verizon network)

LARA-R211 is designed primarily for operation in Europe, Asia and other countries
LARA-R2 series modules are form-factor compatible with u-blox SARA, LISA and TOBY cellular module families:
this facilitates easy migration from u-blox GSM/GPRS, CDMA, UMTS/HSPA, and LTE high data rate modules,
maximizes the investments of customers, simplifies logistics, and enables very short time-to-market.
The modules are ideal for applications that are transitioning to LTE from 2G and 3G, due to the long term
availability and scalability of LTE networks.
With a range of interface options and an integrated IP stack, the modules are designed to support a wide range
of data-centric applications. The unique combination of performance and flexibility make these modules ideally
suited for medium speed M2M applications, such as smart energy gateways, remote access video cameras,
digital signage, telehealth and telematics.
LARA-R2 series modules support Voice over LTE (VoLTE) and voice service over 2G (CSFB) for applications that
require voice, such as security and surveillance systems.
Table 1 summarizes the main features and interfaces of LARA-R2 series modules.
●
●
● ● ● ● ● ● ●
●
●
●
●
●
●
●
●
●
●
● ● ● ● ● ● ● ● ●
●
Table 1: LARA-R2 series main features summary
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Automotive
●
Professional
●
Dual stack IPv4/IPv6
●
FOTA
●
Standard
eCall / ERA GLONASS
Embedded HTTP,FTP,SSL
Embedded TCP/UDP stack
Network indication
●
Jamming detection
Digital audio
●
Rx Diversity
GPIOs
●
Antenna supervisor
DDC (I2C)
●
Analog audio
SDIO
900,1800
HSIC
3,7,20
USB 2.0
Europe,
APAC
Grade
UART
LARA-R211
Features
CellLocate®
4,13
Audio
Assist Now Software
North
America
Interfaces
GNSS via modem
LARA-R204
GSM Bands
Region Radio Access Technology Positioning
LTE Bands
Model
LARA-R2 series - System Integration Manual
Table 2 reports a summary of cellular radio access technologies characteristics of LARA-R2 series modules.
4G LTE
2G GSM/GPRS/EDGE
3GPP Release 9
Long Term Evolution (LTE)
Evolved Uni.Terrestrial Radio Access (E-UTRA)
Frequency Division Duplex (FDD)
DL Rx diversity
3GPP Release 9
Enhanced Data rate GSM Evolution (EDGE)
GSM EGPRS Radio Access (GERA)
Time Division Multiple Access (TDMA)
DL Advanced Rx Performance
Band support1:

LARA-R204:

Band 13 (750 MHz)

Band 4 (1700 MHz)

LARA-R211:

Band 20 (800 MHz)

Band 3 (1800 MHz)

Band 7 (2600 MHz)
Band support:
LTE Power Class

Power Class 3 (23 dBm)
GSM/GPRS (GMSK) Power Class

Power Class 4 (33 dBm) for E-GSM band

Power Class 1 (30 dBm) for DCS band
EDGE (8-PSK) Power Class
Power Class E2 (27 dBm) for E-GSM band

Power Class E2 (26 dBm) for DCS band
Data rate

LTE category 1:
up to 10.3 Mb/s DL, 5.2 Mb/s UL
Data Rate2

GPRS multi-slot class 123, CS1-CS4,
up to 85.6 kb/s DL/UL

EDGE multi-slot class 123, MCS1-MCS9,
up to 236.8 kb/s DL/UL

LARA-R211:

E-GSM 900 MHz

DCS 1800 MHz
Table 2: LARA-R2 series LTE and 2G characteristics
LARA-R2 modules provide Voice over LTE (VoLTE) as well as Circuit-Switched-Fall-Back (CSFB) audio capability .
LARA-R2 series modules support all the E-UTRA channel bandwidths for each operating band according to 3GPP TS 36.521-1 .
GPRS/EDGE multi-slot class determines the number of timeslots available for upload and download and thus the speed at which data can
be transmitted and received, with higher classes typically allowing faster data transfer rates.
GPRS/EDGE multi-slot class 12 implies a maximum of 4 slots in DL (reception) and 4 slots in UL (transmission) with 5 slots in total.
Not supported by LARA-R204 module “02” product version.
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1.2
Architecture
Figure 1 summarizes the internal architecture of LARA-R2 series modules.
Duplexer
ANT1
Switch
Filters
Filters
LNAs
Filters
PAs
Filters
ANT_DET
SIM
26 MHz
DDC(I2C)
Duplexer
LNAs
Filters
Filters
LNAs
Filters
Filters
LNAs
Filters
Filters
ANT2
PAs
SDIO
RF
transceiver
UART
Memory
Cellular
Base-band
processor
Switch
32.768 kHz
USB
HSIC
GPIO
Digital audio (I2S)
Host Select
VCC (Supply)
V_BCKP (RTC)
Power Management Unit
Power On
External Reset
V_INT (I/O)
Figure 1: LARA-R2 series modules simplified block diagram
LARA-R2 series modules internally consists of the RF, Baseband and Power Management sections here described
with more details than the simplified block diagrams of Figure 1.
RF section
The RF section is composed of RF transceiver, PAs, LNAs, crystal oscillator, filters, duplexers and RF switches.
Tx signal is pre-amplified by RF transceiver, then output to the primary antenna input/output port (ANT1) of the
module via power amplifier (PA), SAW band pass filters band, specific duplexer and antenna switch.
Dual receiving paths are implemented according to LTE Receiver Diversity radio technology supported by the
modules as LTE category 1 User Equipments: incoming signal is received through the primary (ANT1) and the
secondary (ANT2) antenna input ports which are connected to the RF transceiver via specific antenna switch,
diplexer, duplexer, LNA, SAW band pass filters.

RF transceiver performs modulation, up-conversion of the baseband I/Q signals for Tx, down-conversion and
demodulation of the dual RF signals for Rx. The RF transceiver contains:
Single chain high linearity receivers with integrated LNAs for multi band multi mode operation,
Highly linear RF demodulator / modulator capable GMSK, 8-PSK, QPSK, 16-QAM,
RF synthesizer,
VCO.

Power Amplifiers (PA) amplify the Tx signal modulated by the RF transceiver

RF switches connect primary (ANT1) and secondary (ANT2) antenna ports to the suitable Tx / Rx path

SAW duplexers and band pass filters separate the Tx and Rx signal paths and provide RF filtering

26 MHz voltage-controlled temperature-controlled crystal oscillator generates the clock reference in
active-mode or connected-mode.
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Baseband and power management section
The Baseband and Power Management section is composed of the following main elements:

A mixed signal ASIC, which integrates
Microprocessor for control functions
DSP core for cellular Layer 1 and digital processing of Rx and Tx signal paths
Memory interface controller
Dedicated peripheral blocks for control of the USB, SIM and generic digital interfaces
Interfaces to RF transceiver ASIC

Memory system, which includes NAND flash and LPDDR2 RAM

Voltage regulators to derive all the subsystem supply voltages from the module supply input VCC

Voltage sources for external use: V_BCKP and V_INT

Hardware power on

Hardware reset

Low power idle-mode support

32.768 kHz crystal oscillator to provide the clock reference in the low power idle-mode, which can be set by
enable power saving configuration using the AT+UPSV command.
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1.3
Pin-out
Table 3 lists the pin-out of the LARA-R2 series modules, with pins grouped by function.
Function
Pin Name
Pin No
I/O
Description
Remarks
Power
VCC
51, 52, 53
Module supply input
VCC supply circuit affects the RF performance and
compliance of the device integrating the module with
applicable required certification schemes.
See section 1.5.1 for description and requirements.
See section 2.2.1 for external circuit design-in.
GND
1, 3, 5, 14, 20, N/A
22, 30, 32, 43,
50, 54, 55, 57,
58, 60, 61, 63,
64, 65-96
Ground
GND pins are internally connected each other.
External ground connection affects the RF and thermal
performance of the device.
See section 1.5.1 for functional description.
See section 2.2.1 for external circuit design-in.
V_BCKP
I/O
RTC supply
input/output
V_BCKP = 1.8 V (typical) generated by internal regulator
when valid VCC supply is present.
See section 1.5.2 for functional description.
See section 2.2.2 for external circuit design-in.
V_INT
Generic Digital
Interfaces supply
output
V_INT = 1.8 V (typical), generated by internal DC/DC
regulator when the module is switched on.
Test-Point for diagnostic access is recommended.
See section 1.5.3 for functional description.
See section 2.2.3 for external circuit design-in.
PWR_ON
15
Power-on input
Internal 10 k pull-up resistor to V_BCKP.
See section 1.6.1 for functional description.
See section 2.3.1 for external circuit design-in.
RESET_N
18
External reset input
Internal 10 k pull-up resistor to V_BCKP.
Test-Point for diagnostic access is recommended.
See section 1.6.3 for functional description.
See section 2.3.2 for external circuit design-in.
HOST_SELECT
21
I/O
Selection of module /
host configuration
Not supported by “02” product versions.
Pin available to select, enable, connect, disconnect and
subsequently re-connect the HSIC interface.
Test-Point for diagnostic access is recommended.
See section 1.6.4 for functional description.
See section 2.3.3 for external circuit design-in.
ANT1
56
I/O
Primary antenna
Main Tx / Rx antenna interface.
50  nominal characteristic impedance.
Antenna circuit affects the RF performance and compliance
of the device integrating the module with applicable
required certification schemes.
See section 1.7 for description and requirements.
See section 2.4 for external circuit design-in.
ANT2
62
Secondary antenna
Rx only for Rx diversity.
50  nominal characteristic impedance.
Antenna circuit affects the RF performance and compliance
of the device integrating the module with applicable
required certification schemes.
See section 1.7 for description and requirements.
See section 2.4 for external circuit design-in.
ANT_DET
59
Input for antenna
detection
ADC for antenna presence detection function.
See section 1.7.2 for functional description.
See section 2.4.2 for external circuit design-in.
System
Antenna
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Function
Pin Name
Pin No
I/O
Description
Remarks
SIM
VSIM
41
SIM supply output
VSIM = 1.8 V / 3 V output as per the connected SIM type.
See section 1.8 for functional description.
See section 2.5 for external circuit design-in.
SIM_IO
39
I/O
SIM data
Data input/output for 1.8 V / 3 V SIM
Internal 4.7 k pull-up to VSIM.
See section 1.8 for functional description.
See section 2.5 for external circuit design-in.
SIM_CLK
38
SIM clock
3.25 MHz clock output for 1.8 V / 3 V SIM
See section 1.8 for functional description.
See section 2.5 for external circuit design-in.
SIM_RST
40
SIM reset
Reset output for 1.8 V / 3 V SIM
See section 1.8 for functional description.
See section 2.5 for external circuit design-in.
RXD
13
UART data output
1.8 V output, Circuit 104 (RXD) in ITU-T V.24,
for AT commands, data communication, FOAT, FW update
by u-blox EasyFlash tool and diagnostic.
Test-Point and series 0  for diagnostic access recommended.
See section 1.9.1 for functional description.
See section 2.6.1 for external circuit design-in.
TXD
12
UART data input
1.8 V input, Circuit 103 (TXD) in ITU-T V.24,
for AT commands, data communication, FOAT, FW update
by u-blox EasyFlash tool and diagnostic.
Internal active pull-up to V_INT.
Test-Point and series 0  for diagnostic access recommended.
See section 1.9.1 for functional description.
See section 2.6.1 for external circuit design-in.
CTS
11
UART clear to send
output
1.8 V output, Circuit 106 (CTS) in ITU-T V.24.
See section 1.9.1 for functional description.
See section 2.6.1 for external circuit design-in.
RTS
10
UART ready to send
input
1.8 V input, Circuit 105 (RTS) in ITU-T V.24.
Internal active pull-up to V_INT.
See section 1.9.1 for functional description.
See section 2.6.1 for external circuit design-in.
DSR
UART data set ready
output
1.8 V output, Circuit 107 (DSR) in ITU-T V.24.
See section 1.9.1 for functional description.
See section 2.6.1 for external circuit design-in.
RI
UART ring indicator
output
1.8 V output, Circuit 125 (RI) in ITU-T V.24.
See section 1.9.1 for functional description.
See section 2.6.1 for external circuit design-in.
DTR
UART data terminal
ready input
1.8 V input, Circuit 108/2 (DTR) in ITU-T V.24.
Internal active pull-up to V_INT.
Test-Point and series 0  for diagnostic access recommended.
See section 1.9.1 for functional description.
See section 2.6.1 for external circuit design-in.
DCD
UART data carrier
detect output
1.8 V input, Circuit 109 (DCD) in ITU-T V.24.
Test-Point and series 0  for diagnostic access recommended.
See section 1.9.1 for functional description.
See section 2.6.1 for external circuit design-in.
UART
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Function
Pin Name
Pin No
I/O
Description
Remarks
USB
VUSB_DET
17
USB detect input
VBUS (5 V typical) USB supply generated by the host must
be connected to this input pin to enable the USB interface.
If the USB interface is not used by the Application Processor,
Test-Point for diagnostic / FW update access is recommended
See section 1.9.2 for functional description.
See section 2.6.2 for external circuit design-in.
USB_D-
28
I/O
USB Data Line D-
USB interface for AT commands, data communication,
FOAT, FW update by u-blox EasyFlash tool and diagnostic.
90  nominal differential impedance (Z0)
30  nominal common mode impedance (ZCM)
Pull-up or pull-down resistors and external series resistors as
required by the USB 2.0 specifications [9] are part of the
USB pin driver and need not be provided externally.
If the USB interface is not used by the Application Processor,
Test-Point for diagnostic / FW update access is recommended
See section 1.9.2 for functional description.
See section 2.6.2 for external circuit design-in.
USB_D+
29
I/O
USB Data Line D+
USB interface for AT commands, data communication,
FOAT, FW update by u-blox EasyFlash tool and diagnostic.
90  nominal differential impedance (Z0)
30  nominal common mode impedance (ZCM)
Pull-up or pull-down resistors and external series resistors as
required by the USB 2.0 specifications [9] are part of the
USB pin driver and need not be provided externally.
If the USB interface is not used by the Application Processor,
Test-Point for diagnostic / FW update access is recommended
See section 1.9.2 for functional description.
See section 2.6.2 for external circuit design-in.
HSIC_DATA
99
I/O
HSIC USB data line
Not supported by “02” product versions.
USB High-Speed Inter-Chip compliant interface for AT
commands, data communication, FOAT, FW update by ublox EasyFlash tool and diagnostic.
50  nominal characteristic impedance.
Test-Point for diagnostic / FW update access is recommended.
See section 1.9.3 for functional description.
See section 2.6.3 for external circuit design-in.
HSIC_STRB
100
I/O
HSIC USB strobe line
Not supported by “02” product versions.
HSIC interface for AT commands, data communication,
FOAT, FW update by u-blox EasyFlash tool and diagnostic.
50  nominal characteristic impedance.
Test-Point for diagnostic / FW update access is recommended.
See section 1.9.3 for functional description.
See section 2.6.3 for external circuit design-in.
SCL
27
I2C bus clock line
1.8 V open drain, for communication with I2C-slave devices.
See section 1.9.4 for functional description.
See section 2.6.4 for external circuit design-in.
SDA
26
I/O
I2C bus data line
1.8 V open drain, for communication with I2C-slave devices.
See section 1.9.4 for functional description.
See section 2.6.4 for external circuit design-in.
HSIC
DDC
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Function
Pin Name
Pin No
I/O
Description
Remarks
SDIO
SDIO_D0
47
I/O
SDIO serial data [0]
Not supported by “02” product versions.
SDIO interface for communication with u-blox Wi-Fi module
See section 1.9.5 for functional description.
See section 2.6.5 for external circuit design-in.
SDIO_D1
49
I/O
SDIO serial data [1]
Not supported by “02” product versions.
SDIO interface for communication with u-blox Wi-Fi module
See section 1.9.5 for functional description.
See section 2.6.5 for external circuit design-in.
SDIO_D2
44
I/O
SDIO serial data [2]
Not supported by “02” product versions.
SDIO interface for communication with u-blox Wi-Fi module
See section 1.9.5 for functional description.
See section 2.6.5 for external circuit design-in.
SDIO_D3
48
I/O
SDIO serial data [3]
Not supported by “02” product versions.
SDIO interface for communication with u-blox Wi-Fi module
See section 1.9.5 for functional description.
See section 2.6.5 for external circuit design-in.
SDIO_CLK
45
SDIO serial clock
Not supported by “02” product versions.
SDIO interface for communication with u-blox Wi-Fi module
See section 1.9.5 for functional description.
See section 2.6.5 for external circuit design-in.
SDIO_CMD
46
I/O
SDIO command
Not supported by “02” product versions.
SDIO interface for communication with u-blox Wi-Fi module
See section 1.9.5 for functional description.
See section 2.6.5 for external circuit design-in.
I2S_TXD
35
O/
I/O
I2S transmit data /
GPIO
I2S transmit data output, alternatively configurable as GPIO.
I2S not supported by LARA-R204 module ‘02’ product version.
See sections 1.10 and 1.12 for functional description.
See sections 2.7 and 2.8 for external circuit design-in.
I2S_RXD
37
I/
I/O
I2S receive data /
GPIO
I2S receive data input, alternatively configurable as GPIO.
I2S not supported by LARA-R204 module ‘02’ product version.
See sections 1.10 and 1.12 for functional description.
See sections 2.7 and 2.8 for external circuit design-in.
I2S_CLK
36
I/O /
I/O
I2S clock /
GPIO
I2S serial clock, alternatively configurable as GPIO.
I2S not supported by LARA-R204 module ‘02’ product version.
See sections 1.10 and 1.12 for functional description.
See sections 2.7 and 2.8 for external circuit design-in.
I2S_WA
34
I/O /
I/O
I2S word alignment /
GPIO
I2S word alignment, alternatively configurable as GPIO.
I2S not supported by LARA-R204 module ‘02’ product version.
See sections 1.10 and 1.12 for functional description.
See sections 2.7 and 2.8 for external circuit design-in.
GPIO6
19
Clock output
1.8 V configurable clock output.
See section 1.11 for functional description.
See section 2.7 for external circuit design-in.
Audio
Clock
output
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Function
Pin Name
Pin No
I/O
Description
Remarks
GPIO
GPIO1
16
I/O
GPIO
1.8 V GPIO with alternatively configurable functions.
See section 1.12 for functional description.
See section 2.8 for external circuit design-in.
GPIO2
23
I/O
GPIO
1.8 V GPIO with alternatively configurable functions.
See section 1.12 for functional description.
See section 2.8 for external circuit design-in.
GPIO3
24
I/O
GPIO
1.8 V GPIO with alternatively configurable functions.
See section 1.12 for functional description.
See section 2.8 for external circuit design-in.
GPIO4
25
I/O
GPIO
1.8 V GPIO with alternatively configurable functions.
See section 1.12 for functional description.
See section 2.8 for external circuit design-in.
GPIO5
42
I/O
GPIO
1.8 V GPIO with alternatively configurable functions.
See section 1.12 for functional description.
See section 2.8 for external circuit design-in.
RSVD
33
N/A
RESERVED pin
This pin must be connected to ground.
See sections 1.13 and 2.9
RSVD
31, 97, 98
N/A
RESERVED pin
Internally not connected. Leave unconnected.
See sections 1.13 and 2.9
Reserved
Table 3: LARA-R2 series modules pin definition, grouped by function
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1.4
Operating modes
LARA-R2 series modules have several operating modes. The operating modes defined in Table 4 and described in
detail in Table 5 provide general guidelines for operation.
General Status
Operating Mode
Definition
Power-down
Not-Powered Mode
Power-Off Mode
VCC supply not present or below operating range: module is switched off.
VCC supply within operating range and module is switched off.
Normal operation
Idle-Mode
Active-Mode
Module processor core runs with 32 kHz reference generated by the internal oscillator.
Module processor core runs with 26 MHz reference generated by the internal oscillator.
Connected-Mode
RF Tx/Rx data connection enabled and processor core runs with 26 MHz reference.
Table 4: Module operating modes definition
Mode
Description
Transition between operating modes
Not-Powered
Module is switched off.
Application interfaces are not accessible.
When VCC supply is removed, the module enters not-powered mode.
When in not-powered mode, the modules cannot be switched on by
PWR_ON, RESET_N or RTC alarm.
When in not-powered mode, the modules can be switched on applying
VCC supply (see 2.3.1) so that the module switches from not-powered
to active-mode.
Power-Off
Module is switched off: normal shutdown by an
appropriate power-off event (see 1.6.2).
Application interfaces are not accessible.
When the module is switched off by an appropriate power-off event
(see 1.6.2), the module enters power-off mode from active-mode.
When in power-off mode, the modules can be switched on by
PWR_ON, RESET_N or RTC alarm (see 2.3.1): the module switches
from power-off to active-mode.
When in power-off mode, the modules enter not-powered mode by
removing VCC supply.
Idle
Module is switched on with application
interfaces temporarily disabled or suspended:
the module is temporarily not ready to
communicate with an external device by means
of the application interfaces as configured to
reduce the current consumption.
The module enters the low power idle-mode
whenever possible if power saving is enabled by
AT+UPSV (see u-blox AT Commands Manual [2])
reducing power consumption (see 1.5.1.4).
The CTS output line indicates when the UART
interface is disabled/enabled due to the module
idle/active-mode according to power saving and
HW flow control settings (see 1.9.1.3, 1.9.1.4).
Power saving configuration is not enabled by
default: it can be enabled by AT+UPSV (see the
u-blox AT Commands Manual [2]).
The module automatically switches from active-mode to idle-mode
whenever possible if power saving is enabled (see sections 1.5.1.4,
1.9.1.4, 1.9.2.4 and to the u-blox AT Commands Manual [2], AT+UPSV
command).
The module wakes up from idle to active mode in the following events:

Automatic periodic monitoring of the paging channel for the
paging block reception according to network conditions (see
1.5.1.3, 1.9.1.4)

Automatic periodic enable of the UART interface to receive and
send data, if AT+UPSV=1 power saving is set (see 1.9.1.4)

Data received on UART interface, according to HW flow control
(AT&K) and power saving (AT+UPSV) settings (see 1.9.1.4)

RTS input set ON by the host DTE, with HW flow control disabled
and AT+UPSV=2 (see 1.9.1.4)

DTR input set ON by the host DTE, with AT+UPSV=3 (see 1.9.1.4)

USB detection, applying 5 V (typ.) to VUSB_DET input (see 1.9.2)

The connected USB host forces a remote wakeup of the module
as USB device (see 1.9.2.4)

The connected u-blox GNSS receiver forces a wakeup of the
cellular module using the GNSS Tx data ready function over the
GPIO3 pin (see 1.9.4)

The connected SDIO device forces a wakeup of the module as
SDIO host (see 1.9.5)

RTC alarm occurs (see u-blox AT Commands Manual [2], +CALA)
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Mode
Description
Transition between operating modes
Active
The module is ready to communicate with an
external device by means of the application
interfaces unless power saving configuration is
enabled by the AT+UPSV command (see
sections 1.5.1.3, 1.9.1.4 and to the u-blox AT
Commands Manual [2]).
When the module is switched on by an appropriate power-on event
(see 2.3.1), the module enters active-mode from not-powered or
power-off mode.
If power saving configuration is enabled by the AT+UPSV command,
the module automatically switches from active to idle-mode whenever
possible and the module wakes up from idle to active-mode in the
events listed above (see idle to active transition description).
When a voice call or a data call is initiated, the module switches from
active-mode to connected-mode.
Connected
A voice call or a data call is in progress.
The module is ready to communicate with an
external device by means of the application
interfaces unless power saving configuration is
enabled by the AT+UPSV command (see
sections 1.5.1.3, 1.9.1.4 and the u-blox AT
Commands Manual [2]).
When a data or voice connection is initiated, the module enters
connected-mode from active-mode.
Connected-mode is suspended if Tx/Rx data is not in progress, due to
connected discontinuous reception and fast dormancy capabilities of
the module and according to network environment settings and
scenario. In such case, the module automatically switches from
connected to active mode and then, if power saving configuration is
enabled by the AT+UPSV command, the module automatically switches
to idle-mode whenever possible. Vice-versa, the module wakes up from
idle to active mode and then connected mode if RF Tx/Rx is necessary.
When a data connection is terminated, the module returns to the
active-mode.
Table 5: Module operating modes description
Figure 2 describes the transition between the different operating modes.
Not
powered
Remove VCC
Switch ON:
• Apply VCC
Power off
Switch ON:
• PWR_ON
• RTC alarm
• RESET_N
Switch OFF:
• AT+CPWROFF
Incoming/outgoing call or
other dedicated device
network communication
Connected
If power saving is enabled
and there is no activity for
a defined time interval
Active
No RF Tx/Rx in progress,
Call terminated,
Communication dropped
Idle
Any wake up event described
in the module operating
modes summary table above
Figure 2: Operating modes transition
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1.5
Supply interfaces
1.5.1 Module supply input (VCC)
The modules must be supplied via the three VCC pins that represent the module power supply input.
The VCC pins are internally connected to the RF power amplifier and to the integrated Power Management Unit:
all supply voltages needed by the module are generated from the VCC supply by integrated voltage regulators,
including V_BCKP Real Time Clock supply, V_INT digital interfaces supply and VSIM SIM card supply.
During operation, the current drawn by the LARA-R2 series modules through the VCC pins can vary by several
orders of magnitude. This ranges from the pulse of current consumption during GSM transmitting bursts at
maximum power level in connected-mode (as described in section 1.5.1.2) to the low current consumption
during low power idle-mode with power saving enabled (as described in section 1.5.1.4).
LARA-R211 modules provide separate supply inputs over the three VCC pins:

VCC pins #52 and #53 represent the supply input for the internal RF power amplifier, demanding most of
the total current drawn of the module when RF transmission is enabled during a voice/data call

VCC pin #51 represents the supply input for the internal baseband Power Management Unit and the internal
transceiver, demanding minor part of the total current drawn of the module when RF transmission is
enabled during a voice/data call
Figure 3 provides a simplified block diagram of LARA-R2 series modules internal VCC supply routing.
LARA-R204
LARA-R211
LTE PA
VCC 53
RF PMU
VCC 51
VCC 53
Transceiver
VCC 52
Power
Management
Unit
LTE / 2G PAs
Baseband
Processor
RF PMU
Transceiver
VCC 52
VCC 51
Memory
Power
Management
Unit
Baseband
Processor
Memory
Figure 3: LARA-R2 series modules internal VCC supply routing simplified block diagram
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1.5.1.1 VCC supply requirements
Table 6 summarizes the requirements for the VCC module supply. See section 2.2.1 for all the suggestions to
properly design a VCC supply circuit compliant to the requirements listed in Table 6.
VCC supply circuit affects the RF compliance of the device integrating LARA-R2 series modules
with applicable required certification schemes as well as antenna circuit design. Compliance is
guaranteed if the VCC requirements summarized in the Table 6 are fulfilled.
Item
Requirement
Remark
VCC nominal voltage
Within VCC normal operating range:
3.30 V min. / 4.40 V max
RF performance is guaranteed when VCC PA voltage is
inside the normal operating range limits.
RF performance may be affected when VCC PA voltage is
outside the normal operating range limits, though the
module is still fully functional until the VCC voltage is
inside the extended operating range limits.
VCC voltage during
normal operation
Within VCC extended operating range:
3.00 V min. / 4.50 V max
VCC voltage must be above the extended operating
range minimum limit to switch-on the module.
The module may switch-off when the VCC voltage drops
below the extended operating range minimum limit.
Operation above VCC extended operating range is not
recommended and may affect device reliability.
VCC average current
Support with adequate margin the highest averaged
VCC current consumption value in connected-mode
conditions specified in LARA-R2 series Data Sheet [1]
The highest averaged VCC current consumption can be
greater than the specified value according to the actual
antenna mismatching, temperature and VCC voltage.
See 1.5.1.2, 1.5.1.3 for connected-mode current profiles.
VCC peak current
Support with margin the highest peak VCC current
consumption value in connected-mode conditions
specified in LARA-R2 series Data Sheet [1]
The specified highest peak of VCC current consumption
occurs during GSM single transmit slot in 850/900 MHz
connected-mode, in case of mismatched antenna.
See 1.5.1.2 for 2G connected-mode current profiles.
VCC voltage drop
during 2G Tx slots
Lower than 400 mV
VCC voltage drop directly affects the RF compliance with
applicable certification schemes.
Figure 5 describes VCC voltage drop during Tx slots.
VCC voltage ripple
during 2G/LTE Tx
Noise in the supply has to be minimized
VCC voltage ripple directly affects the RF compliance with
applicable certification schemes.
Figure 5 describes VCC voltage ripple during Tx slots.
VCC under/over-shoot
at start/end of Tx slots
Absent or at least minimized
VCC under/over-shoot directly affects the RF compliance
with applicable certification schemes.
Figure 5 describes VCC voltage under/over-shoot.
Table 6: Summary of VCC supply requirements
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1.5.1.2 VCC current consumption in 2G connected-mode
When a GSM call is established, the VCC consumption is determined by the current consumption profile typical
of the GSM transmitting and receiving bursts.
The current consumption peak during a transmission slot is strictly dependent on the transmitted power, which
is regulated by the network. The transmitted power in the transmit slot is also the more relevant factor for
determining the average current consumption.
If the module is transmitting in 2G single-slot mode (as in GSM talk mode) in the 850 or 900 MHz bands, at the
maximum RF power control level (approximately 2 W or 33 dBm in the Tx slot/burst), the current consumption
can reach an high peak / pulse (see LARA-R2 series Data Sheet [1]) for 576.9 µs (width of the transmit slot/burst)
with a periodicity of 4.615 ms (width of 1 frame = 8 slots/burst), so with a 1/8 duty cycle according to GSM
TDMA (Time Division Multiple Access).
If the module is transmitting in 2G single-slot mode in the 1800 or 1900 MHz bands, the current consumption
figures are quite less high than the one in the low bands, due to 3GPP transmitter output power specifications.
During a GSM call, current consumption is not so significantly high in receiving or in monitor bursts and it is low
in the bursts unused to transmit / receive.
Figure 4 shows an example of the module current consumption profile versus time in GSM talk mode.
Current [A]
2.0
1900 mA
1.5
Peak current depends
on TX power and
actual antenna load
1.0
0.5
200 mA
60-120 mA
0.0
RX
slot
60-120 mA
10-40 mA
unused unused
slot
slot
TX
slot
unused unused
slot
slot
MON
slot
unused
slot
RX
slot
unused unused
slot
slot
GSM frame
4.615 ms
(1 frame = 8 slots)
TX
slot
unused unused
slot
slot
MON
slot
unused
slot
Time [ms]
GSM frame
4.615 ms
(1 frame = 8 slots)
Figure 4: VCC current consumption profile versus time during a GSM call (1 TX slot, 1 RX slot)
Figure 5 illustrates VCC voltage profile versus time during a GSM call, according to the related VCC current
consumption profile described in Figure 4.
Voltage
overshoot
3.8 V
(typ)
drop
ripple
RX
slot
unused unused
slot
slot
TX
slot
undershoot
unused unused
slot
slot
GSM frame
4.615 ms
(1 frame = 8 slots)
MON
slot
unused
slot
RX
slot
unused unused
slot
slot
TX
slot
unused unused
slot
slot
GSM frame
4.615 ms
(1 frame = 8 slots)
MON
slot
unused
slot
Time
Figure 5: Description of the VCC voltage profile versus time during a GSM call (1 TX slot, 1 RX slot)
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When a GPRS connection is established, more than one slot can be used to transmit and/or more than one slot
can be used to receive. The transmitted power depends on network conditions, which set the peak current
consumption, but following the 3GPP specifications the maximum Tx RF power is reduced if more than one slot
is used to transmit, so the maximum peak of current is not as high as can be in case of a 2G single-slot call.
The multi-slot transmission power can be further reduced by configuring the actual Multi-Slot Power Reduction
profile with the dedicated AT command, AT+UDCONF=40 (see the u-blox AT Commands Manual [2]).
If the module transmits in GPRS class 12 in the 850 or 900 MHz bands, at the maximum RF power control level,
the current consumption can reach a quite high peak but lower than the one achievable in 2G single-slot mode.
This happens for 2.307 ms (width of the 4 transmit slots/bursts) with a periodicity of 4.615 ms (width of 1 frame
= 8 slots/bursts), so with a 1/2 duty cycle, according to 2G TDMA.
If the module is in GPRS connected mode in the 1800 or 1900 MHz bands, the current consumption figures are
quite less high than the one in the low bands, due to 3GPP transmitter output power specifications.
Figure 6 reports the current consumption profiles in GPRS class 12 connected mode, in the 850 or 900 MHz
bands, with 4 slots used to transmit and 1 slot used to receive.
Current [A]
2.0
1600 mA
1.5
1.0
Peak current depends
on TX power and
actual antenna load
0.5
200mA
60-130mA
0.0
RX
slot
unused
slot
TX
slot
TX
slot
TX
slot
TX
slot
GSM frame
4.615 ms
(1 frame = 8 slots)
MON
slot
unused
slot
RX
slot
unused
slot
TX
slot
TX
slot
TX
slot
TX
slot
MON
slot
unused
slot
Time [ms]
GSM frame
4.615 ms
(1 frame = 8 slots)
Figure 6: VCC current consumption profile versus time during a 2G GPRS/EDGE multi-slot connection (4 TX slots, 1 RX slot)
In case of EDGE connections the VCC current consumption profile is very similar to the GPRS current profile, so
the image shown in Figure 6, representing the current consumption profile in GPRS class 12 connected mode, is
valid for the EDGE class 12 connected mode as well.
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1.5.1.3 VCC current consumption in LTE connected-mode
During an LTE connection, the module can transmit and receive continuously due to the Frequency Division
Duplex (FDD) mode of operation used in LTE radio access technology.
The current consumption depends on output RF power, which is always regulated by the network (the current
base station) sending power control commands to the module. These power control commands are logically
divided into a slot of 0.5 ms (time length of one Resource Block), thus the rate of power change can reach a
maximum rate of 2 kHz.
The current consumption profile is similar to that in 3G radio access technology. Unlike the 2G connection
mode, which uses the TDMA mode of operation, there are no high current peaks since transmission and
reception are continuously enabled in FDD.
In the worst scenario, corresponding to a continuous transmission and reception at maximum output power
(approximately 250 mW or 24 dBm), the average current drawn by the module at the VCC pins is considerable
(see the “Current consumption” section in LARA-R2 series Data Sheet [1]). At the lowest output RF power
(approximately 0.1 µW or –40 dBm), the current drawn by the internal power amplifier is strongly reduced and
the total current drawn by the module at the VCC pins is due to baseband processing and transceiver activity.
Figure 7 shows an example of the module current consumption profile versus time in LTE connected-mode.
Detailed current consumption values can be found in LARA-R2 series Data Sheet [1].
Current [mA]
700
600
500
Current consumption value
depends on TX power and
actual antenna load
400
300
200
100
1 Slot
1 Resource Block
(0.5 ms)
1 LTE Radio Frame
(10 ms)
Time
[ms]
Figure 7: VCC current consumption profile versus time during LTE connection (TX and RX continuously enabled)
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1.5.1.4 VCC current consumption in cyclic idle/active-mode (power saving enabled)
The power saving configuration is by default disabled, but it can be enabled using the appropriate AT command
(see u-blox AT Commands Manual [2], AT+UPSV command). When power saving is enabled, the module
automatically enters low power idle-mode whenever possible, reducing current consumption.
When the power saving configuration is enabled and the module is registered or attached to a network, the
module automatically enters the low power idle-mode whenever possible, but it must periodically monitor the
paging channel of the current base station (paging block reception), in accordance to the 2G / LTE system
requirements, even if connected-mode is not enabled by the application. When the module monitors the paging
channel, it wakes up to the active-mode, to enable the reception of paging block. In between, the module
switches to low power idle-mode. This is known as discontinuous reception (DRX).
The module processor core is activated during the paging block reception, and automatically switches its
reference clock frequency from 32 kHz to the 26 MHz used in active-mode.
The time period between two paging block receptions is defined by the network. This is the paging period
parameter, fixed by the base station through broadcast channel sent to all users on the same serving cell:

In case of 2G radio access technology, the paging period can vary from 470.8 ms (DRX = 2, length of 2 x 51
2G frames = 2 x 51 x 4.615 ms) up to 2118.4 ms (DRX = 9, length of 9 x 51 2G frames = 9 x 51 x 4.615 ms)

In case of LTE radio access technology, the paging period can vary from 320 ms (DRX = 5, i.e. length of 2
LTE frames = 32 x 10 ms) up to 2560 ms (DRX = 8, length of 2 LTE frames = 256 x 10 ms).
Figure 8 illustrates a typical example of the module current consumption profile when power saving is enabled.
The module is registered with network, automatically enters the low power idle-mode and periodically wakes up
to active-mode to monitor the paging channel for the paging block reception. Detailed current consumption
values can be found in LARA-R2 series Data Sheet [1]).
Current [mA]
100
Time [s]
Current [mA]
IDLE MODE
ACTIVE MODE
2G case: 0.44-2.09 s
LTE case: 0.27-2.51 s
~50 ms
100
Active Mode
Enabled
IDLE MODE
RX
Enabled
Idle Mode
Enabled
~50 ms
ACTIVE MODE
Time [ms]
IDLE MODE
Figure 8: VCC current consumption profile with power saving enabled and module registered with the network: the module is
in low-power idle-mode and periodically wakes up to active-mode to monitor the paging channel for paging block reception
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1.5.1.5 VCC current consumption in fixed active-mode (power saving disabled)
Power saving configuration is by default disabled, or it can be disabled using the appropriate AT command (see
u-blox AT Commands Manual [2], AT+UPSV command). When power saving is disabled, the module does not
automatically enter idle-mode whenever possible: the module remains in active-mode.
The module processor core is activated during active-mode, and the 26 MHz reference clock frequency is used.
Figure 9 illustrates a typical example of the module current consumption profile when power saving is disabled.
In such case, the module is registered with the network and while active-mode is maintained, the receiver is
periodically activated to monitor the paging channel for paging block reception. Detailed current consumption
values can be found in LARA-R2 series Data Sheet [1].
Current [mA]
100
Time [s]
Current [mA]
Paging period
2G case: 0.44-2.09 s
3G case: 0.61-5.09 s
LTE case: 0.32-2.56 s
100
Time [ms]
RX
Enabled
ACTIVE MODE
Figure 9: VCC current consumption profile with power saving disabled and module registered with the network: active-mode is
always held and the receiver is periodically activated to monitor the paging channel for paging block reception
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1.5.2 RTC supply input/output (V_BCKP)
The V_BCKP pin of LARA-R2 series modules connects the supply for the Real Time Clock (RTC) and Power-On
internal logic. This supply domain is internally generated by a linear LDO regulator integrated in the Power
Management Unit, as described in Figure 10. The output of this linear regulator is always enabled when the
main voltage supply provided to the module through the VCC pins is within the valid operating range, with the
module switched off or switched on.
LARA-R2 series
VCC 51
Power
Management
Baseband
Processor
Linear
LDO
RTC
VCC 52
VCC 53
V_BCKP 2
32 kHz
Figure 10: RTC supply input/output (V_BCKP) and 32 kHz RTC timing reference clock simplified block diagram
The RTC provides the module time reference (date and time) that is used to set the wake-up interval during the
low power idle-mode periods, and is able to make available the programmable alarm functions.
The RTC functions are available also in power-down mode when the V_BCKP voltage is within its valid range
(specified in the “Input characteristics of Supply/Power pins” table in LARA-R2 series Data Sheet [1]). The RTC
can be supplied from an external back-up battery through the V_BCKP, when the main module voltage supply is
not applied to the VCC pins. This lets the time reference (date and time) run until the V_BCKP voltage is within
its valid range, even when the main supply is not provided to the module.
Consider that the module cannot switch on if a valid voltage is not present on VCC even when the RTC is
supplied through V_BCKP (meaning that VCC is mandatory to switch on the module).
The RTC has very low current consumption, but is highly temperature dependent. For example, V_BCKP current
consumption at the maximum operating temperature can be higher than the typical value at 25 °C specified in
the “Input characteristics of Supply/Power pins” table in the LARA-R2 series Data Sheet [1].
If V_BCKP is left unconnected and the module main voltage supply is removed from VCC, the RTC is supplied
from the bypass capacitor mounted inside the module. However, this capacitor is not able to provide a long
buffering time: within few milliseconds the voltage on V_BCKP will go below the valid range. This has no impact
on cellular connectivity, as all the module functionalities do not rely on date and time setting.
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1.5.3 Generic digital interfaces supply output (V_INT)
The V_INT output pin of the LARA-R2 series modules is connected to an internal 1.8 V supply with current
capability specified in the LARA-R2 series Data Sheet [1]. This supply is internally generated by a switching stepdown regulator integrated in the Power Management Unit and it is internally used to source the generic digital
I/O interfaces of the cellular module, as described in Figure 11. The output of this regulator is enabled when the
module is switched on and it is disabled when the module is switched off.
LARA-R2 series
VCC 51
Power
Management
Baseband
Processor
Switching
Step-Down
Digital I/O
Interfaces
VCC 52
VCC 53
V_INT 4
Figure 11: LARA-R2 series interfaces supply output (V_INT) simplified block diagram
The switching regulator operates in Pulse Width Modulation (PWM) mode for greater efficiency at high output
loads and it automatically switches to Pulse Frequency Modulation (PFM) power save mode for greater efficiency
at low output loads. The V_INT output voltage ripple is specified in the LARA-R2 series Data Sheet [1].
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1.6
System function interfaces
1.6.1 Module power-on
When the LARA-R2 series modules are in the not-powered mode (switched off, i.e. the VCC module supply is
not applied), they can be switched on as following:

Rising edge on the VCC input pins to a valid voltage for module supply: the modules switch on if the VCC
supply is applied with a rise time of less than 10 ms from 2.1 V to 3.0 V, reaching a proper nominal voltage
value within the VCC operating range.
Alternately, in case for example the fast rise time on VCC rising edge cannot be guaranteed by the application,
LARA-R2 series modules can be switched on from not-powered mode as following:

RESET_N input pin is held low by the external application during the VCC rising edge, so that the modules
will switch on when the external application releases the RESET_N input pin from the low logic level after
that the VCC supply voltage stabilizes at its proper nominal value within the operating range

PWR_ON input pin is held low by the external application during the VCC rising edge, so that the modules
will switch on when the external application releases the PWR_ON input pin from the low logic level after
that the VCC supply voltage stabilizes at its proper nominal value within the operating range
When the LARA-R2 series modules are in the power-off mode (i.e. switched off with valid VCC module supply
applied), they can be switched on as following:

Low pulse on the PWR_ON pin, which is normally set high by an internal pull-up, for a valid time period: the
modules start the internal power-on sequence when the external application releases the PWR_ON pin from
the low logic level after that it has been set low for an appropriate time period

Rising edge on the RESET_N pin, i.e. releasing the pin from the low level, as that the pin is normally set high
by an internal pull-up: the modules start the internal power-on sequence when the external application
releases the RESET_N pin from the low logic level

RTC alarm, i.e. pre-programmed alarm by AT+CALA command (see u-blox AT Commands Manual [2]).
As described in Figure 12, the LARA-R2 series PWR_ON input is equipped with an internal active pull-up resistor
to the V_BCKP supply: the PWR_ON input voltage thresholds are different from the other generic digital
interfaces. Detailed electrical characteristics are described in LARA-R2 series Data Sheet [1].
LARA-R2 series
V_BCKP
Power
Management
Baseband
Processor
Power-on
Power-on
10k
PWR_ON 15
Figure 12: LARA-R2 series PWR_ON input description
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Figure 13 shows the module power-on sequence from the not-powered mode, describing the following phases:

The external supply is applied to the VCC module supply inputs, representing the start-up event.

The V_BCKP RTC supply output is suddenly enabled by the module as VCC reaches a valid voltage value.

The PWR_ON and the RESET_N pins suddenly rise to high logic level due to internal pull-ups.

All the generic digital pins of the module are tri-stated until the switch-on of their supply source (V_INT).

The internal reset signal is held low: the baseband core and all the digital pins are held in the reset state. The
reset state of all the digital pins is reported in the pin description table of LARA-R2 series Data Sheet [1].

When the internal reset signal is released, any digital pin is set in a proper sequence from the reset state to
the default operational configured state. The duration of this pins’ configuration phase differs within generic
digital interfaces and the USB interface due to host / device enumeration timings (see section 1.9.2).

The module is fully ready to operate after all interfaces are configured.
Start of interface
configuration
Start-up
event
Module interfaces
are configured
VCC
V_BCKP
PWR_ON
RESET_N
V_INT
Internal Reset
OFF
System State
BB Pads State
Tristate / Floating
ON
Internal Reset Internal Reset → Operational Operational
Figure 13: LARA-R2 series power-on sequence description
The greeting text can be activated by means of +CSGT AT command (see u-blox AT Commands Manual [2]) to
notify the external application that the module is ready to operate (i.e. ready to reply to AT commands) and the
first AT command can be sent to the module, given that autobauding has to be disabled on the UART to let the
module sending the greeting text: the UART has to be configured at fixed baud rate (the baud rate of the
application processor) instead of the default autobauding, otherwise the module does not know the baud rate
to be used for sending the greeting text (or any other URC) at the end of the internal boot sequence.
The Internal Reset signal is not available on a module pin, but the host application can monitor the V_INT
pin to sense the start of the LARA-R2 series module power-on sequence.
Before the switch-on of the generic digital interface supply source (V_INT) of the module, no voltage
driven by an external application should be applied to any generic digital interface of the module.
Before the LARA-R2 series module is fully ready to operate, the host application processor should not send
any AT command over the AT communication interfaces (USB, UART) of the module.
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1.6.2 Module power-off
LARA-R2 series can be properly switched off by:

AT+CPWROFF command (see u-blox AT Commands Manual [2]). The current parameter settings are saved in
the module’s non-volatile memory and a proper network detach is performed.
An abrupt under-voltage shutdown occurs on LARA-R2 series modules when the VCC module supply is
removed. If this occurs, it is not possible to perform the storing of the current parameter settings in the module’s
non-volatile memory or to perform the proper network detach.
It is highly recommended to avoid an abrupt removal of the VCC supply during LARA-R2 series modules
normal operations: the power off procedure must be started by the AT+CPWROFF command, waiting the
command response for a proper time period (see u-blox AT Commands Manual [2]), and then a proper
VCC supply has to be held at least until the end of the modules’ internal power off sequence, which
occurs when the generic digital interfaces supply output (V_INT) is switched off by the module.
An abrupt hardware shutdown occurs on LARA-R2 series modules when a low level is applied on RESET_N pin.
In this case, the current parameter settings are not saved in the module’s non-volatile memory and a proper
network detach is not performed.
It is highly recommended to avoid an abrupt hardware shutdown of the module by forcing a low level on
the RESET_N input pin during module normal operation: the RESET_N line should be set low only if reset
or shutdown via AT commands fails or if the module does not reply to a specific AT command after a time
period longer than the one defined in the u-blox AT Commands Manual [2].
An over-temperature or an under-temperature shutdown occurs on LARA-R2 series modules when the
temperature measured within the cellular module reaches the dangerous area, if the optional Smart
Temperature Supervisor feature is enabled and configured by the dedicated AT command. For more details see
section 1.14.15 and u-blox AT Commands Manual [2], +USTS AT command.
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Figure 14 describes the LARA-R2 series modules power-off sequence, properly started sending the AT+CPWROFF
command, allowing storage of current parameter settings in the module’s non-volatile memory and a proper
network detach, with the following phases:

When the +CPWROFF AT command is sent, the module starts the switch-off routine.

The module replies OK on the AT interface: the switch-off routine is in progress.

At the end of the switch-off routine, all the digital pins are tri-stated and all the internal voltage regulators
are turned off, including the generic digital interfaces supply (V_INT), except the RTC supply (V_BCKP).

Then, the module remains in power-off mode as long as a switch on event does not occur (e.g. applying a
proper low level to the PWR_ON input, or applying a proper low level to the RESET_N input), and enters
not-powered mode if the supply is removed from the VCC pins.
AT+CPWROFF
sent to the module
OK
replied by the module
VCC
can be removed
VCC
V_BCKP
PWR_ON
RESET_N
V_INT
Internal Reset
ON
System State
BB Pads State
Operational
OFF
Tristate / Floating
Operational → Tristate
0s
~2.5 s
Figure 14: LARA-R2 series power-off sequence description
~5 s
The Internal Reset signal is not available on a module pin, but the application can monitor the V_INT pin
to sense the end of the LARA-R2 series power-off sequence.
The duration of each phase in the LARA-R2 series modules’ switch-off routines can largely vary depending
on the application / network settings and the concurrent module activities.
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1.6.3 Module reset
LARA-R2 series modules can be properly reset (rebooted) by:
 AT+CFUN command (see the u-blox AT Commands Manual [2] for more details).
This command causes an “internal” or “software” reset of the module, which is an asynchronous reset of the
module baseband processor. The current parameter settings are saved in the module’s non-volatile memory and
a proper network detach is performed: this is the proper way to reset the modules.
An abrupt hardware reset occurs on LARA-R2 series modules when a low level is applied on the RESET_N input
pin for a specific time period. In this case, the current parameter settings are not saved in the module’s nonvolatile memory and a proper network detach is not performed.
It is highly recommended to avoid an abrupt hardware reset of the module by forcing a low level on the
RESET_N input during modules normal operation: the RESET_N line should be set low only if reset or
shutdown via AT commands fails or if the module does not provide a reply to a specific AT command
after a time period longer than the one defined in the u-blox AT Commands Manual [2].
As described in Figure 15, the RESET_N input pins are equipped with an internal pull-up to the V_BCKP supply.
LARA-R2 series
V_BCKP
Power
Management
Baseband
Processor
Reset
Reset
10k
RESET_N 18
Figure 15: LARA-R2 series RESET_N input equivalent circuit description
For more electrical characteristics details see LARA-R2 series Data Sheet [1].
1.6.4 Module / host configuration selection
Selection of module / host configuration over HOST_SELECT is not supported by “02” product versions.
The modules include one pin (HOST_SELECT) to select the module / host application processor configuration:
the pin is available to select, enable, connect, disconnect and subsequently re-connect the HSIC interface.
LARA-R2 series Data Sheet [1] describes the detailed electrical characteristics of the HOST_SELECT pin.
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1.7
Antenna interface
1.7.1 Antenna RF interfaces (ANT1 / ANT2)
LARA-R2 series modules provide two RF interfaces for connecting the external antennas:

The ANT1 represents the primary RF input/output for transmission and reception of LTE/3G/2G RF signals.
The ANT1 pin has a nominal characteristic impedance of 50  and must be connected to the primary Tx / Rx
antenna through a 50  transmission line to allow proper RF transmission and reception.

The ANT2 represents the secondary RF input for the reception of the LTE RF signals for the Down-Link Rx
diversity radio technology supported by LARA-R2 series modules as required feature for LTE category 1 UEs.
The ANT2 pin has a nominal characteristic impedance of 50  and must be connected to the secondary Rx
antenna through a 50  transmission line to allow proper RF reception.
1.7.1.1
Antenna RF interface requirements
Table 7, Table 8 and Table 9 summarize the requirements for the antennas RF interfaces (ANT1 / ANT2). See
section 0 for suggestions to properly design antennas circuits compliant with these requirements.
The antenna circuits affect the RF compliance of the device integrating LARA-R2 series modules
with applicable required certification schemes (for more details see section 4). Compliance is
guaranteed if the antenna RF interfaces (ANT1 / ANT2) requirements summarized in Table 7,
Table 8 and Table 9 are fulfilled.
Item
Requirements
Remarks
Impedance
50  nominal characteristic impedance
Frequency Range
See the LARA-R2 series Data Sheet [1]
The impedance of the antenna RF connection must match the 50 
impedance of the ANT1 port.
The required frequency range of the antenna connected to ANT1 port
depends on the operating bands of the used cellular module and the
used mobile network.
Return Loss
S11 < -10 dB (VSWR < 2:1) recommended
S11 < -6 dB (VSWR < 3:1) acceptable
Efficiency
> -1.5 dB ( > 70% ) recommended
> -3.0 dB ( > 50% ) acceptable
Maximum Gain
According to radiation exposure limits
Input Power
> 33 dBm ( > 2 W )
The Return loss or the S11, as the VSWR, refers to the amount of
reflected power, measuring how well the antenna RF connection
matches the 50  characteristic impedance of the ANT1 port.
The impedance of the antenna termination must match as much as
possible the 50  nominal impedance of the ANT1 port over the
operating frequency range, reducing as much as possible the amount
of reflected power.
The radiation efficiency is the ratio of the radiated power to the power
delivered to antenna input: the efficiency is a measure of how well an
antenna receives or transmits.
The radiation efficiency of the antenna connected to the ANT1 port
needs to be enough high over the operating frequency range to
comply with the Over-The-Air (OTA) radiated performance
requirements, as Total Radiated Power (TRP) and the Total Isotropic
Sensitivity (TIS), specified by applicable related certification schemes.
The power gain of an antenna is the radiation efficiency multiplied by
the directivity: the gain describes how much power is transmitted in
the direction of peak radiation to that of an isotropic source.
The maximum gain of the antenna connected to ANT1 port must not
exceed the herein stated value to comply with regulatory agencies
radiation exposure limits.
For additional info see sections 4.2.2 and/or 4.3.1
The antenna connected to the ANT1 port must support with adequate
margin the maximum power transmitted by the modules
Table 7: Summary of primary Tx/Rx antenna RF interface (ANT1) requirements
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Item
Requirements
Remarks
Impedance
50  nominal characteristic impedance
Frequency Range
See the LARA-R2 series Data Sheet [1]
Return Loss
S11 < -10 dB (VSWR < 2:1) recommended
S11 < -6 dB (VSWR < 3:1) acceptable
Efficiency
> -1.5 dB ( > 70% ) recommended
> -3.0 dB ( > 50% ) acceptable
The impedance of the antenna RF connection must match the 50 
impedance of the ANT2 port.
The required frequency range of the antennas connected to ANT2
port depends on the operating bands of the used cellular module and
the used Mobile Network.
The Return loss or the S11, as the VSWR, refers to the amount of
reflected power, measuring how well the antenna RF connection
matches the 50  characteristic impedance of the ANT2 port.
The impedance of the antenna termination must match as much as
possible the 50  nominal impedance of the ANT2 port over the
operating frequency range, reducing as much as possible the amount
of reflected power.
The radiation efficiency is the ratio of the radiated power to the power
delivered to antenna input: the efficiency is a measure of how well an
antenna receives or transmits.
The radiation efficiency of the antenna connected to the ANT2 port
needs to be enough high over the operating frequency range to
comply with the Over-The-Air (OTA) radiated performance
requirements, as the TIS, specified by applicable related certification
schemes.
Table 8: Summary of secondary Rx antenna RF interface (ANT2) requirements
Item
Requirements
Remarks
Efficiency
imbalance
< 0.5 dB recommended
< 1.0 dB acceptable
Envelope
Correlation
Coefficient
< 0.4 recommended
< 0.5 acceptable
Isolation
> 15 dB recommended
> 10 dB acceptable
The radiation efficiency imbalance is the ratio of the primary (ANT1)
antenna efficiency to the secondary (ANT2) antenna efficiency: the
efficiency imbalance is a measure of how much better an antenna
receives or transmits compared to the other antenna.
The radiation efficiency of the secondary antenna needs to be roughly
the same of the radiation efficiency of the primary antenna for good
RF performance.
The Envelope Correlation Coefficient (ECC) between the primary
(ANT1) and the secondary (ANT2) antenna is an indicator of 3D
radiation pattern similarity between the two antennas: low ECC results
from antenna patterns with radiation lobes in different directions.
The ECC between primary and secondary antenna needs to be enough
low to comply with radiated performance requirements specified by
related certification schemes.
The antenna to antenna isolation is the loss between the primary
(ANT1) and the secondary (ANT2) antenna: high isolation results from
low coupled antennas.
The isolation between primary and secondary antenna needs to be
high for good RF performance.
Table 9: Summary of primary (ANT1) and secondary (ANT2) antennas relationship requirements
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1.7.2 Antenna detection interface (ANT_DET)
The antenna detection is based on ADC measurement. The ANT_DET pin is an Analog to Digital Converter
(ADC) provided to sense the antenna presence.
The antenna detection function provided by ANT_DET pin is an optional feature that can be implemented if the
application requires it. The antenna detection is forced by the +UANTR AT command. See the u-blox AT
Commands Manual [2] for more details on this feature.
The ANT_DET pin generates a DC current (for detailed characteristics see the LARA-R2 series Data Sheet [1]) and
measures the resulting DC voltage, thus determining the resistance from the antenna connector provided on the
application board to GND. So, the requirements to achieve antenna detection functionality are the following:

an RF antenna assembly with a built-in resistor (diagnostic circuit) must be used

an antenna detection circuit must be implemented on the application board
See section 2.4.2 for antenna detection circuit on application board and diagnostic circuit on antenna assembly
design-in guidelines.
1.8
SIM interface
1.8.1 SIM card interface
LARA-R2 series modules provide a high-speed SIM/ME interface, including automatic detection and
configuration of the voltage required by the connected SIM card or chip.
Both 1.8 V and 3 V SIM types are supported: activation and deactivation with automatic voltage switch from
1.8 V to 3 V is implemented, according to ISO-IEC 7816-3 specifications. The VSIM supply output pin provides
internal short circuit protection to limit start-up current and protect the device in short circuit situations.
The SIM driver supports the PPS (Protocol and Parameter Selection) procedure for baud-rate selection, according
to the values determined by the SIM Card.
1.8.2 SIM card detection interface (SIM_DET)
The GPIO5 pin is by default configured to detect the external SIM card mechanical / physical presence. The pin is
configured as input, and it can sense SIM card presence as intended to be properly connected to the mechanical
switch of a SIM card holder as described in section 2.5:

Low logic level at GPIO5 input pin is recognized as SIM card not present

High logic level at GPIO5 input pin is recognized as SIM card present
The SIM card detection function provided by GPIO5 pin is an optional feature that can be implemented / used or
not according to the application requirements: an Unsolicited Result Code (URC) is generated each time that
there is a change of status (for more details see u-blox AT Commands Manual [2], +UGPIOC, +CIND, +CMER).
The optional function “SIM card hot insertion/removal” can be additionally configured on the GPIO5 pin by
specific AT command (see the u-blox AT Commands Manual [2], +UDCONF=50), in order to enable / disable the
SIM interface upon detection of external SIM card physical insertion / removal.
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1.9
Data communication interfaces
LARA-R2 series modules provide the following serial communication interfaces:

UART interface: Universal Asynchronous Receiver/Transmitter serial interface available for the communication
with a host application processor (AT commands, data communication, FW update by means of FOAT), for
FW update by means of the u-blox EasyFlash tool and for diagnostic. (see section 1.9.1)

USB interface: Universal Serial Bus 2.0 compliant interface available for the communication with a host
application processor (AT commands, data communication, FW update by means of the FOAT feature), for
FW update by means of the u-blox EasyFlash tool and for diagnostic. (see section 1.9.2)

HSIC interface: High-Speed Inter-Chip USB compliant interface available for the communication with a host
application processor (AT commands, data communication, FW update by means of the FOAT feature), for
FW update by means of the u-blox EasyFlash tool and for diagnostic. (see section 1.9.3)

DDC interface: I C bus compatible interface available for the communication with u-blox GNSS positioning
chips or modules and with external I C devices as an audio codec. (see section 1.9.4)

SDIO interface: Secure Digital Input Output interface available for the communication with compatible
u-blox short range radio communication Wi-Fi modules. (see section 1.9.5)
1.9.1 UART interface
1.9.1.1
UART features
The UART interface is a 9-wire 1.8 V unbalanced asynchronous serial interface available on all the LARA-R2 series
modules, supporting:

AT command mode

Data mode and Online command mode

Multiplexer protocol functionality (see 1.9.1.5)

FW upgrades by means of the FOAT feature (see 1.14.13 and Firmware update application note [23])

FW upgrades by means of the u-blox EasyFlash tool (see the Firmware update application note [23])

Trace log capture (diagnostic purpose)
UART interface provides RS-232 functionality conforming to the ITU-T V.24 Recommendation [5], with CMOS
compatible signal levels: 0 V for low data bit or ON state, and 1.8 V for high data bit or OFF state (for detailed
electrical characteristics see LARA-R2 series Data Sheet [1]), providing:

data lines (RXD as output, TXD as input),

hardware flow control lines (CTS as output, RTS as input),

modem status and control lines (DTR as input, DSR as output, DCD as output, RI as output).
LARA-R2 series modules are designed to operate as cellular modems, i.e. as the data circuit-terminating
equipment (DCE) according to the ITU-T V.24 Recommendation [5]. A host application processor connected to
the module through the UART interface represents the data terminal equipment (DTE).
UART signal names of the modules conform to the ITU-T V.24 Recommendation [5]: e.g. TXD line
represents data transmitted by the DTE (host processor output) and received by the DCE (module input).
LARA-R2 series modules’ UART interface is by default configured in AT command mode: the module waits for
AT command instructions and interprets all the characters received as commands to execute.
See the u-blox AT Commands Manual [2] for the definition of the command mode, data mode, and online command mode.
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All the functionalities supported by LARA-R2 series modules can be set and configured by AT commands:

AT commands according to 3GPP TS 27.007 [6], 3GPP TS 27.005 [7], 3GPP TS 27.010 [8]

u-blox AT commands (for the complete list and syntax see the u-blox AT Commands Manual [2])
All flow control handshakes are supported by the UART interface and can be set by appropriate AT commands
(see u-blox AT Commands Manual [2], &K, +IFC, \Q AT commands): hardware, software, or none flow control.
Hardware flow control is enabled by default.
The one-shot autobauding is supported: the automatic baud rate detection is performed only once, at module
start up. After the detection, the module works at the detected baud rate and the baud rate can only be
changed by AT command (see u-blox AT Commands Manual [2], +IPR command).
One-shot automatic baud rate recognition (autobauding) is enabled by default.
The following baud rates can be configured by AT command (see u-blox AT Commands Manual [2], +IPR):

9600 b/s

19200 b/s

38400 b/s

57600 b/s

115200 b/s, default value when one-shot autobauding is disabled

230400 b/s

460800 b/s

921600 b/s

3000000 b/s

3250000 b/s

6000000 b/s

6500000 b/s
Baud rates higher than 460800 b/s cannot be automatically detected by LARA-R2 series modules.
The modules support the one-shot automatic frame recognition in conjunction with the one-shot autobauding.
The following frame formats can be configured by AT command (see u-blox AT Commands Manual [2], +ICF):

8N1 (8 data bits, No parity, 1 stop bit), default frame configuration with fixed baud rate, see Figure 16

8E1 (8 data bits, even parity, 1 stop bit)

8O1 (8 data bits, odd parity, 1 stop bit)

8N2 (8 data bits, No parity, 2 stop bits)

7E1 (7 data bits, even parity, 1 stop bit)

7O1 (7 data bits, odd parity, 1 stop bit)
Normal Transfer, 8N1
Start of 1-Byte
transfer
D0
D1
Possible Start of
next transfer
D2
D3
D4
D5
Start Bit
(Always 0)
D6
D7
Stop Bit
(Always 1)
tbit = 1/(Baudrate)
Figure 16: Description of UART 8N1 frame format (8 data bits, no parity, 1 stop bit)
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1.9.1.2 UART AT interface configuration
The UART interface of LARA-R2 series modules is available as AT command interface with the default
configuration described in Table 10 (for more details and information about further settings, see the u-blox AT
Commands Manual [2]).
Interface
AT Settings
Comments
UART interface
AT interface: enabled
AT+IPR=0
AT command interface is enabled by default on the UART physical interface
One-shot autobauding enabled by default on the modules
AT+ICF=3,1
AT&K3
8N1 frame format enabled by default
HW flow control enabled by default
AT&S1
DSR line (Circuit 107 in ITU-T V.24) set ON in data mode6 and set OFF in command mode6
AT&D1
Upon an ON-to-OFF transition of DTR line (Circuit 108/2 in ITU-T V.24), the module (DCE)
enters online command mode6 and issues an OK result code
DCD line (Circuit 109 in ITU-T V.24) changes in accordance with the Carrier detect status;
ON if the Carrier is detected, OFF otherwise
Multiplexing mode is disabled by default and it can be enabled by AT+CMUX command.
For more details, see the Mux Implementation Application Note [21].
The following virtual channels are defined:

Channel 0: control channel

Channel 1 – 5: AT commands / data connection

Channel 6: GNSS tunneling7
AT&C1
MUX protocol: disabled
Table 10: Default UART AT interface configuration
1.9.1.3
UART signal behavior
At the module switch-on, before the UART interface initialization (as described in the power-on sequence
reported in Figure 13), each pin is first tri-stated and then is set to its related internal reset state . At the end of
the boot sequence, the UART interface is initialized, the module is by default in active-mode, and the UART
interface is enabled as AT commands interface.
The configuration and the behavior of the UART signals after the boot sequence are described below. See
section 1.4 for definition and description of module operating modes referred to in this section.
RXD signal behavior
The module data output line (RXD) is set by default to the OFF state (high level) at UART initialization. The
module holds RXD in the OFF state until the module does not transmit some data.
TXD signal behavior
The module data input line (TXD) is set by default to the OFF state (high level) at UART initialization. The TXD
line is then held by the module in the OFF state if the line is not activated by the DTE: an active pull-up is enabled
inside the module on the TXD input.
See the u-blox AT Commands Manual [2] for the definition of the command mode, data mode, and online command mode
Not supported by “02” product versions
Refer to the pin description table in the LARA-R2 series Data Sheet [1].
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CTS signal behavior
The module hardware flow control output (CTS line) is set to the ON state (low level) at UART initialization.
If the hardware flow control is enabled, as it is by default, the CTS line indicates when the UART interface is
enabled (data can be sent and received). The module drives the CTS line to the ON state or to the OFF state
when it is either able or not able to accept data from the DTE over the UART (see 1.9.1.4 for more details).
If hardware flow control is enabled, then when the CTS line is OFF it does not necessarily mean that the
module is in low power idle-mode, but only that the UART is not enabled, as the module could be forced
to stay in active-mode for other activities, e.g. related to the network or related to other interfaces.
When the multiplexer protocol is active, the CTS line state is mapped to FCon / FCoff MUX command for
flow control issues outside the power saving configuration while the physical CTS line is still used as a
power state indicator. For more details, see Mux Implementation Application Note [21].
The CTS hardware flow control setting can be changed by AT commands (for more details, see u-blox AT
Commands Manual [2], AT&K, AT\Q, AT+IFC, AT+UCTS AT command).
When the power saving configuration is enabled by AT+UPSV command and the hardware flow-control is
not implemented in the DTE/DCE connection, data sent by the DTE can be lost: the first character sent
when the module is in low power idle-mode will not be a valid communication character (see section
1.9.1.4 and in particular the sub-section “Wake up via data reception” for further details).
RTS signal behavior
The hardware flow control input (RTS line) is set by default to the OFF state (high level) at UART initialization.
The module then holds the RTS line in the OFF state if the line is not activated by the DTE: an active pull-up is
enabled inside the module on the RTS input.
If the HW flow control is enabled, as it is by default, the module monitors the RTS line to detect permission from
the DTE to send data to the DTE itself. If the RTS line is set to the OFF state, any on-going data transmission
from the module is interrupted until the subsequent RTS line change to the ON state.
The DTE must still be able to accept a certain number of characters after the RTS line is set to the OFF
state: the module guarantees the transmission interruption within two characters from RTS state change.
Module behavior according to RTS hardware flow control status can be configured by AT commands (for more
details, see u-blox AT Commands Manual [2], AT&K, AT\Q, AT+IFC command descriptions).
If AT+UPSV=2 is set and HW flow control is disabled, the module monitors the RTS line to manage the power
saving configuration (For more details, see section 1.9.1.4 and u-blox AT Commands Manual [2], AT+UPSV):

When an OFF-to-ON transition occurs on the RTS input, the UART is enabled and the module is forced to
active-mode. After ~20 ms, the switch is completed and data can be received without loss. The module
cannot enter low power idle-mode and the UART is enabled as long as the RTS is in the ON state

If the RTS input line is set to the OFF state by the DTE, the UART is disabled (held in low power mode) and
the module automatically enters low power idle-mode whenever possible
DSR signal behavior
If AT&S1 is set, as it is by default, the DSR module output line is set by default to the OFF state (high level) at
UART initialization. The DSR line is then set to the OFF state when the module is in command mode or in online
command mode and is set to the ON state when the module is in data mode .
If AT&S0 is set, the DSR module output line is set by default to the ON state (low level) at UART initialization and
is then always held in the ON state.
See the u-blox AT Commands Manual [2] for the definition of the command mode, data mode, and online command mode
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DTR signal behavior
The DTR module input line is set by default to the OFF state (high level) at UART initialization. The module then
holds the DTR line in the OFF state if the line is not activated by the DTE: an active pull-up is enabled inside the
module on the DTR input.
Module behavior according to DTR status can be changed by AT command (for more details, see u-blox AT
Commands Manual [2], AT&D command description).
If AT+UPSV=3 is set, the DTR line is monitored by the module to manage the power saving configuration (for
more details, see section 1.9.1.4 and u-blox AT Commands Manual [2], AT+UPSV command):

When an OFF-to-ON transition occurs on the DTR input, the UART is enabled and the module is forced to
active-mode. After ~20 ms, the switch is completed and data can be received without loss. The module
cannot enter low power idle-mode and the UART is enabled as long as the DTR is in the ON state

If the DTR input line is set to the OFF state by the DTE, the UART is disabled (held in low power mode) and
the module automatically enters low power idle-mode whenever possible
DCD signal behavior
If AT&C1 is set, as it is by default, the DCD module output line is set by default to the OFF state (high level) at
UART initialization. The module then sets the DCD line according to the carrier detect status: ON if the carrier is
detected, OFF otherwise.
In case of voice calls, DCD is set to the ON state when the call is established.
In case of data calls, there are the following scenarios regarding the DCD signal behavior:

Packet Switched Data call: Before activating the PPP protocol (data mode) a dial-up application must
provide the ATD*99***# to the module: with this command the module switches from
command mode to data mode and can accept PPP packets. The module sets the DCD line to the ON state,
then answers with a CONNECT to confirm the ATD*99 command. The DCD ON is not related to the context
activation but with the data mode

Circuit Switched Data call: To establish a data call, the DTE can send the ATD command to the
module which sets an outgoing data call to a remote modem (or another data module). Data can be
transparent (non reliable) or non transparent (with the reliable RLP protocol). When the remote DCE accepts
the data call, the module DCD line is set to ON and the CONNECT  string is
returned by the module. At this stage the DTE can send characters through the serial line to the data
module which sends them through the network to the remote DCE attached to a remote DTE
The DCD is set to ON during the execution of the +CMGS, +CMGW, +USOWR, +USODL AT commands
requiring input data from the DTE: the DCD line is set to the ON state as soon as the switch to binary/text
input mode is completed and the prompt is issued; DCD line is set to OFF as soon as the input mode is
interrupted or completed (for more details see the u-blox AT Commands Manual [2]).
10
The DCD line is kept in the ON state, even during the online command mode , to indicate that the data
10
call is still established even if suspended, while if the module enters command mode , the DSR line is set
to the OFF state. For more details see DSR signal behavior description.
For scenarios when the DCD line setting is requested for different reasons (e.g. SMS texting during online
10
command mode ), the DCD line changes to guarantee the correct behavior for all the scenarios. For
10
example, in case of SMS texting in online command mode , if the data call is released, DCD is kept ON till
the SMS command execution is completed (even if the data call release would request DCD set OFF).
If AT&C0 is set, the DCD module output line is set by default to the ON state (low level) at UART initialization
and is then always held in the ON state.
10
See the u-blox AT Commands Manual [2] for the definition of the command mode, data mode, and online command mode
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RI signal behavior
The RI module output line is set by default to the OFF state (high level) at UART initialization. Then, during an
incoming call, the RI line is switched from the OFF state to the ON state with a 4:1 duty cycle and a 5 s period
(ON for 1 s, OFF for 4 s, see Figure 17), until the DTE attached to the module sends the ATA string and the
module accepts the incoming data call. The RING string sent by the module (DCE) to the serial port at constant
time intervals is not correlated with the switch of the RI line to the ON state.
1s
RI OFF
RI ON
10
15
time [s]
Call incomes
Figure 17: RI behavior during an incoming call
The RI line can notify an SMS arrival. When the SMS arrives, the RI line switches from OFF to ON for 1 s (see
Figure 18), if the feature is enabled by the AT+CNMI command (see the u-blox AT Commands Manual [2]).
1s
RI OFF
RI ON
time [s]
SMS arrives
Figure 18: RI behavior at SMS arrival
This behavior allows the DTE to stay in power saving mode until the DCE related event requests service.
For SMS arrival, if several events coincidently occur or in quick succession each event independently triggers the
RI line, although the line will not be deactivated between each event. As a result, the RI line may stay to ON for
more than 1 s.
If an incoming call is answered within less than 1 s (with ATA or if auto-answering is set to ATS0=1) than the RI
line is set to OFF earlier.
As a result:
RI line monitoring cannot be used by the DTE to determine the number of received SMSes.
For multiple events (incoming call plus SMS received), the RI line cannot be used to discriminate the two
events, but the DTE must rely on the subsequent URCs and interrogate the DCE with proper commands.
The RI line can additionally notify all the URCs and all the incoming data (PPP, Direct Link, sockets, FTP), if the
feature is enabled by the AT+URING command (for more details see u-blox AT Commands Manual [2]): the RI
line is asserted when one of the configured events occur and it remains asserted for 1 s unless another
configured event will happen, with the same behavior described in Figure 18.
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1.9.1.4 UART and power-saving
The power saving configuration is controlled by the AT+UPSV command (for the complete description, see
u-blox AT Commands Manual [2]). When power saving is enabled, the module automatically enters low power
idle-mode whenever possible, and otherwise the active-mode is maintained by the module (see section 1.4 for
definition and description of module operating modes referred to in this section).
The AT+UPSV command configures both the module power saving and also the UART behavior in relation to the
power saving. The conditions for the module entering low power idle-mode also depend on the UART power
saving configuration, as the module does not enter the low power idle-mode according to any required activity
related to the network (within or outside an active call) or any other required concurrent activity related to the
functions and interfaces of the module, including the UART interface.
Three different power saving configurations can be set by the AT+UPSV command:

AT+UPSV=0, power saving disabled (default configuration)

AT+UPSV=1, power saving enabled cyclically

AT+UPSV=2, power saving enabled and controlled by the UART RTS input line

AT+UPSV=3, power saving enabled and controlled by the UART DTR input line
The different power saving configurations that can be set by the +UPSV AT command are described in details in
the following subsections. Table 11 summarizes the UART interface communication process in the different
power saving configurations, in relation with HW flow control settings and RTS input line status. For more
details on the +UPSV AT command description, refer to u-blox AT commands Manual [2].
AT+UPSV HW flow control
RTS line
DTR line
Communication during idle-mode and wake up
Enabled (AT&K3)
ON
ON or OFF
Data sent by the DTE are correctly received by the module.
Data sent by the module is correctly received by the DTE.
Enabled (AT&K3)
OFF
ON or OFF
Disabled (AT&K0)
ON or OFF
ON or OFF
Enabled (AT&K3)
ON
ON or OFF
Data sent by the DTE are correctly received by the module.
Data sent by the module is buffered by the module and will be correctly
received by the DTE when it is ready to receive data (i.e. RTS line will be ON).
Data sent by the DTE is correctly received by the module.
Data sent by the module is correctly received by the DTE if it is ready to receive
data, otherwise data is lost.
Data sent by the DTE is buffered by the DTE and will be correctly received by
the module when it is ready to receive data (when UART is enabled).
Data sent by the module is correctly received by the DTE.
Enabled (AT&K3)
OFF
ON or OFF
Data sent by the DTE is buffered by the DTE and will be correctly received by
the module when it is ready to receive data (when UART is enabled).
Data sent by the module is buffered by the module and will be correctly
received by the DTE when it is ready to receive data (i.e. RTS line will be ON).
Disabled (AT&K0)
ON or OFF
ON or OFF
The first character sent by the DTE is lost by the module, but after ~20 ms the
UART and the module are woken up: recognition of subsequent characters is
guaranteed only after the UART / module complete wake-up (after ~20 ms).
Data sent by the module is correctly received by the DTE if it is ready to receive
data, otherwise the data is lost.
Enabled (AT&K3)
Disabled (AT&K0)
ON or OFF
ON
ON or OFF
ON or OFF
Disabled (AT&K0)
OFF
ON or OFF
Not Applicable: HW flow control cannot be enabled with AT+UPSV=2.
Data sent by the DTE is correctly received by the module.
Data sent by the module is correctly received by the DTE if it is ready to receive
data, otherwise data is lost.
Data sent by the DTE is lost by the module.
Data sent by the module is correctly received by the DTE if it is ready to receive
data, otherwise data is lost.
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AT+UPSV HW flow control
RTS line
DTR line
Communication during idle-mode and wake up
Enabled (AT&K3)
ON
ON
Enabled (AT&K3)
ON
OFF
Data sent by the DTE is correctly received by the module.
Data sent by the module is correctly received by the DTE.
Data sent by the DTE is lost by the module.
Data sent by the module is correctly received by the DTE.
Enabled (AT&K3)
OFF
ON
Enabled (AT&K3)
OFF
OFF
Disabled (AT&K0)
ON or OFF
ON
Disabled (AT&K0)
ON or OFF
OFF
Data sent by the DTE is correctly received by the module.
Data sent by the module is buffered by the module and will be correctly
received by the DTE when it is ready to receive data (i.e. RTS line will be ON).
Data sent by the DTE is lost by the module.
Data sent by the module is buffered by the module and will be correctly
received by the DTE when it is ready to receive data (i.e. RTS line will be ON).
Data sent by the DTE is correctly received by the module.
Data sent by the module is correctly received by the DTE if it is ready to receive
data, otherwise data are lost.
Data sent by the DTE is lost by the module.
Data sent by the module is correctly received by the DTE if it is ready to receive
data, otherwise data are lost.
Table 11: UART and power-saving summary
AT+UPSV=0: power saving disabled, fixed active-mode
The module does not enter low power idle-mode and the UART interface is enabled (data can be sent and
received): the CTS line is always held in the ON state after UART initialization. This is the default configuration.
AT+UPSV=1: power saving enabled, cyclic idle/active-mode
When the AT+UPSV=1 command is issued by the DTE, the UART will be normally disabled, and then periodically
or upon necessity enabled as following:

During the periodic UART wake up to receive or send data, also according to the module wake up for the
paging reception (see section 1.5.1.4) or other activities

If the module needs to transmit some data (e.g. URC), the UART is temporarily enabled to send data

If the DTE send data with HW flow control disabled, the first character sent causes the UART and module
wake-up after ~20 ms: recognition of subsequent characters is guaranteed only after the complete wake-up
(see the following subsection “wake up via data reception”)
The module automatically enters the low power idle-mode whenever possible but it wakes up to active-mode
according to the UART periodic wake up so that the module cyclically enters the low power idle-mode and the
active-mode. Additionally, the module wakes up to active-mode according to any required activity related to the
network (e.g. for the periodic paging reception described in section 1.5.1.4, or for any other required RF Tx / Rx)
or any other required activity related to module functions / interfaces (including the UART itself).
The time period of the UART enable/disable cycle is configured differently when the module is registered with a
2G network compared to when the module is registered with an LTE network:

2G: UART is enabled synchronously with some paging receptions: UART is enabled concurrently to a paging
reception, and then, as data has not been received or sent, UART is disabled until the first paging reception
that occurs after a timeout of 2.0 s, and therefore the interface is enabled again

LTE: UART is asynchronously enabled to paging receptions, as UART is enabled for ~20 ms, and then, if data
are not received or sent, UART is disabled for 2.5 s, and afterwards the interface is enabled again

Not registered: when a module is not registered with a network, UART is enabled for ~20 ms, and then, if
data has not been received or sent, UART is disabled for 2.5 s, and afterwards the interface is enabled again
When the UART interface is enabled, data can be received. When a character is received, it forces the UART
interface to stay enabled for a longer time and it forces the module to stay in the active-mode for a longer time,
according to the timeout configured by the second parameter of the +UPSV AT command. The timeout can be
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set from 40 2G-frames (i.e. 40 x 4.615 ms = 184 ms) up to 65000 2G-frames (i.e. 65000 x 4.615 ms = 300 s).
Default value is 2000 2G-frames (i.e. 2000 x 4.615 ms = 9.2 s). Every subsequent character received during the
active-mode, resets and restarts the timer; hence the active-mode duration can be extended indefinitely.
The CTS output line is driven to the ON or OFF state when the module is either able or not able to accept data
from the DTE over the UART: Figure 19 illustrates the CTS output line toggling due to paging reception and data
received over the UART, with AT+UPSV=1 configuration.
Data input
CTS OFF
CTS ON
time [s]
~9.2 s (default)
Figure 19: CTS output pin indicates when module’s UART is enabled (CTS = ON = low level) or disabled (CTS = OFF = high level)
AT+UPSV=2: power saving enabled and controlled by the RTS line
This configuration can only be enabled with the module hardware flow control disabled (i.e. AT&K0 setting).
The UART interface is disabled after the DTE sets the RTS line to OFF.
Afterwards, the UART is enabled again, and the module does not enter low power idle-mode, as following:

If an OFF-to-ON transition occurs on the RTS input, this causes the UART / module wake-up after ~20 ms:
recognition of subsequent characters is guaranteed only after the complete wake-up, and the UART is kept
enabled as long as the RTS input line is set to ON.

If the module needs to transmit some data (e.g. URC), the UART is temporarily enabled to send data
The module automatically enters the low power idle-mode whenever possible but it wakes up to active-mode
according to any required activity related to the network (e.g. for the periodic paging reception described in
section 1.5.1.4, or for any other required RF transmission / reception) or any other required activity related to the
module functions / interfaces (including the UART itself).
AT+UPSV=3: power saving enabled and controlled by the DTR line
The UART interface is disabled after the DTE sets the DTR line to OFF.
Afterwards, the UART is enabled again, and the module does not enter low power idle-mode, as following:

If an OFF-to-ON transition occurs on the DTR input, this causes the UART / module wake-up after ~20 ms:
recognition of subsequent characters is guaranteed only after the complete wake-up, and the UART is kept
enabled as long as the DTR input line is set to ON

If the module needs to transmit some data (e.g. URC), the UART is temporarily enabled to send data
The module automatically enters the low power idle-mode whenever possible but it wakes up to active-mode
according to any required activity related to the network (e.g. for the periodic paging reception described in
section 1.5.1.4, or for any other required RF signal transmission or reception) or any other required activity
related to the functions / interfaces of the module.
The AT+UPSV=3 configuration can be enabled regardless the flow control setting on UART. In particular, the HW
flow control can be enabled (AT&K3) or disabled (AT&K0) on UART during this configuration. In both cases, with
the AT+UPSV=3 configuration, the CTS line indicates when the module is either able or not able to accept data
from the DTE over the UART.
When the AT+UPSV=3 configuration is enabled, the DTR input line can still be used by the DTE to control the
module behavior according to AT&D command configuration (see u-blox AT commands Manual [2]).
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Wake up via data reception
The UART wake up via data reception consists of a special configuration of the module TXD input line that
causes the system wake-up when a low-to-high transition occurs on the TXD input line. In particular, the UART
is enabled and the module switches from the low power idle-mode to active-mode within ~20 ms from the first
character received: this is the system “wake up time”.
As a consequence, the first character sent by the DTE when the UART is disabled (i.e. the wake up character) is
not a valid communication character even if the wake up via data reception configuration is active, because it
cannot be recognized, and the recognition of the subsequent characters is guaranteed only after the complete
system wake-up (i.e. after ~20 ms).
The UART wake up via data reception configuration is active in the following cases:

AT+UPSV=1 is set with HW flow control disabled
Figure 20 and Figure 21 show examples of common scenarios and timing constraints:

AT+UPSV=1 power saving configuration is active and the timeout from last data received to idle-mode start
is set to 2000 frames (AT+UPSV=1,2000)

Hardware flow control is disabled
Figure 20 shows the case where the module UART is disabled and only a wake-up is forced. In this scenario the
only character sent by the DTE is the wake-up character; as a consequence, the DCE module UART is disabled
when the timeout from last data received expires (2000 frames without data reception, as the default case).
UART
DCE UART is enabled for 2000 GSM frames (~9.2 s)
OFF
ON
time
TXD input
Wake up time: ~20 ms
OFF
ON
Wake up character
Not recognized by DCE
time
Figure 20: Wake-up via data reception without further communication
Figure 21 shows the case where in addition to the wake-up character further (valid) characters are sent. The
wake up character wakes-up the module UART. The other characters must be sent after the “wake up time” of
~20 ms. If this condition is satisfied, the module (DCE) recognizes characters. The module will disable the UART
after 2000 GSM frames from the latest data reception.
UART
DCE UART is enabled for 2000 GSM frames (~9.2s)
after the last data received
OFF
ON
TXD input
Wake up time: ~20 ms
time
OFF
ON
Wake up character
Not recognized by DCE
Valid characters
Recognized by DCE
time
Figure 21: Wake-up via data reception with further communication
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The “wake-up via data reception” feature cannot be disabled.
11
In command mode , with “wake-up via data reception” enabled and autobauding enabled, the DTE
should always send a dummy character to the module before the “AT” prefix set at the beginning of each
command line: the first dummy character is ignored if the module is in active-mode, or it represents the
wake-up character if the module is in low power idle-mode.
11
In command mode , with “wake-up via data reception” enabled and autobauding disabled, the DTE
should always send a dummy “AT” to the module before each command line: the first dummy “AT” is
not ignored if the module is in active-mode (i.e. the module replies “OK”), or it represents the wake up
character if the module is in low power idle-mode (i.e. the module does not reply).
Additional considerations
If the USB is connected and not suspended, the module is kept ready to communicate over USB regardless the
AT+UPSV settings, which have instead effect on the UART behavior, as they configure the UART power saving,
so that UART is enabled / disabled according to the AT+UPSV settings.
To set the AT+UPSV=1, AT+UPSV=2 or AT+UPSV=3 configuration over the USB interface, the autobauding must
be previously disabled on the UART by the +IPR AT command over the used USB AT interface, and this +IPR AT
command configuration must be saved in the module’ non-volatile memory (see the u-blox AT Commands
Manual [2]). Then, after the subsequent module re-boot, AT+UPSV=1, AT+UPSV=2 or AT+UPSV=3 can be issued
over the used AT interface (the USB): all the AT profiles are updated accordingly.
1.9.1.5
Multiplexer protocol (3GPP TS 27.010)
LARA-R2 series modules include multiplexer functionality as per 3GPP TS 27.010 [8], on the UART physical link.
This is a data link protocol which uses HDLC-like framing and operates between the module (DCE) and the
application processor (DTE) and allows a number of simultaneous sessions over the used physical link (UART): the
user can concurrently use AT interface on one MUX channel and data communication on another MUX channel.
The following virtual channels are defined (for more details, see Mux implementation Application Note [21]):

Channel 0: Multiplexer control

Channel 1 – 5: AT commands / data connection

Channel 6: GNSS data tunneling
The GNSS data tunneling channel is not supported by “02” product versions.
11
See the u-blox AT Commands Manual [2] for the definition of the command mode, data mode, and online command mode.
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1.9.2 USB interface
1.9.2.1
USB features
LARA-R2 series modules include a High-Speed USB 2.0 compliant interface with 480 Mb/s maximum data rate,
representing the main interface for transferring high speed data with a host application processor, supporting:

AT command mode

Data mode and Online command mode

FW upgrades by means of the FOAT feature (see 1.14.13 and Firmware update application note [23])

FW upgrades by means of the u-blox EasyFlash tool (see the Firmware update application note [23])

Trace log capture (diagnostic purpose)
12
12
The module itself acts as a USB device and can be connected to a USB host such as a Personal Computer or an
embedded application microprocessor equipped with compatible drivers.
The USB_D+/USB_D- lines carry USB serial bus data and signaling according to the Universal Serial Bus Revision
2.0 specification [9], while the VUSB_DET input pin senses the VBUS USB supply presence (nominally 5 V at the
source) to detect the host connection and enable the interface.
The USB interface of the module is enabled only if a valid voltage is detected by the VUSB_DET input (see the
LARA-R2 series Data Sheet [1]). Neither the USB interface, nor the whole module is supplied by the VUSB_DET
input: the VUSB_DET senses the USB supply voltage and absorbs few microamperes.
The USB interface is controlled and operated with:

AT commands according to 3GPP TS 27.007 [6], 3GPP TS 27.005 [7]

u-blox AT commands (for the complete list and syntax see the u-blox AT Commands Manual [2])
The USB interface of LARA-R2 series modules, according to the configured USB profile, can provide different USB
functions with various capabilities and purposes, such as:

CDC-ACM for AT commands and data communication

CDC-ACM for GNSS tunneling

CDC-ACM for SAP (SIM Access Profile)

CDC-ACM for Diagnostic log

CDC-NCM for Ethernet-over-USB
CDC-ACM for GNSS tunneling, CDC-ACM for SAP, and CDC-NCM for Ethernet-over-USB are not
supported by “02” product versions.
The USB profile of LARA-R2 series modules identifies itself by its VID (Vendor ID) and PID (Product ID)
combination, included in the USB device descriptor according to the USB 2.0 specification [9].
If the USB is connected to the host before the module is switched on, or if the module is reset (rebooted) with
the USB connected to the host, the VID and PID are automatically updated during the boot of the module. First,
VID and PID are the following:

VID = 0x8087

PID = 0x0716
This VID and PID combination identifies a USB profile where no USB function described above is available: AT
commands must not be sent to the module over the USB profile identified by this VID and PID combination.
12
See the u-blox AT Commands Manual [2] for the definition of the command mode, data mode, and online command mode.
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Then, after a time period (which depends on the host / device enumeration timings), the VID and PID are
updated to the ones related to the default USB profile providing the following set of USB functions:

6 CDC-ACM modem COM ports enumerated as follows:
USB1: AT and data
USB2: AT and data
USB3: AT and data
USB4: GNSS tunneling
USB5: SAP (SIM Access Profile)
USB6: Primary Log (diagnostic purpose)
VID and PID of this USB profile with the set of functions described above (6 CDC-ACM) are the following:

VID = 0x1546

PID = 0x110A
Figure 22 summarizes the USB end-points available with the default USB profile.
Default profile configuration
Function AT and Data
Interface 0
Abstract Control Model
EndPoint
Interface 1
Function AT and Data
Data
EndPoint
Transfer: Bulk
EndPoint
Transfer: Bulk
Interface 2
Abstract Control Model
EndPoint
Transfer: Interrupt
EndPoint
Transfer: Bulk
EndPoint
Transfer: Bulk
Interface 3
Function AT and Data
Data
Interface 4
Abstract Control Model
EndPoint
Transfer: Interrupt
EndPoint
Transfer: Bulk
EndPoint
Transfer: Bulk
Interface 5
Function GNSS tunneling
Data
Interface 6
Abstract Control Model
EndPoint
Transfer: Interrupt
EndPoint
Transfer: Bulk
EndPoint
Transfer: Bulk
Interface 7
Function SAP
Data
Interface 8
Abstract Control Model
EndPoint
Transfer: Interrupt
EndPoint
Transfer: Bulk
EndPoint
Transfer: Bulk
Interface 9
Function Primary Log
Transfer: Interrupt
Data
Interface 10
Abstract Control Model
EndPoint
Transfer: Interrupt
EndPoint
Transfer: Bulk
EndPoint
Transfer: Bulk
Interface 11
Data
Figure 22: LARA-R2 series USB End-Points summary for the default USB profile configuration
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1.9.2.2 USB in Windows
USB drivers are provided for Windows operating system platforms and should be properly installed / enabled by
following the step-by-step instructions available in the EVK-R2xx User Guide [3] or in the Windows Embedded
OS USB Driver Installation Application Note [4].
USB drivers are available for the following operating system platforms:

Windows 7

Windows 8

Windows 8.1

Windows 10

Windows Embedded CE 6.0

Windows Embedded Compact 7
 Windows Embedded Compact 2013
The module firmware can be upgraded over the USB interface by means of the FOAT feature, or using the u-blox
EasyFlash tool (for more details see Firmware Update Application Note [23].
1.9.2.3
USB in Linux/Android
It is not required to install a specific driver for each Linux-based or Android-based operating system (OS) to use
the module USB interface, which is compatible with standard Linux/Android USB kernel drivers.
The full capability and configuration of the module USB interface can be reported by running “lsusb –v” or an
equivalent command available in the host operating system when the module is connected.
1.9.2.4
USB and power saving
The modules automatically enter the USB suspended state when the device has observed no bus traffic for a
specific time period according to the USB 2.0 specifications [9]. In suspended state, the module maintains any
USB internal status as device. In addition, the module enters the suspended state when the hub port it is
attached to is disabled. This is referred to as USB selective suspend.
If the USB is suspended and a power saving configuration is enabled by the AT+UPSV command, the module
automatically enters the low power idle-mode whenever possible but it wakes up to active-mode according to
any required activity related to the network (e.g. the periodic paging reception described in section 1.5.1.4) or
any other required activity related to the functions / interfaces of the module.
The USB exits suspend mode when there is bus activity. If the USB is connected and not suspended, the module
is kept ready to communicate over USB regardless the AT+UPSV settings, therefore the AT+UPSV settings are
overruled but they have effect on the power saving configuration of the other interfaces (see 1.9.1.4).
The modules are capable of USB remote wake-up signaling: i.e. it may request the host to exit suspend mode or
selective suspend by using electrical signaling to indicate remote wake-up, for example due to incoming call,
URCs, data reception on a socket. The remote wake-up signaling notifies the host that it should resume from its
suspended mode, if necessary, and service the external event. Remote wake-up is accomplished using electrical
signaling described in the USB 2.0 specifications [9].
For the module current consumption description with power saving enabled and USB suspended, or with power
saving disabled and USB not suspended, see sections 1.5.1.4, 1.5.1.5 and LARA-R2 series Data Sheet [1].
The additional VUSB_DET input pin available on LARA-R2 series modules provides the complete bus detach
functionality: the modules disable the USB interface when a low logic level is sensed after a high-to-low logic
level transition on the VUSB_DET input pin. This allows a further reduction of the module current consumption,
in particular as compared to the USB suspended status during low-power idle mode with power saving enabled.
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1.9.3 HSIC interface
The HSIC interface is not supported by “02” modules product versions except for diagnostic purpose.
1.9.3.1 HSIC features
LARA-R2 series modules include a USB High-Speed Inter-Chip compliant interface with maximum 480 Mb/s data
rate according to the High-Speed Inter-Chip USB Electrical Specification Version 1.0 [10] and USB Specification
Revision 2.0 [9]. The module itself acts as a device and can be connected to any compatible host.
The HSIC interface provides:

AT command mode

Data mode and Online command mode

FW upgrades by means of the FOAT feature (see 1.14.13 and Firmware update application note [23])

FW upgrades by means of the u-blox EasyFlash tool (see the Firmware update application note [23])

Trace log capture (diagnostic purpose)
13
13
The HSIC interface consists of a bi-directional DDR data line (HSIC_DATA) for transmitting and receiving data
synchronously with the bi-directional strobe line (HSIC_STRB).
The modules include also the HOST_SELECT pin to select the module / host application processor configuration:
the pin is available to select, enable, connect, disconnect and subsequently re-connect the HSIC interface.
The USB interface is controlled and operated with:

AT commands according to 3GPP TS 27.007 [6], 3GPP TS 27.005 [7]

u-blox AT commands (for the complete list and syntax see the u-blox AT Commands Manual [2])
13
See the u-blox AT Commands Manual [2] for the definition of the command mode, data mode, and online command mode.
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1.9.4 DDC (I2C) interface
Communication with u-blox GNSS receivers over I C bus compatible Display Data Channel interface,
®
AssistNow embedded GNSS positioning aiding, CellLocate positioning through cellular info, and custom
functions over GPIOs for the integration with u-blox positioning chips / modules are not supported by
LARA-R2 series modules “02” product versions.
The SDA and SCL pins represent an I C bus compatible Display Data Channel (DDC) interface available for

communication with u-blox GNSS chips / modules,
 communication with other external I C devices as audio codecs.
The AT commands interface is not available on the DDC (I C) interface.
DDC (I C) slave-mode operation is not supported: the LARA-R2 series module can act as I C master that can
communicate with more I C slaves in accordance to the I C bus specifications [11].
The DDC (I C) interface pins of the module, serial data (SDA) and serial clock (SCL), are open drain outputs
conforming to the I C bus specifications [11].
u-blox has implemented special features to ease the design effort required for the integration of a u-blox cellular
module with a u blox GNSS receiver.
Combining a u-blox cellular module with a u-blox GNSS receiver allows designers to have full access to the
positioning receiver directly via the cellular module: it relays control messages to the GNSS receiver via a
nd
dedicated DDC (I C) interface. A 2 interface connected to the positioning receiver is not necessary: AT
commands via the UART or USB serial interface of the cellular module allows a fully control of the GNSS receiver
from any host processor.
The modules feature embedded GNSS aiding that is a set of specific features developed by u-blox to enhance
GNSS performance, decreasing the Time To First Fix (TTFF), thus allowing to calculate the position in a shorter
time with higher accuracy.
These GNSS aiding types are available:

Local aiding

AssistNow Online

AssistNow Offline

AssistNow Autonomous
The embedded GNSS aiding features can be used only if the DDC (I C) interface of the cellular module is
connected to the u-blox GNSS receivers.
The cellular modules provide additional custom functions over GPIO pins to improve the integration with u-blox
positioning chips and modules. GPIO pins can handle:

GNSS receiver power-on/off: “GNSS supply enable” function provided by GPIO2 improves the positioning
receiver power consumption. When the GNSS functionality is not required, the positioning receiver can be
completely switched off by the cellular module that is controlled by AT commands

The wake up from idle-mode when the GNSS receiver is ready to send data: “GNSS Tx data ready” function
provided by GPIO3 improves the cellular module power consumption. When power saving is enabled in the
cellular module by the AT+UPSV command and the GNSS receiver does not send data by the DDC (I C)
interface, the module automatically enters idle-mode whenever possible. With the “GNSS Tx data ready”
function the GNSS receiver can indicate to the cellular module that it is ready to send data by the DDC (I C)
interface: the positioning receiver can wake up the cellular module if it is in idle-mode, so the cellular
module does not lose the data sent by the GNSS receiver even if power saving is enabled
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
The RTC synchronization signal to the GNSS receiver: “GNSS RTC sharing” function provided by GPIO4
improves GNSS receiver performance, decreasing the Time To First Fix (TTFF), and thus allowing to calculate
the position in a shorter time with higher accuracy. When GPS local aiding is enabled, the cellular module
automatically uploads data such as position, time, ephemeris, almanac, health and ionospheric parameter
from the positioning receiver into its local memory, and restores this to the GNSS receiver at the next power
up of the positioning receiver
For more details regarding the handling of the DDC (I C) interface, the GNSS aiding features and the
GNSS related functions over GPIOs, see section 1.12, to the u-blox AT Commands Manual [2] (AT+UGPS,
AT+UGPRF, AT+UGPIOC AT commands) and the GNSS Implementation Application Note [22].
“GNSS Tx data ready” and “GNSS RTC sharing” functions are not supported by all u-blox GNSS receivers
HW or ROM/FW versions. See the GNSS Implementation Application Note [22] or to the Hardware
Integration Manual of the u-blox GNSS receivers for the supported features.
As additional improvement for the GNSS receiver performance, the V_BCKP supply output of the cellular
modules can be connected to the V_BCKP supply input pin of u-blox positioning chips and modules to provide
the supply for the GNSS real time clock and backup RAM when the VCC supply of the cellular module is within
its operating range and the VCC supply of the GNSS receiver is disabled.
This enables the u-blox positioning receiver to recover from a power breakdown with either a hot start or a
warm start (depending on the duration of the GNSS receiver VCC outage) and to maintain the configuration
settings saved in the backup RAM.
1.9.5
SDIO interface
Secure Digital Input Output interface is not supported by LARA-R2 series modules “02” product versions.
LARA-R2 series modules include a 4-bit Secure Digital Input Output interface (SDIO_D0, SDIO_D1, SDIO_D2,
SDIO_D3, SDIO_CLK, SDIO_CMD) designed to communicate with an external u-blox short range Wi-Fi module:
the cellular module acts as an SDIO host controller which can communicate over the SDIO bus with a compatible
u-blox short range radio communication Wi-Fi module acting as SDIO device.
The SDIO interface is the only one interface of LARA-R2 series modules dedicated for communication between
the u-blox cellular module and the u-blox short range Wi-Fi module.
The AT commands interface is not available on the SDIO interface of LARA-R2 series modules.
Combining a u-blox cellular module with a u-blox short range communication module gives designers full access
to the Wi-Fi module directly via the cellular module, so that a second interface connected to the Wi-Fi module is
not necessary. AT commands via the AT interfaces of the cellular module allows a full control of the Wi-Fi
module from any host processor, because Wi-Fi control messages are relayed to the Wi-Fi module via the
dedicated SDIO interface.
u-blox has implemented special features in the cellular modules to ease the design effort for the integration of a
u-blox cellular module with a u-blox short range Wi-Fi module to provide Router functionality.
Additional custom function over GPIO pins is designed to improve the integration with u-blox Wi-Fi modules:

Wi-Fi enable
Switch-on / switch-off the Wi-Fi
Wi-Fi enable function over GPIO is not supported by LARA-R2 series modules “02” product versions.
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1.10 Audio interface
Audio is not supported by LARA-R204 module “02” product version.
1.10.1 Digital audio interface
LARA-R2 series modules include a 4-wire I S digital audio interface (I2S_TXD data output, I2S_RXD data input,
I2S_CLK clock input/output, I2S_WA world alignment / synchronization signal input/output), which can be
configured by AT command for digital audio communication with external digital audio devices as an audio
codec (for more details see the u-blox AT Commands Manual [2], +UI2S AT command).
The I S interface can be alternatively set in different modes, by  parameter of AT+UI2S command:

PCM mode (short synchronization signal): I S word alignment signal is set high for 1 or 2 clock cycles for the
synchronization, and then is set low for 16 clock cycles according to the 17 or 18 clock cycles frame length.

Normal I S mode (long synchronization signal): I S word alignment is set high / low with a 50% duty cycle
(high for 16 clock cycles / low for 16 clock cycles, according to the 32 clock cycles frame length).
The I S interface can be alternatively set in different roles, by  parameter of AT+UI2S:

Master mode

Slave mode
The sample rate of transmitted/received words, which corresponds to the I S word alignment / synchronization
signal frequency, can be alternatively set by the  parameter of AT+UI2S to:

8 kHz

11.025 kHz

12 kHz

16 kHz

22.05 kHz

24 kHz

32 kHz

44.1 kHz

48 kHz
The modules support I S transmit and I S receive data 16-bit words long, linear, mono (or also dual mono in
Normal I2S mode). Data is transmitted and read in 2’s complement notation. MSB is transmitted and read first.
I S clock signal frequency depends on the frame length, the sample rate and the selected mode of operation:

17 x  or 18 x  in PCM mode (short synchronization signal)

16 x 2 x  in Normal I2S mode (long synchronization signal)
For the complete description of the possible configurations and settings of the I S digital audio interface
for PCM and Normal I S modes refer to the u-blox AT Commands Manual [2], +UI2S AT command.
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1.11 Clock output
LARA-R2 series modules provide master digital clock output function on GPIO6 pin, which can be configured to
provide a 13 MHz or 26 MHz square wave. This is mainly designed to feed the master clock input of an external
audio codec, as the clock output can be configured in “Audio dependent” mode (generating the square wave
only when the audio path is active), or in “Continuous” mode.
For more details see the u-blox AT Commands Manual [2], +UMCLK AT command.
1.12 General Purpose Input/Output (GPIO)
LARA-R2 series modules include 9 pins (GPIO1-GPIO5, I2S_TXD, I2S_RXD, I2S_CLK, I2S_WA) which can be
configured as General Purpose Input/Output or to provide custom functions via u-blox AT commands (for more
details see the u-blox AT Commands Manual [2], +UGPIOC, +UGPIOR, +UGPIOW AT commands), as summarized
in Table 12.
Function
Description
Default GPIO
Configurable GPIOs
Network status
indication
Network status: registered home network, registered
roaming, data transmission, no service
--
GPIO1-GPIO4
GNSS supply enable14
Enable/disable the supply of u-blox GNSS receiver
connected to the cellular module
--
GPIO1-GPIO4
GNSS data ready14
Sense when u-blox GNSS receiver connected to the
module is ready for sending data by the DDC (I2C)
--
GPIO3
GNSS RTC sharing14
RTC synchronization signal to the u-blox GNSS receiver
connected to the cellular module
--
GPIO4
SIM card detection
External SIM card physical presence detection
GPIO5
GPIO5
SIM card hot
insertion/removal
Enable / disable SIM interface upon detection of external
SIM card physical insertion / removal
--
GPIO5
I2S digital audio
interface15
I2S digital audio interface
I2S_RXD, I2S_TXD,
I2S_CLK, I2S_WA
I2S_RXD, I2S_TXD,
I2S_CLK, I2S_WA
Wi-Fi control14
Control of an external Wi-Fi chip or module
--
--
General purpose input
Input to sense high or low digital level
--
All
General purpose output
Output to set the high or the low digital level
GPIO4
All
Pin disabled
Tri-state with an internal active pull-down enabled
GPIO1-GPIO3
All
Table 12: LARA-R2 series GPIO custom functions configuration
1.13 Reserved pins (RSVD)
LARA-R2 series modules have pins reserved for future use, named RSVD: they can all be left unconnected on the
application board, except

14
15
the RSVD pin number 33 that must be externally connected to ground
Not supported by “02” product versions.
Not supported by LARA-R204 module “02” product version.
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1.14 System features
1.14.1 Network indication
GPIOs can be configured by the AT command to indicate network status (for further details see section 1.12 and
to u-blox AT Commands Manual [2], GPIO commands):

No service (no network coverage or not registered)

Registered 2G / LTE home network

Registered 2G / LTE visitor network (roaming)

Call enabled (RF data transmission / reception)
1.14.2 Antenna detection
The antenna detection function provided by the ANT_DET pin is based on an ADC measurement as optional
feature that can be implemented if the application requires it. The antenna supervisor is forced by the +UANTR
AT command (see the u-blox AT Commands Manual [2] for more details).
The requirements to achieve antenna detection functionality are the following:

an RF antenna assembly with a built-in resistor (diagnostic circuit) must be used

an antenna detection circuit must be implemented on the application board
See section 1.7.2 for detailed antenna detection interface functional description and see section 2.4.2 for
detection circuit on application board and diagnostic circuit on antenna assembly design-in guidelines.
1.14.3 Jamming detection
Congestion detection (i.e. jamming detection) is not supported by “02” product versions.
In real network situations modules can experience various kind of out-of-coverage conditions: limited service
conditions when roaming to networks not supporting the specific SIM, limited service in cells which are not
suitable or barred due to operators’ choices, no cell condition when moving to poorly served or highly interfered
areas. In the latter case, interference can be artificially injected in the environment by a noise generator covering
a given spectrum, thus obscuring the operator’s carriers entitled to give access to the LTE/3G/2G service.
The congestion (i.e. jamming) detection feature can be enabled and configured by the +UCD AT command: the
feature consists of detecting an anomalous source of interference and signaling the start and stop of such
conditions to the host application processor with an unsolicited indication, which can react appropriately by e.g.
switching off the radio transceiver of the module (i.e. configuring the module in “airplane mode” by means of
the +CFUN AT command) in order to reduce power consumption and monitoring the environment at constant
periods (for more details see the u-blox AT Commands Manual [2], +UCD AT command).
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1.14.4 Dual stack IPv4/IPv6
LARA-R2 series support both Internet Protocol version 4 and Internet Protocol version 6 in parallel.
For more details about dual stack IPv4/IPv6 see the u-blox AT Commands Manual [2].
1.14.5 TCP/IP and UDP/IP
LARA-R2 series modules provide embedded TCP/IP and UDP/IP protocol stack: a PDP context can be configured,
established and handled via the data connection management packet switched data commands.
LARA-R2 series modules provide Direct Link mode to establish a transparent end-to-end communication with an
already connected TCP or UDP socket via serial interfaces. In Direct Link mode, data sent to the serial interface
from an external application processor is forwarded to the network and vice-versa.
For more details about embedded TCP/IP and UDP/IP functionalities see the u-blox AT Commands Manual [2]
1.14.6 FTP
LARA-R2 series provide embedded File Transfer Protocol (FTP) services. Files are read and stored in the local file
system of the module.
FTP files can also be transferred using FTP Direct Link:

FTP download: data coming from the FTP server is forwarded to the host processor via serial interfaces (for
FTP without Direct Link mode the data is always stored in the module’s Flash File System)

FTP upload: data coming from the host processor via serial interfaces is forwarded to the FTP server (for FTP
without Direct Link mode the data is read from the module’s Flash File System)
When Direct Link is used for a FTP file transfer, only the file content pass through USB / UART serial interface,
whereas all the FTP commands handling is managed internally by the FTP application.
For more details about embedded FTP functionalities see u-blox AT Commands Manual [2].
1.14.7 HTTP
LARA-R2 series modules provide the embedded Hyper-Text Transfer Protocol (HTTP) services via AT commands
for sending requests to a remote HTTP server, receiving the server response and transparently storing it in the
module’s Flash File System (FFS).
For more details about embedded HTTP functionalities see the u-blox AT Commands Manual [2].
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1.14.8 SSL/TLS
LARA-R2 series modules support the Secure Sockets Layer (SSL) / Transport Layer Security (TLS) with certificate
key sizes up to 4096 bits to provide security over the FTP and HTTP protocols.
The SSL/TLS support provides different connection security aspects:

Server authentication: use of the server certificate verification against a specific trusted certificate or a
trusted certificates list

Client authentication: use of the client certificate and the corresponding private key

Data security and integrity: data encryption and Hash Message Authentication Code (HMAC) generation
The security aspects used during a connection depend on the SSL/TLS configuration and features supported.
Table 13 contains the settings of the default SSL/TLS profile and Table 14 to Table 18 report the main SSL/TLS
supported capabilities of the products. For a complete list of supported configurations and settings see the
u-blox AT Commands Manual [2].
Settings
Value
Meaning
Certificates validation level
Level 0
The server certificate will not be checked or verified
Minimum SSL/TLS version
Any
Cipher suite
Automatic
The server can use any of the TLS1.0/TLS1.1/TLS1.2 versions for the
connection
The cipher suite will be negotiated in the handshake process
Trusted root certificate internal name
Expected server host-name
None
None
No certificate will be used for the server authentication
No server host-name is expected
Client certificate internal name
Client private key internal name
None
None
No client certificate will be used
No client private key will be used
Client private key password
Pre-shared key
None
None
No client private key password will be used
No pre-shared key password will be used
Table 13: Default SSL/TLS profile
SSL/TLS Version
SSL 2.0
SSL 3.0
NO
YES
TLS 1.0
TLS 1.1
YES
YES
TLS 1.2
YES
Table 14: SSL/TLS version support
Algorithm
RSA
YES
PSK
YES
Table 15: Authentication
Algorithm
RC4
NO
DES
3DES
YES
YES
AES128
AES256
YES
YES
Table 16: Encryption
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Algorithm
MD5
SHA/SHA1
NO
YES
SHA256
YES
YES
SHA384
Table 17: Message digest
Description
Registry value
TLS_RSA_WITH_AES_128_CBC_SHA
TLS_RSA_WITH_AES_128_CBC_SHA256
0x00,0x2F
0x00,0x3C
YES
YES
TLS_RSA_WITH_AES_256_CBC_SHA
TLS_RSA_WITH_AES_256_CBC_SHA256
0x00,0x35
0x00,0x3D
YES
YES
TLS_RSA_WITH_3DES_EDE_CBC_SHA
TLS_RSA_WITH_RC4_128_MD5
0x00,0x0A
0x00,0x04
YES
NO
TLS_RSA_WITH_RC4_128_SHA
0x00,0x05
NO
TLS_PSK_WITH_AES_128_CBC_SHA
TLS_PSK_WITH_AES_256_CBC_SHA
0x00,0x8C
0x00,0x8D
YES
YES
TLS_PSK_WITH_3DES_EDE_CBC_SHA
TLS_RSA_PSK_WITH_AES_128_CBC_SHA
0x00,0x8B
0x00,0x94
YES
YES
TLS_RSA_PSK_WITH_AES_256_CBC_SHA
TLS_RSA_PSK_WITH_3DES_EDE_CBC_SHA
0x00,0x95
0x00,0x93
YES
YES
TLS_PSK_WITH_AES_128_CBC_SHA256
0x00,0xAE
YES
TLS_PSK_WITH_AES_256_CBC_SHA384
TLS_RSA_PSK_WITH_AES_128_CBC_SHA256
0x00,0xAF
0x00,0xB6
YES
YES
TLS_RSA_PSK_WITH_AES_256_CBC_SHA384
0x00,0xB7
YES
Table 18: TLS cipher suite registry
1.14.9 Bearer Independent Protocol
The Bearer Independent Protocol (BIP) is a mechanism by which a cellular module provides a SIM with access to
the data bearers supported by the network. With the BIP for Over-the-Air SIM provisioning, the data transfer
from and to the SIM uses either an already active PDP context or a new PDP context established with the APN
provided by the SIM card. For more details, see the u-blox AT Commands Manual [2]..
1.14.10 AssistNow clients and GNSS integration
AssistNow clients and u-blox GNSS receiver integration are not supported by “02” product versions.
For customers using u-blox GNSS receivers, the LARA-R2 series cellular modules feature embedded AssistNow
clients. AssistNow A-GPS provides better GNSS performance and faster Time-To-First-Fix. The clients can be
enabled and disabled with an AT command (see the u-blox AT Commands Manual [2]).
LARA-R2 series cellular modules act as a stand-alone AssistNow client, making AssistNow available with no
additional requirements for resources or software integration on an external host micro controller. Full access to
u-blox positioning receivers is available via the cellular modules, through a dedicated DDC (I C) interface, while
the available GPIOs can handle the positioning chipset / module power-on/off. This means that the cellular
module and the GNSS receiver can be controlled through a single serial port from any host processor.
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1.14.11 Hybrid positioning and CellLocate®
®
Hybrid positioning and CellLocate are not supported by “02” product versions.
Although GNSS is a widespread technology, its reliance on the visibility of extremely weak GNSS satellite signals
means that positioning is not always possible. Especially difficult environments for GNSS are indoors, in enclosed
or underground parking garages, as well as in urban canyons where GNSS signals are blocked or jammed by
multipath interference. The situation can be improved by augmenting GNSS receiver data with cellular network
information to provide positioning information even when GNSS reception is degraded or absent. This additional
information can benefit numerous applications.
Positioning through cellular information: CellLocate
®
®
u-blox CellLocate enables the device position estimation based on the parameters of the mobile network cells
®
visible to the specific device. To estimate its position the u-blox cellular module sends the CellLocate server the
parameters of network cells visible to it using a UDP connection. In return the server provides the estimated
®
position based on the CellLocate database. The module can either send the parameters of the visible home
network cells only (normal scan) or the parameters of all surrounding cells of all mobile operators (deep scan).
®
The CellLocate database is compiled from the position of devices which observed, in the past, a specific cell or
set of cells (historical observations) as follows:
®
1. Several devices reported their position to the CellLocate server when observing a specific cell (the As in the
picture represent the position of the devices which observed the same cell A)
®
2. CellLocate server defines the area of Cell A visibility
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®
3. If a new device reports the observation of Cell A CellLocate is able to provide the estimated position from
the area of visibility
4. The visibility of multiple cells provides increased accuracy based on the intersection of areas of visibility.
®
®
CellLocate is implemented using a set of two AT commands that allow configuration of the CellLocate service
(AT+ULOCCELL) and requesting position according to the user configuration (AT+ULOC). The answer is provided
in the form of an unsolicited AT command including latitude, longitude and estimated accuracy.
®
The accuracy of the position estimated by CellLocate depends on the availability of historical observations
in the specific area.
Hybrid positioning
With u-blox hybrid positioning technology, u-blox cellular modules can be triggered to provide their current
®
position using either a u-blox GNSS receiver or the position estimated from CellLocate . The choice depends on
which positioning method provides the best and fastest solution according to the user configuration, exploiting
the benefit of having multiple and complementary positioning methods.
Hybrid positioning is implemented through a set of three AT commands that allow GNSS receiver configuration
®
(AT+ULOCGNSS), CellLocate service configuration (AT+ULOCCELL), and requesting the position according to
the user configuration (AT+ULOC). The answer is provided in the form of an unsolicited AT command including
®
latitude, longitude and estimated accuracy (if the position has been estimated by CellLocate ), and additional
parameters if the position has been computed by the GNSS receiver.
The configuration of mobile network cells does not remain static (e.g. new cells are continuously added or
existing cells are reconfigured by the network operators). For this reason, when a hybrid positioning method has
been triggered and the GNSS receiver calculates the position, a database self-learning mechanism has been
implemented so that these positions are sent to the server to update the database and maintain its accuracy.
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The use of hybrid positioning requires a connection via the DDC (I C) bus between the cellular modules and the
u-blox GNSS receiver (see section 2.6.4).
See GNSS Implementation Application Note [22] for the complete description of the feature.
®
u-blox is extremely mindful of user privacy. When a position is sent to the CellLocate server u-blox is
unable to track the SIM used or the specific device.
1.14.12 Wi-Fi integration
u-blox short range communication Wi-Fi modules integration is not supported by “02” product versions.
Full access to u-blox short range communication Wi-Fi modules is available through a dedicated SDIO interface
(see sections 1.9.5 and 2.6.5). This means that combining a LARA-R2 series cellular module with a u-blox short
range communication module gives designers full access to the Wi-Fi module directly via the cellular module, so
that a second interface connected to the Wi-Fi module is not necessary.
AT commands via the AT interfaces of the cellular module (UART, USB) allows a full control of the Wi-Fi module
from any host processor, because Wi-Fi control messages are relayed to the Wi-Fi module via the dedicated SDIO
interface.
All the management software for Wi-Fi module operations runs inside the cellular module in addition to those
required for cellular-only operation.
1.14.13 Firmware upgrade Over AT (FOAT)
This feature allows upgrading the module firmware over USB / UART serial interfaces, using AT commands.

The +UFWUPD AT command triggers a reboot followed by the upgrade procedure at specified a baud rate

A special boot loader on the module performs firmware installation, security verifications and module reboot

Firmware authenticity verification is performed via a security signature during the download. The firmware is
then installed, overwriting the current version. In case of power loss during this phase, the boot loader
detects a fault at the next wake-up, and restarts the firmware download. After completing the upgrade, the
module is reset again and wakes-up in normal boot
For more details about Firmware update Over AT procedure see the Firmware Update Application Note [23] and
the u-blox AT Commands Manual [2], +UFWUPD AT command.
1.14.14 Firmware update Over The Air (FOTA)
This feature allows upgrading the module firmware over the LTE/3G/2G air interface.
In order to reduce the amount of data to be transmitted over the air, the implemented FOTA feature requires
downloading only a “delta file” instead of the full firmware. The delta file contains only the differences between
the two firmware versions (old and new), and is compressed. The firmware update procedure can be triggered
using dedicated AT command with the delta file stored in the module file system via over the air FTP.
For more details about Firmware update Over The Air procedure see the Firmware Update Application Note [23]
and the u-blox AT Commands Manual [2], .
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1.14.15 Smart temperature management
Cellular modules – independently from the specific model – always have a well-defined operating temperature
range. This range should be respected to guarantee full device functionality and long life span.
Nevertheless there are environmental conditions that can affect operating temperature, e.g. if the device is
located near a heating/cooling source, if there is/is not air circulating, etc.
The module itself can also influence the environmental conditions; such as when it is transmitting at full power.
In this case its temperature increases very quickly and can raise the temperature nearby.
The best solution is always to properly design the system where the module is integrated. Nevertheless an extra
check/security mechanism embedded into the module is a good solution to prevent operation of the device
outside of the specified range.
Smart Temperature Supervisor (STS)
The Smart Temperature Supervisor is activated and configured by a dedicated AT+USTS command. See u-blox
AT Commands Manual [2] for more details. An URC indication is provided once the feature is enabled and at the
module power on.
The cellular module measures the internal temperature (Ti) and its value is compared with predefined thresholds
to identify the actual working temperature range.
Temperature measurement is done inside the module: the measured value could be different from the
environmental temperature (Ta).
Valid temperature range
Dangerous
area
Warning
area
t-2
Safe
area
t-1
Warning
area
t+1
Dangerous
area
t+2
Figure 23: Temperature range and limits
The entire temperature range is divided into sub-regions by limits (see Figure 23) named t-2, t-1, t+1 and t+2.

Within the first limit, (t-1 < Ti < t+1), the cellular module is in the normal working range, the Safe Area

In the Warning Area, (t-2 < Ti < t.1) or (t+1 < Ti < t+2), the cellular module is still inside the valid temperature
range, but the measured temperature is approaching the limit (upper or lower). The module sends a
warning to the user (through the active AT communication interface), which can take, if possible, the
necessary actions to return to a safer temperature range or simply ignore the indication. The module is still in
a valid and good working condition

Outside the valid temperature range, (Ti < t -2) or (Ti > t+2), the device is working outside the specified range
and represents a dangerous working condition. This condition is indicated and the device shuts down to
avoid damage
For security reasons the shutdown is suspended in case an emergency call is in progress. In this case the
device switches off at call termination.
The user can decide at anytime to enable/disable the Smart Temperature Supervisor feature. If the feature
is disabled there is no embedded protection against disallowed temperature conditions.
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Figure 24 shows the flow diagram implemented for the Smart Temperature Supervisor.
No
IF STS
enabled
Feature disabled:
no action
Yes
Feature enabled
(full logic or
indication only)
Read
temperature
Yes
Temperature is
within normal
operating range
No
No
further
actions
IF
(t-1 5V?
No, less than 5 V
Yes, greater than 5 V
Linear LDO
Regulator
Switching Step-Down
Regulator
Figure 25: VCC supply concept selection
The DC/DC switching step-down regulator is the typical choice when the available primary supply source has a
nominal voltage much higher (e.g. greater than 5 V) than the modules VCC operating supply voltage. The use of
switching step-down provides the best power efficiency for the overall application and minimizes current drawn
from the main supply source. See sections 2.2.1.2 and 2.2.1.6, 0, 2.2.1.12 for specific design-in.
The use of an LDO linear regulator becomes convenient for a primary supply with a relatively low voltage (e.g.
less than 5 V). In this case the typical 90% efficiency of the switching regulator diminishes the benefit of voltage
step-down and no true advantage is gained in input current savings. On the opposite side, linear regulators are
not recommended for high voltage step-down as they dissipate a considerable amount of energy in thermal
power. See sections 2.2.1.3 and 2.2.1.6, 0, 2.2.1.12 for specific design-in.
If LARA-R2 series modules are deployed in a mobile unit where no permanent primary supply source is available,
then a battery will be required to provide VCC. A standard 3-cell Li-Ion or Li-Pol battery pack directly connected
to VCC is the usual choice for battery-powered devices. During charging, batteries with Ni-MH chemistry
typically reach a maximum voltage that is above the maximum rating for VCC, and should therefore be avoided.
See sections 2.2.1.4, 2.2.1.6, 2.2.1.7, 0, 2.2.1.12 for specific design-in.
Keep in mind that the use of rechargeable batteries requires the implementation of a suitable charger circuit
which is not included in the modules. The charger circuit has to be designed to prevent over-voltage on VCC
pins, and it should be selected according to the application requirements: a DC/DC switching charger is the
typical choice when the charging source has an high nominal voltage (e.g. ~12 V), whereas a linear charger is
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the typical choice when the charging source has a relatively low nominal voltage (~5 V). If both a permanent
primary supply / charging source (e.g. ~12 V) and a rechargeable back-up battery (e.g. 3.7 V Li-Pol) are available
at the same time as possible supply source, then a proper charger / regulator with integrated power path
management function can be selected to supply the module while simultaneously and independently charging
the battery. See sections 2.2.1.8, 2.2.1.9, and 2.2.1.4, 2.2.1.6, 2.2.1.7, 0, 2.2.1.12 for specific design-in.
An appropriate primary (not rechargeable) battery can be selected taking into account the maximum current
specified in LARA-R2 series Data Sheet [1] during connected-mode, considering that primary cells might have
weak power capability. See sections 2.2.1.5, 2.2.1.6, 0, and 2.2.1.12 for specific design-in.
The usage of more than one DC supply at the same time should be carefully evaluated: depending on the supply
source characteristics, different DC supply systems can result as mutually exclusive.
The usage of a regulator or a battery not able to support the highest peak of VCC current consumption specified
in the LARA-R2 series Data Sheet [1] is generally not recommended. However, if the selected regulator or battery
is not able to support the highest peak current of the module, it must be able to support with adequate margin
at least the highest averaged current consumption value specified in the LARA-R2 series Data Sheet [1]. The
additional energy required by the module during a 2G Tx slot can be provided by an appropriate bypass tank
capacitor or super-capacitor with very large capacitance and very low ESR placed close to the module VCC pins.
Depending on the actual capability of the selected regulator or battery, the required capacitance can be
considerably larger than 1 mF and the required ESR can be in the range of few tens of m. Carefully evaluate
the super-capacitor characteristics since aging and temperature may affect the actual characteristics.
The following sections highlight some design aspects for each of the supplies listed above providing application
circuit design-in compliant with the module VCC requirements summarized in Table 6.
2.2.1.2 Guidelines for VCC supply circuit design using a switching regulator
The use of a switching regulator is suggested when the difference from the available supply rail to the VCC value
is high: switching regulators provide good efficiency transforming a 12 V or greater voltage supply to the typical
3.8 V value of the VCC supply.
The characteristics of the switching regulator connected to VCC pins should meet the following prerequisites to
comply with the module VCC requirements summarized in Table 6:

Power capability: the switching regulator with its output circuit must be capable of providing a voltage
value to the VCC pins within the specified operating range and must be capable of delivering to VCC pins
the specified maximum peak / pulse current consumption during Tx burst at maximum Tx power specified in
LARA-R2 series Data Sheet [1]

Low output ripple: the switching regulator together with its output circuit must be capable of providing a
clean (low noise) VCC voltage profile.

High switching frequency: for best performance and for smaller applications it is recommended to select a
switching frequency ≥ 600 kHz (since L-C output filter is typically smaller for high switching frequency). The
use of a switching regulator with a variable switching frequency or with a switching frequency lower than
600 kHz must be carefully evaluated since this can produce noise in the VCC voltage profile and therefore
negatively impact LTE/2G modulation spectrum performance. An additional L-C low-pass filter between the
switching regulator output to VCC supply pins can mitigate the ripple on VCC, but adds extra voltage drop
due to resistive losses on series inductors.

PWM mode operation: it is preferable to select regulators with Pulse Width Modulation (PWM) mode.
While in connected-mode, the Pulse Frequency Modulation (PFM) mode and PFM/PWM modes transitions
must be avoided to reduce noise on VCC voltage profile. Switching regulators can be used that are able to
switch between low ripple PWM mode and high ripple PFM mode, provided that the mode transition occurs
when the module changes status from the idle/active-modes to connected-mode. It is permissible to use a
regulator that switches from the PWM mode to the burst or PFM mode at an appropriate current threshold.
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Figure 26 and the components listed in Table 19 show an example of a high reliability power supply circuit,
where the module VCC is supplied by a step-down switching regulator capable of delivering to VCC pins the
specified maximum peak / pulse current, with low output ripple and with fixed switching frequency in PWM
mode operation greater than 1 MHz.
12V
LARA-R2 series
VIN
5 RUN
R1
R2
C1
C2
C3 C4
9 VC
BOOST 2
C5
SW
VCC
VCC
53 VCC
51
10 RT
7 PG
R3
BD
52
C6
L1
D1
U1
C7
R4
C8
FB 8
SYNC
GND
11
R5
GND
Figure 26: Example of high reliability VCC supply application circuit using a step-down regulator
Reference
Description
Part Number - Manufacturer
C1
10 µF Capacitor Ceramic X7R 5750 15% 50 V
C5750X7R1H106MB - TDK
C2
C3
10 nF Capacitor Ceramic X7R 0402 10% 16 V
680 pF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R71C103KA01 - Murata
GRM155R71H681KA01 - Murata
C4
22 pF Capacitor Ceramic C0G 0402 5% 25 V
GRM1555C1H220JZ01 - Murata
C5
C6
10 nF Capacitor Ceramic X7R 0402 10% 16 V
470 nF Capacitor Ceramic X7R 0603 10% 25 V
GRM155R71C103KA01 - Murata
GRM188R71E474KA12 - Murata
C7
C8
22 µF Capacitor Ceramic X5R 1210 10% 25 V
330 µF Capacitor Tantalum D_SIZE 6.3 V 45 m
GRM32ER61E226KE15 - Murata
T520D337M006ATE045 - KEMET
D1
L1
Schottky Diode 40 V 3 A
10 µH Inductor 744066100 30% 3.6 A
MBRA340T3G - ON Semiconductor
744066100 - Wurth Electronics
R1
470 k Resistor 0402 5% 0.1 W
2322-705-87474-L - Yageo
R2
15 k Resistor 0402 5% 0.1 W
2322-705-87153-L - Yageo
R3
22 k Resistor 0402 5% 0.1 W
2322-705-87223-L - Yageo
R4
390 k Resistor 0402 1% 0.063 W
RC0402FR-07390KL - Yageo
R5
100 k Resistor 0402 5% 0.1 W
2322-705-70104-L - Yageo
U1
Step-Down Regulator MSOP10 3.5 A 2.4 MHz
LT3972IMSE#PBF - Linear Technology
Table 19: Components for high reliability VCC supply application circuit circuit using a step-down regulator
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Figure 27 and the components listed in Table 20 show an example of a low cost power supply circuit, where the
VCC module supply is provided by a step-down switching regulator capable of delivering to VCC pins the
specified maximum peak / pulse current, transforming a 12 V supply input.
12V
LARA-R2 series
VCC
OUT 1
3 INH
L1
D1
C1
6 FSW
C6
R5
U1
2 SYNC
51 VCC
52 VCC
53 VCC
R1
R3
C3
FB 5
C4
R4
COMP 4
C2
R2
GND
GND
C5
Figure 27: Example of low cost VCC supply application circuit using step-down regulator
Reference
Description
Part Number - Manufacturer
C1
22 µF Capacitor Ceramic X5R 1210 10% 25 V
GRM32ER61E226KE15 – Murata
C2
T520B107M006ATE015 – Kemet
C3
100 µF Capacitor Tantalum B_SIZE 20% 6.3V 15m
5.6 nF Capacitor Ceramic X7R 0402 10% 50 V
C4
C5
6.8 nF Capacitor Ceramic X7R 0402 10% 50 V
56 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM155R71H682KA88 – Murata
GRM1555C1H560JA01 – Murata
C6
D1
220 nF Capacitor Ceramic X7R 0603 10% 25 V
Schottky Diode 25V 2 A
GRM188R71E224KA88 – Murata
STPS2L25 – STMicroelectronics
L1
5.2 µH Inductor 30% 5.28A 22 m
MSS1038-522NL – Coilcraft
R1
4.7 k Resistor 0402 1% 0.063 W
RC0402FR-074K7L – Yageo
R2
910  Resistor 0402 1% 0.063 W
RC0402FR-07910RL – Yageo
R3
82  Resistor 0402 5% 0.063 W
RC0402JR-0782RL – Yageo
R4
8.2 k Resistor 0402 5% 0.063 W
RC0402JR-078K2L – Yageo
R5
39 k Resistor 0402 5% 0.063 W
Step-Down Regulator 8-VFQFPN 3 A 1 MHz
RC0402JR-0739KL – Yageo
U1
GRM155R71H562KA88 – Murata
L5987TR – ST Microelectronics
Table 20: Components for low cost VCC supply application circuit using a step-down regulator
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2.2.1.3 Guidelines for VCC supply circuit design using a Low Drop-Out (LDO) linear regulator
The use of a linear regulator is suggested when the difference from the available supply rail and the VCC value is
low: linear regulators provide high efficiency when transforming a 5 V supply to a voltage value within the
module VCC normal operating range.
The characteristics of the LDO linear regulator connected to the VCC pins should meet the following
prerequisites to comply with the module VCC requirements summarized in Table 6:

Power capabilities: the LDO linear regulator with its output circuit must be capable of providing a voltage
value to the VCC pins within the specified operating range and must be capable of delivering to VCC pins
the maximum peak / pulse current consumption during Tx burst at maximum Tx power specified in LARA-R2
series Data Sheet [1].

Power dissipation: the power handling capability of the LDO linear regulator must be checked to limit its
junction temperature to the maximum rated operating range (i.e. check the voltage drop from the max input
voltage to the min output voltage to evaluate the power dissipation of the regulator).
Figure 28 and the components listed in Table 21 show an example of a high reliability power supply circuit,
where the VCC module supply is provided by an LDO linear regulator capable of delivering the specified highest
peak / pulse current, with proper power handling capability. The regulator described in this example supports a
wide input voltage range, and it includes internal circuitry for reverse battery protection, current limiting, thermal
limiting and reverse current protection.
It is recommended to configure the LDO linear regulator to generate a voltage supply value slightly below the
maximum limit of the module VCC normal operating range (e.g. ~4.1 V as in the circuit described in Figure 28
and Table 21). This reduces the power on the linear regulator and improves the whole thermal design of the
supply circuit.
LARA-R2 series
5V
IN
OUT
VCC
VCC
53 VCC
51
52
U1
C1
R1
SHDN
ADJ
GND
C2
GND
R2
Figure 28: Example of high reliability VCC supply application circuit using an LDO linear regulator
Reference
Description
Part Number - Manufacturer
C1, C2
10 µF Capacitor Ceramic X5R 0603 20% 6.3 V
GRM188R60J106ME47 - Murata
R1
9.1 k Resistor 0402 5% 0.1 W
RC0402JR-079K1L - Yageo Phycomp
R2
3.9 k Resistor 0402 5% 0.1 W
RC0402JR-073K9L - Yageo Phycomp
U1
LDO Linear Regulator ADJ 3.0 A
LT1764AEQ#PBF - Linear Technology
Table 21: Components for high reliability VCC supply application circuit using an LDO linear regulator
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Figure 29 and the components listed in Table 22 show an example of a low cost power supply circuit, where the
VCC module supply is provided by an LDO linear regulator capable of delivering the specified highest peak /
pulse current, with proper power handling capability. The regulator described in this example supports a limited
input voltage range and it includes internal circuitry for current and thermal protection.
It is recommended to configure the LDO linear regulator to generate a voltage supply value slightly below the
maximum limit of the module VCC normal operating range (e.g. ~4.1 V as in the circuit described in Figure 29
and Table 22). This reduces the power on the linear regulator and improves the whole thermal design of the
supply circuit.
LARA-R2 series
5V
IN
OUT
VCC
VCC
53 VCC
51
52
U1
C1
R1
EN
ADJ
GND
C2
GND
R2
Figure 29: Example of low cost VCC supply application circuit using an LDO linear regulator
Reference
Description
Part Number - Manufacturer
C1, C2
10 µF Capacitor Ceramic X5R 0603 20% 6.3 V
GRM188R60J106ME47 - Murata
R1
27 k Resistor 0402 5% 0.1 W
RC0402JR-0727KL - Yageo Phycomp
R2
4.7 k Resistor 0402 5% 0.1 W
RC0402JR-074K7L - Yageo Phycomp
U1
LDO Linear Regulator ADJ 3.0 A
LP38501ATJ-ADJ/NOPB - Texas Instrument
Table 22: Components for low cost VCC supply application circuit using an LDO linear regulator
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2.2.1.4 Guidelines for VCC supply circuit design using a rechargeable Li-Ion or Li-Pol battery
Rechargeable Li-Ion or Li-Pol batteries connected to the VCC pins should meet the following prerequisites to
comply with the module VCC requirements summarized in Table 6:

Maximum pulse and DC discharge current: the rechargeable Li-Ion battery with its related output circuit
connected to the VCC pins must be capable of delivering a pulse current as the maximum peak / pulse
current consumption during Tx burst at maximum Tx power specified in LARA-R2 series Data Sheet [1] and
must be capable of extensively delivering a DC current as the maximum average current consumption
specified in LARA-R2 series Data Sheet [1]. The maximum discharge current is not always reported in the
data sheets of batteries, but the maximum DC discharge current is typically almost equal to the battery
capacity in Amp-hours divided by 1 hour.

DC series resistance: the rechargeable Li-Ion battery with its output circuit must be capable of avoiding a
VCC voltage drop below the operating range summarized in Table 6 during transmit bursts.
2.2.1.5
Guidelines for VCC supply circuit design using a primary (disposable) battery
The characteristics of a primary (non-rechargeable) battery connected to VCC pins should meet the following
prerequisites to comply with the module VCC requirements summarized in Table 6:

Maximum pulse and DC discharge current: the non-rechargeable battery with its related output circuit
connected to the VCC pins must be capable of delivering a pulse current as the maximum peak current
consumption during Tx burst at maximum Tx power specified in LARA-R2 series Data Sheet [1] and must be
capable of extensively delivering a DC current as the maximum average current consumption specified in
LARA-R2 series Data Sheet [1]. The maximum discharge current is not always reported in the data sheets of
batteries, but the max DC discharge current is typically almost equal to the battery capacity in Amp-hours
divided by 1 hour.

DC series resistance: the non-rechargeable battery with its output circuit must be capable of avoiding a
VCC voltage drop below the operating range summarized in Table 6 during transmit bursts.
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2.2.1.6 Additional guidelines for VCC supply circuit design
To reduce voltage drops, use a low impedance power source. The series resistance of the power supply lines
(connected to the VCC and GND pins of the module) on the application board and battery pack should also be
considered and minimized: cabling and routing must be as short as possible to minimize power losses.
Three pins are allocated for VCC supply. Several pins are designated for GND connection. It is recommended to
properly connect all of them to supply the module to minimize series resistance losses.
In case of modules supporting 2G radio access technology, to avoid voltage drop undershoot and overshoot at
the start and end of a transmit burst during a GSM call (when current consumption on the VCC supply can rise
up as specified in the LARA-R2 series Data Sheet [1]), place a bypass capacitor with large capacitance (at least
100 µF) and low ESR near the VCC pins, for example:

330 µF capacitance, 45 m ESR (e.g. KEMET T520D337M006ATE045, Tantalum Capacitor)
To reduce voltage ripple and noise, improving RF performance especially if the application device integrates an
internal antenna, place the following bypass capacitors near the VCC pins:

68 pF capacitor with Self-Resonant Frequency in 800/900 MHz range (e.g. Murata GRM1555C1E560J)

15 pF capacitor with Self-Resonant Frequency in 1800/1900 MHz range (e.g. Murata GRM1555C1E150J)

8.2 pF capacitor with Self-Resonant Frequency in 2500/2600 MHz range (e.g. Murata GRM1555C1H8R2D)

10 nF capacitor (e.g. Murata GRM155R71C103K) to filter digital logic noise from clocks and data sources
 100 nF capacitor (e.g Murata GRM155R61C104K) to filter digital logic noise from clocks and data sources
A suitable series ferrite bead can be properly placed on the VCC line for additional noise filtering if required by
the specific application according to the whole application board design.
LARA-R2 series
3V8
VCC
VCC
VCC
51
52
53
C1
GND
C2
Recommended for
cellular modules
supporting LTE band-7
C3
C4
C5
C6
Recommended for
cellular modules
supporting 2G
Figure 30: Suggested schematic for the VCC bypass capacitors to reduce ripple / noise on supply voltage profile
Reference
Description
Part Number - Manufacturer
C1
8.2 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM1555C1H8R2DZ01 - Murata
C2
C3
15 pF Capacitor Ceramic C0G 0402 5% 50 V
68 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM1555C1H150JA01 - Murata
GRM1555C1H680JA01 - Murata
C4
10 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R71C103KA01 - Murata
C5
C6
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R71C104KA01 - Murata
T520D337M006ATE045 - KEMET
330 µF Capacitor Tantalum D_SIZE 6.3 V 45 m
Table 23: Suggested components to reduce ripple / noise on VCC
The necessity of each part depends on the specific design, but it is recommended to provide all the bypass
capacitors described in Figure 30 / Table 23 if the application device integrates an internal antenna.
ESD sensitivity rating of the VCC supply pins is 1 kV (Human Body Model according to JESD22-A114).
Higher protection level can be required if the line is externally accessible on the application board, e.g. if
accessible battery connector is directly connected to VCC pins. Higher protection level can be achieved by
mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) close to accessible point.
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2.2.1.7 Additional guidelines for VCC supply circuit design of LARA-R211 modules
LARA-R211 modules provide separate supply inputs over the VCC pins (see Figure 3):

VCC pins #52 and #53 represent the supply input for the internal RF power amplifier, demanding most of
the total current drawn of the module when RF transmission is enabled during a voice/data call

VCC pin #51 represents the supply input for the internal baseband Power Management Unit and the internal
transceiver, demanding minor part of the total current drawn of the module when RF transmission is
enabled during a voice/data call
All the VCC pins are in general intended to be connected to the same external power supply circuit, but separate
supply sources can be implemented for specific (e.g. battery-powered) applications considering that the voltage
at the VCC pins #52 and #53 can drop to a value lower than the one at the VCC pin #51, keeping the module
still switched-on and functional. Figure 31 describes a possible application circuit.
L1
D1
LARA-R211
Step-up
Regulator
VIN
51 VCC
SW
SHDNn
C7
R1
FB
C9
R2
GND
C8
U1
Li-Ion/Li-Pol
Battery
52 VCC
53 VCC
C1 C2 C3 C4 C5 C6
GND
Figure 31: VCC circuit example with separate supply for LARA-R211 modules
Reference
Description
Part Number - Manufacturer
C1
330 µF Capacitor Tantalum D_SIZE 6.3 V 45 m
10 nF Capacitor Ceramic X7R 0402 10% 16 V
T520D337M006ATE045 - KEMET
C2
C3
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R61A104KA01 - Murata
C4
C5
68 pF Capacitor Ceramic C0G 0402 5% 50 V
15 pF Capacitor Ceramic C0G 0402 5% 25 V
GRM1555C1H680JA01 - Murata
GRM1555C1E150JA01 - Murata
C6
C7
8.2 pF Capacitor Ceramic C0G 0402 5% 50 V
10 µF Capacitor Ceramic X5R 0603 20% 6.3 V
GRM1555C1H8R2DZ01 - Murata
GRM188R60J106ME47 - Murata
C8
C9
22 µF Capacitor Ceramic X5R 1210 10% 25 V
10 pF Capacitor Ceramic C0G 0402 5% 25 V
GRM32ER61E226KE15 - Murata
GRM1555C1E100JA01 - Murata
D1
Schottky Diode 40 V 1 A
SS14 - Vishay General Semiconductor
L1
10 µH Inductor 20% 1 A 276 m
SRN3015-100M - Bourns Inc.
R1
1 M Resistor 0402 5% 0.063 W
RC0402FR-071ML - Yageo Phycomp
R2
412 k Resistor 0402 5% 0.063 W
Step-up Regulator 350 mA
RC0402FR-07412KL - Yageo Phycomp
U1
GRM155R71C103KA01 - Murata
AP3015 - Diodes Incorporated
Table 24: Example of components for VCC circuit with separate supply for LARA-R211 modules
2.2.1.8
Guidelines for external battery charging circuit
LARA-R2 series modules do not have an on-board charging circuit. Figure 32 provides an example of a battery
charger design, suitable for applications that are battery powered with a Li-Ion (or Li-Polymer) cell.
In the application circuit, a rechargeable Li-Ion (or Li-Polymer) battery cell, that features proper pulse and DC
discharge current capabilities and proper DC series resistance, is directly connected to the VCC supply input of
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the module. Battery charging is completely managed by the STMicroelectronics L6924U Battery Charger IC that,
from a USB power source (5.0 V typ.), charges as a linear charger the battery, in three phases:

Pre-charge constant current (active when the battery is deeply discharged): the battery is charged with a
low current, set to 10% of the fast-charge current

Fast-charge constant current: the battery is charged with the maximum current, configured by the value
of an external resistor to a value suitable for USB power source (~500 mA)

Constant voltage: when the battery voltage reaches the regulated output voltage (4.2 V), the L6924U
starts to reduce the current until the charge termination is done. The charging process ends when the
charging current reaches the value configured by an external resistor to ~15 mA or when the charging timer
reaches the value configured by an external capacitor to ~9800 s
Using a battery pack with an internal NTC resistor, the L6924U can monitor the battery temperature to protect
the battery from operating under unsafe thermal conditions.
The L6924U, as linear charger, is more suitable for applications where the charging source has a relatively low
nominal voltage (~5 V), so that a switching charger is suggested for applications where the charging source has
a relatively high nominal voltage (e.g. ~12 V, see the following section 2.2.1.9 for specific design-in).
Li-Ion/Li-Polymer
Battery Charger IC
LARA-R2 series
5V
USB
Supply
VIN
VINSNS
MODE
R1
R2
R3
VOUT
VOSNS
VREF
ISEL
C3
IUSB
IAC
51 VCC
52 VCC
53 VCC
Li-Ion/Li-Pol
Battery Pack
R4
C4
TH
θ
IEND
C5 C6 C7 C8 C9 C10
TPRG
C1
C2
SD
GND
U1
B1
GND
D1 D2
Figure 32: Li-Ion (or Li-Polymer) battery charging application circuit
Reference
Description
Part Number - Manufacturer
B1
Li-Ion (or Li-Polymer) battery pack with 470  NTC
1 µF Capacitor Ceramic X7R 0603 10% 16 V
Various manufacturer
C1, C4
C2, C6
C3
10 nF Capacitor Ceramic X7R 0402 10% 16 V
1 nF Capacitor Ceramic X7R 0402 10% 50 V
GRM155R71C103KA01 - Murata
GRM155R71H102KA01 - Murata
C5
330 µF Capacitor Tantalum D_SIZE 6.3 V 45 m
100 nF Capacitor Ceramic X7R 0402 10% 16 V
T520D337M006ATE045 - KEMET
C7
C8
68 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM1555C1H680JA01 - Murata
C9
C10
15 pF Capacitor Ceramic C0G 0402 5% 25 V
8.2 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM1555C1E150JA01 - Murata
GRM1555C1H8R2DZ01 - Murata
D1, D2
R1, R2
Low Capacitance ESD Protection
24 k Resistor 0402 5% 0.1 W
CG0402MLE-18G - Bourns
RC0402JR-0724KL - Yageo Phycomp
R3
3.3 k Resistor 0402 5% 0.1 W
RC0402JR-073K3L - Yageo Phycomp
R4
1.0 k Resistor 0402 5% 0.1 W
RC0402JR-071K0L - Yageo Phycomp
U1
Single Cell Li-Ion (or Li-Polymer) Battery Charger IC
for USB port and AC Adapter
L6924U - STMicroelectronics
GRM188R71C105KA12 - Murata
GRM155R61A104KA01 - Murata
Table 25: Suggested components for Li-Ion (or Li-Polymer) battery charging application circuit
2.2.1.9
Guidelines for external battery charging and power path management circuit
Application devices where both a permanent primary supply / charging source (e.g. ~12 V) and a rechargeable
back-up battery (e.g. 3.7 V Li-Pol) are available at the same time as possible supply source should implement a
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suitable charger / regulator with integrated power path management function to supply the module and the
whole device while simultaneously and independently charging the battery.
Figure 33 reports a simplified block diagram circuit showing the working principle of a charger / regulator with
integrated power path management function. This component allows the system to be powered by a permanent
primary supply source (e.g. ~12 V) using the integrated regulator which simultaneously and independently
recharges the battery (e.g. 3.7 V Li-Pol) that represents the back-up supply source of the system: the power path
management feature permits the battery to supplement the system current requirements when the primary
supply source is not available or cannot deliver the peak system currents.
A power management IC should meet the following prerequisites to comply with the module VCC requirements
summarized in Table 6:

High efficiency internal step down converter, compliant with the performances specified in section 2.2.1.2

Low internal resistance in the active path Vout – Vbat, typically lower than 50 m

High efficiency switch mode charger with separate power path control
Power path management IC
12 V
Primary
Source
Vin
System
Vout
DC/DC converter
and battery FET
control logic
Vbat
Li-Ion/Li-Pol
Battery Pack
Charge
controller
GND
GND
θ
Figure 33: Charger / regulator with integrated power path management circuit block diagram
Figure 34 and the components listed in Table 26 provide an application circuit example where the MPS MP2617
switching charger / regulator with integrated power path management function provides the supply to the
cellular module while concurrently and autonomously charging a suitable Li-Ion (or Li-Polymer) battery with
proper pulse and DC discharge current capabilities and proper DC series resistance according to the rechargeable
battery recommendations described in section 2.2.1.4.
The MP2617 IC constantly monitors the battery voltage and selects whether to use the external main primary
supply / charging source or the battery as supply source for the module, and starts a charging phase accordingly.
The MP2617 IC normally provides a supply voltage to the module regulated from the external main primary
source allowing immediate system operation even under missing or deeply discharged battery: the integrated
switching step-down regulator is capable to provide up to 3 A output current with low output ripple and fixed
1.6 MHz switching frequency in PWM mode operation. The module load is satisfied in priority, then the
integrated switching charger will take the remaining current to charge the battery.
Additionally, the power path control allows an internal connection from battery to the module with a low series
internal ON resistance (40 m typical), in order to supplement additional power to the module when the current
demand increases over the external main primary source or when this external source is removed.
Battery charging is managed in three phases:

Pre-charge constant current (active when the battery is deeply discharged): the battery is charged with a
low current, set to 10% of the fast-charge current
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
Fast-charge constant current: the battery is charged with the maximum current, configured by the value
of an external resistor to a value suitable for the application

Constant voltage: when the battery voltage reaches the regulated output voltage (4.2 V), the current is
progressively reduced until the charge termination is done. The charging process ends when the charging
current reaches the 10% of the fast-charge current or when the charging timer reaches the value configured
by an external capacitor
Using a battery pack with an internal NTC resistor, the MP2617 can monitor the battery temperature to protect
the battery from operating under unsafe thermal conditions.
Several parameters as the charging current, the charging timings, the input current limit, the input voltage limit,
the system output voltage can be easily set according to the specific application requirements, as the actual
electrical characteristics of the battery and the external supply / charging source: proper resistors or capacitors
have to be accordingly connected to the related pins of the IC.
Li-Ion/Li-Polymer Battery
Charger / Regulator with
Power Path Managment
BST
12V
L1
SW
Primary
Source
VIN
LARA-R2 series
C4
53 VCC
R4
C5
VLIM
R5
Li-Ion/Li-Pol
Battery Pack
BAT
R1
R2
EN
ILIM
NTC
ISET
VCC
TMR
C1
51 VCC
52 VCC
SYS
C2
AGND PGND
C10 C11 C12 C13 C14 C15
θ
R3
C3
C6 C7 C8
C9
GND
D1 D2
B1
U1
Figure 34: Li-Ion (or Li-Polymer) battery charging and power path management application circuit
Reference
Description
Part Number - Manufacturer
B1
Various manufacturer
C1, C5, C6
Li-Ion (or Li-Polymer) battery pack with 10 k NTC
22 µF Capacitor Ceramic X5R 1210 10% 25 V
C2, C4, C11
C3
100 nF Capacitor Ceramic X7R 0402 10% 16 V
1 µF Capacitor Ceramic X7R 0603 10% 25 V
GRM155R61A104KA01 - Murata
GRM188R71E105KA12 - Murata
C7, C13
C8, C14
68 pF Capacitor Ceramic C0G 0402 5% 50 V
15 pF Capacitor Ceramic C0G 0402 5% 25 V
GRM1555C1H680JA01 - Murata
GRM1555C1E150JA01 - Murata
C9, C15
8.2 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM1555C1H8R2DZ01 - Murata
C10
330 µF Capacitor Tantalum D_SIZE 6.3 V 45 m
T520D337M006ATE045 - KEMET
C12
10 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R71C103KA01 - Murata
D1, D2
Low Capacitance ESD Protection
CG0402MLE-18G - Bourns
R1, R3, R5
10 k Resistor 0402 5% 1/16 W
RC0402JR-0710KL - Yageo Phycomp
R2
1.0 k Resistor 0402 5% 0.1 W
RC0402JR-071K0L - Yageo Phycomp
R4
22 k Resistor 0402 5% 1/16 W
RC0402JR-0722KL - Yageo Phycomp
L1
1.2 µH Inductor 6 A 21 m 20%
Li-Ion/Li-Polymer Battery DC/DC Charger / Regulator
with integrated Power Path Management function
7447745012 - Wurth
U1
GRM32ER61E226KE15 - Murata
MP2617 - Monolithic Power Systems (MPS)
Table 26: Suggested components for Li-Ion (or Li-Polymer) battery charging and power path management application circuit
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2.2.1.10 Guidelines for removing VCC supply
As described in section 1.6.2 and Figure 14, the VCC supply can be removed after the end of LARA-R2 series
modules internal power-off sequence, which has to be properly started sending the AT+CPWROFF command
(see u-blox AT Commands Manual [2]).
Removing the VCC power can be useful in order to minimize the current consumption when the LARA-R2 series
modules are switched off. Then, the modules can be switched on again by re-applying the VCC supply.
If the VCC supply is generated by a switching or an LDO regulator, the application processor may control the
input pin of the regulator which is provided to enable / disable the output of the regulator (as for example the
RUN input pin for the regulator described in Figure 26, the INH input pin for the regulator described in Figure 27,
the SHDNn input pin for the regulator described in Figure 28, the EN input pin for the regulator described in
Figure 29), in order to apply / remove the VCC supply.
If the regulator that generates the VCC supply does not provide an on / off pin, or for other applications such as
the battery-powered ones, the VCC supply can be switched off using an appropriate external p-channel MOSFET
controlled by the application processor by means of a proper inverting transistor as shown in Figure 35, given
that the external p-channel MOSFET has provide:

Very low RDS(ON) (for example, less than 50 m), to minimize voltage drops

Adequate maximum Drain current (see LARA-R2 series Data Sheet [1] for module consumption figures)

Low leakage current, to minimize the current consumption
LARA-R2 series
51 VCC
52 VCC
T1
VCC Supply Source
53 VCC
R3
Application
Processor
GPIO
R2
GND
C1 C2 C3 C4 C5 C6
R1
T2
GND
Figure 35: Example of application circuit for VCC supply removal
Reference
Description
Part Number - Manufacturer
R1
47 k Resistor 0402 5% 0.1 W
RC0402JR-0747KL - Yageo Phycomp
R2
10 k Resistor 0402 5% 0.1 W
RC0402JR-0710KL - Yageo Phycomp
R3
100 k Resistor 0402 5% 0.1 W
P-Channel MOSFET Low On-Resistance
RC0402JR-07100KL - Yageo Phycomp
T2
C1
NPN BJT Transistor
330 µF Capacitor Tantalum D_SIZE 6.3 V 45 m
BC847 - Infineon
T520D337M006ATE045 - KEMET
C2
10 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R71C103KA01 - Murata
C3
C4
100 nF Capacitor Ceramic X7R 0402 10% 16 V
56 pF Capacitor Ceramic C0G 0402 5% 25 V
GRM155R61A104KA01 - Murata
GRM1555C1E560JA01 - Murata
C5
C6
15 pF Capacitor Ceramic C0G 0402 5% 25 V
8.2 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM1555C1E150JA01 - Murata
GRM1555C1H8R2DZ01 - Murata
T1
AO3415 - Alpha & Omega Semiconductor Inc.
Table 27: Components for VCC supply removal application circuit
It is highly recommended to avoid an abrupt removal of the VCC supply during LARA-R2 series modules
normal operations: the power off procedure must be started by the AT+CPWROFF command, waiting the
command response for a proper time period (see u-blox AT Commands Manual [2]), and then a proper
VCC supply has to be held at least until the end of the modules’ internal power off sequence, which
occurs when the generic digital interfaces supply output (V_INT) is switched off by the module.
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2.2.1.11 Guidelines for VCC supply layout design
Good connection of the module VCC pins with DC supply source is required for correct RF performance.
Guidelines are summarized in the following list:

All the available VCC pins must be connected to the DC source.

VCC connection must be as wide as possible and as short as possible.

Any series component with Equivalent Series Resistance (ESR) greater than few milliohms must be avoided.

VCC connection must be routed through a PCB area separated from sensitive analog signals and sensitive
functional units: it is good practice to interpose at least one layer of PCB ground between VCC track and
other signal routing.

Coupling between VCC and audio lines (especially microphone inputs) must be avoided, because the typical
GSM burst has a periodic nature of approx. 217 Hz, which lies in the audible audio range.

The tank bypass capacitor with low ESR for current spikes smoothing described in section 2.2.1.6 should be
placed close to the VCC pins. If the main DC source is a switching DC-DC converter, place the large
capacitor close to the DC-DC output and minimize the VCC track length. Otherwise consider using separate
capacitors for DC-DC converter and cellular module tank capacitor.

The bypass capacitors in the pF range described in section 2.2.1.6 should be placed as close as possible to
the VCC pins. This is highly recommended if the application device integrates an internal antenna.

Since VCC is directly connected to RF Power Amplifiers, voltage ripple at high frequency may result in
unwanted spurious modulation of transmitter RF signal. This is more likely to happen with switching DC-DC
converters, in which case it is better to select the highest operating frequency for the switcher and add a
large L-C filter before connecting to the LARA-R2 series modules in the worst case.

Shielding of switching DC-DC converter circuit, or at least the use of shielded inductors for the switching
DC-DC converter, may be considered since all switching power supplies may potentially generate interfering
signals as a result of high-frequency high-power switching.

If VCC is protected by transient voltage suppressor to ensure that the voltage maximum ratings are not
exceeded, place the protecting device along the path from the DC source toward the cellular module,
preferably closer to the DC source (otherwise protection functionality may be compromised).
2.2.1.12 Guidelines for grounding layout design
Good connection of the module GND pins with application board solid ground layer is required for correct RF
performance. It significantly reduces EMC issues and provides a thermal heat sink for the module.

Connect each GND pin with application board solid GND layer. It is strongly recommended that each GND
pin surrounding VCC pins have one or more dedicated via down to the application board solid ground layer.

The VCC supply current flows back to main DC source through GND as ground current: provide adequate
return path with suitable uninterrupted ground plane to main DC source.

It is recommended to implement one layer of the application board as ground plane as wide as possible.

If the application board is a multilayer PCB, then all the board layers should be filled with GND plane as
much as possible and each GND area should be connected together with complete via stack down to the
main ground layer of the board. Use as many vias as possible to connect the ground planes

Provide a dense line of vias at the edges of each ground area, in particular along RF and high speed lines

If the whole application device is composed by more than one PCB, then it is required to provide a good and
solid ground connection between the GND areas of all the different PCBs.

Good grounding of GND pins also ensures thermal heat sink. This is critical during call connection, when the
real network commands the module to transmit at maximum power: proper grounding helps prevent
module overheating.
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2.2.2 RTC supply (V_BCKP)
2.2.2.1
Guidelines for V_BCKP circuit design
LARA-R2 series modules provide the V_BCKP RTC supply input/output, which can be mainly used to:

Provide RTC back-up when VCC supply is removed
If RTC timing is required to run for a time interval of T [s] when VCC supply is removed, place a capacitor with a
nominal capacitance of C [µF] at the V_BCKP pin. Choose the capacitor using the following formula:
C [µF] = (Current_Consumption [µA] x T [s]) / Voltage_Drop [V]
= 2.5 x T [s]
For example, a 100 µF capacitor can be placed at V_BCKP to provide RTC backup holding the V_BCKP voltage
within its valid range for around 40 s at 25 °C, after the VCC supply is removed. If a longer buffering time is
required, a 70 mF super-capacitor can be placed at V_BCKP, with a 4.7 k series resistor to hold the V_BCKP
voltage within its valid range for approximately 8 hours at 25 °C, after the VCC supply is removed. The purpose
of the series resistor is to limit the capacitor charging current due to the large capacitor specifications, and also
to let a fast rise time of the voltage value at the V_BCKP pin after VCC supply has been provided. These
capacitors allow the time reference to run during battery disconnection.
(a)
LARA-R2 series
(b)
V_BCKP
C1
LARA-R2 series
R2
(c)
LARA-R2 series
V_BCKP
V_BCKP
D3
B3
C2
(superCap)
Figure 36: Real time clock supply (V_BCKP) application circuits: (a) using a 100 µF capacitor to let the RTC run for ~1 minute after
VCC removal; (b) using a 70 mF capacitor to let RTC run for ~10 hours after VCC removal; (c) using a non-rechargeable battery
Reference
Description
Part Number - Manufacturer
C1
100 µF Tantalum Capacitor
GRM43SR60J107M - Murata
R2
4.7 k Resistor 0402 5% 0.1 W
70 mF Capacitor
RC0402JR-074K7L - Yageo Phycomp
C2
XH414H-IV01E - Seiko Instruments
Table 28: Example of components for V_BCKP buffering
If longer buffering time is required to allow the RTC time reference to run during a disconnection of the VCC
supply, then an external battery can be connected to V_BCKP pin. The battery should be able to provide a
proper nominal voltage and must never exceed the maximum operating voltage for V_BCKP (specified in the
Input characteristics of Supply/Power pins table in the LARA-R2 series Data Sheet [1]). The connection of the
battery to V_BCKP should be done with a suitable series resistor for a rechargeable battery, or with an
appropriate series diode for a non-rechargeable battery. The purpose of the series resistor is to limit the battery
charging current due to the battery specifications, and also to allow a fast rise time of the voltage value at the
V_BCKP pin after the VCC supply has been provided. The purpose of the series diode is to avoid a current flow
from the module V_BCKP pin to the non-rechargeable battery.
If the RTC timing is not required when the VCC supply is removed, it is not needed to connect the
V_BCKP pin to an external capacitor or battery. In this case the date and time are not updated when VCC
is disconnected. If VCC is always supplied, then the internal regulator is supplied from the main supply
and there is no need for an external component on V_BCKP.
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Combining a LARA-R2 series cellular module with a u-blox GNSS positioning receiver, the positioning receiver
VCC supply is controlled by the cellular module by means of the “GNSS supply enable” function provided by the
GPIO2 of the cellular module. In this case the V_BCKP supply output of the cellular module can be connected to
the V_BCKP backup supply input pin of the GNSS receiver to provide the supply for the positioning real time
clock and backup RAM when the VCC supply of the cellular module is within its operating range and the VCC
supply of the GNSS receiver is disabled. This enables the u-blox GNSS receiver to recover from a power
breakdown with either a hot start or a warm start (depending on the duration of the positioning VCC outage)
and to maintain the configuration settings saved in the backup RAM. Refer to section 2.6.4 for more details
regarding the application circuit with a u-blox GNSS receiver.
The internal regulator for V_BCKP is optimized for low leakage current and very light loads. Do not apply
loads which might exceed the limit for maximum available current from V_BCKP supply, as this can cause
malfunctions in the module. LARA-R2 series Data Sheet [1] describes the detailed electrical characteristics.
V_BCKP supply output pin provides internal short circuit protection to limit start-up current and protect the
device in short circuit situations. No additional external short circuit protection is required.
ESD sensitivity rating of the V_BCKP supply pin is 1 kV (Human Body Model according to JESD22-A114).
Higher protection level can be required if the line is externally accessible on the application board, e.g. if
an accessible back-up battery connector is directly connected to V_BCKP pin, and it can be achieved by
mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) close to the accessible point.
2.2.2.2
Guidelines for V_BCKP layout design
RTC supply (V_BCKP) requires careful layout: avoid injecting noise on this voltage domain as it may affect the
stability of the 32 kHz oscillator.
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2.2.3 Interface supply (V_INT)
2.2.3.1
Guidelines for V_INT circuit design
LARA-R2 series provide the V_INT generic digital interfaces 1.8 V supply output, which can be mainly used to:

Indicate when the module is switched on (see sections 1.6.1, 1.6.2 for more details)

Pull-up SIM detection signal (see section 2.5 for more details)

Supply voltage translators to connect digital interfaces of the module to a 3.0 V device (see section 2.6.1)

Pull-up DDC (I C) interface signals (see section 2.6.4 for more details)

Supply a 1.8 V u-blox 6 or subsequent GNSS receiver (see section 2.6.4 for more details)

Supply an external device, as an external 1.8 V audio codec (see section 2.7.1 for more details)
V_INT supply output pin provides internal short circuit protection to limit start-up current and protect the device
in short circuit situations. No additional external short circuit protection is required.
Do not apply loads which might exceed the limit for maximum available current from V_INT supply (see
the LARA-R2 series Data Sheet [1]) as this can cause malfunctions in internal circuitry.
Since the V_INT supply is generated by an internal switching step-down regulator, the V_INT voltage
ripple can range as specified in the LARA-R2 series Data Sheet [1]: it is not recommended to supply
sensitive analog circuitry without adequate filtering for digital noise.
V_INT can only be used as an output: do not connect any external supply source on V_INT.
ESD sensitivity rating of the V_INT supply pin is 1 kV (Human Body Model according to JESD22-A114).
Higher protection level could be required if the line is externally accessible and it can be achieved by
mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) close to the accessible point.
It is recommended to provide direct access to the V_INT pin on the application board by means of an
accessible test point directly connected to the V_INT pin.
2.2.3.2
Guidelines for V_INT layout design
V_INT supply output is generated by an integrated switching step-down converter, used internally to supply the
generic digital interfaces. Because of this, it can be a source of noise: avoid coupling with sensitive signals.
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2.3
System functions interfaces
2.3.1 Module power-on (PWR_ON)
2.3.1.1 Guidelines for PWR_ON circuit design
LARA-R2 series modules’ PWR_ON input is equipped with an internal active pull-up resistor to the VCC module
supply as described in Figure 37: an external pull-up resistor is not required and should not be provided.
If connecting the PWR_ON input to a push button, the pin will be externally accessible on the application
device. According to EMC/ESD requirements of the application, an additional ESD protection should be provided
close to the accessible point, as described in Figure 37 and Table 29.
ESD sensitivity rating of the PWR_ON pin is 1 kV (Human Body Model according to JESD22-A114). Higher
protection level can be required if the line is externally accessible on the application board, e.g. if an
accessible push button is directly connected to PWR_ON pin. Higher protection level can be achieved by
mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) close to accessible point.
An open drain or open collector output is suitable to drive the PWR_ON input from an application processor, as
the pin is equipped with an internal active pull-up resistor to the V_BCKP supply, as described in Figure 37.
A compatible push-pull output of an application processor can also be used. In any case, take care to set the
proper level in all the possible scenarios to avoid an inappropriate module switch-on.
Application
Processor
LARA-R2 series
V_BCKP
Open
Drain
Output
10 k
Power-on
push button
TP
LARA-R2 series
15 PWR_ON
V_BCKP
10 k
TP
15 PWR_ON
ESD
Figure 37: PWR_ON application circuits using a push button and an open drain output of an application processor
Reference
Description
Remarks
ESD
CT0402S14AHSG - EPCOS
Varistor array for ESD protection
Table 29: Example of pull-up resistor and ESD protection for the PWR_ON application circuit
It is recommended to provide direct access to the PWR_ON pin on the application board by means of
accessible testpoint directly connected to the PWR_ON pin.
2.3.1.2
Guidelines for PWR_ON layout design
The power-on circuit (PWR_ON) requires careful layout since it is the sensitive input available to switch on the
LARA-R2 series modules. It is required to ensure that the voltage level is well defined during operation and no
transient noise is coupled on this line, otherwise the module might detect a spurious power-on request.
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2.3.2 Module reset (RESET_N)
2.3.2.1
Guidelines for RESET_N circuit design
LARA-R2 series RESET_N is equipped with an internal pull-up to the V_BCKP supply as described in Figure 38.
An external pull-up resistor is not required.
If connecting the RESET_N input to a push button, the pin will be externally accessible on the application device.
According to EMC/ESD requirements of the application, an additional ESD protection device (e.g. the EPCOS
CA05P4S14THSG varistor) should be provided close to accessible point on the line connected to this pin, as
described in Figure 38 and Table 30.
ESD sensitivity rating of the RESET_N pin is 1 kV (Human Body Model according to JESD22-A114). Higher
protection level can be required if the line is externally accessible on the application board, e.g. if an
accessible push button is directly connected to RESET_N pin. Higher protection level can be achieved by
mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) close to accessible point.
An open drain output is suitable to drive the RESET_N input from an application processor as it is equipped with
an internal pull-up to V_BCKP supply, as described in Figure 38.
A compatible push-pull output of an application processor can also be used. In any case, take care to set the
proper level in all the possible scenarios to avoid an inappropriate module reset, switch-on or switch-off.
Application
Processor
LARA-R2 series
V_BCKP
Power-on
push button
Open
Drain
Output
10 k
TP
LARA-R2 series
18
RESET_N
V_BCKP
10 k
TP
18 RESET_N
ESD
Figure 38: RESET_N application circuits using a push button and an open drain output of an application processor
Reference
Description
Remarks
ESD
Varistor for ESD protection
CT0402S14AHSG - EPCOS
Table 30: Example of ESD protection component for the RESET_N application circuit
If the external reset function is not required by the customer application, the RESET_N input pin can be
left unconnected to external components, but it is recommended providing direct access on the
application board by means of accessible testpoint directly connected to the RESET_N pin.
2.3.2.2
Guidelines for RESET_N layout design
The reset circuit (RESET_N) requires careful layout due to the pin function: ensure that the voltage level is well
defined during operation and no transient noise is coupled on this line, otherwise the module might detect a
spurious reset request. It is recommended to keep the connection line to RESET_N as short as possible.
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2.3.3 Module / host configuration selection
2.3.3.1
Guidelines for HOST_SELECT circuit design
Selection of module / host configuration over HOST_SELECT is not supported by “02” product versions.
LARA-R2 series modules include one pin (HOST_SELECT) to select the module / host application processor
configuration: the pin is available to select, enable, connect, disconnect and subsequently re-connect the HSIC
(USB High-Speed Inter-Chip) interface.
LARA-R2 series Data Sheet [1] describes the detailed electrical characteristics of the HOST_SELECT pin.
Further guidelines for HOST_SELECT pin circuit design will be described in detail in a successive release of
the System Integration Manual.
Do not apply voltage to HOST_SELECT pin before the switch-on of its supply source (V_INT), to avoid
latch-up of circuits and allow a proper boot of the module. If the external signal connected to the cellular
module cannot be tri-stated or set low, insert a multi channel digital switch (e.g. TI SN74CB3Q16244,
TS5A3159, or TS5A63157) between the two-circuit connections and set to high impedance before V_INT
switch-on.
ESD sensitivity rating of the HOST_SELECT pin is 1 kV (HBM as per JESD22-A114). Higher protection level
could be required if the lines are externally accessible and it can be achieved by mounting an ESD
protection (e.g. EPCOS CA05P4S14THSG varistor array) close to accessible points
If the HOST_SELECT pin is not used, they can be left unconnected on the application board.
2.3.3.2
Guidelines for HOST_SELECT layout design
The pin for the selection of the module / host application processor configuration (HOST_SELECT) is generally
not critical for layout.
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2.4
Antenna interface
LARA-R2 series modules provide two RF interfaces for connecting the external antennas:

The ANT1 pin represents the primary RF input/output for LTE/3G/2G RF signals transmission and reception.

The ANT2 pin represents the secondary RF input for LTE Rx diversity RF signals reception.
Both the ANT1 and the ANT2 pins have a nominal characteristic impedance of 50  and must be connected to
the related antenna through a 50  transmission line to allow proper transmission / reception of RF signals.
Two antennas (one connected to ANT1 pin and one connected to ANT2 pin) must be used to support the
LTE Rx diversity radio technology. This is a required feature for LTE category 1 User Equipments (up to
10.2 Mb/s Down-Link data rate) according to 3GPP specifications.
2.4.1 Antenna RF interface (ANT1 / ANT2)
2.4.1.1
General guidelines for antenna selection and design
The antenna is the most critical component to be evaluated. Designers must take care of the antennas from all
perspective at the very start of the design phase when the physical dimensions of the application board are
under analysis/decision, since the RF compliance of the device integrating LARA-R2 series modules with all the
applicable required certification schemes depends on antennas radiating performance.
Cellular antennas are typically available in the types of linear monopole or PCB antennas such as patches or
ceramic SMT elements.


External antennas (e.g. linear monopole)
o External antennas basically do not imply physical restriction to the design of the PCB where the LARA-R2
series module is mounted.
o The radiation performance mainly depends on the antennas. It is required to select antennas with
optimal radiating performance in the operating bands.
RF cables should be carefully selected to have minimum insertion losses. Additional insertion loss will be
introduced by low quality or long cable. Large insertion loss reduces both transmit and receive radiation
performance.
A high quality 50  RF connector provides proper PCB-to-RF-cable transition. It is recommended to
strictly follow the layout and cable termination guidelines provided by the connector manufacturer.
If antenna detection functionality is required, select an antenna assembly provided with a proper built-in
diagnostic circuit with a resistor connected to ground: see guidelines in section 2.4.2.
Integrated antennas (e.g. patch-like antennas):
Internal integrated antennas imply physical restriction to the design of the PCB:
Integrated antenna excites RF currents on its counterpoise, typically the PCB ground plane of the device
that becomes part of the antenna: its dimension defines the minimum frequency that can be radiated.
Therefore, the ground plane can be reduced down to a minimum size that should be similar to the
quarter of the wavelength of the minimum frequency that has to be radiated, given that the orientation
of the ground plane relative to the antenna element must be considered.
The isolation between the primary and the secondary antennas has to be as high as possible and the
correlation between the 3D radiation patterns of the two antennas has to be as low as possible. In
general, a separation of at least a quarter wavelength between the two antennas is required to achieve
a good isolation and low pattern correlation.
As numerical example, the physical restriction to the PCB design can be considered as following:
Frequency = 750 MHz  Wavelength = 40 cm  Minimum GND plane size = 10 cm
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Radiation performance depends on the whole PCB and antenna system design, including product
mechanical design and usage. Antennas should be selected with optimal radiating performance in the
operating bands according to the mechanical specifications of the PCB and the whole product.
It is recommended to select a pair of custom antennas designed by an antennas’ manufacturer if the
required ground plane dimensions are very small (e.g. less than 6.5 cm long and 4 cm wide). The
antenna design process should begin at the start of the whole product design process
It is highly recommended to strictly follow the detailed and specific guidelines provided by the antenna
manufacturer regarding correct installation and deployment of the antenna system, including PCB layout
and matching circuitry
Further to the custom PCB and product restrictions, antennas may require tuning to obtain the required
performance for compliance with all the applicable required certification schemes. It is recommended to
consult the antenna manufacturer for the design-in guidelines for antenna matching relative to the
custom application
In both of cases, selecting external or internal antennas, these recommendations should be observed:

Select antennas providing optimal return loss (or V.S.W.R.) figure over all the operating frequencies.

Select antennas providing optimal efficiency figure over all the operating frequencies.

Select antennas providing similar efficiency for both the primary (ANT1) and the secondary (ANT2) antenna.

Select antennas providing appropriate gain figure (i.e. combined antenna directivity and efficiency figure) so
that the electromagnetic field radiation intensity do not exceed the regulatory limits specified in some
countries (e.g. by FCC in the United States, as reported in the section 4.2.2).

Select antennas capable to provide low Envelope Correlation Coefficient between the primary (ANT1) and
the secondary (ANT2) antenna: the 3D antenna radiation patterns should have lobes in different directions.
2.4.1.2
Guidelines for antenna RF interface design
Guidelines for ANT1 / ANT2 pins RF connection design
Proper transition between ANT1 / ANT2 pads and the application board PCB must be provided, implementing
the following design-in guidelines for the layout of the application PCB close to the ANT1 / ANT2 pads:

On a multilayer board, the whole layer stack below the RF connection should be free of digital lines

Increase GND keep-out (i.e. clearance, a void area) around the ANT1 / ANT2 pads, on the top layer of the
application PCB, to at least 250 µm up to adjacent pads metal definition and up to 400 µm on the area
below the module, to reduce parasitic capacitance to ground, as described in the left picture in Figure 39

Add GND keep-out (i.e. clearance, a void area) on the buried metal layer below the ANT1 / ANT2 pads if
the top-layer to buried layer dielectric thickness is below 200 µm, to reduce parasitic capacitance to ground,
as described in the right picture in Figure 39
GND clearance
on top layer
around ANT1 pad
GND clearance
on very close buried layer
below ANT1 pad
GND clearance
on top layer
around ANT2 pad
GND clearance
on very close buried layer
below ANT2 pad
Min.
250 µm
Min.
250 µm
GND
ANT1
Min. 400 µm
GND
ANT2
Min. 400 µm
Figure 39: GND keep-out area on top layer around ANT1 / ANT2 pads and on very close buried layer below ANT1 / ANT2 pads
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Guidelines for RF transmission line design
Any RF transmission line, such as the ones from the ANT1 and ANT2 pads up to the related antenna connector
or up to the related internal antenna pad, must be designed so that the characteristic impedance is as close as
possible to 50 .
RF transmission lines can be designed as a micro strip (consists of a conducting strip separated from a ground
plane by a dielectric material) or a strip line (consists of a flat strip of metal which is sandwiched between two
parallel ground planes within a dielectric material). The micro strip, implemented as a coplanar waveguide, is the
most common configuration for printed circuit board.
Figure 40 and Figure 41 provide two examples of proper 50  coplanar waveguide designs. The first example of
RF transmission line can be implemented in case of 4-layer PCB stack-up herein described, and the second
example of RF transmission line can be implemented in case of 2-layer PCB stack-up herein described.
500 um 380 um 500 um
L1 Copper
35 um
FR-4 dielectric
270 um
L2 Copper
35 um
FR-4 dielectric
760 um
L3 Copper
35 um
FR-4 dielectric
270 um
L4 Copper
35 um
Figure 40: Example of 50  coplanar waveguide transmission line design for the described 4-layer board layup
400 um 1200 um 400 um
L1 Copper
35 um
FR-4 dielectric
1510 um
L2 Copper
35 um
Figure 41: Example of 50  coplanar waveguide transmission line design for the described 2-layer board layup
If the two examples do not match the application PCB layup, the 50  characteristic impedance calculation can
be made using the HFSS commercial finite element method solver for electromagnetic structures from Ansys
Corporation, or using freeware tools like AppCAD from Agilent (www.agilent.com) or TXLine from Applied
Wave Research (www.mwoffice.com), taking care of the approximation formulas used by the tools for the
impedance computation.
To achieve a 50  characteristic impedance, the width of the transmission line must be chosen depending on:

the thickness of the transmission line itself (e.g. 35 µm in the example of Figure 40 and Figure 41)

the thickness of the dielectric material between the top layer (where the transmission line is routed) and the
inner closer layer implementing the ground plane (e.g. 270 µm in Figure 40, 1510 µm in Figure 41)
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
the dielectric constant of the dielectric material (e.g. dielectric constant of the FR-4 dielectric material in
Figure 40 and Figure 41)

the gap from the transmission line to the adjacent ground plane on the same layer of the transmission line
(e.g. 500 µm in Figure 40, 400 µm in Figure 41)
If the distance between the transmission line and the adjacent GND area (on the same layer) does not exceed 5
times the track width of the micro strip, use the “Coplanar Waveguide” model for the 50  calculation.
Additionally to the 50  impedance, the following guidelines are recommended for the transmission line design:

Minimize the transmission line length: the insertion loss should be minimized as much as possible, in the
order of a few tenths of a dB.

Add GND keep-out (i.e. clearance, a void area) on buried metal layers below any pad of component present
on the RF transmission line, if top-layer to buried layer dielectric thickness is below 200 µm, to reduce
parasitic capacitance to ground.

The transmission line width and spacing to GND must be uniform and routed as smoothly as possible: avoid
abrupt changes of width and spacing to GND.

Add GND vias around transmission line, as described in Figure 42.

Ensure solid metal connection of the adjacent metal layer on the PCB stack-up to main ground layer,
providing enough on the adjacent metal layer, as described in Figure 42.

Route RF transmission line far from any noise source (as switching supplies and digital lines) and from any
sensitive circuit (as analog audio lines).

Avoid stubs on the transmission line.

Avoid signal routing in parallel to transmission line or crossing the transmission line on buried metal layer.

Do not route microstrip line below discrete component or other mechanics placed on top layer.
An example of proper RF circuit design is reported in Figure 42. In this case, the ANT1 and ANT2 pins are
directly connected to SMA connectors by means of proper 50  transmission lines, designed with proper layout.
LARA
SMA
SMA
Figure 42: Example of circuit and layout for antenna RF circuits on application board
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Guidelines for RF termination design
RF terminations must provide a characteristic impedance of 50  as well as the RF transmission lines up to the RF
terminations themselves, to match the characteristic impedance of the ANT1 / ANT2 ports of the modules.
However, real antennas do not have perfect 50  load on all the supported frequency bands. Therefore, to
reduce as much as possible performance degradation due to antennas mismatch, RF terminations must provide
optimal return loss (or V.S.W.R.) figure over all the operating frequencies, as summarized in Table 7 and Table 8.
If external antennas are used, the antenna connectors represent the RF termination on the PCB:

Use suitable 50  connectors providing proper PCB-to-RF-cable transition.

Strictly follow the connector manufacturer’s recommended layout, for example:

SMA Pin-Through-Hole connectors require GND keep-out (i.e. clearance, a void area) on all the layers
around the central pin up to annular pads of the four GND posts, as shown in Figure 42.
U.FL surface mounted connectors require no conductive traces (i.e. clearance, a void area) in the area
below the connector between the GND land pads.
Cut out the GND layer under RF connectors and close to buried vias, to remove stray capacitance and thus
keep the RF line 50 , e.g. the active pad of UFL connectors needs to have a GND keep-out (i.e. clearance, a
void area) at least on first inner layer to reduce parasitic capacitance to ground.
If integrated antennas are used, the RF terminations are represented by the integrated antennas themselves. The
following guidelines should be followed:

Use antennas designed by an antenna manufacturer, providing the best possible return loss (or V.S.W.R.).

Provide a ground plane large enough according to the relative integrated antenna requirements. The ground
plane of the application PCB can be reduced down to a minimum size that must be similar to one quarter of
wavelength of the minimum frequency that has to be radiated. As numerical example,
Frequency = 750 MHz  Wavelength = 40 cm  Minimum GND plane size = 10 cm

It is highly recommended to strictly follow the detailed and specific guidelines provided by the antenna
manufacturer regarding correct installation and deployment of the antenna system, including PCB layout
and matching circuitry.

Further to the custom PCB and product restrictions, antennas may require a tuning to comply with all the
applicable required certification schemes. It is recommended to consult the antenna manufacturer for the
design-in guidelines for the antenna matching relative to the custom application.
Additionally, these recommendations regarding the antenna system placement must be followed:

Do not place antennas within closed metal case.

Do not place the antennas in close vicinity to end user since the emitted radiation in human tissue is limited
by regulatory requirements.

Place the antennas far from sensitive analog systems or employ countermeasures to reduce EMC issues.

Take care of interaction between co-located RF systems since the cellular transmitted power may interact or
disturb the performance of companion systems.

Place the two LTE antennas providing low Envelope Correlation Coefficient (ECC) between primary (ANT1)
and secondary (ANT2) antenna: the antenna 3D radiation patterns should have lobes in different directions.
The ECC between primary and secondary antenna needs to be enough low to comply with the radiated
performance requirements specified by related certification schemes, as indicated in Table 9.

Place the two LTE antennas providing enough high isolation (see Table 9) between primary (ANT1) and
secondary (ANT2) antenna. The isolation depends on the distance between antennas (separation of at least
a quarter wavelength required for good isolation), antenna type (using antennas with different polarization
improves isolation), antenna 3D radiation patterns (uncorrelated patterns improve isolation).
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Examples of antennas
Table 31 lists some examples of possible internal on-board surface-mount antennas.
Manufacturer
Part Number
Product Name
Description
Taoglas
PA.710.A
Warrior
Taoglas
PA.711.A
Warrior II
Taoglas
PCS.06.A
Havok
Antenova
SR4L002
Lucida
GSM / WCDMA / LTE SMD Antenna
698..960 MHz, 1710..2170 MHz, 2300..2400 MHz, 2490..2690 MHz
40.0 x 6.0 x 5.0 mm
GSM / WCDMA / LTE SMD Antenna
Pairs with the Taoglas PA.710.A Warrior for LTE MIMO applications
698..960 MHz, 1710..2170 MHz, 2300..2400 MHz, 2490..2690 MHz
40.0 x 6.0 x 5.0 mm
GSM / WCDMA / LTE SMD Antenna
698..960 MHz, 1710..2170 MHz, 2500..2690 MHz
42.0 x 10.0 x 3.0 mm
GSM / WCDMA / LTE SMD Antenna
698..960 MHz, 1710..2170 MHz, 2300..2400 MHz, 2490..2690 MHz
35.0 x 8.5 x 3.2 mm
Table 31: Examples of internal surface-mount antennas
Table 32 lists some examples of possible internal off-board PCB-type antennas with cable and connector.
Manufacturer
Part Number
Taoglas
FXUB63.07.0150C
Product Name
Taoglas
FXUB66.07.0150C
Taoglas
FXUB70.A.07.C.001
Ethertronics
5001537
Prestta
EAD
FSQS35241-UF-10
SQ7
Maximus
Description
GSM / WCDMA / LTE PCB Antenna with cable and U.FL
698..960 MHz, 1575.42 MHz, 1710..2170 MHz, 2400..2690 MHz
96.0 x 21.0 mm
GSM / WCDMA / LTE PCB Antenna with cable and U.FL
698..960 MHz, 1390..1435 MHz, 1575.42 MHz, 1710..2170 MHz,
2400..2700 MHz, 3400..3600 MHz, 4800..6000 MHz
120.2 x 50.4 mm
GSM / WCDMA / LTE PCB MIMO Antenna with cables and U.FL
698..960 MHz, 1575.42 MHz, 1710..2170 MHz, 2400..2690 MHz
182.2 x 21.2 mm
GSM / WCDMA / LTE PCB Antenna with cable
704..960 MHz, 1710..2170 MHz, 2300..2400 MHz, 2500..2690 MHz
80.0 x 18.0 mm
GSM / WCDMA / LTE PCB Antenna with cable and U.FL
690..960 MHz, 1710..2170 MHz, 2500..2700 MHz
110.0 x 21.0 mm
Table 32: Examples of internal antennas with cable and connector
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Table 33 lists some examples of possible external antennas.
Manufacturer
Part Number
Product Name
Description
Taoglas
GSA.8827.A.101111
Phoenix
Taoglas
TG.30.8112
Taoglas
MA241.BI.001
GSM / WCDMA / LTE adhesive-mount antenna with cable and SMA(M)
698..960 MHz, 1575.42 MHz, 1710..2170 MHz, 2490..2690 MHz
105 x 30 x 7.7 mm
GSM / WCDMA / LTE swivel dipole antenna with SMA(M)
698..960 MHz, 1575.42 MHz, 1710..2170 MHz, 2400..2700 MHz
148.6 x 49 x 10 mm
GSM / WCDMA / LTE MIMO 2in1 adhesive-mount combination antenna
waterproof IP67 rated with cable and SMA(M)
698..960 MHz, 1710..2170 MHz, 2400..2700 MHz
205.8 x 58 x 12.4 mm
Laird Tech.
TRA6927M3PW-001
Laird Tech.
CMS69273
Laird Tech.
OC69271-FNM
Laird Tech.
CMD69273-30NM
Pulse Electronics
WA700/2700SMA
Genesis
GSM / WCDMA / LTE screw-mount antenna with N-type(F)
698..960 MHz, 1710..2170 MHz, 2300..2700 MHz
83.8 x Ø 36.5 mm
GSM / WCDMA / LTE ceiling-mount antenna with cable and N-type(F)
698..960 MHz, 1575.42 MHz, 1710..2700 MHz
86 x Ø 199 mm
GSM / WCDMA / LTE pole-mount antenna with N-type(M)
698..960 MHz, 1710..2690 MHz
248 x Ø 24.5 mm
GSM / WCDMA / LTE ceiling-mount MIMO antenna with cables & N-type(M)
698..960 MHz, 1710..2700 MHz
43.5 x Ø 218.7 mm
GSM / WCDMA / LTE clip-mount MIMO antenna with cables and SMA(M)
698..960 MHz,1710..2700 MHz
149 x 127 x 5.1 mm
Table 33: Examples of external antennas
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2.4.2 Antenna detection interface (ANT_DET)
2.4.2.1
Guidelines for ANT_DET circuit design
Figure 43 and Table 34 describe the recommended schematic / components for the antennas detection circuit
that must be provided on the application board and for the diagnostic circuit that must be provided on the
antennas’ assembly to achieve primary and secondary antenna detection functionality.
LARA-R2 series
ANT2 62
Z0 = 50 ohm
C3
J2
L2
ANT1 56
Z0 = 50 ohm
J1
L4
Radiating
Element
Diagnostic
Circuit
R3
C4
Antenna Cable
L3
L1
ANT_DET 59
C5
Antenna Cable
Z0 = 50 ohm
Z0 = 50 ohm
C2
Radiating
Element
Z0 = 50 ohm
Z0 = 50 ohm
Diagnostic
Circuit
Secondary Antenna Assembly
R2
R1
C1
D1
Application Board
Primary Antenna Assembly
Figure 43: Suggested schematic for antenna detection circuit on application board and diagnostic circuit on antennas assembly
Reference
Description
Part Number - Manufacturer
C1
27 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM1555C1H270J - Murata
C2, C3
D1
33 pF Capacitor Ceramic C0G 0402 5% 50 V
Very Low Capacitance ESD Protection
GRM1555C1H330J - Murata
PESD0402-140 - Tyco Electronics
L1, L2
R1
68 nH Multilayer Inductor 0402 (SRF ~1 GHz)
LQG15HS68NJ02 - Murata
RK73H1ETTP1002F - KOA Speer
J1, J2
SMA Connector 50  Through Hole Jack
22 pF Capacitor Ceramic C0G 0402 5% 25 V
SMA6251A1-3GT50G-50 - Amphenol
C4, C5
L3, L4
68 nH Multilayer Inductor 0402 (SRF ~1 GHz)
LQG15HS68NJ02 - Murata
R2, R3
15 k Resistor for Diagnostic
Various Manufacturers
10 k Resistor 0402 1% 0.063 W
GRM1555C1H220J - Murata
Table 34: Suggested components for antenna detection circuit on application board and diagnostic circuit on antennas assembly
The antenna detection circuit and diagnostic circuit suggested in Figure 43 and Table 34 are explained here:

When antenna detection is forced by AT+UANTR command, ANT_DET generates a DC current measuring
the resistance (R2 // R3) from antenna connectors (J1, J2) provided on the application board to GND.

DC blocking capacitors are needed at the ANT1 / ANT2 pins (C2, C3) and at the antenna radiating element
(C4, C5) to decouple the DC current generated by the ANT_DET pin.

Choke inductors with a Self Resonance Frequency (SRF) in the range of 1 GHz are needed in series at the
ANT_DET pin (L1, L2) and in series at the diagnostic resistor (L3, L4), to avoid a reduction of the RF
performance of the system, improving the RF isolation of the load resistor.

Additional components (R1, C1 and D1 in Figure 43) are needed at the ANT_DET pin as ESD protection

The ANT1 / ANT2 pins must be connected to the antenna connector by means of a transmission line with
nominal characteristics impedance as close as possible to 50 .
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The DC impedance at RF port for some antennas may be a DC open (e.g. linear monopole) or a DC short to
reference GND (e.g. PIFA antenna). For those antennas, without the diagnostic circuit of Figure 43, the measured
DC resistance is always at the limits of the measurement range (respectively open or short), and there is no
means to distinguish between a defect on antenna path with similar characteristics (respectively: removal of
linear antenna or RF cable shorted to GND for PIFA antenna).
Furthermore, any other DC signal injected to the RF connection from ANT connector to radiating element will
alter the measurement and produce invalid results for antenna detection.
It is recommended to use an antenna with a built-in diagnostic resistor in the range from 5 k to 30 k
to assure good antenna detection functionality and avoid a reduction of module RF performance. The
choke inductor should exhibit a parallel Self Resonance Frequency (SRF) in the range of 1 GHz to improve
the RF isolation of load resistor.
For example:
Consider an antenna with built-in DC load resistor of 15 k. Using the +UANTR AT command, the module
reports the resistance value evaluated from the antenna connector provided on the application board to GND:

Reported values close to the used diagnostic resistor nominal value (i.e. values from 13 k to 17 k if a
15 k diagnostic resistor is used) indicate that the antenna is properly connected.

Values close to the measurement range maximum limit (approximately 50 k) or an open-circuit
“over range” report (see u-blox AT Commands Manual [2]) means that that the antenna is not connected or
the RF cable is broken.

Reported values below the measurement range minimum limit (1 k) highlights a short to GND at antenna
or along the RF cable.

Measurement inside the valid measurement range and outside the expected range may indicate an improper
connection, damaged antenna or wrong value of antenna load resistor for diagnostic.

Reported value could differ from the real resistance value of the diagnostic resistor mounted inside the
antenna assembly due to antenna cable length, antenna cable capacity and the used measurement method.
If the primary / secondary antenna detection function is not required by the customer application, the
ANT_DET pin can be left not connected and the ANT1 / ANT2 pins can be directly connected to the
related antenna connector by means of a 50  transmission line as described in Figure 42.
2.4.2.2
Guidelines for ANT_DET layout design
The recommended layout for the primary antenna detection circuit to be provided on the application board to
achieve the primary antenna detection functionality, implementing the recommended schematic described in
Figure 43 and Table 34, is explained here:

The ANT1 / ANT2 pins have to be connected to the antenna connector by means of a 50  transmission
line, implementing the design guidelines described in section 2.4.1 and the recommendations of the SMA
connector manufacturer.

DC blocking capacitor at ANT1 / ANT2 pins (C2, C3) has to be placed in series to the 50  RF line.

The ANT_DET pin has to be connected to the 50  transmission line by means of a sense line.

Choke inductors in series at the ANT_DET pin (L1, L2) have to be placed so that one pad is on the 50 
transmission line and the other pad represents the start of the sense line to the ANT_DET pin.

The additional components (R1, C1 and D1) on the ANT_DET line have to be placed as ESD protection.
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2.5
2.5.1.1
SIM interface
Guidelines for SIM circuit design
Guidelines for SIM cards, SIM connectors and SIM chips selection
The ISO/IEC 7816, the ETSI TS 102 221 and the ETSI TS 102 671 specifications define the physical, electrical and
functional characteristics of Universal Integrated Circuit Cards (UICC) which contains the Subscriber Identification
Module (SIM) integrated circuit that securely stores all the information needed to identify and authenticate
subscribers over the cellular network.
Removable UICC / SIM card contacts mapping is defined by ISO/IEC 7816 and ETSI TS 102 221 as follows:

Contact C1 = VCC (Supply)
 It must be connected to VSIM

Contact C2 = RST (Reset)
 It must be connected to SIM_RST

Contact C3 = CLK (Clock)
 It must be connected to SIM_CLK

Contact C4 = AUX1 (Auxiliary contact)
 It must be left not connected

Contact C5 = GND (Ground)
 It must be connected to GND

Contact C6 = VPP (Programming supply)
 It can be left not connected

Contact C7 = I/O (Data input/output)
 It must be connected to SIM_IO
 Contact C8 = AUX2 (Auxiliary contact)
 It must be left not connected
A removable SIM card can have 6 contacts (C1, C2, C3, C5, C6, C7) or 8 contacts, also including the auxiliary
contacts C4 and C8. Only 6 contacts are required and must be connected to the module SIM interface.
Removable SIM cards are suitable for applications requiring a change of SIM card during the product lifetime.
A SIM card holder can have 6 or 8 positions if a mechanical card presence detector is not provided, or it can
have 6+2 or 8+2 positions if two additional pins relative to the normally-open mechanical switch integrated in
the SIM connector for the mechanical card presence detection are provided. Select a SIM connector providing
6+2 or 8+2 positions if the optional SIM detection feature is required by the custom application, otherwise a
connector without integrated mechanical presence switch can be selected.
Solderable UICC / SIM chip contact mapping (M2M UICC Form Factor) is defined by ETSI TS 102 671 as:

Case Pin 8 = UICC Contact C1 = VCC (Supply)
 It must be connected to VSIM

Case Pin 7 = UICC Contact C2 = RST (Reset)
 It must be connected to SIM_RST

Case Pin 6 = UICC Contact C3 = CLK (Clock)
 It must be connected to SIM_CLK

Case Pin 5 = UICC Contact C4 = AUX1 (Aux.contact)  It must be left not connected

Case Pin 1 = UICC Contact C5 = GND (Ground)
 It must be connected to GND

Case Pin 2 = UICC Contact C6 = VPP (Progr. supply)
 It can be left not connected

Case Pin 3 = UICC Contact C7 = I/O (Data I/O)
 It must be connected to SIM_IO

Case Pin 4 = UICC Contact C8 = AUX2 (Aux. contact)  It must be left not connected
A solderable SIM chip has 8 contacts and can also include the auxiliary contacts C4 and C8 for other uses, but
only 6 contacts are required and must be connected to the module SIM card interface as described above.
Solderable SIM chips are suitable for M2M applications where it is not required to change the SIM once installed.
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Guidelines for single SIM card connection without detection
A removable SIM card placed in a SIM card holder has to be connected to the SIM card interface of LARA-R2
series modules as described in Figure 44, where the optional SIM detection feature is not implemented.
Follow these guidelines connecting the module to a SIM connector without SIM presence detection:

Connect the UICC / SIM contacts C1 (VCC) to the VSIM pin of the module.

Connect the UICC / SIM contact C7 (I/O) to the SIM_IO pin of the module.

Connect the UICC / SIM contact C3 (CLK) to the SIM_CLK pin of the module.

Connect the UICC / SIM contact C2 (RST) to the SIM_RST pin of the module.

Connect the UICC / SIM contact C5 (GND) to ground.

Provide a 100 nF bypass capacitor (e.g. Murata GRM155R71C104K) at the SIM supply line (VSIM), close to
the related pad of the SIM connector, to prevent digital noise.

Provide a bypass capacitor of about 22 pF to 47 pF (e.g. Murata GRM1555C1H470J) on each SIM line
(VSIM, SIM_CLK, SIM_IO, SIM_RST), very close to each related pad of the SIM connector, to prevent RF
coupling especially in case the RF antenna is placed closer than 10 - 30 cm from the SIM card holder.

Provide a low capacitance (i.e. less than 10 pF) ESD protection (e.g. Tyco Electronics PESD0402-140) on each
externally accessible SIM line, close to each related pad of the SIM connector: ESD sensitivity rating of the
SIM interface pins is 1 kV (HBM), so that, according to the EMC/ESD requirements of the custom application,
higher protection level can be required if the lines are externally accessible on the application device.

Limit capacitance and series resistance on each signal of the SIM interface (SIM_CLK, SIM_IO, SIM_RST), to
match the SIM interface specifications requirements (27.7 ns is the maximum allowed rise time on the
SIM_CLK line, 1.0 µs is the maximum allowed rise time on the SIM_IO and SIM_RST lines).
LARA-R2 series
V_INT
TP
SIM CARD
HOLDER
GPIO5 42
VPP (C6)
VSIM 41
VCC (C1)
SIM_IO 39
IO (C7)
SIM_CLK 38
CLK (C3)
SIM_RST 40
RST (C2)
C1
C2
C3 C4
GND (C5)
C5
D1 D2 D3 D4
C C C C
5 6 7 8
C C C C
1 2 3 4
SIM Card
Bottom View
(contacts side)
J1
Figure 44: Application circuit for the connection to a single removable SIM card, with SIM detection not implemented
Reference
Description
Part Number - Manufacturer
C1, C2, C3, C4
47 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM1555C1H470JA01 - Murata
C5
D1, D2, D3, D4
100 nF Capacitor Ceramic X7R 0402 10% 16 V
Very Low Capacitance ESD Protection
GRM155R71C104KA01 - Murata
PESD0402-140 - Tyco Electronics
J1
SIM Card Holder
6 positions, without card presence switch
Various Manufacturers,
C707 10M006 136 2 - Amphenol
Table 35: Example of components for the connection to a single removable SIM card, with SIM detection not implemented
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Guidelines for single SIM chip connection
A solderable SIM chip (M2M UICC Form Factor) has to be connected the SIM card interface of LARA-R2 series
modules as described in Figure 45.
Follow these guidelines connecting the module to a solderable SIM chip without SIM presence detection:

Connect the UICC / SIM contacts C1 (VCC) to the VSIM pin of the module.

Connect the UICC / SIM contact C7 (I/O) to the SIM_IO pin of the module.

Connect the UICC / SIM contact C3 (CLK) to the SIM_CLK pin of the module.

Connect the UICC / SIM contact C2 (RST) to the SIM_RST pin of the module.

Connect the UICC / SIM contact C5 (GND) to ground.

Provide a 100 nF bypass capacitor (e.g. Murata GRM155R71C104K) at the SIM supply line (VSIM) close to
the related pad of the SIM chip, to prevent digital noise.

Provide a bypass capacitor of about 22 pF to 47 pF (e.g. Murata GRM1555C1H470J) on each SIM line
(VSIM, SIM_CLK, SIM_IO, SIM_RST), to prevent RF coupling especially in case the RF antenna is placed
closer than 10 - 30 cm from the SIM card holder.

Limit capacitance and series resistance on each signal of the SIM interface (SIM_CLK, SIM_IO, SIM_RST), to
match the SIM specifications requirements (27.7 ns is the maximum allowed rise time on the SIM_CLK line,
1.0 µs is the maximum allowed rise time on the SIM_IO and SIM_RST lines).
LARA-R2 series
V_INT
TP
SIM CHIP
GPIO5 42
VSIM 41
SIM_IO 39
SIM_CLK 38
SIM_RST 40
C1 C2 C3 C4
C5
VPP (C6)
VCC (C1)
8 C1
C5 1
7 C2
C6 2
6 C3
C7 3
CLK (C3)
5 C4
C8 4
RST (C2)
SIM Chip
Bottom View
(contacts side)
IO (C7)
GND (C5)
U1
Figure 45: Application circuit for the connection to a single solderable SIM chip, with SIM detection not implemented
Reference
Description
Part Number - Manufacturer
C1, C2, C3, C4
47 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM1555C1H470JA01 - Murata
C5
U1
100 nF Capacitor Ceramic X7R 0402 10% 16 V
SIM chip (M2M UICC Form Factor)
GRM155R71C104KA01 - Murata
Various Manufacturers
Table 36: Example of components for the connection to a single solderable SIM chip, with SIM detection not implemented
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Guidelines for single SIM card connection with detection
A removable SIM card placed in a SIM card holder must be connected to the SIM card interface of LARA-R2
series modules as described in Figure 46, where the optional SIM card detection feature is implemented.
Follow these guidelines connecting the module to a SIM connector implementing SIM presence detection:

Connect the UICC / SIM contacts C1 (VCC) to the VSIM pin of the module.

Connect the UICC / SIM contact C7 (I/O) to the SIM_IO pin of the module.

Connect the UICC / SIM contact C3 (CLK) to the SIM_CLK pin of the module.

Connect the UICC / SIM contact C2 (RST) to the SIM_RST pin of the module.

Connect the UICC / SIM contact C5 (GND) to ground.

Connect one pin of the normally-open mechanical switch integrated in the SIM connector (e.g. the SW2 pin
as described in Figure 46) to the GPIO5 input pin of the module.

Connect the other pin of the normally-open mechanical switch integrated in the SIM connector (e.g. the
SW1 pin as described in Figure 46) to the V_INT 1.8 V supply output of the module by means of a strong
(e.g. 1 k) pull-up resistor, as the R1 resistor in Figure 46.

Provide a 100 nF bypass capacitor (e.g. Murata GRM155R71C104K) at the SIM supply line (VSIM), close to
the related pad of the SIM connector, to prevent digital noise.

Provide a bypass capacitor of about 22 pF to 47 pF (e.g. Murata GRM1555C1H470J) on each SIM line
(VSIM, SIM_CLK, SIM_IO, SIM_RST), very close to each related pad of the SIM connector, to prevent RF
coupling especially in case the RF antenna is placed closer than 10 - 30 cm from the SIM card holder.

Provide a low capacitance (i.e. less than 10 pF) ESD protection (e.g. Tyco Electronics PESD0402-140) on each
externally accessible SIM line, close to each related pad of the SIM connector: ESD sensitivity rating of SIM
interface pins is 1 kV (HBM according to JESD22-A114), so that, according to the EMC/ESD requirements of
the custom application, higher protection level can be required if the lines are externally accessible.

Limit capacitance and series resistance on each SIM signal to match the SIM specifications requirements
(27.7 ns = max allowed rise time on SIM_CLK, 1.0 µs = max allowed rise time on SIM_IO and SIM_RST).
SIM CARD
HOLDER
LARA-R2 series
V_INT
TP
R1
GPIO5 42
R2
VSIM 41
SW1
SW2
VPP (C6)
VCC (C1)
SIM_IO 39
IO (C7)
SIM_CLK 38
CLK (C3)
SIM_RST 40
RST (C2)
C1 C2 C3 C4
C5
GND (C5)
D1 D2 D3 D4 D5 D6
C C C C
5 6 7 8
C C C C
1 2 3 4
SIM Card
Bottom View
(contacts side)
J1
Figure 46: Application circuit for the connection to a single removable SIM card, with SIM detection implemented
Reference
Description
Part Number - Manufacturer
C1, C2, C3, C4
47 pF Capacitor Ceramic C0G 0402 5% 50 V
GRM1555C1H470JA01 - Murata
C5
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R71C104KA01 - Murata
D1 – D6
R1
Very Low Capacitance ESD Protection
PESD0402-140 - Tyco Electronics
RC0402JR-071KL - Yageo Phycomp
R2
470 k Resistor 0402 5% 0.1 W
SIM Card Holder
6 + 2 positions, with card presence switch
J1
1 k Resistor 0402 5% 0.1 W
RC0402JR-07470KL- Yageo Phycomp
Various Manufacturers,
CCM03-3013LFT R102 - C&K Components
Table 37: Example of components for the connection to a single removable SIM card, with SIM detection implemented
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Guidelines for dual SIM card / chip connection
Two SIM card / chip can be connected to the SIM interface of LARA-R2 series modules as described in Figure 47.
LARA-R2 series modules do not support the usage of two SIM at the same time, but two SIM can be populated
on the application board, providing a proper switch to connect only the first or only the second SIM at a time to
the SIM interface of the modules, as described in Figure 47.
LARA-R2 series modules support SIM hot insertion / removal on the GPIO5 pin, to enable / disable SIM interface
upon detection of external SIM card physical insertion / removal: if the feature is enabled using the specific AT
commands (see sections 1.8.2 and 1.12, and u-blox AT Commands Manual [2], +UGPIOC, +UDCONF=50
commands), the switch from first SIM to the second SIM can be properly done when a Low logic level is present
on the GPIO5 pin (“SIM not inserted” = SIM interface not enabled), without the necessity of a module re-boot,
so that the SIM interface will be re-enabled by the module to use the second SIM when a high logic level is reapplied on the GPIO5 pin.
In the application circuit example represented in Figure 47, the application processor will drive the SIM switch
using its own GPIO to properly select the SIM that is used by the module. Another GPIO may be used to handle
the SIM hot insertion / removal function of LARA-R2 series modules, which can also be handled by other external
circuits or by the cellular module GPIO according to the application requirements.
The dual SIM connection circuit described in Figure 47 can be implemented for SIM chips as well, providing
proper connection between SIM switch and SIM chip as described in Figure 45.
If it is required to switch between more than 2 SIM, a circuit similar to the one described in Figure 47 can be
implemented: in case of 4 SIM circuit, using proper 4-throw switch instead of the suggested 2-throw switches.
Follow these guidelines connecting the module to two SIM connectors:

Use a proper low on resistance (i.e. few ohms) and low on capacitance (i.e. few pF) 2-throw analog switch
(e.g. Fairchild FSA2567) as SIM switch to ensure high-speed data transfer according to SIM requirements.

Connect the contacts C1 (VCC) of the two UICC / SIM to the VSIM pin of the module by means of a proper
2-throw analog switch (e.g. Fairchild FSA2567).

Connect the contact C7 (I/O) of the two UICC / SIM to the SIM_IO pin of the module by means of a proper
2-throw analog switch (e.g. Fairchild FSA2567).

Connect the contact C3 (CLK) of the two UICC / SIM to the SIM_CLK pin of the module by means of a
proper 2-throw analog switch (e.g. Fairchild FSA2567).

Connect the contact C2 (RST) of the two UICC / SIM to the SIM_RST pin of the module by means of a
proper 2-throw analog switch (e.g. Fairchild FSA2567).

Connect the contact C5 (GND) of the two UICC / SIM to ground.

Provide a 100 nF bypass capacitor (e.g. Murata GRM155R71C104K) at the SIM supply line (VSIM), close to
the related pad of the two SIM connectors, to prevent digital noise.

Provide a bypass capacitor of about 22 pF to 47 pF (e.g. Murata GRM1555C1H470J) on each SIM line
(VSIM, SIM_CLK, SIM_IO, SIM_RST), very close to each related pad of the two SIM connectors, to prevent
RF coupling especially in case the RF antenna is placed closer than 10 - 30 cm from the SIM card holders.

Provide a very low capacitance (i.e. less than 10 pF) ESD protection (e.g. Tyco Electronics PESD0402-140) on
each externally accessible SIM line, close to each related pad of the two SIM connectors, according to the
EMC/ESD requirements of the custom application.

Limit capacitance and series resistance on each SIM signal to match the SIM specifications requirements
(27.7 ns = max allowed rise time on SIM_CLK, 1.0 µs = max allowed rise time on SIM_IO and SIM_RST).
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FIRST
SIM CARD
LARA-R2 series
VSIM 41
3V8
VPP (C6)
4PDT
C11
Analog
Switch
VCC
1VSIM
VSIM
2VSIM
VCC (C1)
DAT
1DAT
2DAT
SIM_CLK 38
CLK
1CLK
2CLK
SIM_RST 40
RST
1RST
2RST
SIM_IO 39
IO (C7)
CLK (C3)
RST (C2)
C1 C2 C3 C4
C5
GND (C5)
D1 D2 D3 D4
J1
SECOND
SIM CARD
VPP (C6)
SEL
GND
VCC (C1)
U1
IO (C7)
CLK (C3)
Application
Processor
RST (C2)
GPIO
C6 C7 C8 C9 C10
R1
GND (C5)
D5 D6 D7 D8
J2
Figure 47: Application circuit for the connection to two removable SIM cards, with SIM detection not implemented
Reference
Description
Part Number - Manufacturer
C1 – C4, C6 – C9
C5, C10, C11
33 pF Capacitor Ceramic C0G 0402 5% 25 V
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM1555C1H330JZ01 - Murata
GRM155R71C104KA01 - Murata
D1 – D8
R1
Very Low Capacitance ESD Protection
47 kΩ Resistor 0402 5% 0.1 W
PESD0402-140 - Tyco Electronics
RC0402JR-0747KL- Yageo Phycomp
J1, J2
SIM Card Holder
6 positions, without card presence switch
4PDT Analog Switch,
with Low On-Capacitance and Low On-Resistance
Various Manufacturers,
C707 10M006 136 2 - Amphenol
FSA2567 - Fairchild Semiconductor
U1
Table 38: Example of components for the connection to two removable SIM cards, with SIM detection not implemented
2.5.1.2
Guidelines for SIM layout design
The layout of the SIM card interface lines (VSIM, SIM_CLK, SIM_IO, SIM_RST) may be critical if the SIM card is
placed far away from the LARA-R2 series modules or in close proximity to the RF antenna: these two cases
should be avoided or at least mitigated as described below.
In the first case, the long connection can cause the radiation of some harmonics of the digital data frequency as
any other digital interface: keep the traces short and avoid coupling with RF line or sensitive analog inputs.
In the second case, the same harmonics can be picked up and create self-interference that can reduce the
sensitivity of cellular receiver channels whose carrier frequency is coincidental with harmonic frequencies: placing
the RF bypass capacitors suggested in Figure 46 near the SIM connector will mitigate the problem.
In addition, since the SIM card is typically accessed by the end user, it can be subjected to ESD discharges: add
adequate ESD protection as suggested in Figure 46 to protect module SIM pins near the SIM connector.
Limit capacitance and series resistance on each SIM signal to match the SIM specifications: the connections
should always be kept as short as possible.
Avoid coupling with any sensitive analog circuit, since the SIM signals can cause the radiation of some harmonics
of the digital data frequency.
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2.6
Data communication interfaces
2.6.1 UART interface
2.6.1.1
Guidelines for UART circuit design
Providing the full RS-232 functionality (using the complete V.24 link)
If RS-232 compatible signal levels are needed, two different external voltage translators can be used to provide
full RS-232 (9 lines) functionality: e.g. using the Texas Instruments SN74AVC8T245PW for the translation from
1.8 V to 3.3 V, and the Maxim MAX3237E for the translation from 3.3 V to RS-232 compatible signal level.
If a 1.8 V Application Processor (DTE) is used and complete RS-232 functionality is required, then the complete
1.8 V UART interface of the module (DCE) should be connected to a 1.8 V DTE, as described in Figure 48.
Application Processor
(1.8V DTE)
LARA-R2 series
(1.8V DCE)
TxD
RxD
0Ω
TP
0Ω
TP
12 TXD
13 RXD
RTS
10 RTS
CTS
0Ω
DTR
11 CTS
TP
DSR
RI
0Ω
DCD
TP
DTR
DSR
RI
DCD
GND
GND
Figure 48: UART interface application circuit with complete V.24 link in DTE/DCE serial communication (1.8 V DTE)
If a 3.0 V Application Processor (DTE) is used, then it is recommended to connect the 1.8 V UART interface of the
module (DCE) by means of appropriate unidirectional voltage translators using the module V_INT output as
1.8 V supply for the voltage translators on the module side, as described in Figure 49.
Application Processor
(3.0V DTE)
Unidirectional
Voltage Translator
3V0
VCC
C1
VCCA
DIR1
DIR3
LARA-R2 series
(1.8V DCE)
1V8
TP
VCCB
C2
0Ω
TP
0Ω
TP
V_INT
TxD
A1
B1
RxD
A2
B2
RTS
A3
B3
10 RTS
CTS
A4
B4
11 CTS
DIR2
DIR4
C3
VCCA
13 RXD
OE
GND
U1
Unidirectional
Voltage Translator
3V0
12 TXD
VCCB
DIR1
1V8
C4
0Ω
TP
DTR
A1
B1
DTR
DSR
A2
B2
DSR
RI
A3
B3
RI
DCD
A4
B4
DCD
GND
DIR2
DIR3
DIR4
0Ω
OE
GND
TP
GND
U2
Figure 49: UART interface application circuit with complete V.24 link in DTE/DCE serial communication (3.0 V DTE)
Reference
Description
Part Number - Manufacturer
C1, C2, C3, C4
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R61A104KA01 - Murata
U1, U2
Unidirectional Voltage Translator
SN74AVC4T77416 - Texas Instruments
Table 39: Component for UART application circuit with complete V.24 link in DTE/DCE serial communication (3.0 V DTE)
16
Voltage translator providing partial power down feature so that the DTE 3.0 V supply can be also ramped up before V_INT 1.8 V supply
UBX-16010573 - R02
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Providing the TXD, RXD, RTS, CTS and DTR lines only (not using the complete V.24 link)
If the functionality of the DSR, DCD and RI lines is not required, or the lines are not available:

Leave DSR, DCD and RI lines of the module floating, with a test-point on DCD
If RS-232 compatible signal levels are needed, two different external voltage translators (e.g. Maxim MAX3237E
and Texas Instruments SN74AVC4T774) can be used. The Texas Instruments chips provide the translation from
1.8 V to 3.3 V, while the Maxim chip provides the translation from 3.3 V to RS-232 compatible signal level.
Figure 50 describes the circuit that should be implemented as if a 1.8 V Application Processor (DTE) is used,
given that the DTE will behave properly regardless DSR input setting.
Application Processor
(1.8V DTE)
LARA-R2 series
(1.8V DCE)
TxD
RxD
RTS
CTS
0Ω
TP
0Ω
0Ω
TP
TP
0Ω
TP
DTR
15 TXD
16 RXD
13 RTS
14 CTS
12 DTR
DSR
RI
DSR
10 RI
DCD
11 DCD
GND
GND
Figure 50: UART interface application circuit with partial V.24 link (6-wire) in the DTE/DCE serial communication (1.8 V DTE)
If a 3.0 V Application Processor (DTE) is used, then it is recommended to connect the 1.8 V UART interface of the
module (DCE) by means of appropriate unidirectional voltage translators using the module V_INT output as
1.8 V supply for the voltage translators on the module side, as described in Figure 51, given that the DTE will
behave properly regardless DSR input setting.
Application Processor
(3.0V DTE)
VCC
Unidirectional
Voltage Translator
3V0
VCCA
DIR1
DIR3
C1
V_INT
15
TXD
16
RXD
13
RTS
14
CTS
B1
B2
12
DTR
DSR
OE
GND
10
RI
11
DCD
VCCB
TxD
A1
B1
RxD
A2
B2
RTS
A3
B3
CTS
A4
B4
DIR2
DIR4
LARA-R2 series
(1.8V DCE)
1V8
C2
0Ω
TP
0Ω
TP
0Ω
TP
0Ω
TP
OE
GND
U1
Unidirectional
Voltage Translator
3V0
C3
DTR
VCCA
DIR1
A1
A2
DSR
RI
DCD
VCCB
DIR2
1V8
C4
U2
GND
GND
Figure 51: UART interface application circuit with partial V.24 link (6-wire) in DTE/DCE serial communication (3.0 V DTE)
Reference
Description
Part Number - Manufacturer
C1, C2, C3, C4
U1
100 nF Capacitor Ceramic X7R 0402 10% 16 V
Unidirectional Voltage Translator
GRM155R61A104KA01 - Murata
SN74AVC4T77417 - Texas Instruments
U2
Unidirectional Voltage Translator
SN74AVC2T24517 - Texas Instruments
Table 40: Component for UART application circuit with partial V.24 link (6-wire) in DTE/DCE serial communication (3.0 V DTE)
17
Voltage translator providing partial power down feature so that the DTE 3.0 V supply can be also ramped up before V_INT 1.8 V supply
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Providing the TXD, RXD, RTS and CTS lines only (not using the complete V.24 link)

Connect the module DTR input to GND using a 0  series resistor, since it may be useful to set DTR active if
not specifically handled (see u-blox AT Commands Manual [2], &D, S0, +CSGT, +CNMI AT commands)

Leave DSR, DCD and RI lines of the module floating, with a test-point on DCD
If RS-232 compatible signal levels are needed, the Maxim MAX13234E voltage level translator can be used. This
chip translates voltage levels from 1.8 V (module side) to the RS-232 standard.
If a 1.8 V Application Processor is used, the circuit should be implemented as described in Figure 52.
Application Processor
(1.8V DTE)
LARA-R2 series
(1.8V DCE)
TxD
RxD
0Ω
TP
0Ω
TP
12 TXD
13
RXD
RTS
10
RTS
CTS
11 CTS
0Ω
DTR
TP
DSR
RI
TP
DCD
DTR
DSR
RI
DCD
GND
GND
Figure 52: UART interface application circuit with partial V.24 link (5-wire) in the DTE/DCE serial communication (1.8 V DTE)
If a 3.0 V Application Processor (DTE) is used, then it is recommended to connect the 1.8 V UART interface of the
module (DCE) by means of appropriate unidirectional voltage translators using the module V_INT output as
1.8 V supply for the voltage translators on the module side, as described in Figure 53.
Application Processor
(3.0V DTE)
Unidirectional
Voltage Translator
3V0
VCC
C1
VCCA
DIR1
DIR3
VCCB
LARA-R2 series
(1.8V DCE)
1V8
TP
C2
0Ω
TP
0Ω
TP
V_INT
TxD
A1
B1
RxD
A2
B2
RTS
A3
B3
10 RTS
CTS
A4
B4
11 CTS
DIR2
DIR4
U1
DTR
12 TXD
13 RXD
OE
GND
0Ω
TP
DTR
DSR
DSR
RI
RI
DCD
DCD
GND
TP
GND
Figure 53: UART interface application circuit with partial V.24 link (5-wire) in DTE/DCE serial communication (3.0 V DTE)
Reference
Description
Part Number - Manufacturer
C1, C2
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R61A104KA01 - Murata
U1
Unidirectional Voltage Translator
SN74AVC4T77418 - Texas Instruments
Table 41: Component for UART application circuit with partial V.24 link (5-wire) in DTE/DCE serial communication (3.0 V DTE)
18
Voltage translator providing partial power down feature so that the DTE 3.0 V supply can be also ramped up before V_INT 1.8 V supply
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Providing the TXD and RXD lines only (not using the complete V24 link)
If the functionality of the CTS, RTS, DSR, DCD, RI and DTR lines is not required in the application, or the lines
are not available:

Connect the module RTS input line to GND or to the CTS output line of the module: since the module
requires RTS active (low electrical level) if HW flow-control is enabled (AT&K3, which is the default setting).

Connect the module DTR input to GND using a 0  series resistor, since it may be useful to set DTR active if
not specifically handled (see u-blox AT Commands Manual [2], &D, S0, +CSGT, +CNMI AT commands)

Leave DSR, DCD and RI lines of the module floating, with a test-point on DCD
If RS-232 compatible signal levels are needed, the Maxim MAX13234E voltage level translator can be used. This
chip translates voltage levels from 1.8 V (module side) to the RS-232 standard.
If a 1.8 V Application Processor (DTE) is used, the circuit that should be implemented as described in Figure 54:
Application Processor
(1.8V DTE)
LARA-R2 series
(1.8V DCE)
TxD
0Ω
TP
0Ω
TP
12
TXD
13
RXD
RTS
10
RTS
CTS
11
CTS
DTR
DSR
RI
DCD
RxD
0Ω
DTR
TP
DSR
RI
TP
DCD
GND
GND
Figure 54: UART interface application circuit with partial V.24 link (3-wire) in the DTE/DCE serial communication (1.8 V DTE)
If a 3.0 V Application Processor (DTE) is used, then it is recommended to connect the 1.8 V UART interface of the
module (DCE) by means of appropriate unidirectional voltage translators using the module V_INT output as
1.8 V supply for the voltage translators on the module side, as described in Figure 55.
Application Processor
(3.0V DTE)
Unidirectional
Voltage Translator
3V0
VCC
C1
VCCA
1V8
TP
VCCB
V_INT
12
TXD
13
RXD
10
RTS
11
CTS
DTR
DSR
RI
DCD
C2
DIR1
TxD
A1
B1
RxD
A2
B2
DIR2
LARA-R2 series
(1.8V DCE)
0Ω
TP
0Ω
TP
0Ω
TP
OE
GND
U1
RTS
CTS
DTR
DSR
RI
DCD
GND
TP
GND
Figure 55: UART interface application circuit with partial V.24 link (3-wire) in DTE/DCE serial communication (3.0 V DTE)
Reference
Description
Part Number - Manufacturer
C1, C2
U1
100 nF Capacitor Ceramic X7R 0402 10% 16 V
Unidirectional Voltage Translator
GRM155R61A104KA01 - Murata
SN74AVC2T24519 - Texas Instruments
Table 42: Component for UART application circuit with partial V.24 link (3-wire) in DTE/DCE serial communication (3.0 V DTE)
19
Voltage translator providing partial power down feature so that the DTE 3.0 V supply can be also ramped up before V_INT 1.8 V supply
UBX-16010573 - R02
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Additional considerations
If a 3.0 V Application Processor (DTE) is used, the voltage scaling from any 3.0 V output of the DTE to the
apposite 1.8 V input of the module (DCE) can be implemented, as an alternative low-cost solution, by means of
an appropriate voltage divider. Consider the value of the pull-up integrated at the input of the module (DCE) for
the correct selection of the voltage divider resistance values and mind that any DTE signal connected to the
module has to be tri-stated or set low when the module is in power-down mode and during the module poweron sequence (at least until the activation of the V_INT supply output of the module), to avoid latch-up of circuits
and allow a proper boot of the module (see the remark below).
Moreover, the voltage scaling from any 1.8 V output of the cellular module (DCE) to the apposite 3.0 V input of
the Application Processor (DTE) can be implemented by means of an appropriate low-cost non-inverting buffer
with open drain output. The non-inverting buffer should be supplied by the V_INT supply output of the cellular
module. Consider the value of the pull-up integrated at each input of the DTE (if any) and the baud rate required
by the application for the appropriate selection of the resistance value for the external pull-up biased by the
application processor supply rail.
If power saving is enabled the application circuit with the TXD and RXD lines only is not recommended.
During command mode the DTE must send to the module a wake-up character or a dummy “AT” before
each command line (see section 1.9.1.4 for the complete description), but during data mode the wake-up
character or the dummy “AT” would affect the data communication.
Do not apply voltage to any UART interface pin before the switch-on of the UART supply source (V_INT),
to avoid latch-up of circuits and allow a proper boot of the module. If the external signals connected to
the cellular module cannot be tri-stated or set low, insert a multi channel digital switch (e.g. TI
SN74CB3Q16244, TS5A3159, or TS5A63157) between the two-circuit connections and set to high
impedance before V_INT switch-on.
ESD sensitivity rating of UART interface pins is 1 kV (Human Body Model according to JESD22-A114).
Higher protection level could be required if the lines are externally accessible and it can be achieved by
mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) close to accessible points.
If the UART interface pins are not used, they can be left unconnected on the application board, but it is
recommended providing accessible test points directly connected to the TXD, RXD, DTR and DCD pins
for diagnostic purpose, in particular providing a 0  series jumper on each line to detach each UART pin
of the module from the DTE application processor.
2.6.1.2
Guidelines for UART layout design
The UART serial interface requires the same consideration regarding electro-magnetic interference as any other
digital interface. Keep the traces short and avoid coupling with RF line or sensitive analog inputs, since the
signals can cause the radiation of some harmonics of the digital data frequency.
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2.6.2 USB interface
2.6.2.1
Guidelines for USB circuit design
The USB_D+ and USB_D- lines carry the USB serial data and signaling. The lines are used in single ended mode
for full speed signaling handshake, as well as in differential mode for high speed signaling and data transfer.
USB pull-up or pull-down resistors and external series resistors on USB_D+ and USB_D- lines as required by the
USB 2.0 specification [9] are part of the module USB pins driver and do not need to be externally provided.
The USB interface of the module is enabled only if a valid voltage is detected by the VUSB_DET input (see the
LARA-R2 series Data Sheet [1]). Neither the USB interface, nor the whole module is supplied by the VUSB_DET
input: the VUSB_DET senses the USB supply voltage and absorbs few microamperes.
Routing the USB pins to a connector, they will be externally accessible on the application device. According to
EMC/ESD requirements of the application, an additional ESD protection device with very low capacitance should
be provided close to accessible point on the line connected to this pin, as described in Figure 56 and Table 43.
The USB interface pins ESD sensitivity rating is 1 kV (Human Body Model according to JESD22-A114F).
Higher protection level could be required if the lines are externally accessible and it can be achieved by
mounting a very low capacitance (i.e. less or equal to 1 pF) ESD protection (e.g. Tyco Electronics
PESD0402-140 ESD protection device) on the lines connected to these pins, close to accessible points.
The USB pins of the modules can be directly connected to the USB host application processor without additional
ESD protections if they are not externally accessible or according to EMC/ESD requirements.
USB DEVICE
CONNECTOR
LARA-R2 series
VBUS
17 VUSB_DET
USB HOST
PROCESSOR
LARA-R2 series
17 VUSB_DET
VBUS
D+
29 USB_D+
D+
29 USB_D+
D-
28 USB_D-
D-
28 USB_D-
GND
D1 D2
D3
C1
GND
GND
C1
GND
Figure 56: USB Interface application circuits
Reference
Description
Part Number - Manufacturer
C1
100 nF Capacitor Ceramic X7R 0402 10% 16 V
GRM155R61A104KA01 - Murata
D1, D2, D3
Very Low Capacitance ESD Protection
PESD0402-140 - Tyco Electronics
Table 43: Component for USB application circuits
If the USB interface pins are not used, they can be left unconnected on the application board, but it is
recommended providing accessible test points directly connected to VUSB_DET, USB_D+, USB_D- pins.
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2.6.2.2 Guidelines for USB layout design
The USB_D+ / USB_D- lines require accurate layout design to achieve reliable signaling at the high speed data
rate (up to 480 Mb/s) supported by the USB serial interface.
The characteristic impedance of the USB_D+ / USB_D- lines is specified by the Universal Serial Bus Revision 2.0
specification [9]. The most important parameter is the differential characteristic impedance applicable for the
odd-mode electromagnetic field, which should be as close as possible to 90  differential. Signal integrity may
be degraded if PCB layout is not optimal, especially when the USB signaling lines are very long.
Use the following general routing guidelines to minimize signal quality problems:

Route USB_D+ / USB_D- lines as a differential pair.

Route USB_D+ / USB_D- lines as short as possible.

Ensure the differential characteristic impedance (Z 0) is as close as possible to 90 .

Ensure the common mode characteristic impedance (ZCM) is as close as possible to 30 .

Consider design rules for USB_D+ / USB_D- similar to RF transmission lines, being them coupled differential
micro-strip or buried stripline: avoid any stubs, abrupt change of layout, and route on clear PCB area.

Avoid coupling with any RF line or sensitive analog inputs, since the signals can cause the radiation of some
harmonics of the digital data frequency.
Figure 57 and Figure 58 provide two examples of coplanar waveguide designs with differential characteristic
impedance close to 90  and common mode characteristic impedance close to 30 . The first transmission line
can be implemented in case of 4-layer PCB stack-up herein described, the second transmission line can be
implemented in case of 2-layer PCB stack-up herein described.
400 µm 350 µm 400 µm 350 µm 400 µm
L1 Copper
35 µm
FR-4 dielectric
270 µm
L2 Copper
35 µm
FR-4 dielectric
760 µm
L3 Copper
35 µm
FR-4 dielectric
270 µm
L4 Copper
35 µm
Figure 57: Example of USB line design, with Z0 close to 90  and ZCM close to 30 , for the described 4-layer board layup
410 µm 740 µm 410 µm 740 µm 410 µm
L1 Copper
35 µm
FR-4 dielectric
1510 µm
L2 Copper
35 µm
Figure 58: Example of USB line design, with Z0 close to 90  and ZCM close to 30 , for the described 2-layer board layup
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2.6.3 HSIC interface
2.6.3.1
Guidelines for HSIC circuit design
The HSIC interface is not supported by “02” modules product versions except for diagnostic purpose.
LARA-R2 series modules include a USB High-Speed Inter-Chip compliant interface with maximum 480 Mb/s data
rate according to the High-Speed Inter-Chip USB Electrical Specification Version 1.0 [10] and USB Specification
Revision 2.0 [9]. The module itself acts as a device and can be connected to any compatible host.
The HSIC interface consists of a bi-directional DDR data line (HSIC_DATA) for transmitting and receiving data
synchronously with the bi-directional strobe line (HSIC_STRB), intended to be directly connected to the Data and
Strobe pins of the compatible USB High-Speed Inter-Chip host mounted on the same PCB of the LARA-R2 series
module, without using connectors / cables, as described in Figure 59.
The modules include also the HOST_SELECT pin to select the module / host application processor configuration:
the pin is available to select, enable, connect, disconnect and subsequently re-connect the HSIC interface.
USB HSIC
HOST PROCESSOR
LARA-R2 series
DATA
99
HSIC_DATA
STROBE
100
HSIC_STRB
GND
GND
Figure 59: HSIC interface application circuit
Further guidelines for HSIC interface circuit design will be described in detail in a successive release of the
System Integration Manual.
ESD sensitivity rating of HSIC interface pins is 1 kV (HBM as per JESD22-A114). Higher protection level
could be required if the lines are externally accessible and it can be achieved by mounting an ESD
protection (e.g. EPCOS CA05P4S14THSG varistor array) close to accessible points
If the HSIC interface pins are not used, they can be left unconnected on the application board, but it is
recommended providing accessible test points directly connected to HSIC_DATA and HSIC_STRB pins.
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2.6.3.2 Guidelines for HSIC layout design
HSIC lines require accurate layout design to achieve reliable signaling at high speed data rate (up to 480 Mb/s),
as supported by the HSIC serial interface: signal integrity may be degraded if PCB layout is not optimal, especially
when the HSIC lines are very long.
The characteristic impedance of the HSIC_DATA and HSIC_STRB lines has to be as close as possible to 50 , as
specified by the High-Speed Inter-Chip USB Electrical Specification Version 1.0 [10].
Use the following general routing guidelines to minimize signal quality problems:

Route HSIC_DATA and HSIC_STRB lines as short as possible.

HSIC interface is only recommended for intra-board interconnect. The connection should be point-to-point.
Connectors and cables are not recommended.

HSIC_DATA and HSIC_STRB lines must be matched in length to within 10 mils.

Ensure the characteristic impedance of HSIC_DATA and HSIC_STRB lines is as close as possible to 50 .

HSIC_DATA and HSIC_STRB signals are not differential signals and should not be routed as such.

Consider design rules for HSIC_DATA and HSIC_STRB lines similar to RF transmission lines, routing them as
micro-strips (conducting strips separated from ground plane by dielectric material) or striplines (flat strips of
metal sandwiched between two parallel ground planes within a dielectric material).

Avoid any stubs, abrupt change of layout, and route on clear PCB area.

Avoid coupling with any RF line or sensitive analog inputs, since the signals can cause the radiation of some
harmonics of the digital data frequency.
Figure 40 and Figure 41 provide two examples of proper 50  coplanar waveguide designs. The first example of
RF transmission line can be implemented in case of 4-layer PCB stack-up herein described, and the second
example of RF transmission line can be implemented in case of 2-layer PCB stack-up herein described.
If the two examples do not match the application PCB layup, the 50  characteristic impedance calculation can
be made using the HFSS commercial finite element method solver for electromagnetic structures from Ansys
Corporation, or using freeware tools like AppCAD from Agilent (www.agilent.com) or TXLine from Applied
Wave Research (www.mwoffice.com), taking care of the approximation formulas used by the tools for the
impedance computation.
To achieve a 50  characteristic impedance, the width of the transmission line must be chosen depending on:

the thickness of the transmission line itself (e.g. 35 µm in the example of Figure 40 and Figure 41)

the thickness of the dielectric material between the top layer (where the transmission line is routed) and the
inner closer layer implementing the ground plane (e.g. 270 µm in Figure 40, 1510 µm in Figure 41)

the dielectric constant of the dielectric material (e.g. dielectric constant of the FR-4 dielectric material in
Figure 40 and Figure 41)

the gap from the transmission line to the adjacent ground plane on the same layer of the transmission line
(e.g. 500 µm in Figure 40, 400 µm in Figure 41)
If the distance between the transmission line and the adjacent GND area (on the same layer) does not exceed 5
times the track width of the micro strip, use the “Coplanar Waveguide” model for the 50  calculation.
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2.6.4 DDC (I2C) interface
2.6.4.1
Guidelines for DDC (I C) circuit design
General considerations
Communication with u-blox GNSS receivers over DDC (I C) is not supported by “02” product versions.
The DDC I C-bus master interface can be used to communicate with u-blox GNSS receivers and other external
I C-bus slaves as an audio codec. Beside the general considerations reported below, see:

the following parts of this section for specific guidelines for the connection to u-blox GNSS receivers.

the section 2.7.1 for an application circuit example with an external audio codec I C-bus slave.
To be compliant to the I C-bus specifications, the module bus interface pins are open drain output and pull up
resistors must be mounted externally. Resistor values must conform to I C bus specifications [11]: for example,
4.7 k resistors can be commonly used. Pull-ups must be connected to a supply voltage of 1.8 V (typical), since
this is the voltage domain of the DDC pins which are not tolerant to higher voltage values (e.g. 3.0 V).
Connect the DDC (I C) pull-ups to the V_INT 1.8 V supply source, or another 1.8 V supply source enabled
after V_INT (e.g., as the GNSS 1.8 V supply present in Figure 60 application circuit), as any external signal
connected to the DDC (I C) interface must not be set high before the switch-on of the V_INT supply of
the DDC (I C) pins, to avoid latch-up of circuits and let a proper boot of the module.
The signal shape is defined by the values of the pull-up resistors and the bus capacitance. Long wires on the bus
increase the capacitance. If the bus capacitance is increased, use pull-up resistors with nominal resistance value
lower than 4.7 k, to match the I C bus specifications [11] regarding rise and fall times of the signals.
Capacitance and series resistance must be limited on the bus to match the I C specifications (1.0 µs is the
maximum allowed rise time on the SCL and SDA lines): route connections as short as possible.
ESD sensitivity rating of the DDC (I C) pins is 1 kV (Human Body Model according to JESD22-A114).
Higher protection level could be required if the lines are externally accessible and it can be achieved by
mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) close to accessible points.
If the pins are not used as DDC bus interface, they can be left unconnected.
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Connection with u-blox 1.8 V GNSS receivers
Figure 60 shows an application circuit for connecting the cellular module to a u-blox 1.8 V GNSS receiver:

The SDA and SCL pins of the cellular module are directly connected to the related pins of the u-blox 1.8 V
GNSS receiver, with appropriate pull-up resistors connected to the 1.8 V GNSS supply enabled after the
V_INT supply of the I C pins of the cellular module.

The GPIO2 pin is connected to the active-high enable pin of the voltage regulator that supplies the u-blox
1.8 V GNSS receiver providing the “GNSS supply enable” function. A pull-down resistor is provided to avoid
a switch on of the positioning receiver when the cellular module is switched off or in the reset state.

The GPIO3 and GPIO4 pins are directly connected respectively to TXD1 and EXTINT0 pins of the u-blox
1.8 V GNSS receiver providing “GNSS Tx data ready” and “GNSS RTC sharing” functions.

The V_BCKP supply output of the cellular module is connected to the V_BCKP backup supply input pin of
the GNSS receiver to provide the supply for the GNSS real time clock and backup RAM when the VCC supply
of the cellular module is within its operating range and the VCC supply of the GNSS receiver is disabled. This
enables the u-blox GNSS receiver to recover from a power breakdown with either a hot start or a warm start
(depending on the actual duration of the GNSS VCC outage) and to maintain the configuration settings
saved in the backup RAM.
u-blox GNSS
1.8 V receiver
LARA-R2 series
(except ‘02’ product version)
V_BCKP
GNSS LDO
Regulator
1V8
VCC
OUT
V_BCKP
VMAIN
IN
GNSS supply enabled
23
GPIO2
SDA2
26
SDA
SCL2
27
SCL
24
GPIO3
25
GPIO4
1V8
1V8
SHDN
C1
GND
R3
U1
R1
R2
GNSS data ready
TxD1
GNSS RTC sharing
EXTINT0
Figure 60: Application circuit for connecting LARA-R2 series modules to u-blox 1.8 V GNSS receivers
Reference
Description
Part Number - Manufacturer
R1, R2
4.7 kΩ Resistor 0402 5% 0.1 W
RC0402JR-074K7L - Yageo Phycomp
R3
U1
47 kΩ Resistor 0402 5% 0.1 W
Voltage Regulator for GNSS receiver
RC0402JR-0747KL - Yageo Phycomp
See GNSS receiver Hardware Integration Manual
Table 44: Components for connecting LARA-R2 series modules to u-blox 1.8 V GNSS receivers
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Figure 61 illustrates an alternative solution as supply for u-blox 1.8 V GNSS receivers: the V_INT 1.8 V regulated
supply output of the cellular module can be used to supply a u-blox 1.8 V GNSS receiver of the u-blox 6
generation (or any newer u-blox GNSS receiver generation) instead of using an external voltage regulator as
shown in the previous Figure 60. The V_INT supply is able to support the maximum current consumption of
these positioning receivers.
The internal switching step-down regulator that generates the V_INT supply is set to 1.8 V (typical) when the
cellular module is switched on and it is disabled when the module is switched off.
The supply of the u-blox 1.8 V GNSS receiver can be switched off using an external p-channel MOSFET
controlled by the GPIO2 pin by means of a proper inverting transistor as shown in Figure 61, implementing the
“GNSS supply enable” function. If this feature is not required, the V_INT supply output can be directly
connected to the u-blox 1.8 V GNSS receiver, so that it will be switched on when V_INT output is enabled.
According to the V_INT supply output voltage ripple characteristic specified in LARA-R2 series Data Sheet [1]:

Additional filtering may be needed to properly supply an external LNA, depending on the characteristics of
the used LNA, adding a series ferrite bead and a bypass capacitor (e.g. the Murata BLM15HD182SN1 ferrite
bead and the Murata GRM1555C1H220J 22 pF capacitor) at the input of the external LNA supply line.
LARA-R2 series
u-blox GNSS
1.8 V receiver
(except ‘02’ product version)
V_BCKP
V_BCKP
V_INT
23
GPIO2
SDA2
26
SDA
SCL2
27
SCL
24
GPIO3
25
GPIO4
1V8
T1
VCC
R5
C1
1V8
R4
1V8
T2
R1
TP
GNSS supply enabled
R3
R2
GNSS data ready
TxD1
GNSS RTC sharing
EXTINT0
Figure 61: Application circuit for connecting LARA-R2 series modules to u-blox 1.8 V GNSS receivers using V_INT as supply
Reference
Description
Part Number - Manufacturer
R1, R2
4.7 k Resistor 0402 5% 0.1 W
RC0402JR-074K7L - Yageo Phycomp
R3
47 k Resistor 0402 5% 0.1 W
RC0402JR-0747KL - Yageo Phycomp
R4
10 k Resistor 0402 5% 0.1 W
RC0402JR-0710KL - Yageo Phycomp
R5
100 k Resistor 0402 5% 0.1 W
RC0402JR-07100KL - Yageo Phycomp
T1
P-Channel MOSFET Low On-Resistance
IRLML6401 - International Rectifier or NTZS3151P - ON Semi
T2
C1
NPN BJT Transistor
100 nF Capacitor Ceramic X7R 0402 10% 16 V
BC847 - Infineon
GRM155R71C104KA01 - Murata
Table 45: Components for connecting LARA-R2 series modules to u-blox 1.8 V GNSS receivers using V_INT as supply
For additional guidelines regarding the design of applications with u-blox 1.8 V GNSS receivers see the GNSS
Implementation Application Note [22] and to the Hardware Integration Manual of the u-blox GNSS receivers.
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Connection with u-blox 3.0 V GNSS receivers
Figure 62 shows an application circuit for connecting the cellular module to a u-blox 3.0 V GNSS receiver:

As the SDA and SCL pins of the cellular module are not tolerant up to 3.0 V, the connection to the related
I C pins of the u-blox 3.0 V GNSS receiver must be provided using a proper I C-bus Bidirectional Voltage
Translator (e.g. TI TCA9406, which additionally provides the partial power down feature so that the GNSS
3.0 V supply can be ramped up before the V_INT 1.8 V cellular supply), with proper pull-up resistors.

The GPIO2 is connected to the active-high enable pin of the voltage regulator that supplies the u-blox 3.0 V
GNSS receiver providing the “GNSS supply enable” function. A pull-down resistor is provided to avoid a
switch on of the positioning receiver when the cellular module is switched off or in the reset state.

As the GPIO3 and GPIO4 pins of the cellular module are not tolerant up to 3.0 V, the connection to the
related pins of the u-blox 3.0 V GNSS receiver must be provided using a proper Unidirectional General
Purpose Voltage Translator (e.g. TI SN74AVC2T245, which additionally provides the partial power down
feature so that the 3.0 V GNSS supply can be also ramped up before the V_INT 1.8 V cellular supply).

The V_BCKP supply output of the cellular module can be directly connected to the V_BCKP backup supply
input pin of the GNSS receiver as in the application circuit for a u-blox 1.8 V GNSS receiver.
u-blox GNSS
3.0 V receiver
LARA-R2 series
(except ‘02’ product versions)
V_BCKP
3V0
GNSS LDO Regulator
VCC
C1
OUT
IN
GND
SHDNn
GNSS supply enabled
I2C-bus Bidirectional
Voltage Translator
VCCB
GPIO2
V_INT
C3
OE
R2
SDA_B
SCL2
23
1V8
VCCA
C2
SDA2
V_BCKP
R3
U1
R1
VMAIN
SCL_B
R4
R5
SDA_A
26 SDA
SCL_A
27
SCL
24
GPIO3
25
GPIO4
GND
U2
Unidirectional
Voltage Translator
3V0
C4
VCCA
DIR1
VCCB
TxD1
A1
B1
EXTINT0
A2
B2
DIR2 GND
1V8
C5
GNSS data ready
GNSS RTC sharing
OEn
U3
Figure 62: Application circuit for connecting LARA-R2 series modules to u-blox 3.0 V GNSS receivers
Reference
Description
Part Number - Manufacturer
R1, R2, R4, R5
R3
4.7 kΩ Resistor 0402 5% 0.1 W
47 kΩ Resistor 0402 5% 0.1 W
RC0402JR-074K7L - Yageo Phycomp
RC0402JR-0747KL - Yageo Phycomp
C2, C3, C4, C5
U1, C1
100 nF Capacitor Ceramic X5R 0402 10% 10V
Voltage Regulator for GNSS receiver and related
output bypass capacitor
GRM155R71C104KA01 - Murata
See GNSS receiver Hardware Integration Manual
U2
U3
I2C-bus Bidirectional Voltage Translator
Generic Unidirectional Voltage Translator
TCA9406DCUR - Texas Instruments
SN74AVC2T245 - Texas Instruments
Table 46: Components for connecting LARA-R2 series modules to u-blox 3.0 V GNSS receivers
For additional guidelines regarding the design of applications with u-blox 3.0 V GNSS receivers see the GNSS
Implementation Application Note [22] and to the Hardware Integration Manual of the u-blox GNSS receivers.
2.6.4.2 Guidelines for DDC (I C) layout design
The DDC (I C) serial interface requires the same consideration regarding electro-magnetic interference as any
other digital interface. Keep the traces short and avoid coupling with RF line or sensitive analog inputs, since the
signals can cause the radiation of some harmonics of the digital data frequency.
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2.6.5
SDIO interface
2.6.5.1
Guidelines for SDIO circuit design
The functionality of the SDIO Secure Digital Input Output interface pins is not supported by LARA-R2
series modules “02” product versions: the pins should not be driven by any external device.
LARA-R2 series modules include a 4-bit Secure Digital Input Output interface (SDIO_D0, SDIO_D1, SDIO_D2,
SDIO_D3, SDIO_CLK, SDIO_CMD) designed to communicate with an external u-blox short range Wi-Fi module.
Combining a u-blox cellular module with a u-blox short range communication module gives designers full access
to the Wi-Fi module directly via the cellular module, so that a second interface connected to the Wi-Fi module is
not necessary. AT commands via the AT interfaces of the cellular module allows full control of the Wi-Fi module
from any host processor, because Wi-Fi control messages are relayed to the Wi-Fi module via the dedicated SDIO
interface.
Further guidelines for SDIO interface circuit design will be described in detail in a successive release of the
System Integration Manual.
Do not apply voltage to any SDIO interface pin before the switch-on of SDIO interface supply source
(V_INT), to avoid latch-up of circuits and allow a proper boot of the module.
ESD sensitivity rating of SDIO interface pins is 1 kV (HMB according to JESD22-A114). Higher protection
level could be required if the lines are externally accessible and it can be achieved by mounting a very low
capacitance ESD protection (e.g. Tyco Electronics PESD0402-140 ESD), close to accessible points.
If the SDIO interface pins are not used, they can be left unconnected on the application board.
2.6.5.2
Guidelines for SDIO layout design
The SDIO serial interface requires the same consideration regarding electro-magnetic interference as any other
high speed digital interface.
Keep the traces short, avoid stubs and avoid coupling with RF lines / parts or sensitive analog inputs, since the
signals can cause the radiation of some harmonics of the digital data frequency.
Consider the usage of low value series damping resistors to avoid reflections and other losses in signal integrity,
which may create ringing and loss of a square wave shape.
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2.7 Audio interface
Audio is not supported by LARA-R204 module “02” product version.
2.7.1 Digital audio interface
2.7.1.1
Guidelines for digital audio circuit design
I S digital audio interface can be connected to an external digital audio device for voice applications.
Any external digital audio device compliant with the configuration of the digital audio interface of the LARA-R2
series cellular module can be used, given that the external digital audio device must provide:

The opposite role: slave or master role, as LARA-R2 series modules may act as master or slave

The same mode and frame format: PCM / short synch mode or Normal I S / long synch mode with


data in 2’s complement notation
MSB transmitted first
data word length = 16-bit (16 clock cycles)
frame length = synch signal period:
17-bit or 18-bit in PCM / short alignment mode (16 + 1 or 16 + 2 clock cycles, with the Word
Alignment / Synchronization signal set high for 1 clock cycle or 2 clock cycles)

32-bit in Normal I S mode / long alignment mode (16 x 2 clock cycles)
The same sample rate, i.e. synch signal frequency, configurable by AT+UI2S  parameter
o 8 kHz
11.025 kHz
12 kHz
16 kHz
22.05 kHz
24 kHz
32 kHz
44.1 kHz
48 kHz
The same serial clock frequency:


17 x  or 18 x  in PCM / short alignment mode, or
16 x 2 x  in Normal I S mode / long alignment mode
Compatible voltage levels (1.80 V typ.), otherwise it is recommended to connect the 1.8 V digital audio
interface of the module to the external 3.0 V (or similar) digital audio device by means of appropriate
unidirectional voltage translators (e.g. TI SN74AVC4T774 or SN74AVC2T245, providing partial power down
feature so that the digital audio device 3.0 V supply can be also ramped up before V_INT 1.8 V supply),
using the module V_INT output as 1.8 V supply for the voltage translators on the module side
For the appropriate selection of a compliant external digital audio device, see section 1.10.1 and see the +UI2S
AT command description in the u-blox AT Commands Manual [2] for further details regarding the capabilities
and the possible settings of I S digital audio interface of LARA-R2 series modules.
An appropriate specific application circuit has to be implemented and configured according to the particular
external digital audio device or audio codec used and according to the application requirements.
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Examples of manufacturers offering compatible audio codec parts are the following:

Maxim Integrated (as the MAX9860, MAX9867, MAX9880A audio codecs)

Texas Instruments / National Semiconductor

Cirrus Logic / Wolfson Microelectronics

Nuvoton Technology

Asahi Kasei Microdevices

Realtek Semiconductor
Figure 63 and Table 47 describe an application circuit for the I S digital audio interface providing basic voice
capability using an external audio voice codec, in particular the Maxim MAX9860 audio codec.

DAC and ADC integrated in the external audio codec respectively converts an incoming digital data stream
to analog audio output through a mono amplifier and converts the microphone input signal to the digital bit
stream over the digital audio interface,

A digital side-tone mixer integrated in the external audio codec provides loopback of the microphones/ADC
signal to the DAC/headphone output.

The module’s I S interface (I S master) is connected to the related pins of the external audio codec (I S slave).

The GPIO6 of the LARA-R2 series module (that provides a suitable digital output clock) is connected to the
clock input of the external audio codec to provide clock reference.

The external audio codec is controlled by the LARA-R2 series module using the DDC (I C) interface, which
can concurrently communicate with other I C devices and control an external audio codec.

The V_INT output supplies the external audio codec, defining proper digital interfaces voltage level.

Additional components are provided for EMC and ESD immunity conformity: a 10 nF bypass capacitor and a
series chip ferrite bead noise/EMI suppression filter provided on each microphone line input and speaker line
output of the external codec as described in Figure 63 and Table 47. The necessity of these or other
additional parts for EMC improvement may depend on the specific application board design.
Specific AT commands are available to configure the Maxim MAX9860 audio codec: for more details see the
u-blox AT Commands Manual [2], +UEXTDCONF AT command.
As various external audio codecs other than the one described in Figure 63 and Table 47 can be used to provide
voice capability, the appropriate specific application circuit has to be implemented and configured according to
the particular external digital audio device or audio codec used and according to the application requirements.
LARA-R2 series
(except LARA-R204 module “02” product version)
V_INT
1V8
R1
R2
R3
Audio
Codec
C1
IRQn
SDA 26
SCL 27
C2
C3
VDD
MICBIAS
C4
SDA
SCL
I2S_TXD 35
SDIN
I2S_RXD 37
SDOUT
I2S_CLK 36
BCLK
I2S_WA 34
LRCLK
GPIO6 19
MCLK
MICLP
MICLN
EMI1
C5
OUTP
EMI2
C6
J1
R5
MICGND
OUTN
Microphone
Connector MIC
R4
C12 C11
C8
C7
D1
EMI3
Speaker SPK
Connector
EMI4
J2
GND
GND
C14 C13
C10 C9
U1
D2
Figure 63: I2S interface application circuit with an external audio codec to provide voice capability
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Reference
Description
Part Number – Manufacturer
C1
C2, C4, C5, C6
100 nF Capacitor Ceramic X5R 0402 10% 10V
1 µF Capacitor Ceramic X5R 0402 10% 6.3 V
GRM155R71C104KA01 – Murata
GRM155R60J105KE19 – Murata
C3
C7, C8, C9, C10
10 µF Capacitor Ceramic X5R 0603 20% 6.3 V
27 pF Capacitor Ceramic COG 0402 5% 25 V
GRM188R60J106ME47 – Murata
GRM1555C1H270JZ01 – Murata
C11, C12, C13, C14
D1, D2
10 nF Capacitor Ceramic X5R 0402 10% 50V
Low Capacitance ESD Protection
GRM155R71C103KA88 – Murata
USB0002RP or USB0002DP – AVX
EMI1, EMI2, EMI3,
EMI4
J1
Chip Ferrite Bead Noise/EMI Suppression Filter
1800 Ohm at 100 MHz, 2700 Ohm at 1 GHz
Microphone Connector
BLM15HD182SN1 – Murata
J2
MIC
Speaker Connector
2.2 k Electret Microphone
Various manufacturers
Various manufacturers
R1, R2
4.7 k Resistor 0402 5% 0.1 W
RC0402JR-074K7L - Yageo Phycomp
R3
10 k Resistor 0402 5% 0.1 W
RC0402JR-0710KL - Yageo Phycomp
R4, R5
2.2 k Resistor 0402 5% 0.1 W
RC0402JR-072K2L – Yageo Phycomp
SPK
32  Speaker
16-Bit Mono Audio Voice Codec
Various manufacturers
U1
Various manufacturers
MAX9860ETG+ - Maxim
Table 47: Example of components for audio voice codec application circuit
Do not apply voltage to any I S pin before the switch-on of I S supply source (V_INT), to avoid latch-up of
circuits and allow a proper boot of the module. If the external signals connected to the cellular module
cannot be tri-stated or set low, insert a multi channel digital switch (e.g. TI SN74CB3Q16244, TS5A3159,
or TS5A63157) between the two-circuit connections and set to high impedance before V_INT switch-on.
ESD sensitivity rating of I S interface pins is 1 kV (Human Body Model according to JESD22-A114). Higher
protection level could be required if the lines are externally accessible and it can be achieved by mounting
a general purpose ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) close to accessible points.
If the I S digital audio pins are not used, they can be left unconnected on the application board.
2.7.1.2
Guidelines for digital audio layout design
I S interface and clock output lines require the same consideration regarding electro-magnetic interference as
any other high speed digital interface. Keep the traces short and avoid coupling with RF lines / parts or sensitive
analog inputs, since the signals can cause the radiation of some harmonics of the digital data frequency.
2.7.1.3
Guidelines for analog audio layout design
Accurate design of the analog audio circuit is very important to obtain clear and high quality audio. The GSM
signal burst has a repetition rate of 217 Hz that lies in the audible range. A careful layout is required to reduce
the risk of noise from audio lines due to both VCC burst noise coupling and RF detection.
General guidelines for the uplink path (microphone), which is commonly the most sensitive, are the following:

Avoid coupling of any noisy signal to microphone lines: it is strongly recommended to route microphone
lines away from module VCC supply line, any switching regulator line, RF antenna lines, digital lines and any
other possible noise source.

Avoid coupling between microphone and speaker / receiver lines.

Optimize the mechanical design of the application device, the position, orientation and mechanical fixing
(for example, using rubber gaskets) of microphone and speaker parts in order to avoid echo interference
between uplink path and downlink path.
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
Keep ground separation from microphone lines to other noisy signals. Use an intermediate ground layer or
vias wall for coplanar signals.

In case of external audio device providing differential microphone input, route microphone signal lines as a
differential pair embedded in ground to reduce differential noise pick-up. The balanced configuration will
help reject the common mode noise.

Cross other signals lines on adjacent layers with 90° crossing.

Place bypass capacitor for RF very close to active microphone. The preferred microphone should be designed
for GSM applications which typically have internal built-in bypass capacitor for RF very close to active device.
If the integrated FET detects the RF burst, the resulting DC level will be in the pass-band of the audio
circuitry and cannot be filtered by any other device.
General guidelines for the downlink path (speaker / receiver) are the following:

The physical width of the audio output lines on the application board must be wide enough to minimize
series resistance since the lines are connected to low impedance speaker transducer.

Avoid coupling of any noisy signal to speaker lines: it is recommended to route speaker lines away from
module VCC supply line, any switching regulator line, RF antenna lines, digital lines and any other possible
noise source.

Avoid coupling between speaker / receiver and microphone lines.

Optimize the mechanical design of the application device, the position, orientation and mechanical fixing
(for example, using rubber gaskets) of speaker and microphone parts in order to avoid echo interference
between downlink path and uplink path.

In case of external audio device providing differential speaker / receiver output, route speaker signal lines as
a differential pair embedded in ground up to reduce differential noise pick-up. The balanced configuration
will help reject the common mode noise.

Cross other signals lines on adjacent layers with 90° crossing.

Place bypass capacitor for RF close to the speaker.
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2.8
General Purpose Input/Output (GPIO)
2.8.1.1
Guidelines for GPIO circuit design
A typical usage of LARA-R2 series modules’ GPIOs can be the following:

Network indication provided over GPIO1 pin (see Figure 64 / Table 48 below)

GNSS supply enable function provided by the GPIO2 pin (see section 2.6.4)

GNSS Tx data ready function provided by the GPIO3 pin (see section 2.6.4)

GNSS RTC sharing function provided by the GPIO4 pin (see section 2.6.4)

SIM card detection provided over GPIO5 pin (see Figure 46 / Table 37 in section 2.5)
3V8
LARA-R2 series
R3
GPIO1 16
Network Indicator
DL1
R1
T1
R2
Figure 64: Application circuit for network indication provided over GPIO1
Reference
Description
Part Number - Manufacturer
R1
10 k Resistor 0402 5% 0.1 W
Various manufacturers
R2
47 k Resistor 0402 5% 0.1 W
Various manufacturers
R3
Various manufacturers
DL1
820  Resistor 0402 5% 0.1 W
LED Red SMT 0603
T1
NPN BJT Transistor
BC847 - Infineon
LTST-C190KRKT - Lite-on Technology Corporation
Table 48: Components for network indication application circuit
Use transistors with at least an integrated resistor in the base pin or otherwise put a 10 kΩ resistor on the
board in series to the GPIO of LARA-R2 series modules.
Do not apply voltage to any GPIO of the module before the switch-on of the GPIOs supply (V_INT), to
avoid latch-up of circuits and allow a proper module boot. If the external signals connected to the module
cannot be tri-stated or set low, insert a multi channel digital switch (e.g. TI SN74CB3Q16244, TS5A3159,
TS5A63157) between the two-circuit connections and set to high impedance before V_INT switch-on.
ESD sensitivity rating of the GPIO pins is 1 kV (Human Body Model according to JESD22-A114).
Higher protection level could be required if the lines are externally accessible and it can be achieved by
mounting an ESD protection (e.g. EPCOS CA05P4S14THSG varistor array) close to accessible points.
If the GPIO pins are not used, they can be left unconnected on the application board.
2.8.1.2
Guidelines for GPIO layout design
The general purpose input/output pins are generally not critical for layout.
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2.9
Reserved pins (RSVD)
LARA-R2 series modules have pins reserved for future use, marked as RSVD. All the RSVD pins are to be left
unconnected on the application board except the following RSVD pin, as described in Figure 65:

the RSVD pin number 33 that must be externally connected to ground
LARA-R2
RSVD 33
RSVD
Figure 65: Application circuit for the reserved pins (RSVD)
2.10 Module placement
Optimize placement for minimum length of RF line and closer path from DC source for VCC.
Make sure that the module, RF and analog parts / circuits are clearly separated from any possible source of
radiated energy, including digital circuits that can radiate some digital frequency harmonics, which can produce
Electro-Magnetic Interference affecting module, RF and analog parts / circuits’ performance or implement proper
countermeasures to avoid any possible Electro-Magnetic Compatibility issue.
Make sure that the module, RF and analog parts / circuits, high speed digital circuits are clearly separated from
any sensitive part / circuit which may be affected by Electro-Magnetic Interference or employ countermeasures to
avoid any possible Electro-Magnetic Compatibility issue.
Provide enough clearance between the module and any external part.
The heat dissipation during continuous transmission at maximum power can significantly raise the
temperature of the application base-board below the LARA-R2 series modules: avoid placing temperature
sensitive devices close to the module.
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2.11 Module footprint and paste mask
Figure 66 and Table 49 describe the suggested footprint (i.e. copper mask) and paste mask layout for LARA
modules: the proposed land pattern layout reflects the modules’ pins layout, while the proposed stencil
apertures layout is slightly different (see the F’’, H’’, I’’, J’’, O’’ parameters compared to the F’, H’, I’, J’, O’ ones).
The Non Solder Mask Defined (NSMD) pad type is recommended over the Solder Mask Defined (SMD) pad type,
implementing the solder mask opening 50 µm larger per side than the corresponding copper pad.
The recommended solder paste thickness is 150 µm, according to application production process requirements.
G ANT2
J’
J’’
H’ H’ ANT1 G
G ANT2
Pin 1
Pin 1
M1
M1
M1
M1
M2
M2
O’
H’’ H’’ ANT1 G
O’
O’’
Foot-print
H’
Top View
J’
F1’
H’
J’
H’
Paste-mask
H’’
Top View
J’’
F2’
O’’
J’
F1’’ K
F2’’
H’’
J’’
H’’
J’’
Figure 66: LARA-R2 series modules suggested footprint and paste mask (application board top view)
Parameter
Value
Parameter
Value
Parameter
Value
F1’
F1’’
F2’
26.0 mm
24.0 mm
2.60 mm
2.00 mm
6.50 mm
1.05 mm
1.00 mm
5.05 mm
F2’’
H’
H’’
I’
I’’
J’
J’’
5.00 mm
1.10 mm
0.80 mm
0.75 mm
1.50 mm
1.55 mm
0.30 mm
0.35 mm
M1
M2
O’
O’’
2.75 mm
6.75 mm
1.80 mm
3.60 mm
2.10 mm
1.10 mm
1.05 mm
Table 49: LARA-R2 series modules suggested footprint and paste mask dimensions
These are recommendations only and not specifications. The exact copper, solder and paste mask
geometries, distances, stencil thicknesses and solder paste volumes must be adapted to the specific
production processes (e.g. soldering etc.) of the customer.
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2.12 Thermal guidelines
Modules’ operating temperature range is specified in LARA-R2 series Data Sheet [1].
The most critical condition concerning module thermal performance is the uplink transmission at maximum
power (data upload in connected-mode), when the baseband processor runs at full speed, radio circuits are all
active and the RF power amplifier is driven to higher output RF power. This scenario is not often encountered in
real networks (for example, see the Terminal Tx Power distribution for WCDMA, taken from operation on a live
network, described in the GSMA TS.09 Battery Life Measurement and Current Consumption Technique [16]);
however the application should be correctly designed to cope with it.
During transmission at maximum RF power the LARA-R2 series modules generate thermal power that may
exceed 2 W: this is an indicative value since the exact generated power strictly depends on operating condition
such as the actual antenna return loss, the number of allocated TX resource blocks, the transmitting frequency
band, etc. The generated thermal power must be adequately dissipated through the thermal and mechanical
design of the application.
The spreading of the Module-to-Ambient thermal resistance (Rth,M-A) depends on the module operating
condition. The overall temperature distribution is influenced by the configuration of the active components
during the specific mode of operation and their different thermal resistance toward the case interface.
The Module-to-Ambient thermal resistance value and the relative increase of module temperature will
differ according to the specific mechanical deployments of the module, e.g. application PCB with different
dimensions and characteristics, mechanical shells enclosure, or forced air flow.
The increase of the thermal dissipation, i.e. the reduction of the Module-to-Ambient thermal resistance, will
decrease the temperature of the modules’ internal circuitry for a given operating ambient temperature. This
improves the device long-term reliability in particular for applications operating at high ambient temperature.
Recommended hardware techniques to be used to improve heat dissipation in the application:

Connect each GND pin with solid ground layer of the application board and connect each ground area of
the multilayer application board with complete thermal via stacked down to main ground layer.

Provide a ground plane as wide as possible on the application board.

Optimize antenna return loss, to optimize overall electrical performance of the module including a decrease
of module thermal power.

Optimize the thermal design of any high-power components included in the application, such as linear
regulators and amplifiers, to optimize overall temperature distribution in the application device.

Select the material, the thickness and the surface of the box (i.e. the mechanical enclosure) of the
application device that integrates the module so that it provides good thermal dissipation.
Further hardware techniques that may be considered to improve the heat dissipation in the application:

Force ventilation air-flow within mechanical enclosure.

Provide a heat sink component attached to the module top side, with electrically insulated / high thermal
conductivity adhesive, or on the backside of the application board, below the cellular module, as a large part
of the heat is transported through the GND pads of the LARA-R2 series LGA modules and dissipated over
the backside of the application board.
For example, the Module-to-Ambient thermal resistance (Rth,M-A) is strongly reduced with forced air ventilation
and a heat-sink installed on the back of the application board, decreasing the module temperature variation.
Beside the reduction of the Module-to-Ambient thermal resistance implemented by proper application hardware
design, the increase of module temperature can be moderated by proper application software implementation:

Enable power saving configuration using the AT+UPSV command (see section 1.14.16).

Enable module connected-mode for a given time period and then disable it for a time period enough long to
properly mitigate temperature increase.
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2.13 ESD guidelines
The sections 2.13.1 and 2.13.2 are related to EMC / ESD immunity. The modules are ESD sensitive devices and
the ESD sensitivity for each pin (as Human Body Model according to JESD22-A114F) is specified in LARA-R2
series Data Sheet [1]. Special precautions are required when handling: see section 3.2 for handling guidelines.
2.13.1 ESD immunity test overview
The immunity of devices integrating LARA-R2 series modules to Electro-Static Discharge (ESD) is part of the
Electro-Magnetic Compatibility (EMC) conformity, which is required for products bearing the CE marking,
compliant with the R&TTE Directive (99/5/EC), the EMC Directive (89/336/EEC) and the Low Voltage Directive
(73/23/EEC) issued by the Commission of the European Community.
Compliance with these directives implies conformity to the following European Norms for device ESD immunity:
ESD testing standard CENELEC EN 61000-4-2 [17] and the radio equipment standards ETSI EN 301 489-1 [18],
ETSI EN 301 489-7 [19], ETSI EN 301 489-24 [20], which requirements are summarized in Table 50.
The ESD immunity test is performed at the enclosure port, defined by ETSI EN 301 489-1 [18] as the physical
boundary through which the electromagnetic field radiates. If the device implements an integral antenna, the
enclosure port is defined as all insulating and conductive surfaces housing the device. If the device implements a
removable antenna, the antenna port can be separated from the enclosure port. The antenna port includes the
antenna element and its interconnecting cable surfaces.
The applicability of the ESD immunity test to the whole device depends on the device classification as defined by
ETSI EN 301 489-1 [18]. Applicability of the ESD immunity test to the relative device ports or the relative
interconnecting cables to auxiliary equipments, depends on device accessible interfaces and manufacturer
requirements, as defined by ETSI EN 301 489-1 [18].
Contact discharges are performed at conductive surfaces, while air discharges are performed at insulating
surfaces. Indirect contact discharges are performed on the measurement setup horizontal and vertical coupling
planes as defined in CENELEC EN 61000-4-2 [17].
For the definition of integral antenna, removable antenna, antenna port, device classification see ETSI EN
301 489-1 [18], whereas for contact and air discharges definitions see CENELEC EN 61000-4-2 [17]
Application
Category
Immunity Level
All exposed surfaces of the radio equipment and ancillary equipment in a
representative configuration
Contact Discharge
4 kV
Air Discharge
8 kV
Table 50: EMC / ESD immunity requirements as defined by CENELEC EN 61000-4-2, ETSI EN 301 489-1, 301 489-7, 301 489-24
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2.14 Schematic for LARA-R2 series module integration
Figure 67 is an example of a schematic diagram where a LARA-R2 series cellular module “02” product version is
integrated into an application board, using all the available interfaces and functions of the module.
LARA-R2 series
(‘02’ product version)
330µF 100nF 10nF
Mount for modules
supporting 2G
56pF
15pF
51
VCC
52
VCC
53
VCC
8.2pF
GND
ANT1
56
82nH
ANT2
62
ANT_DET
59
Secondary
Cellular
Antenna
Connector
33pF
82nH
Mount for modules
supporting LTE band-7
RTC
back-up
Primary
Cellular
Antenna
Connector
33pF
3V8
100µF
V_BCKP
10k
27pF
GND
Application
Processor
ESD
SIM Card Holder
V_INT
TP
Open
Drain
Output
TP
Open
Drain
Output
15
18
PWR_ON
TP
0Ω
TP
12
TXD
13
RXD
RTS
10
RTS
CTS
11
CTS
TXD
RXD
0Ω
TP
DTR
DSR
DSR
RI
RI
DCD
DTR
DCD
0Ω
TP
GPIO5
42
SW2
VSIM
41
CCVCC (C1)
SIM_IO
39
CCIO (C7)
SIM_CLK
38
CCCLK (C3)
SIM_RST
40
CCRST (C2)
47pF 47pF 47pF 47pF 100nF
470k
GPIO2
LDO Regulator
23
IN
OUT
SHDNn
GND
4.7k
VUSB_DET
D+
29
USB_D+
D-
28
USB_D-
VCCB
4.7k
100nF
GND
TP
99
HSIC_DATA
4.7k
SDA2
SCL_A GND SCL_B
SCL2
SN74AVC2T245
Voltage Translator
VCCB
3V0
VCCA
100nF
DIR1
GPIO3
24
B1
A1
TxD1
GPIO4
25
B2
A2
EXTINT0
100 HSIC_STRB
21
4.7k
SDA_B
SDA_A
100nF
TP
VCC
100nF
OE
V_INT
100nF
u-blox GNSS
3.0 V receiver
TCA9406DCUR
I2C Voltage Translator
VCCA
17
3V0
47k
V_INT
100nF
VBUS
GND (C5)
ESD ESD ESD ESD ESD ESD
Not supported by LARA-R2 series “02” product version
3V8
USB 2.0 Host
GND
SW1
CCVPP (C6)
GND
GND
1k
RESET_N
1.8V DTE
0Ω
TP
V_INT
OEn
HOST_SELECT
GND
DIR2
Not supported by LARA-R204 module “02” product version
3V8
44
SDIO_D2
45
SDIO_CLK
46
SDIO_CMD
47
SDIO_D0
48
SDIO_D3
49
SDIO_D1
Network
Indicator
16
GPIO1
RSVD
33
RSVD
V_INT
Audio Codec
MAX9860
10k
IRQn
MICBIAS
SDA
26
SDA
SCL
27
SCL
I2S_TXD
35
SDIN
MICLP
MICLN
I2S_RXD
37
I2S_CLK
36
SDOUT
MICGND
BCLK
I2S_WA
34
LRCLK
GPIO6
19
MCLK
GND
100nF
1µF
1µF
10µF
2.2k
MIC
EMI
1µF
EMI
1µF
2.2k
10nF 10nF
27pF 27pF
ESD ESD
SPK
OUTP
OUTN
GND
V_INT
VDD
EMI
EMI
10nF 10nF
27pF 27pF ESD ESD
Figure 67: Example of schematic diagram to integrate a LARA-R2 module “02” product version using all available interfaces
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2.15 Design-in checklist
This section provides a design-in checklist.
2.15.1 Schematic checklist
The following are the most important points for a simple schematic check:


DC supply must provide a nominal voltage at VCC pin within the operating range limits.

VCC voltage supply should be clean, with very low ripple/noise: provide the suggested bypass capacitors,
in particular if the application device integrates an internal antenna.



Do not apply loads which might exceed the limit for maximum available current from V_INT supply.




Capacitance and series resistance must be limited on each SIM signal to match the SIM specifications.


Capacitance and series resistance must be limited on each high speed line of the USB interface.



Capacitance and series resistance must be limited on each high speed line of the HSIC interface.




Check the digital audio interface specifications to connect a proper external audio device.


Provide proper precautions for ESD immunity as required on the application board.

All unused pins of LARA-R2 series modules can be left unconnected except the RSVD pin number 33,
which must be connected to GND.
DC supply must be capable of supporting both the highest peak and the highest averaged current
consumption values in connected-mode, as specified in the LARA-R2 series Data Sheet [1].
Check that voltage level of any connected pin does not exceed the relative operating range.
Provide accessible test points directly connected to the following pins of the LARA-R2 series modules:
V_INT, PWR_ON and RESET_N for diagnostic purpose.
Insert the suggested pF capacitors on each SIM signal and low capacitance ESD protections if accessible.
Check UART signals direction, as the modules’ signal names follow ITU-T V.24 Recommendation [5].
Provide accessible test points directly connected to all the UART pins of the LARA-R2 series modules
(TXD, RXD, DTR, DCD) for diagnostic purpose, in particular providing a 0  series jumper on each line
to detach each UART pin of the module from the DTE application processor.
If the USB is not used, provide accessible test points directly connected to the USB interface (VUSB_DET,
USB_D+ and USB_D- pins).
Consider providing appropriate low value series damping resistors on SDIO lines to avoid reflections.
Add a proper pull-up resistor (e.g. 4.7 k) to V_INT or another proper 1.8 V supply on each DDC (I C)
interface line, if the interface is used.
Capacitance and series resistance must be limited on master clock output line and each I S interface line
Consider passive filtering parts on each used analog audio line.
Use transistors with at least an integrated resistor in the base pin or otherwise put a 10 k resistor on
the board in series to the GPIO when those are used to drive LEDs.
Do not apply voltage to any generic digital interface pin of LARA-R2 series modules before the switch-on
of the generic digital interface supply source (V_INT).
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2.15.2 Layout checklist
The following are the most important points for a simple layout check:

Check 50  nominal characteristic impedance of the RF transmission line connected to the ANT1 and
the ANT2 ports (antenna RF interfaces).

Ensure no coupling occurs between the RF interface and noisy or sensitive signals (primarily analog audio
input/output signals, SIM signals, high-speed digital lines such as SDIO, USB and other data lines).





Optimize placement for minimum length of RF line.


Ensure an optimal grounding connecting each GND pin with application board solid ground layer.


Keep routing short and minimize parasitic capacitance on the SIM lines to preserve signal integrity.


HSIC traces has to be designed as 50  nominal characteristic impedance transmission lines


Ensure appropriate RF precautions for the Wi-Fi and Cellular technologies coexistence


Route analog audio signals away from noisy sources (primarily RF interface, VCC, switching supplies).
Check the footprint and paste mask designed for LARA-R2 series module as illustrated in section 2.11.
VCC line should be wide and as short as possible.
Route VCC supply line away from RF lines / parts and other sensitive analog lines / parts.
The VCC bypass capacitors in the picoFarad range should be placed as close as possible to the VCC pins,
in particular if the application device integrates an internal antenna.
Use as many vias as possible to connect the ground planes on multilayer application board, providing a
dense line of vias at the edges of each ground area, in particular along RF and high speed lines.
USB_D+ / USB_D- traces should meet the characteristic impedance requirement (90  differential and
30  common mode) and should not be routed close to any RF line / part.
Keep the SDIO traces short, avoid stubs, avoid coupling with any RF line / part and consider low value
series damping resistors to avoid reflections and other losses in signal integrity.
Ensure appropriate RF precautions for the GNSS and Cellular technologies coexistence as described in
the GNSS Implementation Application Note [22].
The audio outputs lines on the application board must be wide enough to minimize series resistance
2.15.3 Antenna checklist

Antenna termination should provide 50  characteristic impedance with V.S.W.R at least less than 3:1
(recommended 2:1) on operating bands in deployment geographical area.

Follow the recommendations of the antenna producer for correct antenna installation and deployment
(PCB layout and matching circuitry).

Ensure compliance with any regulatory agency RF radiation requirement, as reported in sections 4.2.2
and/or 4.3.1 for products marked with the FCC and/or IC.



Ensure high and similar efficiency for both the primary (ANT1) and the secondary (ANT2) antenna.

Ensure high isolation between the cellular antennas and any other antenna or transmitter.
Ensure high isolation between the primary (ANT1) and the secondary (ANT2) antenna.
Ensure low Envelope Correlation Coefficient between the primary (ANT1) and the secondary (ANT2)
antenna: the 3D antenna radiation patterns should have radiation lobes in different directions.
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3 Handling and soldering
No natural rubbers, no hygroscopic materials or materials containing asbestos are employed.
3.1
Packaging, shipping, storage and moisture preconditioning
For information pertaining to LARA-R2 series reels / tapes, Moisture Sensitivity levels (MSD), shipment and
storage information, as well as drying for preconditioning, see the LARA-R2 series Data Sheet [1] and the u-blox
Package Information Guide [25].
3.2
Handling
The LARA-R2 series modules are Electro-Static Discharge (ESD) sensitive devices.
Ensure ESD precautions are implemented during handling of the module.
Electrostatic discharge (ESD) is the sudden and momentary electric current that flows between two objects at
different electrical potentials caused by direct contact or induced by an electrostatic field. The term is usually
used in the electronics and other industries to describe momentary unwanted currents that may cause damage
to electronic equipment.
The ESD sensitivity for each pin of LARA-R2 series modules (as Human Body Model according to JESD22-A114F)
is specified in the LARA-R2 series Data Sheet [1].
ESD prevention is based on establishing an Electrostatic Protective Area (EPA). The EPA can be a small working
station or a large manufacturing area. The main principle of an EPA is that there are no highly charging materials
near ESD sensitive electronics, all conductive materials are grounded, workers are grounded, and charge build-up
on ESD sensitive electronics is prevented. International standards are used to define typical EPA and can be
obtained for example from International Electrotechnical Commission (IEC) or American National Standards
Institute (ANSI).
In addition to standard ESD safety practices, the following measures should be taken into account whenever
handling the LARA-R2 series modules:

Unless there is a galvanic coupling between the local GND (i.e. the work table) and the PCB GND, then the
first point of contact when handling the PCB must always be between the local GND and PCB GND.

Before mounting an antenna patch, connect ground of the device.

When handling the module, do not come into contact with any charged capacitors and be careful when
contacting materials that can develop charges (e.g. patch antenna, coax cable, soldering iron,…).

To prevent electrostatic discharge through the RF pin, do not touch any exposed antenna area. If there is any
risk that such exposed antenna area is touched in non ESD protected work area, implement proper ESD
protection measures in the design.

When soldering the module and patch antennas to the RF pin, make sure to use an ESD safe soldering iron.
For more robust designs, employ additional ESD protection measures on the application device integrating the
LARA-R2 series modules, as described in section 2.13.3.
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3.3
Soldering
3.3.1 Soldering paste
Use of "No Clean" soldering paste is strongly recommended, as it does not require cleaning after the soldering
process has taken place. The paste listed in the example below meets these criteria.
Soldering Paste:
OM338 SAC405 / Nr.143714 (Cookson Electronics)
Alloy specification:
95.5% Sn / 3.9% Ag / 0.6% Cu (95.5% Tin / 3.9% Silver / 0.6% Copper)
95.5% Sn / 4.0% Ag / 0.5% Cu (95.5% Tin / 4.0% Silver / 0.5% Copper)
Melting Temperature:
217 °C
Stencil Thickness:
150 µm for base boards
The final choice of the soldering paste depends on the approved manufacturing procedures.
The paste-mask geometry for applying soldering paste should meet the recommendations in section 2.11
The quality of the solder joints on the connectors (’half vias’) should meet the appropriate IPC
specification.
3.3.2 Reflow soldering
A convection type-soldering oven is strongly recommended over the infrared type radiation oven.
Convection heated ovens allow precise control of the temperature and all parts will be heated up evenly,
regardless of material properties, thickness of components and surface color.
Consider the "IPC-7530 Guidelines for temperature profiling for mass soldering (reflow and wave) processes,
published 2001".
Reflow profiles are to be selected according to the following recommendations.
Failure to observe these recommendations can result in severe damage to the device!
Preheat phase
Initial heating of component leads and balls. Residual humidity will be dried out. Note that this preheat phase
will not replace prior baking procedures.

Temperature rise rate: max 3 °C/s
If the temperature rise is too rapid in the preheat phase it may cause
excessive slumping.

Time: 60 to 120 s
If the preheat is insufficient, rather large solder balls tend to be
generated. Conversely, if performed excessively, fine balls and large
balls will be generated in clusters.

End Temperature: 150 to 200 °C
If the temperature is too low, non-melting tends to be caused in
areas containing large heat capacity.
Heating/ reflow phase
The temperature rises above the liquidus temperature of 217 °C. Avoid a sudden rise in temperature as the
slump of the paste could become worse.

Limit time above 217 °C liquidus temperature: 40 to 60 s

Peak reflow temperature: 245 °C
Cooling phase
A controlled cooling avoids negative metallurgical effects (solder becomes more brittle) of the solder and
possible mechanical tensions in the products. Controlled cooling helps to achieve bright solder fillets with a good
shape and low contact angle.

Temperature fall rate: max 4 °C/s
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To avoid falling off, modules should be placed on the topside of the motherboard during soldering.
The soldering temperature profile chosen at the factory depends on additional external factors like choice of
soldering paste, size, thickness and properties of the base board, etc.
Exceeding the maximum soldering temperature and the maximum liquidus time limit in the
recommended soldering profile may permanently damage the module.
Preheat
[°C]
250
Heating
Peak Temp. 245°C
Cooling
[°C]
250
Liquidus Temperature
217
200
217
200
40 - 60 s
End Temp.
150 - 200°C
max 4°C/s
150
150
max 3°C/s
60 - 120 s
Typical Leadfree
Soldering Profile
100
50
100
50
Elapsed time [s]
Figure 68: Recommended soldering profile
LARA-R2 series modules must not be soldered with a damp heat process.
3.3.3 Optical inspection
After soldering the LARA-R2 series modules, inspect the modules optically to verify that the module is properly
aligned and centered.
3.3.4 Cleaning
Cleaning the soldered modules is not recommended. Residues underneath the modules cannot be easily
removed with a washing process.

Cleaning with water will lead to capillary effects where water is absorbed in the gap between the baseboard
and the module. The combination of residues of soldering flux and encapsulated water leads to short circuits
or resistor-like interconnections between neighboring pads. Water will also damage the sticker and the inkjet printed text.

Cleaning with alcohol or other organic solvents can result in soldering flux residues flooding into the two
housings, areas that are not accessible for post-wash inspections. The solvent will also damage the sticker
and the ink-jet printed text.

Ultrasonic cleaning will permanently damage the module, in particular the quartz oscillators.
For best results use a "no clean" soldering paste and eliminate the cleaning step after the soldering.
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3.3.5 Repeated reflow soldering
Only a single reflow soldering process is encouraged for boards with a LARA-R2 series module populated on it.
3.3.6 Wave soldering
Boards with combined through-hole technology (THT) components and surface-mount technology (SMT) devices
require wave soldering to solder the THT components. Only a single wave soldering process is encouraged for
boards populated with LARA-R2 series modules.
3.3.7 Hand soldering
Hand soldering is not recommended.
3.3.8 Rework
Rework is not recommended.
Never attempt a rework on the module itself, e.g. replacing individual components. Such actions
immediately terminate the warranty.
3.3.9 Conformal coating
®
Certain applications employ a conformal coating of the PCB using HumiSeal or other related coating products.
These materials affect the RF properties of the LARA-R2 series modules and it is important to prevent them from
flowing into the module.
The RF shields do not provide 100% protection for the module from coating liquids with low viscosity, therefore
care is required in applying the coating.
Conformal Coating of the module will void the warranty.
3.3.10 Casting
If casting is required, use viscose or another type of silicon pottant. The OEM is strongly advised to qualify such
processes in combination with the LARA-R2 series modules before implementing this in the production.
Casting will void the warranty.
3.3.11 Grounding metal covers
Attempts to improve grounding by soldering ground cables, wick or other forms of metal strips directly onto the
EMI covers is done at the customer's own risk. The numerous ground pins should be sufficient to provide
optimum immunity to interferences and noise.
u-blox gives no warranty for damages to the LARA-R2 series modules caused by soldering metal cables or
any other forms of metal strips directly onto the EMI covers.
3.3.12 Use of ultrasonic processes
LARA-R2 series modules contain components which are sensitive to Ultrasonic Waves. Use of any Ultrasonic
Processes (cleaning, welding etc.) may cause damage to the module.
u-blox gives no warranty against damages to the LARA-R2 series modules caused by any Ultrasonic
Processes.
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4 Approvals
For the complete list and specific details regarding the certification schemes approvals, see LARA-R2 series
Data Sheet [1], or please contact the u-blox office or sales representative nearest you.
4.1
Product certification approval overview
Product certification approval is the process of certifying that a product has passed all tests and criteria required
by specifications, typically called “certification schemes” that can be divided into three distinct categories:


Regulatory certification
o Country specific approval required by local government in most regions and countries, as:

CE (Conformité Européenne) marking for European Union

FCC (Federal Communications Commission) approval for United States
Industry certification
Telecom industry specific approval verifying the interoperability between devices and networks:
 GCF (Global Certification Forum), partnership between device manufacturers and network
operators to ensure and verify global interoperability between devices and networks


PTCRB (PCS Type Certification Review Board), created by United States network operators to ensure
and verify interoperability between devices and North America networks
Operator certification
Operator specific approval required by some mobile network operator, as:
 Verizon Wireless network operator in United States
Even if the LARA-R2 series modules are approved under all major certification schemes, the application device
that integrates the modules must be approved under all the certification schemes required by the specific
application device to be deployed in the market.
The required certification scheme approvals and relative testing specifications differ depending on the country or
the region where the device that integrates LARA-R2 series modules must be deployed, on the relative vertical
market of the device, on type, features and functionalities of the whole application device, and on the network
operators where the device must operate.
The certification of the application device that integrates a LARA-R2 series module and the compliance of
the application device with all the applicable certification schemes, directives and standards are the sole
responsibility of the application device manufacturer.
LARA-R2 series modules are certified according to capabilities and options stated in the Protocol Implementation
Conformance Statement document (PICS) of the module. The PICS, according to 3GPP Technical Specifications
51.010-2 [12], 36.521-2 [14] and 36.523-2 [15], is a statement of device capabilities and options.
The PICS document of the application device integrating a LARA-R2 series module must be updated from
the module PICS statement if any feature stated as supported by the module in its PICS document is not
implemented or disabled in the application device. For more details regarding the AT commands settings
that affect the PICS, see the u-blox AT Commands Manual [2].
Check the specific settings required for mobile network operators approvals as they may differ from the
AT commands settings defined in the module as integrated in the application device.
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4.2
US Federal Communications Commission notice
United States Federal Communications Commission (FCC) IDs:

u-blox LARA-R204 cellular modules:
XPY1EIQN2NN
4.2.1 Safety warnings review the structure

Equipment for building-in. The requirements for fire enclosure must be evaluated in the end product

The clearance and creepage current distances required by the end product must be withheld when the
module is installed

The cooling of the end product shall not negatively be influenced by the installation of the module

Excessive sound pressure from earphones and headphones can cause hearing loss

No natural rubbers, no hygroscopic materials nor materials containing asbestos are employed
4.2.2 Declaration of conformity
This device complies with Part 15 of the FCC rules and with Industry Canada licence-exempt RSS standard(s).
Operation is subject to the following two conditions:

this device may not cause harmful interference

this device must accept any interference received, including interference that may cause undesired operation
Radiofrequency radiation exposure Information: this equipment complies with FCC radiation
exposure limits prescribed for an uncontrolled environment for fixed and mobile use conditions.
This equipment should be installed and operated with a minimum distance of 20 cm between
the radiator and the body of the user or nearby persons. This transmitter must not be
co-located or operating in conjunction with any other antenna or transmitter except in
accordance with FCC procedures and as authorized in the module certification filing.
The gain of the system antenna(s) used for the LARA-R2 series modules (i.e. the combined
transmission line, connector, cable losses and radiating element gain) must not exceed 7.6 dBi
(1700 MHz , i.e. LTE FDD-4) and 10.2 dBi (700 MHz, i.e. LTE FDD-13) for mobile and fixed or
mobile operating configurations.
4.2.3 Modifications
The FCC requires the user to be notified that any changes or modifications made to this device that are not
expressly approved by u-blox could void the user's authority to operate the equipment.
Manufacturers of mobile or fixed devices incorporating the LARA-R2 series modules are
authorized to use the FCC Grants of the LARA-R2 series modules for their own final products
according to the conditions referenced in the certificates.
The FCC Label shall in the above case be visible from the outside, or the host device shall bear a
second label stating:
"Contains FCC ID: XPY1EIQN2NN" resp.
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IMPORTANT: Manufacturers of portable applications incorporating the LARA-R2 series modules
are required to have their final product certified and apply for their own FCC Grant related to
the specific portable device. This is mandatory to meet the SAR requirements for portable
devices.
Changes or modifications not expressly approved by the party responsible for compliance could
void the user's authority to operate the equipment.
Additional Note: as per 47CFR15.105 this equipment has been tested and found to comply with
the limits for a Class B digital device, pursuant to part 15 of the FCC Rules. These limits are
designed to provide reasonable protection against harmful interference in a residential
installation. This equipment generates, uses and can radiate radio frequency energy and, if not
installed and used in accordance with the instructions, may cause harmful interference to radio
communications. However, there is no guarantee that interference will not occur in a particular
installation. If this equipment does cause harmful interference to radio or television reception,
which can be determined by turning the equipment off and on, the user is encouraged to try to
correct the interference by one or more of the following measures:
Reorient or relocate the receiving antenna
Increase the separation between the equipment and receiver
Connect the equipment into an outlet on a circuit different from that to which the receiver
is connected
Consultant the dealer or an experienced radio/TV technician for help
4.3
Industry Canada notice
Industry Canada (IC) Certification Numbers:

u-blox LARA-R204 cellular modules:
4.3.1
8595A-1EIQN2NN
Declaration of Conformity
Radiofrequency radiation exposure Information: this equipment complies with radiation
exposure limits prescribed for an uncontrolled environment for fixed and mobile use conditions.
This equipment should be installed and operated with a minimum distance of 20 cm between
the radiator and the body of the user or nearby persons. This transmitter must not be colocated or operating in conjunction with any other antenna or transmitter except as authorized
in the certification of the product.
The gain of the system antenna(s) used for the LARA-R2 series modules (i.e. the combined
transmission line, connector, cable losses and radiating element gain) must not exceed 7.6 dBi
(1700 MHz , i.e. LTE FDD-4) and 7.0 dBi (700 MHz, i.e. LTE FDD-13) for mobile and fixed or mobile
operating configurations.
4.3.2
Modifications
The IC requires the user to be notified that any changes or modifications made to this device that are not
expressly approved by u-blox could void the user's authority to operate the equipment.
Manufacturers of mobile or fixed devices incorporating the LARA-R2 series modules are
authorized to use the Industry Canada Certificates of the LARA-R2 series modules for their own
final products according to the conditions referenced in the certificates.
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The IC Label shall in the above case be visible from the outside, or the host device shall bear a
second label stating:
"Contains IC: 8595A-1EIQN2NN " resp.
Canada, Industry Canada (IC) Notices
This Class B digital apparatus complies with Canadian CAN ICES-3(B) / NMB-3(B) and RSS-210.
Operation is subject to the following two conditions:
this device may not cause interference
this device must accept any interference, including interference that may cause undesired
operation of the device
Radio Frequency (RF) Exposure Information
The radiated output power of the u-blox Cellular Module is below the Industry Canada (IC)
radio frequency exposure limits. The u-blox Cellular Module should be used in such a manner
such that the potential for human contact during normal operation is minimized.
This device has been evaluated and shown compliant with the IC RF Exposure limits under
mobile exposure conditions (antennas are greater than 20 cm from a person's body).
This device has been certified for use in Canada. Status of the listing in the Industry Canada’s
REL (Radio Equipment List) can be found at the following web address:
http://www.ic.gc.ca/app/sitt/reltel/srch/nwRdSrch.do?lang=eng
Additional Canadian information on RF exposure also can be found at the following web
address: http://www.ic.gc.ca/eic/site/smt-gst.nsf/eng/sf08792.html
IMPORTANT: Manufacturers of portable applications incorporating the LARA-R2 series modules
are required to have their final product certified and apply for their own Industry Canada
Certificate related to the specific portable device. This is mandatory to meet the SAR
requirements for portable devices.
Changes or modifications not expressly approved by the party responsible for compliance could
void the user's authority to operate the equipment.
Canada, avis d'Industrie Canada (IC)
Cet appareil numérique de classe B est conforme aux normes canadiennes CAN ICES-3(B) /
NMB-3(B) et CNR-210.
Son fonctionnement est soumis aux deux conditions suivantes:
cet appareil ne doit pas causer d'interférence
cet appareil doit accepter toute interférence, notamment les interférences qui peuvent
affecter son fonctionnement
Informations concernant l'exposition aux fréquences radio (RF)
La puissance de sortie émise par l’appareil de sans fil u-blox Cellular Module est inférieure à la
limite d'exposition aux fréquences radio d'Industrie Canada (IC). Utilisez l’appareil de sans fil
u-blox Cellular Module de façon à minimiser les contacts humains lors du fonctionnement
normal.
Ce périphérique a été évalué et démontré conforme aux limites d'exposition aux fréquences
radio (RF) d'IC lorsqu'il est installé dans des produits hôtes particuliers qui fonctionnent dans
des conditions d'exposition à des appareils mobiles (les antennes se situent à plus de 20
centimètres du corps d'une personne).
Ce périphérique est homologué pour l'utilisation au Canada. Pour consulter l'entrée
correspondant à l’appareil dans la liste d'équipement radio (REL - Radio Equipment List)
d'Industrie Canada rendez-vous sur:
http://www.ic.gc.ca/app/sitt/reltel/srch/nwRdSrch.do?lang=fra
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Pour des informations supplémentaires concernant l'exposition aux RF au Canada rendez-vous
sur: http://www.ic.gc.ca/eic/site/smt-gst.nsf/fra/sf08792.html
IMPORTANT: les fabricants d'applications portables contenant les modules LARA-R2 series
doivent faire certifier leur produit final et déposer directement leur candidature pour une
certification FCC ainsi que pour un certificat Industrie Canada délivré par l'organisme chargé de
ce type d'appareil portable. Ceci est obligatoire afin d'être en accord avec les exigences SAR
pour les appareils portables.
Tout changement ou modification non expressément approuvé par la partie responsable de la
certification peut annuler le droit d'utiliser l'équipement.
4.4
R&TTED / RED and European Conformance CE mark
LARA-R211 modules have been evaluated against the essential requirements of the 1999/5/EC Directive.
In order to satisfy the essential requirements of the 1999/5/EC Directive, the modules are compliant with the
following standards:

Radio Frequency spectrum use (R&TTE art. 3.2):
o EN 301 511
o EN 301 908-1
o EN 301 908-2
o EN 301 908-13

Electromagnetic Compatibility (R&TTE art. 3.1b):
o EN 301 489-1
o EN 301 489-7
o EN 301 489-24

Health and Safety (R&TTE art. 3.1a)
o EN 60950-1:2006 + A11:2009 + A1:2010 + A12:2011 + A2:2013
o EN 62311:2008
Radiofrequency radiation exposure Information: this equipment complies with radiation
exposure limits prescribed for an uncontrolled environment for fixed and mobile use conditions.
This equipment should be installed and operated with a minimum distance of 20 cm between
the radiator and the body of the user or nearby persons. This transmitter must not be colocated or operating in conjunction with any other antenna or transmitter except as authorized
in the certification of the product.
The conformity assessment procedure for the modules, referred to in Article 10 and detailed in Annex IV of
Directive 1999/5/EC, has been followed with the involvement of the following Notified Body number: 1588
Thus, the following marking is included in the product:
1588
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5 Product testing
5.1
u-blox in-series production test
u-blox focuses on high quality for its products. All units produced are fully tested automatically in production
line. Stringent quality control process has been implemented in the production line. Defective units are analyzed
in detail to improve the production quality.
This is achieved with automatic test equipment (ATE) in production line, which logs all production and
measurement data. A detailed test report for each unit can be generated from the system. Figure 69 illustrates
typical automatic test equipment (ATE) in a production line.
The following typical tests are among the production tests.

Digital self-test (firmware download, Flash firmware verification, IMEI programming)

Measurement of voltages and currents

Adjustment of ADC measurement interfaces

Functional tests (serial interface communication, SIM card communication)

Digital tests (GPIOs and other interfaces)

Measurement and calibration of RF characteristics in all supported bands (such as receiver S/N verification,
frequency tuning of reference clock, calibration of transmitter and receiver power levels, etc.)

Verification of RF characteristics after calibration (i.e. modulation accuracy, power levels, spectrum, etc. are
checked to ensure they are all within tolerances when calibration parameters are applied)
Figure 69: Automatic test equipment for module tests
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5.2
Test parameters for OEM manufacturer
Because of the testing done by u-blox (with 100% coverage), an OEM manufacturer does not need to repeat
firmware tests or measurements of the module RF performance or tests over analog and digital interfaces in their
production test.
An OEM manufacturer should focus on:


Module assembly on the device; it should be verified that:
o Soldering and handling process did not damaged the module components
All module pins are well soldered on device board
There are no short circuits between pins
Component assembly on the device; it should be verified that:
Communication with host controller can be established
The interfaces between module and device are working
Overall RF performance test of the device including antenna
Dedicated tests can be implemented to check the device. For example, the measurement of module current
consumption when set in a specified status can detect a short circuit if compared with a “Golden Device” result.
In addition, module AT commands can be used to perform functional tests on digital interfaces (communication
with host controller, check SIM interface, GPIOs, etc.), on audio interfaces (audio loop for test purposes can be
enabled by the AT+UPAR=2 command as described in the u-blox AT Commands Manual [2]), and to perform RF
performance tests (see the following section 5.2.2 for details).
5.2.1 “Go/No go” tests for integrated devices
A “Go/No go” test is typically to compare the signal quality with a “Golden Device” in a location with excellent
network coverage and known signal quality. This test should be performed after data connection has been
established. AT+CSQ is the typical AT command used to check signal quality in term of RSSI. See the u-blox AT
Commands Manual [2] for detail usage of the AT command.
These kinds of test may be useful as a “go/no go” test but not for RF performance measurements.
This test is suitable to check the functionality of communication with host controller, SIM card as well as power
supply. It is also a means to verify if components at antenna interface are well soldered.
5.2.2 Functional tests providing RF operation
The overall RF functional test of the device including the antenna can be performed with basic instruments such
as a spectrum analyzer (or an RF power meter) and a signal generator with the assistance of AT+UTEST
command over AT command user interface.
The AT+UTEST command provides a simple interface to set the module to Rx or Tx test modes ignoring the
cellular signaling protocol. The command can set the module into:

transmitting mode in a specified channel and power level in all supported modulation schemes and bands

receiving mode in a specified channel to returns the measured power level in all supported bands
See the u-blox AT Commands Manual [2] and the End user test Application Note [24], for the AT+UTEST
command syntax description and examples of use.
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This feature allows the measurement of the transmitter and receiver power levels to check component assembly
related to the module antenna interface and to check other device interfaces from which depends the RF
performance.
To avoid module damage during transmitter test, a proper antenna according to module
specifications or a 50  termination must be connected to ANT1 port.
To avoid module damage during receiver test the maximum power level received at ANT1 and
ANT2 ports must meet module specifications.
The AT+UTEST command sets the module to emit RF power ignoring cellular signaling protocol. This
emission can generate interference that can be prohibited by law in some countries. The use of this
feature is intended for testing purpose in controlled environments by qualified user and must not be used
during the normal module operation. Follow instructions suggested in u-blox documentation. u-blox
assumes no responsibilities for the inappropriate use of this feature.
Figure 70 illustrates a typical test setup for such RF functional test.
Application
Processor
LARA-R2 series
Cellular
antenna
Wideband
antenna
IN
Spectrum
Analyzer
or
Power
Meter
OUT
Signal
Generator
AT
commands
ANT1
TX
Application Board
Cellular
antennas
Application
Processor
Wideband
antenna
LARA-R2 series
AT
commands
ANT1
RX
ANT2
Application Board
Figure 70: Setup with spectrum analyzer or power meter and signal generator for radiated measurements
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Appendix
A Migration between SARA-U2 and LARA-R2
A.1 Overview
Migrating between u-blox SARA-U2 series 3G / 2G cellular modules and LARA-R2 series LTE Cat 1 / 2G cellular
modules is a straightforward procedure that allows customers to take maximum advantage of their hardware
and software investments.
64 63 62 61 60 59 58 57 56 55 54
51
VCC
GND
50
GND
V_INT
49
RSVD
GND
48
RSVD
DSR
RI
47
RSVD
RI
DCD
46
RSVD
DCD
DTR
45
RSVD
DTR
RTS
10
44
RSVD
RTS 10
LARA-R2
CTS
11
Top View
43
GND
CTS 11
TXD
12
Pin 65-96: GND
42
SIM_DET
TXD 12
RXD
13
41
VSIM
RXD 13
GND
14
40
SIM_RST
GND 14
PWR_ON
15
39
SIM_IO
GPIO1
16
38
SIM_CLK
GPIO1 16
VUSB_DET
17
37
I2S_RXD
VUSB_DET 17
RESET_N
18
36
I2S_CLK
RESET_N 18
CODEC_CLK
19
35
I2S_TXD
GPIO6 19
GND
20
34
I2S_WA
GND 20
GND
21
33
RSVD
75
76
77
78
79
80
SARA-U2
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
71
GND
GND
VCC
50
GND
49
SDIO_D1
48
SDIO_D3
47
SDIO_D0
46
SDIO_CMD
45
SDIO_CLK
44
SDIO_D2
Top View
43
GND
Pin 65-96: GND
42
GPIO5
41
VSIM
40
SIM_RST
39
SIM_IO
38
SIM_CLK
37
I2S_RXD
36
I2S_CLK
35
I2S_TXD
34
I2S_WA
33
RSVD
72
68
73
77
69
74
97
98
70
75
76
78
79
80
81
83
82
99
100
84
85
86
87
88
89
90
91
92
93
94
95
96
HOST_SELECT 21
GND
22 23 24 25 26 27 28 29 30 31 32
GND
RSVD
GND
USB_D+
USB_D–
SCL
SDA
GPIO4
GPIO3
GND
VCC
51
PWR_ON 15
22 23 24 25 26 27 28 29 30 31 32
GPIO2
VCC
52
67
GND
74
53
66
RSVD
73
65
GND
72
70
USB_D+
DSR
71
69
RSVD
ANT1
68
HSIC_STRB
GND
GND
V_BCKP
67
USB_D–
GND
VCC
66
SCL
V_INT
ANT_DET
52
65
RSVD
GND
HSIC_DATA
GND
GND
GND
SDA
ANT2
VCC
GPIO4
V_BCKP
64 63 62 61 60 59 58 57 56 55 54
53
GPIO3
GPIO2
GND
GND
GND
GND
GND
ANT
GND
GND
GND
GND
GND
ANT_DET
GND
GND
The SARA cellular modules (26.0 x 16.0 mm, 96-pin LGA) have a different form factor than the LARA cellular
modules (26.0 x 24.0 mm, 100-pin LGA), but the footprint of SARA and LARA modules has been developed to
ensure layout compatibility as described in Figure 71, so that the modules can be alternatively mounted on the
same single common application board.
Figure 71: SARA-U2 and LARA-R2 series modules pin layout and pin assignment
SARA-U2 and LARA-R2 series modules are basically pin-to-pin compatible, given that LARA-R2 series modules
provide further additional functions and interfaces, as shown in Figure 71:

Secondary antenna

SDIO interface

HSIC interface

HOST_SELECT function
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SARA and LARA modules are also form-factor compatible with u-blox LISA and TOBY cellular module families:
although SARA, LARA, LISA (33.2 x 22.4 mm, 76-pin LCC) and TOBY (35.6 x 24.8 mm, 152-pin LGA) modules
each have different form factors, the footprints of all the SARA, LARA, LISA and TOBY modules have been
developed to ensure layout compatibility.
With the u-blox “nested design” solution, any SARA, LARA, LISA or TOBY module can be alternatively mounted
on the same space of a single “nested” application board as described in Figure 72, enabling straightforward
development of products supporting different cellular radio access technologies.
TOBY cellular module
LISA cellular module
LARA cellular module
SARA cellular module
Nested application board
Figure 72: Nested design concept description: SARA, LARA, LISA and TOBY modules alternatively mounted on the same PCB
A different top-side stencil (paste mask) is needed for each form factor (SARA, LARA, LISA and TOBY) to be
alternatively mounted on the same space of a single “nested” application board, as described in Figure 73.
ANT pad
ANT pad
ANT pad
ANT pad
TOBY
LISA
SARA
LARA
TOBY mounting option
with TOBY paste mask
LISA mounting option
with LISA paste mask
SARA mounting option
with SARA paste mask
LARA mounting option
with LARA paste mask
Figure 73: Top-side stencil (paste mask) designs to alternatively mount SARA, LARA, LISA and TOBY modules on the same PCB
Detailed guidelines to implement a nested application board, comprehensive description of the u-blox reference
nested design and detailed comparison between u-blox SARA, LARA, LISA and TOBY modules are provided in
the Nested Design Application Note [26].
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Table 51 summarizes the interfaces provided by SARA-U2 and LARA-R2 series modules: all the interfaces
provided by different modules are electrically compatible, so that the same compatible external circuit can be
implemented on the application board.
●
●
●
●
●
●
●
●
●
●
●
●
12
850
1900
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
12
900
1800
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
●
■
●
●
●
●
■
■
●
■
●
●
●
■
■
900
●
1800
●
●
●
●
●
●
■
●
●
●
●
■
■
●
●
●
●
●
■
■
12
● = supported by all product versions
Wi-Fi control
●
Analog audio
●
DDC (I2C) 1.8 V
GNSS control
3,7,20
Clock output
Network indication
LARA-R211
GPIOs 1.8 V
4,13
Digital audio
●
SDIO 1.8 V
LTE bands
LARA-R204
●
HSIC
2,5
USB 2.0
UART 1.8 V
SIM detection
SARA-U280
SIM 1.8 V / 3.0 V
1,8
12 Quad
Host select
RESET_N
Other
PWR_ON
SARA-U270
Audio
V_INT 1.8 V supply out
2,5
Serial
V_BCKP
SIM
VCC module supply in
System
Antenna Detection
SARA-U260
Power
Rx diversity
1,2,5
8,19
2G bands
Multi-slot class
3G bands
SARA-U201
LTE category
HSUPA category
RF / Radio Access Technology
HSDPA category
Module
■ = supported by all product versions except version ‘02’
Table 51: Summary of SARA-U2 and LARA-R2 series modules interfaces
Figure 74 summarizes the LTE, 3G and 2G operating frequency bands of SARA-U2 and LARA-R2 series modules.
VI
VI
850
SARA-U201
700
750
800
850
824
850
SARA-U260
700
750
VIII
850
900
800
900
850
850
824
900
SARA-U270
750
800
850
900
880
SARA-U280
700
750
800
850
824
LARA-R204
13
700
750
900
950
960
950
750
1700
1800
1800
1850
1900
II
1900
1750
1800
1850
1900
1950
950
960
1800
1700
1750
2050
2100
1950
1700
850
900
800
791
1700
2000
2050
2100
1850
1900
1950
900
900
1750
1800
950
960
1700
1710
2650
2700
2150
2200
2500
2550
2600
2650
2700
2000
2050
2100
2150
2200
2500
2550
2600
2650
2700
1850
1900
1950
2000
2050
2100
2550
2600
2650
2700
1750
2550
2600
2650
2700
2150
2200
2500
2150
2200
2500
1990
1800
1850
1900
1950
2000
2050
2100
2155
1800
900
2600
II
1710
850
2550
1850
950
2500
2170
894
20
2200
2170
800
2150
1710
II
950
2000
II
1900
1990
1800
1800
900
II
1900
1850
13
20
700
1750
II
1900
1710
VIII
900
746 787
LARA-R211
1800
1700
894
VIII
900
700
VIII
1750
1800
1800
1850
1900
1950
2000
2050
2100
2150
2200
1880
2500
2500
2550
2600
2650
2700
2690
LEGENDA
= LTE bands
= 3G bands
= 2G bands
Figure 74: Summary of SARA-U2 and LARA-R2 series modules operating frequency bands
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A.2 Pin-out comparison between SARA-U2 and LARA-R2
SARA-U2
LARA-R2
Pin No
Pin Name
Description
Pin Name
Description
GND
Ground
GND
Ground
Remarks for migration
V_BCKP
RTC Supply I/O
Output characteristics:
1.8 V typ, 3 mA max
Input op. range:
1.0 V – 1.9 V
V_BCKP
RTC Supply I/O
Output characteristics:
1.8 V typ, 3 mA max
Input op. range:
1.0 V – 1.9 V
GND
Ground
GND
Ground
V_INT
Interfaces Supply Out
Output characteristics:
1.8 V typ, 50 mA max
V_INT
Interfaces Supply Out
Output characteristics:
1.8 V typ, 50 mA max
GND
Ground
GND
Ground
DSR
UART DSR Output
1.8 V, Driver strength: 1 mA
DSR
UART DSR Output
1.8 V, Driver strength: 6 mA
No functional difference
RI
UART RI Output
1.8 V, Driver strength: 2 mA
RI
UART RI Output
1.8 V, Driver strength: 6 mA
No functional difference
DCD
UART DCD Output
1.8 V, Driver strength: 2 mA
DCD
UART DCD Output
1.8 V, Driver strength: 6 mA
No functional difference
DTR
UART DTR Input
1.8 V, Internal pull-up: ~14 k
DTR
UART DTR Input
1.8 V, Internal pull-up: ~7.5 k
No functional difference
10
RTS
UART RTS Input
1.8 V, Internal pull-up: ~8 k
RTS
UART RTS Input
1.8 V, Internal pull-up: ~7.5 k
No functional difference
11
CTS
UART CTS Output
1.8 V, Driver strength: 6 mA
CTS
UART CTS Output
1.8 V, Driver strength: 6 mA
No functional difference
12
TXD
UART Data Input
1.8 V, Internal pull-up: ~8 k
TXD
UART Data Input
1.8 V, Internal pull-up: ~7.5 k
No functional difference
13
RXD
UART Data Output
1.8 V, Driver strength: 6 mA
RXD
UART Data Output
1.8 V, Driver strength: 6 mA
No functional difference
14
GND
Ground
GND
Ground
15
PWR_ON
Power-on Input
No internal pull-up
L-level: -0.30 V – 0.65 V
H-level: 1.50 V – 4.40 V
ON L-level pulse time:
50 µs min / 80 µs max
OFF L-level pulse time:
1 s min
PWR_ON
Power-on Input
10 k internal pull-up to V_BCKP
L-level: –0.30 V … 0.54 V
H-level: 1.26 V … 2.10 V
ON L-level pulse time:
50 µs min
OFF L-level pulse time:
Not supported
No functional difference
No functional difference
External  Internal pull-up
Sligtlhy different input levels
Switch-off over this pin is not
supported by LARA-R2 series
16
GPIO1
1.8 V GPIO
Driver strength: 6 mA
GPIO1
1.8 V GPIO
Driver strength: 6 mA
No functional difference
17
VUSB_DET
USB Detect Input
5 V, Supply detection
VUSB_DET
USB Detect Input
5 V, Supply detection
No functional difference
18
RESET_N
Reset signal
10 k internal pull-up
L-level: -0.30 V – 0.51 V
H-level: 1.32 V – 2.01 V
Reset L-level pulse time:
50 ms min
RESET_N
Reset signal
10 k internal pull-up
L-level: -0.30 V – 0.51 V
H-level: 1.32 V – 2.01 V
Reset L-level pulse time:
50 ms min
No functional difference
19
CODEC_CLK
1.8 V Clock Output
Driver strength: 4 mA
GPIO6
1.8 V Clock Output
Driver strength: 6 mA
No functional difference
20
GND
Ground
GND
Ground
21
GND
Ground
HOST_SELECT
1.8 V pin for module / host
configuration selection20
22
GND
Ground
GND
Ground
23
GPIO2
1.8 V GPIO
Driver strength: 1 mA
GPIO2
1.8 V GPIO
Driver strength: 6 mA
No functional difference
24
GPIO3
1.8 V GPIO
Driver strength: 6 mA
GPIO3
1.8 V GPIO
Driver strength: 6 mA
No functional difference
25
GPIO4
1.8 V GPIO
Driver strength: 6 mA
GPIO4
1.8 V GPIO
Driver strength: 6 mA
No functional difference
20
GND  HOST_SELECT
Not supported by “02” product versions
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Appendix
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LARA-R2 series - System Integration Manual
SARA-U2
LARA-R2
Pin No
Pin Name
Description
Pin Name
Description
26
SDA
I C Data I/O
1.8 V, open drain
Driver strength: 1 mA
SDA
I C Data I/O
1.8 V, open drain
Driver strength: 1 mA
No functional difference
27
SCL
I2C Clock Output
1.8 V, open drain
Driver strength: 1 mA
SCL
I2C Clock Output
1.8 V, open drain
Driver strength: 1 mA
No functional difference
28
USB_D-
USB Data I/O (D-)
High-Speed USB 2.0
USB_D-
USB Data I/O (D-)
High-Speed USB 2.0
No functional difference
29
USB_D+
USB Data I/O (D+)
High-Speed USB 2.0
USB_D+
USB Data I/O (D+)
High-Speed USB 2.0
No functional difference
30
GND
Ground
GND
Ground
31
RSVD
Reserved
RSVD
Reserved
32
GND
Ground
GND
Ground
33
RSVD
Reserved
To be externally connected to GND
RSVD
Reserved
To be externally connected to GND
No functional difference
34
I2S_WA
I2S Word Alignment I/O, or GPIO
1.8 V, Driver strength: 2 mA
I2S_WA
I2S Word Alignment I/O21, or GPIO
1.8 V, Driver strength: 6 mA
No functional difference
35
I2S_TXD
I2S Data Output, or GPIO
1.8 V, Driver strength: 2 mA
I2S_TXD
I2S Data Output21, or GPIO
1.8 V, Driver strength: 6 mA
No functional difference
36
I2S_CLK
I2S Clock I/O, or GPIO
1.8 V, Driver strength: 2 mA
I2S_CLK
I2S Clock I/O21, or GPIO
1.8 V, Driver strength: 6 mA
No functional difference
37
I2S_RXD
I2S Data Input, or GPIO
1.8 V, Inner pull-down: ~9 k
I2S_RXD
I2S Data Input21, or GPIO
1.8 V, Inner pull-down: ~7.5 k
No functional difference
38
SIM_CLK
SIM Clock Output
SIM_CLK
SIM Clock Output
No functional difference
39
SIM_IO
SIM Data I/O
SIM_IO
SIM Data I/O
No functional difference
40
SIM_RST
SIM Reset Output
SIM_RST
SIM Reset Output
No functional difference
41
VSIM
SIM Supply Output
VSIM
SIM Supply Output
No functional difference
42
SIM_DET
1.8V SIM Detection
SIM_DET
1.8 V GPIO settable as SIM Detection
No functional difference
43
GND
Ground
GND
Ground
44
RSVD
Reserved
SDIO_D2
1.8 V, SDIO serial data [2]22
RSVD  SDIO
45
RSVD
Reserved
SDIO_CLK
1.8 V, SDIO serial clock22
RSVD  SDIO
46
RSVD
Reserved
SDIO_CMD
1.8 V, SDIO command22
RSVD  SDIO
47
RSVD
Reserved
SDIO_D0
1.8 V, SDIO serial data [0]22
RSVD  SDIO
48
RSVD
Reserved
SDIO_D3
1.8 V, SDIO serial data [3]22
RSVD  SDIO
49
RSVD
Reserved
SDIO_D1
1.8 V, SDIO serial data [1]22
RSVD  SDIO
50
GND
Ground
GND
Ground
51-53
VCC
Module Supply Input
Normal range: 3.3 V – 4.4 V
Extended range: 3.1 V – 4.5 V
VCC
Module Supply Input
Normal range: 3.3 V – 4.4 V
Extended range: 3.0 V – 4.5 V
54-55
GND
Ground
GND
Ground
56
ANT
RF Antenna Input/Output
ANT1
RF Antenna Input/Output (primary)
57-58
GND
Ground
GND
Ground
59
GND
Ground
ANT_DET
Antenna Detection Input
60-61
GND
Ground
GND
Ground
62
ANT_DET
Antenna Detection Input
ANT2
RF Antenna Input (secondary)
63-96
GND
Ground
GND
Ground
97-98
Not Available
RSVD
Reserved
No functional difference
99
Not Available
HSIC_DATA
HSIC USB data line22
Not Available  HSIC
100
Not Available
HSIC_STRB
HSIC USB strobe line22
Not Available  HSIC
Remarks for migration
No functional difference
No functional difference
Larger range for LARA-R2
No functional difference
GND  ANT_DET
ANT_DET  ANT2
Table 52: SARA-U2 and LARA-R2 series modules pin assignment with remarks for migration
For further details regarding the characteristics, capabilities, usage or settings applicable for each interface of the
SARA-U2 and LARA-R2 series modules, see LARA-R2 series Data Sheet [1], SARA-U2 series Data Sheet [27],
SARA-G3 / SARA-U2 series System Integration Manual [28], u-blox AT Commands Manual [2] and Nested Design
Application Note [26].
21
22
Not supported by LARA-R204 module “02” product version.
Not supported by “02” product versions.
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LARA-R2 series - System Integration Manual
A.3 Schematic for SARA-U2 and LARA-R2 integration
Figure 75 shows an example of schematic diagram where a SARA-U2 or a LARA-R2 series module can be
integrated into the same application board, using all the available interfaces and functions of the modules. The
different mounting options for the external parts are herein remarked according to the functions supported by
each module.
SARA-U2 series / LARA-R2 series
BLM18EG221SN1 for SARA-U201
0Ω otherwise
3V8
0Ω
330µF 100nF 10nF
Mount for modules
supporting 2G
56pF
15pF
VCC
52
VCC
53
VCC
8.2pF
ANT / ANT1
39nH
ANT_DET / ANT2
GND
Application
Processor
62
V_BCKP
GND / ANT_DET
TP
TP
18
Open
Drain
Output
TXD
RXD
RTS
CTS
DTR
TP
0Ω
TP
0Ω
TP
0Ω
TP
0Ω
TP
0Ω
TP
DSR
RI
DCD
D+
D-
1k
SIM_DET / GPIO5
42
SW2
VSIM
41
CCVCC (C1)
SIM_IO
39
CCIO (C7)
SIM_CLK
38
CCCLK (C3)
SIM_RST
40
CCRST (C2)
SW1
RESET_N
CCVPP (C6)
TXD
13
RXD
10
RTS
11
CTS
DTR
DSR
RI
DCD
47pF 47pF 47pF 47pF 100nF
470k
GPIO2
23
LDO Regulator
IN
OUT
SHDNn
GND
0Ω
TP
0Ω
TP
29
USB_D+
28
USB_D–
4.7k
100nF
OE
4.7k
GND
99
SDA2
SCL2
SN74AVC2T245
Voltage Translator
VCCB
TP
HSIC_DATA
100nF
DIR1
24
B1
A1
TxD1
GPIO4
25
B2
A2
EXTINT0
OEn
GND
DIR2
GND / HOST_SELECT
0Ω
Not supported by LARA-R204 module “02” product version
Mount for
SARA-U2
3V8
3V0
VCCA
GPIO3
100 HSIC_STRB
21
4.7k
SCL_A GND SCL_B
100nF
TP
4.7k
SDA_B
SDA_A
V_INT
100nF
GND
VCC
100nF
VCCB
VCCA
VUSB_DET
u-blox GNSS
3.0 V receiver
TCA9406DCUR
I2C Voltage Translator
V_INT
100nF
17
3V0
47k
GND
TP
GND (C5)
ESD ESD ESD ESD ESD ESD
Not supported by LARA-R2 series “02” product version
3V8
USB 2.0 Host
VBUS
SIM Card Holder
TP
V_INT
PWR_ON
12
GND
0Ω
Mount for
LARA-R2
ESD
Mount for
LARA-R2
1.8V DTE
0Ω
27pF
0Ω
V_INT
15
Open
Drain
Output
82nH
10k
59
Mount for
SARA-U2
Secondary
Cellular
Antenna
Connector
10k
GND
100k
82nH
33pF
Mount for
SARA-U2
100µF
Primary
Cellular
Antenna
Connector
33pF
56
Mount for modules
supporting LTE band-7
RTC
back-up
0Ω for LARA-R2
15pF
51
V_INT
44
RSVD / SDIO_D2
45
RSVD / SDIO_CLK
46
RSVD / SDIO_CMD
47
RSVD / SDIO_D0
48
RSVD / SDIO_D3
49
RSVD / SDIO_D1
Network
Indicator
16
GPIO1
Audio Codec
MAX9860
10k
IRQn
VDD
MICBIAS
SDA
26
SDA
SCL
27
SCL
MICLP
I2S_TXD
35
SDIN
I2S_RXD
37
I2S_CLK
36
SDOUT
MICGND
BCLK
I2S_WA
34
LRCLK
MICLN
RSVD
CODEC_CLK / GPIO6
19
MCLK
OUTP
OUTN
GND
GND
100nF
1µF
1µF
10µF
2.2k
MIC
EMI
1µF
EMI
1µF
2.2k
10nF 10nF
27pF 27pF
ESD ESD
SPK
RSVD
33
V_INT
EMI
EMI
10nF 10nF
27pF 27pF ESD ESD
Figure 75: Example of complete schematic diagram to integrate SARA-U2 and LARA-R2 modules on the same application board
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LARA-R2 series - System Integration Manual
B Glossary
3GPP
3rd Generation Partnership Project
8-PSK
8 Phase-Shift Keying modulation
16QAM
16-state Quadrature Amplitude Modulation
ACM
Abstract Control Model
ADC
Analog to Digital Converter
AP
Application Processor
ASIC
Application-Specific Integrated Circuit
AT
AT Command Interpreter Software Subsystem, or attention
BAW
Bulk Acoustic Wave
CDC
Communication Device Class
CSFB
Circuit Switched Fall-Back
DC
Direct Current
DCE
Data Communication Equipment
DDC
Display Data Channel interface
DL
Down-Link (Reception)
DRX
Discontinuous Reception
DSP
Digital Signal Processing
DTE
Data Terminal Equipment
EDGE
Enhanced Data rates for GSM Evolution
EMC
Electro-magnetic Compatibility
EMI
Electro-magnetic Interference
ESD
Electro-static Discharge
ESR
Equivalent Series Resistance
FEM
Front End Module
FOAT
Firmware Over AT commands
FOTA
Firmware Over The Air
FTP
File Transfer Protocol
FW
Firmware
GMSK
Gaussian Minimum Shift Keying modulation
GND
Ground
GNSS
Global Navigation Satellite System
GPIO
General Purpose Input Output
GPRS
General Packet Radio Service
GPS
Global Positioning System
GSM
Global System for Mobile Communication
HBM
Human Body Model
HSIC
High Speed Inter Chip
HSDPA
High Speed Downlink Packet Access
HSUPA
High Speed Uplink Packet Access
HTTP
HyperText Transfer Protocol
HW
Hardware
I/Q
In phase and Quadrature
I2C
Inter-Integrated Circuit interface
I2S
Inter IC Sound interface
IP
Internet Protocol
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LARA-R2 series - System Integration Manual
LCC
Leadless Chip Carrier
LDO
Low-Dropout
LGA
Land Grid Array
LNA
Low Noise Amplifier
LPDDR
Low Power Double Data Rate synchronous dynamic RAM memory
LTE
Long Term Evolution
MCS
Modulation Coding Scheme
N/A
Not Applicable
NCM
Network Control Model
OEM
Original Equipment Manufacturer device: an application device integrating a u-blox cellular module
OTA
Over The Air
PA
Power Amplifier
PCM
Pulse Code Modulation
PFM
Pulse Frequency Modulation
PMU
Power Management Unit
PWM
Pulse Width Modulation
QPSK
Quadrature Phase Shift Keying
RF
Radio Frequency
RSE
Radiated Spurious Emission
RTC
Real Time Clock
SAW
Surface Acoustic Wave
SDIO
Secure Digital Input Output
SDN / IN / PCN
Sample Delivery Note / Information Note / Product Change Notification
SIM
Subscriber Identification Module
SMS
Short Message Service
SMTP
Simple Mail Transfer Protocol
SRF
Self Resonant Frequency
TBD
To Be Defined
TCP
Transmission Control Protocol
TDMA
Time Division Multiple Access
TIS
Total Isotropic Sensitivity
TP
Test-Point
TRP
Total Radiated Power
UART
Universal Asynchronous Receiver-Transmitter
UDP
User Datagram Protocol
UICC
Universal Integrated Circuit Card
UL
Up-Link (Transmission)
UMTS
Universal Mobile Telecommunications System
USB
Universal Serial Bus
UTRA
UMTS Terrestrial Radio Access
VCO
Voltage Controlled Oscillator
VoLTE
Voice over LTE
VSWR
Voltage Standing Wave Ratio
Wi-Fi
Wireless Local Area Network (IEEE 802.11 short range radio technology)
WLAN
Wireless Local Area Network (IEEE 802.11 short range radio technology)
WWAN
Wireless Wide Area Network (GSM / UMTS / LTE cellular radio technology)
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Appendix
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LARA-R2 series - System Integration Manual
Related documents
[1]
u-blox LARA-R2 series Data Sheet, Docu No UBX-16005783
[2]
[3]
u-blox AT Commands Manual, Docu No UBX-13002752
u-blox EVK-R2xx User Guide, Docu No UBX-16016088
[4]
u-blox Windows Embedded OS USB Driver Installation Application Note, Docu No UBX-14003263
[5]
ITU-T Recommendation V.24 - 02-2000 - List of definitions for interchange circuits between the Data
Terminal Equipment (DTE) and the Data Circuit-terminating Equipment (DCE).
http://www.itu.int/rec/T-REC-V.24-200002-I/en
[6]
[7]
3GPP TS 27.007 – AT command set for User Equipment (UE) (Release 1999)
3GPP TS 27.005 – Use of Data Terminal Equipment – Data Circuit terminating; Equipment (DTE – DCE)
interface for Short Message Service (SMS) and Cell Broadcast Service (CBS) (Release 1999)
[8]
[9]
3GPP TS 27.010 – Terminal Equipment to User Equipment (TE-UE) multiplexer protocol (Release 1999)
Universal Serial Bus Revision 2.0 specification, http://www.usb.org/developers/docs/usb20_docs/
[10]
High-Speed Inter-Chip USB Specification, Ver. 1.0, http://www.usb.org/developers/docs/usb20_docs/
[11]
I2C-bus specification and user manual - Rev. 5 - 9 October 2012 - NXP Semiconductors,
http://www.nxp.com/documents/user_manual/UM10204.pdf
[12]
3GPP TS 51.010-2 – Technical Specification Group GSM/EDGE Radio Access Network; Mobile Station
(MS) conformance specification; Part 2: Protocol Implementation Conformance Statement (PICS)
3GPP TS 36.521-1 - Evolved Universal Terrestrial Radio Access; User Equipment conformance
specification; Radio transmission and reception; Part 1: Conformance Testing
3GPP TS 36.521-2 - Evolved Universal Terrestrial Radio Access (E-UTRA); User Equipment conformance
specification; Radio transmission and reception; Part 2: Implementation Conformance Statement (ICS)
3GPP TS 36.523-2 - Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Packet Core (EPC);
User Equipment conformance specification; Part 2: Implementation Conformance Statement (ICS)
GSM Association TS.09 - Battery Life Measurement and Current Consumption Technique
http://www.gsma.com/newsroom/wp-content/uploads//TS.09_v8.0.pdf
[13]
[14]
[15]
[16]
[17]
[18]
CENELEC EN 61000-4-2 (2001) – Electromagnetic compatibility (EMC); Part 4-2: Testing and
measurement techniques; Electrostatic discharge immunity test
ETSI EN 301 489-1 V1.8.1 – Electromagnetic compatibility and Radio spectrum Matters; EMC standard
for radio equipment and services; Part 1: Common technical requirements
[19]
ETSI EN 301 489-7 V1.3.1 – Electromagnetic compatibility and Radio spectrum Matters; EMC standard
for radio equipment and services; Part 7: Specific conditions for mobile and portable radio and ancillary
equipment of digital cellular radio telecommunications systems (GSM and DCS)
[20]
ETSI EN 301 489-24 V1.4.1 – Electromagnetic compatibility and Radio spectrum Matters; EMC
standard for radio equipment and services; Part 24: Specific conditions for IMT-2000 CDMA Direct
Spread (UTRA) for Mobile and portable (UE) radio and ancillary equipment
[21]
[22]
u-blox Multiplexer Implementation Application Note, Docu No UBX-13001887
u-blox GNSS Implementation Application Note, Docu No UBX-13001849
[23]
u-blox Firmware Update Application Note, Docu No UBX-13001845
[24]
[25]
u-blox End user test Application Note, Docu No UBX-13001922
u-blox Package Information Guide, Docu No UBX-14001652
[26]
u-blox Nested Design Application Note, Docu No UBX-16007243
[27]
[28]
u-blox SARA-U2 series Data Sheet, Docu No UBX-13005287
u-blox SARA-G3 and SARA-U2 series System Integration Manual, Docu No UBX-13000995
Some of the above documents can be downloaded from u-blox web-site (http://www.u-blox.com).
UBX-16010573 - R02
Objective Specification
Related documents
Page 146 of 148
LARA-R2 series - System Integration Manual
Revision history
Revision
Date
Name
Status / Comments
R01
20-Sep-2016
sses
Initial release
UBX-16010573 - R02
Objective Specification
Revision history
Page 147 of 148
LARA-R2 series - System Integration Manual
Contact
For complete contact information visit us at www.u-blox.com.
u-blox Offices
North, Central and South America
u-blox America, Inc.
Phone:
+1 703 483 3180
E-mail:
info_us@u-blox.com
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E-mail:
info_us@u-blox.com
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E-mail:
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Support: support@u-blox.com
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Objective Specification
Contact
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