SY8088 Datasheet. Www.s Manuals.com. Silergy

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Application Notes: AN_SY8088
High Efficiency 1.5MHz, 1A
Synchronous Step Down Regulator
Preliminary Specification

General Description

Features

SY8088 is a high efficiency 1.5MHz synchronous step
down DC/DC regulator IC capable of delivering up to
1A output current. It can operate over a wide input
voltage range from 2.5V to 5.5V and integrate main
switch and synchronous switch with very low RDS (ON)
to minimize the conduction loss.

• Low RDS(ON) for internal switches (top/bottom)
260mΩ/170mΩ
• 2.5~5.5V input voltage range
• 40µA typical quiescent current

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• High light load efficiency
• High switching frequency 1.5MHz minimizes the
external components

Ordering Information

• Internal soft-start limits the inrush current

Temperature Code
Package Code
Optional Spec Code
Temperature Range: -40°C to 85°C

• 100% dropout operation

• Compact package: SOT23-5

Note
1A

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Package Type
SOT23-5

• RoHS Compliant and Halogen Free

Applications

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Ordering Number
SY8088AAC

SY8088 □(□□)□

Portable Navigation Device
Set Top Box
USB Dongle
Media Player
Smart phone

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Typical Application

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•
•
•
•
•

Efficiency vs. Load Current
95

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VIN=3.3V,VOUT=1.8V
VIN=4.2V,VOUT=1.8V
75

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VIN=5.0V,VOUT=1.8V

100

1000

Load Current (mA)

Figure1. Schematic Diagram

AN_SY8088 Rev. 0.1

Figure2. Efficiency

Silergy Corp. Confidential- Prepared for Customer Use Only

AN_SY8088
Pinout (Top View)

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(SOT23-5)

Top Mark: LDxyz (device code: LD, x=year code, y=week code, z= lot number code)

Pin Description
Enable control. Pull high to turn on. Do not float.
Ground pin.
Inductor pin. Connect this pin to the switching node of the inductor.
Input pin. Decouple this pin to the GND pin with at least 4.7uF ceramic
capacitor.
Output Feedback Pin. Connect this pin to the center point of the output resistor
divider (as shown in Figure 1) to program the output voltage:
VOUT=0.6*(1+R1/R2).Add optional C1 (10pF~47pF) to speed up the transient
response.

Pin Number
1
2
3
4

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Pin Name
EN
GND
LX
IN

Absolute Maximum Ratings (Note 1)

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Supply Input Voltage -------------------------------------------------------------------------------------------------------- 6.0V
Enable, FB Voltage---------------------------------------------------------------------------------------------------- VIN + 0.6V
Power Dissipation, PD @ TA = 25°C, SOT23-5--------------------------------------------------------------------------- 0.6W
Package Thermal Resistance (Note 2)
θ JA -------------------------------------------------------------------------------------------------------------- 170°C/W
θ JC ---------------------------------------------------------------------------------------------------------- ----130°C/W
Junction Temperature Range ----------------------------------------------------------------------------------------------125°C
Lead Temperature (Soldering, 10 sec.) ---------------------------------------------------------------------------------- 260°C
Storage Temperature Range ----------------------------------------------------------------------------------- -65°C to 150°C

Recommended Operating Conditions (Note 3)

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Supply Input Voltage ----------------------------------------------------------------------------------------------- 2.5V to 5.5V
Junction Temperature Range ----------------------------------------------------------------------------------- -40°C to 125°C
Ambient Temperature Range ------------------------------------------------------------------------------------ -40°C to 85°C

AN_SY8088 Rev. 0.1

Silergy Corp. Confidential- Prepared for Customer Use Only

AN_SY8088
Electrical Characteristics
(VIN = 5V, VOUT = 2.5V, L = 2.2uH, COUT = 10uF, TA = 25°C, unless otherwise specified)

0.588

40
0.1
0.6
260

Max
5.5
1
0.612

170
1.3
1.5

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TSS
TSD
THYS

Typ

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RDS(ON),N
ILIM
VENH
VENL
VUVLO
VHYS
FOSC

IOUT=0, VFB=VREF ⋅ 105%
EN=0

Min
2.5

NFET RON
PFET Current Limit
EN rising threshold
EN falling threshold
Input UVLO threshold
UVLO hysteresis
Oscillator Frequency
Min ON Time
Max Duty Cycle
Soft Start Time
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis

Test Conditions

Symbol
VIN
IQ
ISHDN
VREF
RDS(ON),P

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Parameter
Input Voltage Range
Quiescent Current
Shutdown Current
Feedback Reference Voltage
PFET RON

0.4
2.5

0.1
1.5
80

100
1
160
15

Unit
V
µA
µA
V
mΩ
mΩ
A
V
V
V
V
MHz
ns
%
ms
°C
°C

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Note 1: Stresses beyond the “Absolute Maximum Ratings” may cause permanent damage to the device. These are
for stress ratings. Functional operation of the device at these or any other conditions beyond those indicated in the
operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for
extended periods may remain possibility to affect device reliability.

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Note 2: θ JA is measured in the natural convection at TA = 25°C on a low effective single layer thermal conductivity
test board of JEDEC 51-3 thermal measurement standard. Exposed Paddle of DFN package is the case position for
θ JC measurement.

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Note 3: The device is not guaranteed to function outside its operating conditions.

AN_SY8088 Rev. 0.1

Silergy Corp. Confidential- Prepared for Customer Use Only

AN_SY8088
Typical Performance Characteristics
Efficiency vs. Load Current

Efficiency vs. Load Current
95

85
85
80
80
75

VIN=3.3V,VOUT=1.2V

VIN=3.3V,VOUT=1.8V
75

1000

100

VIN=5.0V,VOUT=1.8V

VIN=4.2V,VOUT=1.8V

VIN=5.0V,VOUT=1.2V

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VIN=4.2V,VOUT=1.2V

Load Current (mA)
Output Ripple

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Efficiency vs. Load Current
100

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85
VIN=4.2V,VOUT=3.3V

VIN=5V,VOUT=3.3V

100

20mV/div

2.0V/div

0.5A/div

1000

Time (400ns/div)

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(VIN=5.0V, VOUT=1.8V, ILOAD=0A)

∆Vout

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1000

Load Current (mA)

100

Load Current (mA)

20mV/div

∆Vout

2.0V/div

1.0A/div

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Output Ripple
(VIN=5.0V, VOUT=1.8V, ILOAD=1A)

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∆Vout

Output Ripple

(VIN=5.0V, VOUT=1.8V, ILOAD=0.2A)

20mV/div

0.5A/div

Time (400ns/div)

AN_SY8088 Rev. 0.1

Time (400ns/div)

Silergy Corp. Confidential- Prepared for Customer Use Only

AN_SY8088
Startup from Enable

Shutdown from Enable

(VIN=5.0V, VOUT=1.8V, ILOAD=1.0A)

5.0V/div

VOUT

1.0V/div

VOUT

1.0V/div

5.0V/div

1.0A/div

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Time (40µs/div)

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Time (400µs/div)

AN_SY8088 Rev. 0.1

Silergy Corp. Confidential- Prepared for Customer Use Only

AN_SY8088

(V − 0.6 V) ⋅ R2
R1 = OUT
0.6V

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Input capacitor CIN:
A typical X7R or better grade ceramic capacitor with
6V rating and greater than 4.7uF capacitance is
recommended. To minimize the potential noise
problem, place this ceramic capacitor really close to the
IN and GND pins. Care should be taken to minimize
the loop area formed by CIN, and IN/GND pins.

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Output capacitor COUT:
The output capacitor is selected to handle the output
ripple noise requirements. Both steady state ripple and
transient requirements must be taken into consideration
when selecting this capacitor. For the best performance,
it is recommended to use X7R or better grade ceramic
capacitor with 6V rating and greater than 4.7uF
capacitance.
Output inductor L:
There are several considerations in choosing this
inductor.
1) Choose the inductance to provide the desired
ripple current. It is suggested to choose the ripple
current to be about 40% of the maximum output
current. The inductance is calculated as:
VOUT (1 − VOUT/VIN,MAX )
L=
FSW × IOUT,MAX × 40%

AN_SY8088 Rev. 0.1

Layout Design:
The layout design of SY8088 regulator is relatively
simple. For the best efficiency and minimum noise
problems, we should place the following components
close to the IC: CIN, L, R1 and R2.

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Feedback resistor dividers R1 and R2:
Choose R1 and R2 to program the proper output
voltage. To minimize the power consumption under
light loads, it is desirable to choose large resistance
values for both R1 and R2. A value of between 100kΩ
and 1MΩ is highly recommended for both resistors. If
R2=120kΩ is chosen, then R1 can be calculated to be:

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Because of the high integration in the SY8088 IC, the
application circuit based on this regulator IC is rather
simple. Only input capacitor CIN, output capacitor COUT,
output inductor L and feedback resistors (R1 and R2)
need to be selected for the targeted applications
specifications.

Applications Information

The SY8088 is a high-efficiency 1.5MHz synchronous
step-down DC-DC converters capable of delivering up
to 1A output current. It operates over a wide input
voltage range from 2.5V to 5.5V and integrates main
switch and synchronous switch with very low RDS(ON)
to minimize the conduction loss.

where Fsw is the switching frequency and Iout,max is
the maximum load current.
The SY8088 regulator IC is quite tolerant of different
ripple current amplitude. Consequently, the final choice
of inductance can be slightly off the calculation value
without significantly impacting the performance.
2) The saturation current rating of the inductor must
be selected to be greater than the peak inductor
current under full load conditions.
VOUT(1-VOUT/VIN,MAX)
ISAT, MIN > IOUT, MAX +
2 ⋅ FSW ⋅ L
3) The DCR of the inductor and the core loss at the
switching frequency must be low enough to achieve the
desired efficiency requirement. It is desirable to choose
an inductor with DCR<50mohm to achieve a good
overall efficiency.

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Operation

1) It is desirable to maximize the PCB copper area
connecting to GND pin to achieve the best thermal and
noise performance. If the board space allowed, a
ground plane is highly desirable.

2) CIN must be close to Pins IN and GND. The loop
area formed by CIN and GND must be minimized.
3) The PCB copper area associated with LX pin must
be minimized to avoid the potential noise problem.
4) The components R1 and R2, and the trace
connecting to the FB pin must NOT be adjacent to the
LX net on the PCB layout to avoid the noise problem.
5) If the system chip interfacing with the EN pin has a
high impedance state at shutdown mode and the IN pin
is connected directly to a power source such as a LiIon
battery, it is desirable to add a pull down 1Mohm
resistor between the EN and GND pins to prevent the
noise from falsely turning on the regulator at shutdown
mode.
Load Transient Considerations:
The SY8088 regulator IC integrates the compensation
components to achieve good stability and fast transient
responses. In some applications, adding a 22pF ceramic
cap in parallel with R1 may further speed up the load
transient responses and is thus recommended for
applications with large load transient step requirements.

Silergy Corp. Confidential- Prepared for Customer Use Only

AN_SY8088
SOT23-5 Package outline & PCB layout design
0.55

1.50 - 1.70

0.80

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2.70 - 3.00

2.40

2.80 - 3.10

0.30 - 0.50

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0.95 TYP

0.01 - 0.1

1.0 - 1.3

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0.1 - 0.15

0.25 REF

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Recommended Pad Layout

0.95 TYP
1.90 TYP

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0.3 - 0.6

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Notes: All dimensions are in millimeters.
All dimensions don’t include mold flash & metal burr.

AN_SY8088 Rev. 0.1

Silergy Corp. Confidential- Prepared for Customer Use Only

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Title                           : SY8088 - Datasheet. www.s-manuals.com.
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