CR6850 Datasheet. Www.s Manuals.com. Chip Rail

User Manual: Datasheets CR6850S, CR6850T.

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CR6850
Novel Low Cost Green-Power PWM Controller
Features
z
z
z
z
z
z
z
z
z

Low Cost, PWM&PFM&CRM (Cycle
Reset Mode)
Low Start-up Current (about 8µA)
Low Operating Current (about 2mA)
Current Mode Operation
Under Voltage Lockout (UVLO)
Built-in Synchronized Slope
Compensation
Programmable PWM Frequency
Audio Noise Free Operation
Leading edge Blanking on Sense input

z
z
z
z

Constant output power limiting for
universal AC input
Cycle-by-cycle current limiting
Soft clamped gate output voltage 16.8V
Over voltage protect 25.5V
High-Voltage CMOS Process with ESD

z

SOT-23-6L、SOP8 & DIP-8 Pb-Free

z

Packaging
Compatible with SG5701 & SG5848 &
LD7535 & OB2262/63

z
z

Open Frame Switching Power Supply
384X Replacement

z

Applications
z
z

Switching AC/DC Adaptor
Battery Charger

General Description
The CR6850 is a highly integrated low cost
current mode PWM controller, which is ideal
for small power current mode of offline
AC-DC fly-back converter applications.
Making use of external resistors, the IC
changes the operating frequency and
automatically enters the PFM/CRM (Cycle
Reset Mode) under light-load/zero-load
conditions. This can minimize standby
power
consumption
and
achieve
green-power functions. With a very low
start-up current, the CR6850 could use a
large value start-up resistor (2Mohm).
Built-in synchronized slope compensation
enhances the stability of the system and
avoids sub-harmonic oscillation. Dynamic
peak limiting circuit minimizes output power
change caused by delay time of the system

Dec, 2006

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over a universal AC input range. Leading
edge blanking circuit on current sense input
could remove the signal glitch due to
snubber circuit diode reverse recovery and
thus
greatly
reduces
the
external
component count and system cost in the
design. Pulse-by-pulse current limiting
ensures safe operation even during
short-circuit.
The CR6850 offers more protection like
OVP (Over Voltage Protection) and OCP
(Over current protection). The CR6850’s
output driver is soft clamped to maximum
16.8V to protect the power MOSFET.
Excellent EMI performance is achieved soft
switching control at the totem pole gate
driver output. CR6850 is offered in
SOT-23-6, SOT-8 and DIP-8 packages.

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CR6850

CR68XX Series
Part
Number

PWM
Frequency

Package

CR6848

External
Adjustable

DIP-8、SOP8
SOT-23-6L

CR6850

External
Adjustable

DIP-8、SOP8
SOT-23-6L

CR6851

External
Adjustable

DIP-8、SOP8
SOT-23-6L

Description
PWM&PF&CRM 、 Current Mode 、 Slope
Compensation Leading-edge Blanking 、 Gate
Clamped、Over-voltage Protection、Over-current
Protection、 Soft Drive.
With All Functions of CR6848 、 Gate soft
Clamped
With All Functions of CR6850、Frequency jitter、
Soft start、Sense Fault Protect、OLP、SCP、
OTP

TYPICAL APPLICATION

Pin Assignment

Pin Descriptions
Name
GND
FB
RI
SEN
VDD
GATE
Dec, 2006

Description
GND Pin
Analog Input. Voltage feedback pin (same as the COMP pin in UC384X),
This pin is to program the switching frequency. By connecting a resistor
to ground to set the switching frequency.
Current sense pin, connect to sense the MOSFET current.
Supply voltage pin.
Totem output to drive the external Power MOSFET.

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CR6850

Block Diagram

Simplified Internal Circuit Architecture

Absolute Maximum Ratings
Symbol
VDD
IOVP
VFB
VSEN
PD

Parameter
Supply voltage Pin Voltage
VDD OVP maximal enter current
Input Voltage to FB Pin
Input Voltage to SEN Pin
Power Dissipation
ESD Capability, HBM Model
ESD Capability, Machine Model
20second
SOT-23-6L
Lead Temperature
(Soldering)
10second
DIP-8
Storage Temperature Range

ESD

TL

TSTG

Rating
40
20
-0.3 to 6V
-0.3 to 6V
300
2500
250

Unit
V
mA
V
V
mW
V
V

220

℃

260

℃

-55 to + 150

℃

RECOMMENDED OPERATION CONDITION
Symbol
VDD
RI
TOA

Parameter
VDD Supply Voltage
RI PIN Resistor Value
Operation Ambient Temperature

Min ~ Max
11~20
65~130
-20~85

Unit
V
K ohm

PO
FPWM

Output Power
Frequency of PWM

0~60
50~100

W
kHz

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CR6850

Electrical Characteristics (Ta=25°C unless otherwise noted, VDD = 15V.)
Symbol

Parameter

Conditions

Min.

Typ.

Max.

Unit

Supply Voltage (VDD Pin)
IST

ISS

Startup Current

Operating Current

8

µA

VFB=0V

2.9

mA

VFB=3V

1.9

mA

VFB=Open

1.44

mA

VDDON

Turn-on Threshold Voltage

15.3

V

VDDOFF

Turn-off Threshold Voltage

9.8

V

VDCLAMP

VDD Clamp Voltage

IVDD=20mA

25.5

V

Voltage Feedback (FB Pin)
IFB

Short Circuit Current

VFB=0V

1.68

mA

VFB

Open Loop Voltage

VFB=Open

4.7

V

IPFM

Enter PFM&PWM, FB current

1.2

mA

ICRM

Enter CRM, FB current

1.5

mA

VPFM

PFM Threshold VFB

1.15

V

Current Sensing (SEN Pin)
VTH_L

Minimum Voltage Lever

0.55

0.65

0.75

V

VTH_H

Maximum Voltage Lever

0.75

0.85

0.95

V

TPD

Delay to Output

300

ns

RCS

Input Impedance

50

KΩ

Oscillator (RI Pin)
FOSC

Normal Frequency

RI=100Kohm

FPFM

PFM Frequency

RI=100Kohm

20.6

KHZ

DCMAX

Maximum Duty Cycle

RI=100Kohm

77

%

ΔFTEMP

Frequency Temp. Stability

-30-85℃

5

%

300

nS

TBLANK

60

Leading-Edge Blanking Time

65

70

KHz

GATE Drive Output (GATE Pin)
VOL

Output Low Level

VDD=15V, IO=20mA

VOH

Output High Level

VDD=15V, IO=20mA

TR

Rising Time

CL=1000pF

420

ns

TF

Falling Time

CL=1000pF

120

ns

Output Clamp Voltage

VDD=20V

16.8

VGCLAMP

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V
V

17.8

4/15

V

CR6850

TYPICAL CHARACTERISTICS

VDD startup Current VS Temperature

VDD (OFF) VS Temperature

VDD Operation Current VS Temperature

PWM frequency VS Temperature

VDD (ON) VS Temperature
Duty cycle VS Temperature

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CR6850

FOSC VS RI Resistor

OVP VS Temperature

FOSC VS FB Current

Dec, 2006

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CR6850

OPERATION DESCRIPTION
Current Model
Compared to voltage model control,
current model control has a current
feedback loop. When the voltage of the
sense resistor peak current of the primary
winding reaches the internal setting value
VTH, comparator reverse, register reset and
power MOSFET cut-off. So that to detect
and modulate the peak current cycle by
cycle could control the output of the power
supply. The current feedback has a good
linear modulation rate and a fast input and
output dynamic impact avoid the pole that
the output filter inductance brings and the
second class system descends to first class
and so it widens the frequency range and
optimizes overload protection and short
circuit protection.

Startup Current and Under Voltage
Lockout
The startup current of CR6850 is set to be
very low so that a large value startup
resistor can therefore be used to minimize
the power loss. For AC to DC adaptor with
universal input range design, a 2 MΩ, 1/8 W
startup resistor and a 10uF/25V VDD hold
capacitor could be used.
The turn-on and turn-off threshold of the
CR6850 is designed to 15.3V/9.8V. During
startup, the hold-up capacitor must be
charge to 15.3V through the startup resistor.
The hysteresis is implemented to prevent
the shutdown from the voltage dip during
startup.

Internal Bias and OSC Operation
A resistor connected between RI pin and
GND pin set the internal constant current
source to charge or discharge the internal
fixed cap. The charge time and discharge
time determine the internal clock speed and
the switching frequency. Increasing the
resistance will reduce the value of the input
current and reduce the switching frequency.
The relationship between RI pin and PWM
switching frequency follows the below
equation within the RI allowed range.

FOSC =

Green Power Operation
The power dissipation of switching mode
power supply is very important in zero load
or light load condition. The major dissipation
result from conduction loss、switching loss
and consume of the control circuit. However,
all of them related to the switching
frequency. There are many difference
topologies has been implemented in
different chip. The basic operation theory of
all these approaches intended to reduce the
switching frequency under light-load or
no-load condition.
CR6850`s green power function adapts
PWM、PFM and CRM combining modulation.
When RI resistor is 100k, the PWM
frequency is 65kHz in medium or heavy load
operation. Through modifying the pulse
width, CR6850 could control output voltage.
The current of FB pin increases when the
load is in light condition and the internal
mode controller enters PFM&PWM when
the feedback current is over 1.2mA. The
operation frequency of oscillator is to
descend gradually. The invariable frequency
of oscillator is 21kHz when the feedback
current is over 1.35mA. To decrease the
standby consumption of the power supply ,
Chip-Rail introduces the Cycle Reset Mode
technology；If the feedback current were
over 1.5mA, mode controller of CR6850
would reset internal register all the time and
cut off the gate pin, while the output voltage
is lower than the set value, it would set
register, gate pin operating again. Although
the frequency of the internal OSC is
invariable, the register would reset some
pulses so that the practical frequency is
decreased at the gate pin.

6500
(kHz )
RI ( KΩ)

For example, a 100kΩ resistor RI could
generate a 50uA constant current and a
65kHz PWM switching frequency. The
Dec, 2006

suggested operating frequency range of
CR6850 is within 50KHz to 100KHz.

CR6850 Green-Power Function

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CR6850

Internal
Synchronized
Compensation

Slop

Although there are more advantages of the
current mode control than conventional
voltage mode control, there are still several
drawbacks of peak-sensing current-mode
converter. Especially the open loop
instability when it operates in higher than
50% of the duty-cycle. CR6850 is introduced
an internal slope compensation adding
voltage ramp to the current sense input
voltage for PWM generation to solve this
problem. It improves the close loop stability
greatly at CCM, prevents the sub-harmonic
oscillation and thus reduces the output
ripple voltage.

VSLOP = 0.33 ×

DUTY
= 0.4389 × DUTY
DUTYMAX

primary wind inductance. V IN ranges from
85VAC to 264VAC. To guarantee the output
power is a constant for universal input AC
voltage, there is a dynamic peak limit circuit
to compensate the system delay T that the
system delay brings on.

Leading-edge Blanking (LEB)
Each time the power MOSFET is switched
on, a turn-on spike will inevitably occur at
the sense pin, which would disturb the
internal signal from the sampling of the
RSENSE. There is a 300n sec leading edge
blanking time built in to avoid the effect of
the turn-on spike and the power MOSFET
cannot be switched off during this time. So
that the conventional external RC filtering on
sense input is no longer required.

Current Sensing & Dynamic peak
limiting
The current flowing by the power MOSFET
comes in to being a voltage VSENSE on the
sense pin cycle by cycle, which compares to
the internal reference voltage, controls the
reverse of the internal register, limits the
peak current IMAX of the primary of the
transformer. The energy E =

1
2
× L × I MAX
2

deposited by the transformer. So adjusting
the RSENSE can set the Max output power of
the power supple mode. The current flowing
by the power MOSFET has an extra value

∆I =

V IN
× TD due to the system delay T
LP

that the current detected from the sense pin
to power MOSFET cut off in the CR6850
(Among these, VIN is the primary winding
voltage of the transformer and LP is the

Dec, 2006

Over Voltage Protection (OVP)
There is a 25.5V over-voltage protection
circuit in the CR6850 to improve the
credibility and extend the life of the chip. The
GATE is to shutdown immediately when the
voltage of the VDD is over 25.5V and the
voltage of VDD is to descend rapidly.

Gate Driver & Soft Clamped
CR6850’ output designs a totem pole to
drive a periphery power MOSFET. The dead
time is introduced to minimize the transfixion
current when the output is drove. The
NMOS is shut off when the other NMOS is
turned on. The novel soft clamp technology
is introduced to protect the periphery power
MOSFET from breaking down and current
saturation of the Zener.

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CR6850

PACKAGE DEMENSIONS
DIP-8L

Dimensions

Symbol

Millimeters
Min.

Typ.

A

Min.

Typ.

5.334

A1

0.381

A2

3.175

0.210

3.302

3.429

0.125

0.130

b

1.524

0.060

0.457

0.018

9.017

E
E1

9.271

10.160

0.355

7.620
6.223

e

Max.

0.015

b1
D

Dec, 2006

Inches
Max.

6.350

0.365

0.135

0.400

0.300
6.477

0.245

2.540

0.250

0.255

0.100

L

2.921

3.302

3.810

0.115

0.130

0.150

eB

8.509

9.017

9.525

0.335

0.355

0.375

θ˚

0˚

7˚

15˚

0˚

7˚

15˚

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CR6850

SOT-23-6L

Symbol

Dimensions In Millimeters

Dimensions In Inches

Min

Max

Min

Max

A

0.700

1.000

0.028

0.039

A1

0.000

0.100

0.000

0.004

B

1.397

1.803

0.055

0.071

b

0.300

0.559

0.012

0.022

C

2.591

3.000

0.102

0.118

D

2.692

3.099

0.106

0.122

e

0.838

1.041

0.033

0.041

H

0.080

0.254

0.003

0.010

L

0.300

0.610

0.012

0.024

SOP-8L
Dec, 2006

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CR6850

Dimensions DISCLAIMERS
Symbol

Min.

A

1.346

A1

0.101

Max.

Min.

1.752

0.053

0.254

0.004

Inch
Typ.

0.010

0.406

0.016

c

0.203

0.008

D

4.648

4.978

0.183

E

3.810

3.987

0.150

e

1.016

1.524

0.040

1.270
0.381X45
°

Max.
0.069

b

F

Dec, 2006

Millimeter
Typ.

0.196
0.157
0.050
0.015X45
°

0.060

H

5.791

6.197

0.228

0.244

L

0.406

1.270

0.016

0.050

θ˚

0°

8°

0°

8°

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CR6850

REFERENCE CIRCUIT 1
CR6850 drives a periphery Power MOSFET.
5V/6A 30W Power Supply

Quantity
1
1
1
1
1
1
1
2
1
1
1
1
1
1
1
1

Part Number
C1
C2
C3
C4
C5
C7
C8
C6、C7
C8
BD1
D1
D2
D3
D4
T1
T2

Description

Quantity

102/1000V
103/1000V
104
33uF/400V
223/1000V
103/1000V
102/100V

1
1
1
2
1
1
1
1

1000 uF/25V
104
KBL406
FR107
1N4007
Y2010D
LED
20mH
EI-22

1
1
2
1
1
1
1

Part Number

Description

F1
L1
R1
R2、R3
R4
R5
R6

0.25A
10uH
20R
1K
100K
100K/0.5W
47R

R7
R8
R9
R11、R12
U1
U2
U3
Q1

1.5M
0R51
20R
3.3K
CR6850
PC817
TL431
2N60

Notice: Q1 is a Power MOSFET

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CR6850

REFERENCE CIRCUIT 2
CR6850 drives a periphery Power MOSFET
12V/1A& 5V/3A 27W Dual Power Supply
D2

L

F1

T1

1

C1

R1

3

2

D3

4

R2

D8
1

C5

C3
+

N

D6

D4

Input:AC 100V-240V

C6

R6

C4

+

T2

C2

+12V
2

L1

C8

C9

+

8
7

U1
8
7
6
5

2

GND
FB
NC
RI

GATE
VDD
NC
SENSE

6

R4

1
2
3
4

R3

1

Q1
R5

+

C13

2

D7

+5V

L2

R7

C7

+

C10 C11

+

R8
D5
+12V

3

U2
C

A

E

K

1

+5V

+5V

R9

R10

2

R11

3

4

U3

C14

C15

2

1

Quantity
1
3
1
1
2
4
1
1
1
1
1
1
1
5
1
2
Dec, 2006

Part Number

Description

F1
F2A/250V AC
C1、C2、C3
104/400V
C4
100uF/400V
C5
103/1000V
C6、C7
102/100V
C8、C9、C10、
C11
1000uF/25V
C12
472
C13
C14
C15
U1
U2
U3
D1、D2、D3、
D4、D5
D6
D7、D8

22uF/50V
223/1000V
104
CR6848
PC817
TL431
1N4007
FR107
1N5822

Quantity

Part Number

Description

1
1
1
1
1
2

R1
R2
R3
R4
R5

1.5M
100K/0.5W
100K
47Ω
10Ω

R6、R7
R8

20Ω
0.51Ω/1W

R9
R10
R11
R12
Q1
L1、L2

510Ω
2.8K
39K
2.2K
4N60
10uH

T1
T2

20mH
PQ20-20

1
1
1
1
1
1
2
1
1

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R12

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CR6850

REFERENCE CIRCUIT 3
CR6850 drives a periphery Power BJT（5V/3A 15W Power Supply ）

Quantity
2
1
1
1
1
1
1
1
2
1
5
2
1
1
2
1
1
1

Part Number

Description

Quantity

C1、C2
C3
C4
C5
C6
C7
C8

104/400V
472
102
33uF/400V
10uF/50V
103/1000V
102/100V

C9
C10、C11
C12
D1、D2、D3、
D4、D5
D6、D7
D8
D9
D10、D11
T1
T2
F1

223/1000V
220uF/16V
1.0uF/16V

1
1
1
1
2
1
1
2

1N4007
1N4148
18V
SB560
FR107
20mH
EI-22
0.25A

Part Number

Description

R2
R3
R4
R5
R6、R7
R8
R9

100K
100K/0.5W
1K
1.5M
220R/1W
220R
20K

1
1

R10、R11
R12
R13

20R
1R2/1W
20K

1
1
1
1
1
1
1

R14
U1
U2
U3
U4
Q1
Q2

2K2
CR6850
PC817
TL431
LM358
13003
9013

Notice: Q1 is a Power BJT
Dec, 2006

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CR6850

REFERENCE CIRCUIT 4
The Power supply consisted of CR6850 is used to drive 2 LEDS of 1 watt.

Quantity
2
1
1
1
1
1
1
1
1
3
2
5
4
1
1
2
2
1
1
1
1

Dec, 2006

Part Number

Description

Quantity

C1、C2
C3
C4
C5
C6
C7
C8

104/400V
472
102
33uF/400V
10uF/50V
103/1000V
102/100V

C9
C10
C11、C12、C14
C13、C15
D1、D2、D3、
D4、D5
D6、D7、D12、
D13
D8
D9
D10、D11
D14、D15
D16
T1
T2
F1

223/1000V
220uF/16V
1.0uF/16V
104

1
1
2
1
1
1
1
2
1
2
2
1

1N4007

Part Number

Description

R2
R3
R4、R9
R5
R6
R7
R8

100K
100K/0.5W
1K
1.5M
220R/1W
510R/1W
220R

R10、R11
R12
R13、R14
R15、R16

20R
1R2/1W
2K2
100R

R17

1R/1W

R18
R19
RP1
U1
U2
U3
U4
Q1
Q2

18K
10K
2K
CR6850
PC817
TL431
LM358
13003
9013

1
1N4148
18V
SB560
FR107
LED/1W
1N60
20mH
EI-22
0.25A

1
1
1
1
1
1
1
1

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File Type                       : PDF
File Type Extension             : pdf
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Title                           : CR6850 - Datasheet. www.s-manuals.com.
Subject                         : CR6850 - Datasheet. www.s-manuals.com.
Producer                        : ScanSoft PDF Create!
Create Date                     : 2006:12:13 15:58:37+08:00
Metadata Date                   : 2013:10:13 11:49:01+03:00
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Keywords                        : CR6850, -, Datasheet., www.s-manuals.com.
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