Chip-Rail CR6853, CR6853S, CR6853T Schematics

Novel Low Cost Green-Power PWM Controller

Feature

 Low Cost, PWM&PFM&CRM (Cycle

Reset Mode)

 Low Start-up Current (about 1.5µA)
 Low Operating Current (about 1.4mA)
 Current Mode Operation
 Under Voltage Lockout (UVLO)
 Built-in Synchronized Slope

Compensation

 Built-in Low EMI Technique
 Programmable PWM Frequency
 Audio Noise Free Operation
 Leading edge Blanking on Sense input
 Constant output power limiting for

universal AC input Range

 SOT-23-6L 、SOP8 and DIP-8 Pb-Free

Applications

 Switching AC/DC Adaptor
 Battery Charger
 Open Frame Switching Power Supply

General Description

The CR6853 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 power­saving functions. With a very low start-up
current, the CR6853 could use a large value
start-up resistor (2MΩ).
Built-in synchronized slope compensation
enhances the stability of the system and
avoids sub-harmonic oscillation. Dynamic
peak current limiting circuit minimizes output
power change caused by delay time of the
system over a universal AC input range.
Leading edge blanking circuit on current

CR6853

With Low EMI Technique

Packaging

 Compatible with SG6848 (6849) /

SG5701/SG5848/LD7535 (7550) /
OB2262 (2263)/OB2278（（（（2279））））

 Complete Protection with
 Soft Clamped GATE output voltage

18.0V

 VDD over voltage protect 34.0V
 Cycle-by-cycle current limiting
 Sense Fault Protection
 OTP (Over Temperature Protection)
 Output SCP (Short circuit Protection)
 Output OLP (Over Load Protection)
 Latch mode After OLP&SCP
 High-Voltage CMOS Process with ESD

 Standby Power Supplies
 Set-Top Box Power Supplies
 384X Replacement

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. Cycle-by-Cycle current
limiting ensures safe operation even during
short-circuit.
Excellent EMI performance is achieved
built-in soft driver and low EMI technique.
The CR6853 offers perfect protection like
OVP(Over Voltage Protection)、OLP(Over

Load Protection) 、 SCP(Short circuit
protection)、OTP、Sense Fault Protection

and OCP(Over current protection). The
CR6853’s output driver is soft clamped to
maximum 18.0V to protect the power
MOSFET. CR6853 is offered in SOT-23-6L,
SOT-8 and DIP-8 packages.

Dec, 2007 V1.1 1/11

Chengdu Chip-Rail Tech. Co., Ltd. http://www.chiprail.com

CR6853

Pin Assignment

Pin Descriptions

Name Description

GND GND Pin

Voltage feedback pin. Output current of this pin could controls the PWM

FB

duty cycle、OLP and SCP.

RI

SEN

VDD

GATE

This pin is to program the switching frequency. By connecting a resistor
to ground to set the switching frequency.
Current sense pin, a resistor connects to sense the MOSFET current.
Supply voltage pin.
Totem output to drive the external power MOSFET.

TYPICAL APPLICATION

Dec, 2007 V1.1 2/11

Chengdu Chip-Rail Tech. Co., Ltd. http://www.chiprail.com

8 (10S)

CR6853

Block Diagram

Simplified Internal Circuit Architecture

Absolute Maximum Ratings

Symbol Parameter Rating Unit

V

DD

I

OVP

V

FB

V

SEN

P

D

T

L

T

STG

Supply voltage Pin Voltage 40 V
VDD OVP maximal enter current 20 mA
Input Voltage to FB Pin -0.3 to 6V V
Input Voltage to SEN Pin -0.3 to 6V V
Power Dissipation 300 mW
ESD Capability, HBM Model 2500 V
ESD Capability, Machine Model 250 V

Lead Temperature
(Soldering)

Storage Temperature Range -55 to + 150

SOT-23-6L (20S)
DIP­SOP-8 (10S)

220
260
230

℃
℃
℃
℃

RECOMMENDED OPERATION CONDITION

Symbol Parameter Min ~ Max Unit

VDD VDD Supply Voltage 10~30 V
RI RI PIN Resistor Value 100 K ohm
TOA Operation Ambient Temperature -20~85

P

Maximal Output Power 0~80 W

OMAX

F

PWM

Frequency of PWM 30~150 kHz

℃

Dec, 2007 V1.1 3/11

Chengdu Chip-Rail Tech. Co., Ltd. http://www.chiprail.com

CR6853

Electrical Characteristics

Symbol

Supply Voltage (VDD Pin)

VDD
VDD
VDD

I

ST

I

SS

ON

OFF

CLAMP

Startup Current 3.0 20.0

Operating Current

Turn-on Threshold Voltage 13.0 14.0 15.0 V

Turn-off Threshold Voltage 7.8 8.8 9.8 V

VDD Clamp Voltage I
Anti Intermission Surge

VDD

AIS

VDD Voltage

T

OFF

T

RESTART

Over temperature Protection 130
Temperature restart 100

Parameter Conditions Min. Typ. Max. Unit

(Ta=25°C unless otherwise noted, VDD = 15V)

VFB=0V 3.0
VFB=3V 1.4
VFB=Open 1.0

=10mA 34.0

VDD

12.7

µA
mA
mA
mA

V

V

℃
℃

Voltage Feedback (FB Pin)

IFB Short Circuit Current VFB=0V 1.2

VFB Open Loop Voltage VFB=Open 4.8

I

Zero Duty Cycle FB current 1.47

FB_0D

I

PFM

I

CRM

V

PFM

V

CRM

I

OLP&SCP

V

OLP&SCP

T

OLP&SCP

Enter PFM FB current 1.37
Enter CRM FB current 1.45

Enter PFM Threshold V

FB

0.51

Enter CRM Threshold VFB 0.30

Enter OLP&SCP FB current 152
Enter OLP&SCP FB voltage 3.7
OLP&SCP min. delay Time RI=100K 33 35 50 mS

Current Sensing (SEN Pin)

SEN Minimum Voltage Level RI=100K,

V

TH_L

0.70

FB=3.3V

mA
V
mA
mA
mA
V
V
uA
V

V

V

TH_H

0.80

V

FB=3.3V

TPD Delay to Output FB=3.3V 75 ns

SEN Maximum Voltage Level RI=100K,

RCS Input Impedance

V

SCP

Dec, 2007 V1.1 4/11

Sense short protect voltage 177

40 KΩ

mV

Chengdu Chip-Rail Tech. Co., Ltd. http://www.chiprail.com