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CR6842

Green-Power PWM Controller with Freq. Jittering

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CR6842

Green-Power PWM Controller with Freq. Jittering

Features

z Low Cost, Green-Power Burst-Mode PWM

z Very Low Start-up Current ( about 7.5µA)

z Low Operating Current ( about 3.0mA)

z Current Mode Operation

z Under Voltage Lockout (UVLO)

z VDD Over Voltage Protection(OVP)

z programmable over-temperature protection

z Internal Latch Circuit(OTP,OVP)

z Built-in soft start with 1ms

z Built-in Frequency jitter for better EMI Signature

z Soft Clamped gate output voltage 16.5V

z VDD over voltage protect 25.5V

z Cycle-by-cycle current limiting

z Sense Fault Protection

z Output SCP (Short circuit Protection)

z Built-in Synchronized Slope Compensation

z Leading-edge blanking on Sense input

z Programmable PWM Frequency

z High-Voltage CMOS Process with ESD

z DIP-8 & SOP-8 Pb-Free Package

z Compatible with SG6842J&LD7552&OB2269

Applications

z Power Adaptor

z Battery Charger Adapter

z Open Frame Switching Power Supply

z LCD Monitor

General Description

The CR6842 is a low startup current , low cost, current

mode PWM controller with Green-Power & burst-mode

power-saving operation. The integrated functions such as

the leading-edge blanking of the current sensing, internal

slope compensation provide the users a high efficiency,

low external component counts, and low cost solution for

AC/DC power applications. The special Green-Power

function provides off-time modulation to linearly decrease

the switching frequency under light-load conditions. And

under zero-load conditions, the power supply enters

burst-mode to further reduce power consumption by

shutting off PWM output. When the output of power

supply is short or over loaded, the FB voltage will

increase ,and if the FB voltage is higher than 5.2V for

longer than 56msec the PWM output will be turned off. A

external NTC resistor connected from pin RT to ground

can be applied to over-temperature protection. Pulse by

pulse current limit ensures a constant output current even

under short circuit. PWM output will be disabled as long

as VDD exceeds a threshold. When internal latch circuit is

used to latch-off the controller, the latch will be reset when

the power supply VDD is disabled.

Dec.2006 V 1.3

1

Chengdu Chip-Rail Tech.Co.,Ltd

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