©2002 Fairchild Semiconductor Corporation

www.fairchildsemi.com

Rev. 1.0.2

Features

• Low Start up Current

• Maximum Duty Clamp

• UVLO With Hysteresis

• Operating Frequency up to 500KHz

Description

The KA3842B/KA3843B/KA3844B/KA3845B are fixed

frequency current-mode PWM controller. They are

specially designed for Off - Line and DC-to-DC converter

applications with minimum external components.

These

integrated circuits feature a trimmed oscillator for precise

duty cycle control, a temperature compensated reference,

high gain error amplifier, current sensing comparator and a

high current totempole output for driving a power MOSFET.

The KA3842B and KA3844B have UVLO thresholds of

16V (on) and 10V (off). The KA3843B and KA3845B are

8.5V (on) and 7.9V (off). The KA3842B and KA3843B can

operate within

100% duty cycle.

The

KA3844B and

KA3845B can operate with 50% duty cycle.

8-DIP

14-SOP

1

1

Internal Block Diagram

KA3842B/KA3843B/KA3844B/

KA3845B

SMPS Controller