©2000 Fairchild Semiconductor International

www.fairchildsemi.com

Rev. 5.0

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 spe-

cially 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 Ideally suited for driving a

power MOSFET. Protection circuity Includes built in

under-voltage lockout and current limiting. 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

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KA3842B/KA3843B/KA3844B/KA3845B

SMPS Controller