©2001 Fairchild Semiconductor Corporation

www.fairchildsemi.com

Rev. 1.0.0

Features

• Complete PWM control and house keeping circuitry

• Few external components

• Precision voltage reference trimmed to 2%

• Dual output for push-pull operation

• Each output TR for 200mA sink current

• Variable duty cycle by dead time control

• Soft start capability by using dead time control

• Double pulse suppression logic

• Over voltage protection for 3.3V / 5V / 12V

• Under voltage protection for 3.3V / 5V / 12V

• One more external input for various protection (PT)

• Remote on/off control function (PS-ON)

• Latch function controlled by remote and protection input

• Power good signal generator with hysteresis

Precision reference section

The reference voltage trimmed to

± 2%

(4.9V

≤ Vref ≤ 5.1V)

PG (Power good signal generator) section

Power good signal generator is to monitor the voltage level

of power supply for safe operation of a microprocessor.

KA3511DS requires few external components to accomplish

a complete housekeeping circuits for SMPS.

Description

The KA3511DS is a fixed frequency improved performance

pulse width modulation control circuit with complete

housekeeping circuitry for use in the secondary side of

SMPS (Switched mode power supply). It contains various

functions, which are precision voltage reference, over

voltage protection, under voltage protection, remote on/off

control, power good signal generator and etc.

OVP (Over voltage protection) section

It has OVP functions for +3.3V,+5V,+12V and PT outputs.

The circuit is made up of a comparator with four detecting

inputs and without hysteresis voltage. Especially, PT (Pin18)

is prepared for an extra OVP input or another protection

signal.

UVP (Under voltage protection) section

It also has UVP functions for +3.3V, +5V, +12V outputs. The

block is made up of a comparator with three detecting inputs

and without hysteresis voltage.

Remote on/off section

Remote on/off section is used to control SMPS externally. If

a high signal is supplied to the remote on/off input, PWM

signal becomes a high state and all secondary outputs are

grounded. The remote on/off signal is transferred with some

on-delay and off-delay time of 8ms, 24ms respectively.

24-SDIP

1

KA3511DS

Intelligent Voltage Mode PWM IC