©2002 Fairchild Semiconductor Corporation

www.fairchildsemi.com

Rev. 1.0.1

Features

• PC Power Supply Output Monitor Circuitry

• Few External Components

• Over Voltage Protection for 3.3V/5V/12V Output

• Under Voltage Protection for 3.3V/5V/12V Output With

Delay Time

• Over Current Protection for 3.3V/5V/12V Output With

Delay Time

• Fault Protection Output With Open Collector Output

• Power Supply on/off Delay Time Control (PSON)

• Power Good Signal Generator With Hysteresis

• Open Collector PG Output

• 300ms Power Good Delay

• Current Sense Setting Function With RI

• Latch Function Controlled by PSON and Protection Input

• 16-Pin Dual In-line Package

FPO (Fault Protection Output)

Fault Protection Output indicates the fault condition as

protection signal. When fault state occurs, the main power is

to be turned-off and the PGO signal goes LOW.

NORMAL = "LOW", FAULT = "HIGH"

PGO (Power Good Output)

Power Good Signal Generator is to monitor the voltage level

of power supply for safe operation of a microprocessor

having some delay time at turn-on. The delay time is

programmed by a timing capacitor connected to TPG pin of

KA3505. The power good output should be low state before

the output voltage is out of regulation at turn-off.

NORMAL = "HIGH", FAULT = "LOW"

Description

The KA3505 is complete output supervisory circuitry

intended for use in the secondary side of the switched mode

power supply. It provides all the functions necessary to

monitor and control the output of the power supply system.

Power good signal generator, Remote on and off control,

some precision protection features against over-voltage,

under-voltage and over-current are implemented. It directly

senses all the output rails for OVP and UVP without any

external dividers. As for output control, Power Good Output

(PGO) and Fault Protection Output (FPO) are also included.

Utilizing a minimum number of external components, the

KA3505 offers a simple and cost effective solution, greatly

reducing PCB board space for power supply system.

OCP (Over Current Protection)

It has precision OCP functions for +3.3V, +5V, +12V

outputs. The block is made up of three comparators with

current source setting function. Two inputs of each OCP

comparator are connected to both sides of output inductor that

is located in the secondary output of SMPS.

OVP (Over Voltage Protection)

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

circuit is made up of a comparator with three detecting inputs.

UVP (Under Voltage Protection)

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

block is made up of a comparator with three detecting inputs.

Remote ON/OFF

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

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

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 with

0.1

µF external capacitor.

KA3505

PC SMPS Supervisory IC

16-DIP

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