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SS7529

Rev.1.01 4/26/2004

Synchronous Buck PWM and Linear Power Controller

GENERAL DESCRIPTION

The SS7529 consists of a dual-output power controller

and the protection circuits in a single SO-14 package

for graphic cards and other applications.

The dual-output power controller provides regulation by

driving two N-MOSFETs in a synchronous rectified buck

converter, and one N-MOSFET in a linear configuration.

The synchronous rectified buck converter provides

simple, single feedback loop, voltage mode control with

fast transient response, from an internal 0.8V temperature-

compensated

reference

voltage.

A

fixed

600kHz

frequency oscillator reduces design complexity, while

balancing typical application cost and efficiency.

The internal soft-start function and the 12V direct drive

on the switching output help to save the bootstrap circuit.

Furthermore, the internal POR (power on reset) helps to

prevent the system from sequencing issues during the

startup and turn-off.

Reacting to fault conditions,

the SS7529 will shutdown both outputs when the

voltage on either FB or FB2 pins drops below 51% of

their nominal value.

TYPICAL APPLICATIONS

FEATURE

Controller operates from 5V and 12V

Drives two N-channel MOSFETs for switching buck

converter

Drives an N-channel MOSFET on the linear output

Fixed 600kHz constant switching frequency

Full range 0~100% duty cycle

Internal soft start

Fast transient response

UVP monitoring on both outputs

Internal 0.8V reference voltage.

APPLICATIONS

Graphics-GPU and memory supplies

ASIC power supplies

Embedded processor and I/O supplies

Cable Modem, Set Top Box, and DSL Modems

DSP and Core Communications Processor

supplies

OSC

FB

Comp

LGATE

UGATE

5VCC

Control

Logic

GND

Shutdown

Error Amp

Vin (3.3V or 5V)

Vout

Vout

12VCC

PGND

Vref

Linear

Controller

5V

12V

FB2

DRIVE2

Q1

Q2

Q3