1. ABSTRACT

This paper describes the functionality and the operation of the STSR2P device used as the secondary

synchronous rectifier driver in Forward topology switched mode power supplies. A schematic and layout

description of a demo board, able to replace diode rectification with synchronous rectification in Forward

converters, is shown below.

Figure 1: Typical Application Schematic

2. GENERAL DEVICE DESCRIPTION

The STSR2P Smart Driver IC provides two complementary high current outputs to drive Power Mosfets.

The IC is dedicated to properly drive secondary Synchronous Rectifiers in medium power, low output

voltage, high efficiency Forward Converters. From a synchronizing clock input, the IC generates two

driving signals with a certain dead time between complementary pulses. The adopted transitions

+5V

+5V

Vout

Vin

+5V

INDUCTOR

Cout

100nF

R1

R2

R3

R4

R5

D1

D2

100nF

TRANSFORMER

STSR2

4

6

3

Ck

SGLGND

SETANT

MosfetN

Q1

MosfetN

Q2

D3

PWM

Feedback

Loop

option

P

December 2003 (rev.1)

1/22

AN1645

APPLICATION NOTE

STSR2P/STSR2PM SIMPLIFIES IMPLEMENTATION OF

SYNCHRONOUS RECTIFIERS IN FORWARD CONVERTER

F. Librizzi - F. Lentini

Obsolete

Product(s)

- Obsolete

Product(s)