AN1645 Datasheet, PDF (1/22 Pages) STMicroelectronics – STSR2P/STSR2PM SIMPLIFIES IMPLEMENTATION

AN1645
APPLICATION NOTE
STSR2P/STSR2PM SIMPLIFIES IMPLEMENTATION OF
SYNCHRONOUS RECTIFIERS IN FORWARD CONVERTER
1. ABSTRACT
F. Librizzi - F. Lentini
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
) _Feedback
t(s ^Loop
duc ^Vin
TRANSFORMER
bsolete ^{Pro PWM}
MosfetN
Q1
MosfetN
Q2
INDUCTOR
Cout
100nF
Vout
+5V
100nF
R1
SGLGND ⁶
t(s) ^{- O STSR2P}
Produc _D1
Obsolete ^option
3
R2
SETANT
R3
Ck ⁴
D3
R4
+5V
R5
D2
+5V
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
December 2003 (rev.1)
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