STSR3 Datasheet, PDF (1/12 Pages) STMicroelectronics – SYNCHRONOUS RECTIFIERS SMART DRIVER FOR FLYBACK

STSR3
SYNCHRONOUS RECTIFIERS
SMART DRIVER FOR FLYBACK
s SUPPLY VOLTAGE RANGE: 4V TO 5.5V
s TYPICAL PEAK OUTPUT CURRENT:
(SOURCE 2A, SINK 3.5A)
s OPERATING FREQUENCY: 30 TO 750 KHz
s SMART TURN-OFF ANTICIPATION TIMING
s AUTOMATIC TURN OFF FOR DUTY CYCLE
LESS THAN 14%
s POSSIBILITY TO OPERATE IN
DISCONTINUOUS MODE
DESCRIPTION
STSR3 Smart Driver IC provides a high current
outputs to properly drive secondary Power
Mosfets used as Synchronous Rectifier in low
output voltage, high efficiency Flyback
Converters. From a synchronizing clock input,
withdrawn on the secondary side of the isolation
transformer, the IC generates a driving signal with
set dead times with respect to the primary side
PWM signal.
The IC operation prevents secondary side
shoot-through conditions at turn-on of the primary
SO-8
switch providing anticipation in turn-off the output.
This smart function is implemented by a fast
cycle-after-cycle logic control mechanism, based
on a high frequency oscillator synchronized by the
clock signal. This anticipation is externally set
through external component. A special Inhibit
function allows to shut-off the drive output. This
feature makes discontinuous conduction mode
possible and avoids reverse conduction of the
synchronous rectifier.
SCHEMATIC DIAGRAM
June 2003
CK 4
PEAK
DETECTOR
+
HIGH
FREQUENCY
OSCILLATOR
INHIBIT 5
-
+
25mV
Vcc
2
+
BIAS
UVLO
5.7V
ANTICIPATION
SET
3 SETANT
DIGITAL
CONTROL
OUTPUT +
BUFFER
7 OUTGATE
6
SGLGND
8
PWRGND
1 N/C
1/12