STSR2P/
STSR2PM
FORWARD SYNCHRONOUS
RECTIFIERS SMART DRIVER
s SUPPLY VOLTAGE RANGE: 4.5V TO 5.5V
s TYPICAL PEAK OUTPUT CURRENT:
SOURCE -2A, SINK 3.5A
s OPERATING FREQUENCY: 20 TO 750 KHZ
s SMART TURN-OFF ANTICIPATION TIMING
s OPERATION INDEPENDENT FROM THE
FORWARD MAGNETIC RESET TECHNIQUE
s POSSIBILITY TO OPERATE IN
DISCONTINUOUS MODE
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DESCRIPTION
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, STSR2P generates two driving signals with
the self-setting of dead time between
complementary pulses. The IC operation prevents
secondary side shoot-through conditions
providing proper timing at the outputs turn-off
transition. This smart function operates through a
fast cycle-after-cycle control logic mechanism
based on an internal high frequency oscillator,
synchronized by the clock signal. A fixed
SO-8
anticipation in turning-off the OUTGATE1 with
respect to the clock signal transition is provided,
while the anticipation in turning off the OUTGATE2
can be set through external components. The
adopted transitions revelation mechanism makes
circuit operation independent by the forward
magnetic reset technique used, avoiding most of
the common problems inherent in self-driven
synchronous rectifiers. A special Inhibit function
allows the shut-off of OUTGATE2. This feature
makes discontinuous conduction mode possible
and prevents the freewheeling mosfet from
sinking current from the output.
STSR2P automatically turns off the outputs when
duty-cycle is lower than 13%, while STSR2PM
works even at very low duty-cycle values.
SCHEMATIC DIAGRAM
September 2003
CK 4
PEAK
DETECTOR
+
HIGH
FREQUENCY
OSCILLATOR
INHIBIT 5
-
+
25mV
Vcc
2
BIAS
UVLO
+
5.7V
ANTICIPATION
SET
+
DIGITAL OUTPUT
CONTROL BUFFERS
3 SETANT2
1 OUTGate1
7 OUTGate2
6
SGLGND
8
PWRGND
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