STSR2 데이터 시트보기 (PDF) - STMicroelectronics

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STSR2

FORWARD SYNCHRONOUS RECTIFIERS SMART DRIVER

STMicroelectronics 

STSR2

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

DESCRIPTION

STSR2 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, STSR2 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

anticipation in turning-off the OUTGATE1 with

respect to the clock signal transition is provided,

SCHEMATIC DIAGRAM

SO-8

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.

STSR2 automatically turns off the outputs when

duty-cycle is lower than 13%, while STSR2M

works even at very low duty-cycle values.

June 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

1/12

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