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January 2004

s

SUPPLY VOLTAGE RANGE: 4V TO 5.5V

s

TYPICAL PEAK OUTPUT CURRENT:

(SOURCE-SINK: 1.5A)

s

OPERATING FREQUENCY: 20 TO 500 KHz

s

INHIBIT BLANKING TIME: 700 ns

s

AUTOMATIC TURN OFF FOR DUTY-CYCLE

LESS THAN 14%

s

POSSIBILITY TO OPERATE IN

DISCONTINUOUS MODE

DESCRIPTION

STSR30 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withdrawn on the secondary side of the isolation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

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,

detecting

the

voltage

across

the

Synchronous FET, allows to shut-off the drive

output during discontinuous mode condition. A

Disable pin allows turning off the device during

no-load

condition

reducing

overall

current

consumption.

STSR30

SYNCHRONOUS RECTIFIER

SMART DRIVER FOR FLYBACK

BLOCK DIAGRAM

SO-8