Features

• Secondary side synchronous rectification controller optimized for flyback

converter

• Suitable for QR and mixed CCM/DCM fixed frequency operation

• Wide VCC operating voltage range 3.7 to 32 V

• CC regulation operation down to 2V output supported

• Very low quiescent current in low consumption mode (170 μA)

• High-voltage sensing input for SR MOSFET drain-source voltage (185 V AMR)

• Operating frequency up to 300 kHz

• High-current gate-drive output for N-MOSFET

• Fast turn-on with minimum delay time and adaptive turn-off logic

• Programmable minimum TON and TOFF

• Low consumption mode entry by DIS pin, by primary side burst-mode detection

or by detection of SR MOSFET conduction lower than programmed min. TON

• SO8 package

Applications

• AC-DC adapters

• Battery chargers / quick chargers

• USB power delivery (profile 4)

• Industrial SMPS

Description

The SRK1001 controller is designed for secondary side synchronous rectification

(SR) in flyback converters, suitable for operation in QR and mixed CCM/DCM fixed

frequency circuits.

It provides a high-current gate-drive output capable of driving N-channel Power

MOSFETs.

The control scheme of this IC is such that the SR MOSFET is switched on as soon as

current starts flowing through its body diode, and then switched off as current

approaches zero.

The fast turn-on with minimum delay and innovative adaptive turn-off logic allow

maximizing the conduction time of the SR MOSFET and eliminating the effect of

parasitic inductance in the circuit.

The device enters low consumption mode when it detects primary controller burstmode

operation, or when the DIS pin is pulled up by the user, or when the SR

MOSFET conduction falls below the programmed minimum TON. This improves the

converter efficiency at light load, where synchronous rectification is no longer

beneficial.

After the converter restarts switching or the DIS pin goes low again and the IC

detects that the current conduction in the rectifiers has increased 20 above the min

TON programmed value, the IC exits low consumption mode and resumes switching

operation.