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.