SRK1000 / SRK1000A /SRK1000B Datasheet Adaptive synchronous rectification controller for flyback converter Features Secondary side synchronous rectification controller optimized for flyback converter. Suitable for QR and mixed CCM/DCM fixed frequency operation. Wide V operating voltage range 3.75 to 32 V. cc CC regulation operation down to 2 V output supported. Very low quiescent current in low consumption mode (160 A). High-voltage sensing input for SR MOSFET drain-source voltage (100 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 min. T and fixed min. T (3 options: SRK1000, SRK1000A, ON OFF SOT23-6L SRK1000B). Low consumption mode entry by primary side burst-mode detection or by detection of SR MOSFET conduction lower than programmed min T . ON SOT23-6L package. Application Battery chargers / quick chargers Adapters USB power delivery (profile 3) Product status link SRK1000 / SRK1000A /SRK1000B Description Product summary SRK1000 / SRK1000A /SRK1000B are controllers intended for secondary side synchronous rectification (SR) in flyback converters, suitable for operation in QR and SRK1000 mixed CCM/DCM fixed frequency circuits. Order code SRK1000ATR They provide a high-current gate-drive output, capable of driving N-channel Power SRK1000BTR MOSFETs. Package SOT23-6L 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 it is then switched off as current Packing Tape and reel approaches zero. Product label The fast turn-on, with minimum delay, and the 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 burst- mode operation, or when the SR MOSFET conduction becomes lower than the programmed minimum T . In this way, converter efficiency improves at light load ON where synchronous rectification is no longer beneficial. After the converter restarts switching or the IC detects that the current conduction in the rectifiers has increased 20% above the min T programmed value, the IC exits ON low consumption mode and resumes switching operation. DS12787 - Rev 5 - November 2021 www.st.com For further information contact your local STMicroelectronics sales office.SRK1000 / SRK1000A /SRK1000B Block diagram 1 Block diagram Figure 1. Internal block diagram COMPARATORS HV CLAMP TIMER DVS ON ZCD TON ADAPTIVE CONTROL VAUX CONTROL LOGIC DRIVER POWER GD MANAGEMENT & SWITCH OVER VCC GND DS12787 - Rev 5 page 2/26