OB2004Ax is a high performance and tightly integrated secondary side synchronous rectifier for switch mode power supply system. It combines a much lower voltage drop N-channel MOSFET to emulate the traditional diode rectifier at the secondary side of Flyback converter, which can reduce heat dissipation, increases output current capability and efficiency and simplify thermal design. It can support wide range of system output voltage 3V~12V.

It is suitable for multiple mode applications including discontinuous conduction mode (DCM), quasi-resonant mode (QR) and continuous conduction mode (CCM). Specially for CCM, to guarantee system reliability, innovative property prediction algorithm is used in SR turn-off control.

In addition, to balance reliability and efficiency, OB2004Ax generates a driving signal with optimized dead time with respect to the primary side PWM signal from the information on the secondary side of the isolation transformer with the help of innovative property dead time control algorithm.

The innovative property off time control effectively avoid the ring impact induced by parasitic elements so that a reliable and noise free operation of the SR system is insured.

OB2004Ax is offered in SOP8 package.


   Secondary-side synchronous rectifier for 3V~12V output system

   Suitable for DCM, QR and CCM operation

   Prediction algorithm for CCM

   Internal Power MOSFET

   Accurate secondary side MOSFET Vds sensing

   SR turn on/off dead-time control for high efficiency and low thermal with immunity of interference

   Adaptive off time control effectively avoid the ring impact induced by parasitic elements

   VDD UVLO protection


   AC/DC 3V~12V chargers/adaptors

   Low voltage rectification circuits