OB2012x 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. OB2012x can support low system output voltage down to 2V at constant current mode. With its versatility and optimization, OB2005xK can be used in various switch mode power supply topologies including secondary-side control topology and primary-side control topology.
It is suitable for multiple mode application including discontinuous conduction mode (DCM) and quasi-resonant mode (QR). The drain-to-source voltage of SR MOSFET is sensed to control the turn on and off of the SR MOSFET. To reduce SR falling time and turn off the integrated N-channel SR switch in proximity of the zero current transition, soft gate is implemented in OB2012x, which would pull down the gate voltage level before being turned off completely.
In addition, to avoid the ring impact induced by parasitic elements, Vds slpoe detection control scheme also implemented in OB2012x, it can precisely detect the start of demagnetization of transformer so that a reliable and noise free operation of the SR system is insured.
OB2012x is offered in SOP8 package.
■ Secondary-side synchronous rectifier optimized for 5V output system
■ Suitable for DCM, QR operation
■ Soft gate drive for fast and zero current turn-off
■ Accurate secondary side MOSFET Vds sensing
■ Vds slope detection effectively avoid the ring impact induced by parasitic elements
■ Low cost small size CV mode support
■ Up to 200kHz operation frequency
■ Output voltage over-shoot control and under-shoot control
■ VDD UVLO protection