The CS51221 Enhanced Voltage Mode PWM Controller contains all of the features necessary for basic voltage mode operation. This PWM controller has been optimized for high frequency primary side control operation. In addition, this device includes such features as: Soft Start, accurate duty cycle limit control, less than 50uA startup current, over and under voltage protection and bidirectional synchronization. The CS51221 is available in a SOIC-16 and TSSOP-16 surface mount packages.