The SC4810B/E is a 16 pin BICMOS primary side PWM controller for use in Isolated DC-DC and off-line switching power supplies. It is a highly integrated solution, requiring few external components. It features a high frequency of operation, accurately programmable maximum duty cycle, current mode control, line voltage monitoring, supply UVLO, low start-up current, and programmable soft start with user accessible reference. It operates in a fixed frequency, highly desirable for Telecom applications. The output for switch is complementary to each other with programmable delay between each transition. The active technique allows single ended converters beyond 50% duty cycle and greater flux swing for the power transformer while reducing voltage stresses on the switches. The separate sync pin simplifies synchronization to an external clock. Feeding the oscillator of one device to the sync of another forces biphase operation which reduces input ripple and filter size.