onsemi (Ansemi)

SOIC-7

taping

2500

The NCP1239 is a fixed frequency current mode controller with dynamic self-supply capability. This feature activates the internal start-up current source to power the controller during start-up, transients, latch-up, standby, etc., greatly simplifying the design of the auxiliary power supply and Vcc capacitor. The controller has a supply range up to 35 V, has a dithered 65 kHz or 100 kHz switching circuit, and operates under peak current mode control. When the power on the auxiliary side starts to decrease, the controller automatically folds back its switching frequency to a minimum of 26 kHz. As power drops further, the part skips cycles while limiting peak current to ensure excellent efficiency at light loads. It features timer-based fault detection to ensure overload detection and adjustable compensation to help maintain maximum power regardless of input voltage.