The NCP1239 is a fixed-frequency current-mode controller featuring a high-voltage start-up current source to provide a quick and lossless power-on sequence. This function greatly simplifies the design of the auxiliary supply and the VCC capacitor by activating the internal start-up current source to supply the controller during start-up, transients, latch, stand-by etc. With a supply range up to 35 V, the controller hosts a jittered 65 or 100-kHz switching circuitry operated in peak current mode control.

Fixed-Frequency 65-kHz or 100-kHz Current-Mode Control Operation
Frequency Foldback Down to 26 kHz and Skip Mode to Maximize Performance in Light Load Conditions
Adjustable Over Power Protection (OPP) Circuit
High-Voltage Current Source with Brown-Out (BO) Detection
Internal Slope Compensation
Internal Fixed Soft-Start
Frequency Jittering in Normal and Frequency Foldback Modes
64-ms Timer-Based Short-Circuit Protection with Auto-Recovery or Latched Operation