NCP1239 Datasheet (ON Semiconductor) - Fixed Frequency Current-Mode Controller

NCP1239, Fixed Frequency Current-Mode Controller

Pin No.

Pin Name Description 1 Fault The controller enters fault mode if the voltage of this pin is pulled above or below the fault thresholds.

A precise pull up current source allows direct interface with an NTC thermistor.

Fault detection triggers a latch.

2 FB Hooking an optocoupler coll

DATA SHEET www.onsemi.com Fixed Frequency Current‐Mode Controller for Flyback Converter NCP1239 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

NCP1239 Features

* a timer-based fault detection circuitry that ensures a quasi-flat overload detection, independent of the input voltage. Features

* 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