Current-mode PWM controller for isolated and non-isolated supplies
The Texas Instruments UC2845AQ is a current-mode PWM controller supporting boost, buck, flyback, and forward converter topologies — a single chip for step-up or step-up/step-down designs, with an output stage rated for driving a power MOSFET directly. Switching frequency goes up to 500 kHz, letting you shrink the magnetics and output capacitor compared to lower-frequency controllers, at the cost of tighter layout and faster gate-drive edges. The 48% maximum duty cycle limits the on-time per cycle — a deliberate ceiling for flyback and forward converters where the transformer reset voltage sets the off-time requirement.
Operating from 7.6 V to 30 V on Vcc, the UC2845AQ starts up from a standard 12 V or 24 V bias rail and has headroom for a regulated auxiliary winding in a flyback supply. An engine-bay or outdoor base-station supply that sees 105°C ambient still has margin before the thermal shutdown threshold.