The Texas Instruments UCC3809P-1G4 is a current-mode PWM controller built for isolated and non-isolated DC-DC converters. It handles boost, buck, flyback, and forward topologies — one part covers a lot of the power-stage designs you see in telecom bricks, industrial supplies, and auxiliary converters. No internal switch — this is a controller driving an external MOSFET, so you size the FET for your load. The 8-VSSOP package is small enough to fit on a mezzanine card or a cramped PSU board.
1 MHz switching — what it buys you
Switching at 1 MHz reduces transformer and inductor size. The 70% duty cycle is typical for current-mode control.
Rated -55 to 150 °C junction temperature. The soft-start and frequency control features help with inrush limiting and EMI tuning.
No need to panic-buy or stockpile for a BOM freeze.