Multi-topology flexibility for isolated and non-isolated supplies
The UC2843AD: This is a current-mode PWM controller that supports boost, buck, flyback, and forward converter topologies. The output configuration is positive and isolation-capable, meaning it can drive a primary-side transistor while the secondary side is referenced to a different ground — essential for offline flyback supplies or isolated DC-DC converters where the feedback loop crosses the isolation barrier. The single transistor driver output drives an external MOSFET or IGBT. With a maximum duty cycle of 96%, the controller can operate near full on-time in boost or flyback topologies where the switch conducts for most of the switching period.
Switching frequency and supply range — sizing the power stage
The oscillator runs up to 500 kHz. At 500 kHz the transformer or inductor is smaller than a 100 kHz design, but the switching losses in the external FET and the core losses in the magnetics scale with frequency. The frequency control feature lets you set the oscillator timing with an external RT/CT network — no clock sync input, so the switching frequency is free-running. Supply voltage range is 7.6 V to 30 V. The undervoltage lockout (UVLO) thresholds are fixed inside the UC2843 family; the turn-on threshold is typically 8.4 V and the turn-off is 7.6 V. This means the controller starts when the auxiliary winding or bias supply reaches 8.4 V and shuts down if it drops below 7.6 V — a standard hysteresis for offline flyback bias supplies.
Temperature grade and package — board-fit considerations
The tube packaging is typical for prototype quantities; production volumes are available in tape-and-reel by ordering the alternate suffix.