What is UCC3800PWG4?
The Texas Instruments UCC3800PWG4 is a current-mode PWM controller designed for a range of isolated and non-isolated power converter topologies: buck, boost, flyback, and forward converter. It operates with a single transistor driver output, a switching frequency of 46 kHz, and a maximum duty cycle of 99%. The controller runs from a 6.9 V to 12 V supply and is housed in an 8-pin TSSOP package for surface-mount assembly. It is rated for commercial temperature environments from 0°C to 70°C.
46 kHz switching — transformer and filter sizing
At 46 kHz the switching period is about 21.7 µs. For a flyback or forward converter this sets the core area-product and turns ratio; expect a transformer in the RM8 or EE20 class for typical 10–30 W designs. The 99% max duty cycle lets you push the on-time nearly to the full period, which helps in low-input-voltage buck or high-step-down flyback where you need the switch on for most of the cycle.
Supply rail and bias
The 6.9 V to 12 V Vcc range means this controller needs a regulated bias rail — it won't start from a raw rectified line. A 12 V auxiliary winding or a small linear regulator is the usual feed. The undervoltage lockout thresholds are inside that window, so the supply must stay above 6.9 V during normal operation or the output driver shuts down.
Temperature grade and environment
Rated 0°C to 70°C, this is a commercial-temperature part. It belongs in indoor equipment — office power supplies, appliance control boards, telecom indoor racks — not in an engine bay, outdoor base station, or factory floor where ambient can hit 85°C. For extended temperature designs look at the UCC3800 family's industrial-grade variants.
Lifecycle and sourcing
Texas Instruments lists the UCC3800PWG4 as Active with ROHS3 compliance. There is no last-time-buy notice or obsolescence risk for new designs.