800 V N-channel in a TO-220 — what the ratings buy you
The STP4N80K5 is an 800 V, 3 A N-channel MOSFET from ST's SuperMESH5™ series, housed in a TO-220 through-hole package. The 800 V drain-source voltage puts it squarely in offline flyback converters, auxiliary power supplies, and PFC stages where the bus sits at 400 V and the reflected voltage plus leakage spike can push 700 V+ across the drain.
On-resistance and gate charge — the switching loss picture
Rds(on) is 2.5 Ohm maximum at 1.5 A drain current with 10 V gate drive. That is a moderate on-resistance for an 800 V FET — expect conduction losses around 3.75 W at 1.5 A RMS, which the 60 W power dissipation rating can handle with a reasonable heatsink. A gate driver delivering 1 A peak can charge the gate in about 10 ns, so the FET can switch at 100 kHz without the Miller plateau eating into efficiency. Input capacitance is 175 pF at 100 V, which means the driver sees a light capacitive load — good for fast edges and low cross-conduction.
Temperature range and thermal design
The junction temperature range is -55 to 150 °C, covering industrial and automotive auxiliary circuits where the ambient under the hood can hit 105 °C. The TO-220 package with a tab soldered to a copper area on the PCB or bolted to a heatsink gives a junction-to-case thermal path around 2–3 °C/W typical for this class. At 60 W dissipation the junction will rise 150 °C above the case — so keep the case below 100 °C to stay inside the 150 °C limit.
The part is ROHS3 compliant.