The STP3N80K5 is an 800 V N-channel power MOSFET from ST's SuperMESH5™ series, packaged in a through-hole TO-220-3. The 3.5 Ohm on-resistance at 1 A with 10 V gate drive is typical for an 800 V device in this current class — you're trading Rds(on) for the high voltage blocking capability.
That means STMicroelectronics is not actively promoting it for new projects, and while it may still be available through distribution for existing BOMs, the clock is running toward end-of-life. If you're designing a new power supply or converter, look at ST's current-generation SuperMESH5 or MDmesh series parts in the 800 V, 2-3 A range.
Through-hole TO-220 — the rework bench perspective
The TO-220 package is a through-hole part with a metal tab that needs either a heatsink or good copper-plane thermal management on the PCB. On the rework bench, the TO-220 is straightforward: three leads, no hidden thermal pad, easy to desolder with a solder sucker or wick. The 60 W dissipation rating assumes the tab is heatsunk properly; without one, derate aggressively above a few watts.
What the 3.5 Ohm Rds(on) means for your BOM
At 1 A, that's 3.5 W dissipated in the die — within the 60 W package limit, but you'll need a heatsink to keep junction temperature under 150°C. The 800 V drain-source rating gives you a solid 20-30% derating margin for a 400 V DC bus (typical PFC output) or a 350 V flyback rail. Input capacitance is 130 pF at 100 V, which together with the 9.5 nC gate charge means the gate driver sees a light load — a standard 1 A gate drive IC will switch it cleanly at 100 kHz.