800 V SuperMESH for offline flyback and PFC stages
The STP3NK80Z: The through-hole TO-220 package allows easy heatsink attachment, and the 70 W power dissipation ceiling at case temperature provides enough headroom for a 30–50 W offline supply with adequate thermal management.
Gate drive and switching behaviour
The gate threshold voltage maximum is 4.5 V at 50 µA drain current, which means a 10 V gate drive is the recommended operating point to achieve the specified 4.5 Ohm Rds(on). Driving the gate with 5 V logic from a 3.3 V microcontroller would leave the MOSFET in the linear region with significantly higher conduction loss. The ±30 V maximum gate-source rating gives margin against ringing on the gate node in layouts with long PCB traces.
The STP3NK80Z is supplied in the standard TO-220-3 through-hole package, with the tab connected to the drain. For a 50 W output flyback running at 65 kHz, expect the junction temperature to stay within the 150°C absolute maximum when the heatsink thermal resistance is kept below 4°C/W.