1000V N-channel in a fully isolated TO-220FP
The STF8NK100Z: The 1.85Ohm max on-resistance is specified at 3.15A with a 10V gate drive — that is the operating point for conduction loss calculations in a switching converter or offline flyback primary switch.
Gate charge and switching speed
Total gate charge is 102 nC at Vgs=10V, and input capacitance Ciss is 2180 pF at Vds=25V.
Through-hole mounting and thermal path
Housed in a TO-220-3 Full Pack (TO-220FP), the back of the package is fully moulded epoxy — no exposed metal tab. The junction-to-case thermal path is through the epoxy, so the 40W power dissipation limit is lower than an equivalent standard TO-220 with a metal tab. The part mounts into a through-hole PCB with a 2.54 mm pitch lead frame; the heatsink clips onto the plastic body, not the tab.
STMicroelectronics lists the STF8NK100Z as an active product.