800 V N-channel in a TO-251 IPAK — offline flyback and auxiliary supply switch
The STU4N80K5: It is housed in a TO-251 (IPAK) through-hole package with short leads, a common footprint for low-profile board mounting where a TO-220 is too tall. The 10.5 nC total gate charge at 10 V means a standard PWM controller can drive it directly without a separate gate driver IC.
Parametric fit for 240 VAC flyback and PFC stages
The 800 V Vdss provides a 400 V derating margin over a 400 VDC bus (rectified 240 VAC), covering transients and leakage inductance spikes in single-switch flyback converters. The 175 pF input capacitance at 100 V drain bias keeps switching losses low at frequencies up to 100 kHz. Gate threshold voltage is specified at 5 V maximum with 100 µA drain current, ensuring the device is fully enhanced with a standard 10 V gate drive. The ±30 V Vgs max rating gives headroom for gate ringing without avalanche failure.