650 V, 42 A — the switching transistor for offline power
The STB57N65M5: The 650 V rating provides headroom above the nominal rail in single-switch flyback and PFC stages. The 250 W maximum power rating at the case means the thermal interface to the heatsink is the real limiter.
Total gate charge is 98 nC at 10 V. Input capacitance is 4200 pF at 100 V drain-source.
D²Pak — board-level thermal management
The D²Pak (TO-263) surface-mount package puts the exposed drain tab on the bottom. The 150°C absolute maximum junction temperature leaves margin for transient overloads.