620 V primary-side switch for offline flyback converters
Gate charge is 26 nC typ at 10 V drive, which keeps the switching loss manageable in a 50-100 kHz flyback primary without a high-current gate driver. The 680 pF input capacitance at 50 V drain-source confirms a modest drive requirement — a standard PWM controller output stage can drive it directly.
Package and board integration — TO-251 (IPAK)
The STU5N62K3 comes in a TO-251 (IPAK) through-hole package — three short leads, no tab screw hole, smaller than a full TO-220. The drain tab is the centre lead and is electrically live at the drain potential; the PCB layout must keep creepage clearance from the tab to low-voltage nodes. The package footprint matches the standard IPAK land pattern, with the tab soldered to a copper pad on the board for heat sinking. The 70 W power dissipation rating at case temperature assumes the tab is held at 25 °C — real-world derating follows the thermal resistance from junction to ambient, which depends on the PCB copper area under the tab.
