High-voltage N-channel in a DPAK — what the ratings tell you
The STMicroelectronics STD3NK100Z is a 1000 V N-channel MOSFET from the SuperMESH™ series, built for offline flyback converters, LED lighting drivers, and auxiliary power supplies where the primary-side switch sees the full rectified mains. The 1000 V drain-source rating gives you a solid margin on a 240 VAC input with reflected voltage spikes — you won't be chasing avalanche failures on the first surge test. Continuous drain current is 2.5 A at 25°C case temperature, but the TO-252 package (DPAK) is the limiting factor: at elevated ambient you'll derate toward 1.5 A or so, depending on the copper area on the drain tab.
Temperature range and package — where this part lives
The DPAK (TO-252) footprint is a surface-mount package with a large drain tab — the board layout needs a decent copper pour and thermal vias to pull the heat out.