The 700 V drain-source rating puts this MOSFET in the high-voltage class, suitable for offline power supplies, flyback converters, and auxiliary bias rails where the bus voltage can peak above 400 V. The 1.6 A continuous current is modest — think low-power PSUs, LED drivers, or relay coil drivers rather than motor drives. The 7 Ohm Rds(on) at 10 V gate drive means conduction losses are manageable at sub-amp loads; at 800 mA the voltage drop is about 5.6 V, so heatsinking matters. Gate charge of 11.4 nC keeps switching losses reasonable for low-frequency PWM.
Lifecycle status — obsolete, but still sourced
STMicroelectronics lists the STD2NK70ZT4 as obsolete.
Package and mounting — DPAK field reality
On a repair site you can swap it with a soldering iron and a bit of fresh solder, but the tab is connected to the drain — no accidental shorts to ground or nearby traces. The tab wants a decent copper area on the PCB to sink heat; without it, the 45 W power dissipation rating is theoretical.