800 V N-channel in D2PAK — the SuperMESH5™ switching MOSFET
The STB15N80K5 is an 800 V, 14 A N-channel power MOSFET from ST's SuperMESH5™ series, built on a strip-layout vertical DMOS process that cuts the on-resistance per unit area compared to earlier generations. Packaged in a D2PAK (TO-263) surface-mount case, it targets high-voltage switching applications where conduction loss and switching speed both matter — offline flyback converters, PFC stages, two-switch forward topologies, and LLC resonant converters in the 150–500 W range.
375 mOhm on-resistance — conduction loss floor at 7 A
This is the figure to use for worst-case conduction loss calculations at elevated junction temperature — the datasheet's typical curve shows Rds(on) roughly doubles from 25°C to 150°C, so a realistic 150°C junction pushes the effective resistance toward 750 mOhm.
190 W dissipation and the heatsink question
The 190 W maximum power dissipation at case temperature 25°C is a theoretical ceiling under ideal thermal interface — real-world dissipation is set by the junction-to-ambient thermal resistance, which for a D2PAK soldered to a typical 1 oz copper pad on a 2-layer board sits around 40–50°C/W. At 14 A continuous current with 375 mOhm Rds(on) the conduction loss alone is 73.5 W, which would push the junction above 150°C without a heatsink and forced airflow. For any continuous load above a few amps, a heatsink is mandatory. The 5 V typical gate threshold at 100 µA drain current is high enough to keep the device off during power-up transients on a 12 V gate-drive rail.