800 V N-channel MOSFET — MDmesh™ series
The STP5N80K5 is an 800 V, 4 A N-channel MOSFET from STMicroelectronics' MDmesh™ series, housed in a TO-220-3 through-hole package. The 800 V drain-to-source rating places it in the high-voltage class for offline power supplies, flyback converters, and auxiliary power stages where the primary-side switch sees rectified mains voltage plus reflected output and leakage inductance spikes.
On-resistance and gate drive — conduction loss vs switching speed
At 4 A continuous drain current (25°C case temperature), the I²R loss at rated Rds(on) reaches 28 W, well within the 60 W power dissipation limit at the case, but the junction-to-case thermal path demands a heatsink for sustained full-current operation. Gate charge is 5 nC typical at 10 V — a low figure that allows direct drive from a PWM controller output without a dedicated gate-driver IC in many designs.