100 V, 40 A N-Channel — OptiMOS™ 5 in a small footprint
It comes in a PG-TSDSON-8-FL surface-mount package, which keeps the board footprint small while handling up to 52 W of power dissipation.
That is the number you use to calculate I²R losses in the steady state. At lower gate voltages, the drive voltage range of 4.5 V to 10 V means you can run it from a 5 V logic rail, but the Rds(on) will be higher — the 10 V figure is the benchmark for minimum resistance. Gate charge is only 3.2 nC at 4.5 V, which keeps switching losses low in a 100–200 kHz converter. The input capacitance at 50 V drain is 1300 pF — modest enough that a standard gate driver can handle the switching edges without excessive ringing.