40 V, 100 A N-channel — the conduction-loss floor
The Infineon AUIRFR8405 is a 40 V, 100 A N-channel MOSFET from the HEXFET® family, housed in a DPAK (TO-252) surface-mount package.
175°C junction — where it lives
The 175°C ceiling means the die can sustain high-current pulses without immediate thermal shutdown, but the DPAK's copper-pad area on the PCB sets the actual RthJA — a 1-inch² pad on a 2-oz copper pour is typical for keeping the junction below 150°C at 100 A continuous.
Gate charge and switching speed
Total gate charge is 155 nC at 10 V. For a 100 kHz switching frequency, the gate driver must supply 15.5 mA average current; a 60 nC gate at the same frequency draws only 6 mA, so the AUIRFR8405 demands a stronger driver stage. The ±20 V Vgs max gives headroom for gate-drive overshoot in hard-switched topologies.