P-channel high-side switch — 55 V, 42 A, 20 mOhm
The IRF4905STRLPBF: P-Channel MOSFET, 55 V Vdss, 42 A continuous drain, 20 mOhm Rds(on) at 10 V.
Gate charge and switching speed
Total gate charge is 180 nC at 10 V. Input capacitance is 3500 pF at 25 V.
Thermal budget — 170 W at the case
Maximum power dissipation is 170 W at Tc=25 °C, derating to zero at 150 °C junction. The D2PAK's large copper tab is the primary heat path — the PCB copper area under the tab sets the junction-to-ambient thermal resistance. For continuous 42 A operation, the case temperature must stay below 100 °C to keep the junction under 150 °C at full load; that typically requires a heatsink on the tab or a thermal via array to an internal plane. The -55 to 150 °C junction range covers military and industrial environments, but the thermal interface is the practical limit.