3.9 mOhm on-resistance — what it buys the 12 V bus
The IPZ40N04S53R9ATMA1 is an Infineon OptiMOS™-5 N-channel MOSFET rated for 40 V drain-source and 89 A continuous drain at 25°C junction. The headline figure is a maximum 3.9 mOhm Rds(on) at 20 A with 10 V gate drive — that keeps conduction loss under 0.8 W at 20 A, which is the difference between a heatsink and a copper-pour-only layout in an automotive ECU.
Gate charge and switching speed
Total gate charge is 25 nC at 10 V. For a 100 kHz switching regulator, that means the gate driver needs to source about 2.5 mA average current — well within a standard MOSFET driver's capability. The input capacitance (Ciss) is 1737 pF at 25 V drain, which sets the Miller plateau duration and the turn-on/turn-off delay through the driver's source/sink impedance.
Automotive grade and temperature range
The 175°C ceiling is critical for under-hood or high-side switch positions where ambient can exceed 125°C and self-heating from conduction loss pushes the die further.
Package and footprint notes
Supplied in the PG-TSDSON-8-33 package — an 8-lead PowerTDFN with an exposed drain pad on the bottom. The 58 W maximum power dissipation assumes that pad is tied to a suitable heatsink plane; without it, the junction-to-ambient thermal resistance rises sharply and the current rating derates.