Why the AEC-Q101 grade matters for your BOM
The AUIRLR2703 is an Infineon HEXFET N-channel MOSFET rated for 30 V drain-source and 20 A continuous drain current, housed in a DPAK surface-mount package. Its automotive-grade AEC-Q101 qualification and a junction temperature range extending to 175°C make it the part you specify when the standard IRLR2703 cannot guarantee reliability in an under-hood or high-ambient environment.
On-resistance and gate drive — sizing the conduction loss
That 45 mOhm number is the worst-case ceiling at 25°C junction; at 175°C the on-resistance roughly doubles, so the actual conduction loss in a hot engine bay runs higher than the room-temperature calculation suggests. The gate charge is 15 nC at 4.5 V, which means a standard 1 A gate driver can switch this FET in the low-microsecond range without excessive drive power.