P-Channel FET in a 3-pin 3-XFDFN — what the 5.3 A rating buys you
The CSD25485F5T: The 35 mOhm maximum on-resistance at 900 mA and 8 V gate drive defines the conduction loss floor for load switching and power-rail OR-ing applications.
On-resistance and gate drive — sizing the rail and the driver
Rds(on) is specified at 35 mOhm with 8 V gate drive, but the drive voltage range spans 1.8 V to 8 V — the lower gate threshold (1.3 V max at 250 µA) means this FET can be driven from a 1.8 V logic rail, though the on-resistance will be higher than the 35 mOhm figure. Total gate charge is 3.5 nC at 4.5 V.
Package and thermal budget — the 3-PICOSTAR constraint
The 3-XFDFN (3-PICOSTAR) package is a 3-pin, ultra-small surface-mount case. Maximum power dissipation is 1.4 W at 25°C ambient — that 5.3 A continuous rating assumes the PCB copper area is sized to keep the junction below 150°C. In a dense layout with limited copper, derate the continuous current; the part is better suited for pulsed or moderate-duty loads where the thermal time constant of the package averages the dissipation.