56 mOhm at 3.6 A — the conduction-loss floor
The IRLML0040TRPBF: That Rds(on) figure sets the conduction-loss budget for a load switch or low-side driver in a SOT-23 footprint — at 3.6 A the dissipation is about 0.73 W, which sits inside the 1.3 W package limit but leaves little margin for ambient temperature above 25 °C without derating.
SOT-23 footprint and thermal reality
The SOT-23 footprint is a standard small-signal outline. Input capacitance is 266 pF at Vds = 25 V, and total gate charge is 3.9 nC at Vgs = 4.5 V — both low enough that a standard GPIO pin or a small gate-driver IC can switch the MOSFET at moderate frequencies without excessive drive current.