The Infineon BSO203PH is a dual P-channel enhancement-mode MOSFET from the OptiMOS® family, built for low-voltage power switching where two matched P-FETs are needed in a single SOIC-8 footprint. The 1.6 W package-level power limit means the thermal budget is tight for continuous high-current operation; this part is sized for load-switching, battery-protection, or power-rail OR-ing where the average dissipation stays low and the SOIC-8 copper footprint can sink the heat.
21 mOhm at 4.5 V — what the on-resistance means for your BOM
The 21 mOhm Rds(on) is specified at 4.5 V gate drive, not the usual 10 V. At 7 A the conduction loss is roughly 1 W per channel (I² × R), which eats into the 1.6 W package limit — derate for ambient temperature above 25 °C. If your load is intermittent or you parallel the two channels, the effective resistance drops to about 10.5 mOhm, splitting the dissipation across both dice.
Package and thermal handling for the layout
The part ships in an 8-pin SOIC package (PG-DSO-8, 3.90 mm body width). The two P-channel dice share the same substrate; the exposed pad on the bottom of the package is the common drain connection. For the 1.6 W max dissipation to be usable, the PCB copper area under the package must be stitched with vias to an inner-layer ground plane — without that thermal path the junction temperature rises quickly above 150 °C at continuous current. The gate charge is 39 nC at 4.5 V, so the switching losses at moderate frequency (100–200 kHz) are manageable from a standard MCU GPIO.