Small-signal P-FET for load switching
The Infineon BSS209PWH6327XTSA1 is a P-Channel MOSFET from the OptiMOS series, rated for 20 V drain-source breakdown and 630 mA continuous drain current. It comes in a three-lead SOT-323 package (PG-SOT323) that fits tight board layouts where a small P-FET is needed for high-side load switching or battery protection.
550 mOhm on-resistance at 4.5 V drive
The max Rds(on) is 550 mOhm at 630 mA with a 4.5 V gate drive. At 630 mA that's about 218 mV drop — check your load's minimum supply headroom. The gate threshold is 1.2 V max at 3.5 µA, so a 2.5 V logic signal can turn it on, though the Rds(on) is specified at both 2.5 V and 4.5 V drive levels. Gate charge is only 1.3 nC at 4.5 V, and input capacitance is 115 pF at 15 V Vds. That means any microcontroller GPIO or a simple resistor pull-up can drive the gate directly — no dedicated gate driver needed. The switching losses at moderate frequencies are negligible.
Temperature range and power budget
The max power dissipation is 300 mW at 25°C ambient — that's the thermal limit in the SOT-323 body. For continuous 630 mA at 550 mOhm, the conduction loss is about 218 mW, which leaves only 82 mW headroom before hitting the dissipation ceiling. Derate above 25°C.
It is ROHS3 compliant. For a BOM line, this part presents no lifecycle risk and can be committed to production.