100 V P-channel in a SOT223-4 — what the scorch mark tells you
The BSP322PH6327XTSA1 comes in a PG-SOT223-4 surface-mount package — the exposed tab is the drain, so the PCB copper pour under the part is the primary heatsink.
800 mOhm on-resistance — the voltage-drop check
Rds(on) is specified at 800 mOhm maximum at 1 A drain current with 10 V gate drive. That is high enough that a repair tech can confirm the part is turned on by measuring the voltage drop across drain-source — at 1 A load you will see about 800 mV drop.
Temperature range and junction budget
The maximum power dissipation is 1.8 W at 25°C ambient — derate above that per the datasheet's thermal resistance curve. The gate charge is 16.5 nC at 10 V, so a small-signal driver or even a GPIO pin can switch it at moderate frequencies without a dedicated gate-driver IC.
