I want to switch a 12 V DC automotive fuel pump in a bench test rig using a P-channel MOSFET, as follows:
This is a simple on/off switch, no PWM is used. The datasheet for the FQPF47P06 gives its maximum Id as 30 A continuous, 120 A pulsed. Vdss max is -60 V and Vgss is +/-25 V. The data for the pump shows a maximum current draw of 20 A, but the most we observe in the application is about 5 A.
In a previous version of this circuit I didn't include D2 and underspecified the fuse rating; the fuse failed and the MOSFET was destroyed (became short circuit source to drain). I've guessed that this was because the motor inductance created a large negative voltage spike from drain to ground on disconnection, so I've added D2 to handle this situation.
- Does this look like a suitable setup to switch this load reliably, or have I overlooked anything?
- What diodes are suitable for D1/2 - is a 1N4007 OK or should I look for something faster and/or with a higher current rating?