MOSFET reverse polarity protection

[benny_profane]

I'm working on a Laika V2 from DeadEnd FX. This circuit uses a MOSFET for reverse polarity protection. I wanted to get a quick sanity check because it seems like the MOSFET is oriented backward. Shouldn't the V+ input go to the drain of a p-channel MOSFET with source going to the circuit? Also, could this be improved with a gate-to-source protection (9.1V) zener?

[TFZ]

Yes, drain and source are wrong in the schematic. Protection diode: never used one. BS250 has +-25V_GS, the MOSFET I use has +-20V. So far no problems...

[benny_profane]

Thanks for verifying that. I'll send a message to DEFX.

[PMowdes2]

Looks like I drew the symbol upside down in my Eagle library, the pads and orientation are correct on the pcb.

[benny_profane]

Great, thanks!

As an aside, why isn't this method of polarity protection used more often? Is it due to cost and the extra components? It's more efficient and less destructive than diode-based solutions.