I have a PCB with a DC barrel jack, for which I would like to have a reverse polarity protection.
The circuit exists in 2 variants, one with 5V input, the other one with 12V input, at 6A.
Note I also have a TVS (SMBJ5.0CA or SMBJ12CA depending on the variant.)
I was thinking about using a P-MOSFET. In reading here I've found a variety of posts, in particular these:
- Reverse polarity protection
- Does my device need reverse polarity protection?
- Reverse polarity protection on 5-12V input and output
Two solutions include only a P-MOSFET, while one also includes a resistor and a diode.
In my case, I'm not planning on protecting against sudden polarity changes, I only want that if someone plugs an incorrectly wired DC jack, the circuit does not fry.
For the 5V version, I also need the voltage to drop as little as possible (maximum acceptable is 250mV, though something like 10mV would be much better.)
I so far can't wrap my head around whether or not I need an extra resistor and diode.
I would consider using IRF9530 discussed in the first post, but to keep things cooler, would something IRFP9140 be a better choice? (Better drain current, lower Rds, higher power dissipation.) Would I need a heatsink?
Edit: Based on @Andy aka's answer, I'm now considering IRFB7440PbF. It has a low Rds(on), a suitable Vgs in my case (max 3.9V), and the voltage drop should be appropriate, as if I read properly, at 5V it whould be 0.2V
Edit 2: No, this was a terrible idea, IRFB7440PbF is a N-MOSFET, not a P one!