Goto P-fets+fuses for input protection (12-24V)

[gregcope]

Hi,

Does anyone have any goto parts for VCC input protection?  I am thinking poly fuses and P-fets.  Through holes best!  Also I need to protect from VCC being over 36V (regulator accepts upto 55V) for a 24V nominal circuit.  I only need 0.25A at 12V (600ma at 5v).

[Felix]

What types of protection?
Just over voltage?

[gregcope]

Over current/voltage?
Reverse polarity?

[Felix]

You can use a PFET for reverse polarity - drain to your battery, source to your load, gate to GND, easiest thing ever, almost no leakage, no voltage drop:


I would also read this excellent resource from Maxim on reverse protection: https://www.maximintegrated.com/en/app-notes/index.mvp/id/636

You can use a MOV for transient input protection, typically in higher voltage applications.
If you want close to 0 leakage, you can use a set of generic BJTs (ex 2N3904), as explained here.

For overcurrent, use a fuse, PTC etc.

I will also add this video with some extras and demo: