I need to protect the mainboard pin (PIN4) in the attached simple circuit. U$3 will connect to U$4 either through an external button or long wires connected to anything else that create or break the circuit. Whatever is attached to the U$3 & U$4 should never have any power but worried about static charges or other accidental surges. I’ve been studying the various ways to do this and I think every example I see is different. I see the Load module uses Schottky diodes but other examples use Zener diodes.
I’ve mostly settled on the attached design where D13 is a 3.43V Zener diode.
Will this give me the protection I need? If not, what would you recommend instead? I’m interested in all opinions. My board is getting crowded and I need the smallest package to prevent having to step up to the next tier in board pricing. Of course it needs to also be the cheapest solution.