Does a mosfet offer any isolation to the output pin of a microcontroller.
I'm going to make a simple lead/acid battery float charger (sick of them dying when in storage). So we are talking a voltage of up to say 15v at the drain of the mosfet while the gate can only have a max of 5v (connected to the AVR).
I'm having a hard time finding info on drain gate breakdown voltage. With an N type mosfet I'll have the source connected to ground so when the mosfet is off, the full 15v will be at the drain terminal.
I was thinking of protecting the AVR output by using a 10K "dump" resistor to ground then a diode to the gate of the mosfet to prevent any higher gate voltage getting back to the output pin. The 10K dump resistor would be to dump any reverse leakage current from the diode. The mosfet I'm using can turn on with quite a low gate voltage so the diode voltage drop won't be a problem.
Silly ideas ?? Unnecessary ??
I'll be looking into other things like gate inrush current etc but my main concern is the higher voltage getting back to the AVR output pin.