I have an AVR input that the other side might attempt to drive when the AVR with that input is off. I'd like to somehow cut off that input when the AVR is off.
I found isolated level shifters which explicitly guarantee this but I think it's more than I need, and it seems like a FET should be able to do this, but I don't
know exactly how.
I though maybe a 2N7000 with the gate connected to the AVR Vdd or a divider of it, but:
* I notice 2N7000 has "On-State Drain Current" minimum of 75 mA. I'm guessing this is a guarantee and not a requirement, but I'm unsure
* The gate threshold voltage is 0.8 to 3 V. So I'm not sure how I can pick the exact shut-off level I want. A simple divider on Vdd seems not good enough
since the wide Vgh_thresh makes it impossible to pick a value.
Is there a simple circuit to do this, or a simple cheap IC that guarantees it?