How do I arrange my circuit so that the TVS diode can do its ESD/transient job, without being fried in the miswiring/overvoltage scenario?
I have an analog 0-5V output that needs protection from miswiring, transients and ESD. My understanding is that TVS diodes are good for transients/ESD because of the quick response time, and Zener diodes are good for overvoltage because of the greater power dissipation capability.
However, TVS diodes need to be as close to the edge of the board as possible, and are typically the first line of defense in circuits I've seen:
In the circuits below, D1 is the Zener, D2 is a reverse voltage Schottky, and D3 is the TVS diode.
Circuit 1: If I place the TVS diode (D3) out front, the miswiring scenario will fry it.
Analog output protection with overvoltage and TVS:
Circuit 2: If I place the TVS diode (D3) next to the Zener (D1), it is protected from the DC overvoltage. But it seems useless since R2 will be hit with the ESD pulse and it will limit the current into D3.
Analog output protection with TVS protected by Zener:
Circuit idea 3: Just eliminate the TVS (D3) since the resistor can limit the ESD pulse and D1 can handle it. Maybe throw a capacitor or inductor by D1 to slow things down?