I have a microcontroller monitoring a few digital inputs. The max voltage on these inputs is VCC + 0.3v. VCC is 3.6v so these inputs can't be higher than 3.9v. These digital input are just switch closures on a button, toggle, or any other various human operated switch. Input response time is definitely not critical. The switch will be connected to the uC via a length of cable. Cable length will vary based on customer's needs; anywhere from a few feet to 1,000 feet. This will be industrial application so lightning is the main concern.
I wanted to use capacitor --> series resistor --> TVS --> series resistor --> capacitor --> uC input. However, I understand TVS diodes will give fastest response, zeners will be too slow as I understand. The problem is, all TVS diodes that have a working voltage of 3.65-3.8v have a breakdown voltage and clamping voltage way too high. I see some breakdown ratings of 3.8, but clamping is upwards of 6-15v! I'm assuming my input will be fried before the VTS reaches full clamp.
With such low input Vmax, am I limited to zener/schottky diode protection?