It doesn't need to be that complicated because a small series resistor limits the current to something that can easily be handled by a zener diode long enough to open a PTC, or maybe indefinitely. Since it is after the pullup it doesn't affect the reading significantly.
Often a series resistor is all you need as the MCU inputs will have clamping diodes to VDD so as long as you limit the current they survive. And when speed isn't critical a small cap to ground behind the resistor gives ESD protection as well.
Often a series resistor is all you need as the MCU inputs will have clamping diodes to VDD so as long as you limit the current they survive. And when speed isn't critical a small cap to ground behind the resistor gives ESD protection as well.