Yes PTCs don't limit the current, other than the fact they have some small resistance. They have to heat up and then their resistance gets higher but that takes time. I have also known them to catch fire.
A small series resistor after the pullup can be used to limit the current without affecting the reading. Clamping it to 3.3V without affecting the reading is an issue though. Better to use a lower full scale ADC value like 1.5V so there is headroom for clamping.
A small series resistor after the pullup can be used to limit the current without affecting the reading. Clamping it to 3.3V without affecting the reading is an issue though. Better to use a lower full scale ADC value like 1.5V so there is headroom for clamping.