ESP32 Forum

What would be the outcome of applying voltage (3.3V) to the analog input pin of an unpowered chip?

My case is that a user may connect a sensor output to chip's analog input before powering on the chip itself.

The ESD protection inside the chip would probably shunt that voltage to the 3.3V rail. That's probably not a super-big deal if the sensor is current-limited. If it is not, you'd effectively be trying to power the system through a GPIO, and I'm not sure if that poor ESD protection thing is able to handle that.