Posted on April 01, 2017 at 07:53Some pins are 5V tolerant (usually pins without analog function in it), which for example can implement a 5V I2C bus with open drain pull ups. Exposing a pin beyond its guaranteed limit voids normal operation. There is an absolute maximum rating table in datasheet of any IC part which tells that in those conditions, parts may survive up to 1000 hours....
Protection diods on GPIOs are not supposed to be used beyond absorbing ESD shocks. Overall a transistor uses a gate oxide which thickness yields a breakdown voltage. As process makes smaller transistors, gate thickness shrinks vertically too, or they take more real estate on the chip area.... so in short: If you'd like to control a high voltage stage, put between a discrete transistor.
