I regularly see the use of Schottky diodes in order to protect microcontroller inputs from overvoltages (>5V). The Schottky diodes are connected to the 5V power supply (cathode) and the microcontroller input (anode).
I was wondering what happens when current flows through these diodes due to overvoltage? Where does this current flow into? It probably flows into the power supply unit...but what happens there? Isn't it so, in fact, that we are applying an overvoltage to the power supply output and that we expect the power supply to take care of it...?
Anyone with bad experiences with this solution? Are there any better solutions?
(In fact, the ESD protection diodes in the microcontroller itself apply the same trick for short spikes...the spike current flows into the power supply...)