STM32: why pins usable in general pourpose cannot be all 5V tolerant?

[RRadi]

Hi at all. My question: in STM32 microcontroller, why some pins are 5V tolerant and other no? Why I/O pins usable in general purpose config cannot be all 5V tolerant?

Thanks

[Tesla DeLorean · Accepted solution]

Some are used for the ADC, which has less tolerance. There's other circuitry so it doesn't all back-feed into the 3V power ring.