[kragen]

in most cases diode clamping to the rails is still active though? and that's what sinks those 2.4 milliamps and keeps your gate oxides from avalanching. i think the stm32 datasheet only guarantees withstanding 0.5 milliamps of such 'injection current' per pin

there do exist cmos chips with pins without input clamping diodes but they are rather exotic usually