High-end MCUs used to have separate voltage inputs to ADC, for power, and voltage reference.
Older ATX power supplies actually had very high quality 3.3V and 5V outputs because they were coming from linear regs.
I remember some USB gadgets were working in some mobos, but not the others depending on whether 5V was wired from the ATX power, or not
Used to? Almost every MCU I’ve seen recently has had distinct voltage references for the ADCs
High-end MCUs used to have separate voltage inputs to ADC, for power, and voltage reference.
Older ATX power supplies actually had very high quality 3.3V and 5V outputs because they were coming from linear regs.
I remember some USB gadgets were working in some mobos, but not the others depending on whether 5V was wired from the ATX power, or not