> but it also has led to complications with power supply ripple showing in ADC readings. High-end MCUs used to have separate voltage inputs to ADC, for power,

> but it also has led to complications with power supply ripple showing in ADC readings. 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