You're right, after re-reading the Power section on the datasheet it seems conne...

dvdkon · 2024-08-08T21:04:56 1723151096

Maybe not even that:

> A separate, nominally 3.3 V, low noise supply (VREG_AVDD) is required for the regulator’s analogue control circuits.

It seems it would be painful trying to run this without 3.3 V.

crote · 2024-08-09T07:42:50 1723189370

It's quite a bit more complicated.

The chip needs a) 1.1V to power the cores, b) 1.8V-3.3V to power IO, and c) 3.3V to properly operate USB and ADC.

The chip has one onboard voltage regulator, which can operate from 2.7V-5.5V. Usually it'll be used to output 1.1V for the cores, but it can be used to output anything from 0.55V to 3.3V. The regulator requires a 3.3V reference input to operate properly.

So yeah, you could feed the regulator with 4-5V, but you're still going to need an external 5V->3.3V converter to make the chip actually operate...

snvzz · 2024-08-09T03:31:31 1723174291

See section on physical pin gpio electrical tolerances.

The TL;DR is that 3.3v must be fed into IOVDD for 5.5v tolerance to work.