ADC Readings Unstable Under Load with STM32F429IGT6

[KaraAlvarez]

Hey everyone,

I’ve been using the STM32F429IGT6 for an audio project, and I'm running into an issue with the ADC readings. When the system is idle, everything seems fine, but once the load increases, the readings start to fluctuate unexpectedly—particularly when using I2C.

I’ve already tried adding decoupling capacitors and adjusting the wiring, but the issue still persists. Wondering if anyone has dealt with similar issues, especially related to power noise or grounding, and how they managed to stabilize the ADC?

Any advice would be great!

Thanks!

[Ozone]

> When the system is idle, everything seems fine, but once the load increases, the readings start to fluctuate unexpectedly—particularly when using I2C.

I suppose you mean electrically, i.e. the values - not the conversion timing.

The MCU has separate VDDA and VSSA pins.
Does you board / design utilize them, and provide a separately buffered supply path ?
Tying it directly to VDD often causes such issues, as Vref will not be stable.