STM32H725VGT3TR Vref changes when I enable ADC1

[RallyTronics]

I have my internal Vref set to 2.5V (stage 0).  

The value reads correct (2.52V) with a meter on the test point below until I call HAL_ADC_Start_DMA().   Once HAL_ADC_Start_DMA() -> ADC_Enable() -> LL_ADC_Enable() is called the voltage goes up to around 2.9V.

Any thoughts as to why this is happening?

Thanks!

[TDK · Accepted solution]

Are you converting channels out of bounds? (above 2.5 V?)

[RallyTronics]

No, I am currently trying to digitize a 1V DC test signal.

[RallyTronics]

Let me double check my unused channels.

[RallyTronics]

Looks like that's the problem.