STM32H7B0 has a lot of spikes on the ADC signals

[OGhis]

Dear,

Setup:
We using a STM32H7B0 100pins.
We use 1 ADC input at 1M samples
Configured as 16bit, differential input, with an offset of 32768.
We use a Vref of 2.5V.
The other side of the differential input is 1/2 of Vref (buffered with a opamp)
To sample the data of the ADC we use a DMA circulaire mode to internal memory.

When we measure our signal we seen many spikes on the samples.
With the scope is the input signal very clean.
Also we use a opamp to buffering the analog signal before it get tot the ADC input.
The opamps we used are LTC6256

We cannot understand why we seen all these spikes.
What are we doing wrong here or is there an explanation for this phenomenon?

Thereby when we changes our sample rate to 100Ksps it has the same effect.
Also when we change the ADC input from differential to single ended.

regards

[Carl_G]

Is it possible to take your samples not when the SPI is sending data?

These graphs you are showing, are they from an oscilloscope or are they the recreated signal from your ADC data?

[OGhis]

Dear,

It is now confirmed that the QSPI interface introduces interference or has an impact on the ADC measurements when both are used simultaneously.
So the ADC cannot be reliably used in combination with the QSPI interface.

[Carl_G]

You never did show a schematic. Is the noise coupling on the VREF or on the ADC input or on the GND?

Are you able to run the ADC and the SPI separately? When transferring data don't run the ADC?  I have an LED that I drive with PWM. I have an interrupt trigger that ensures my ADC does not run near any PWM edge.