Multiple ADC sample with different frequency interference

[pxueh.1]

Hi,everyone.I'm use NUCLEO-L496ZG platform.

ADC1 sample at a frequency of 5M,ADC3 sample at a frequency of 12.8K(PWM trigger).

when only run ADC3,ADC3's waveform is normal.

when ADC1 and ADC3 run at the same time,ADC3's waveform has a lot of interference.How to solve this problem? if had recommend frequency of ADC1 when ADC3 sample at a frequency of 12.8K? ADC1's frequency nend greater than 2M.

Time-domain waveform of ADC3(only ADC3 sample)

 

Time-domain waveform of ADC3(ADC3 and ADC1 sample together) 

Frequency spectrum waveform of ADC3(ADC3 and ADC1 sample together).

The follow picture is Enlarged view.(ADC3 and ADC1 sample together)

Input signal.

Interference signal. The same of other three. Interval of frequency is 2560Hz

[waclawek.jan]

Do you sample the same signal by both ADCs?

What exactly is the circuitry at the input of both ADCs?

JW

[pxueh.1]

thanks for you reply, ADC1 and ADC3 is not sample the same signal, what ever ADC1 sample Any frequency even if ADC1 is grounding ,only ADC1 run, ADC3 has interference. Pulse signal generator output voltage into STM32 analog IO.(single-ended input)

[Piranha]

The second image clearly shows that every n-th positive sample is 0 and every n-th negative sample is 1, which is probably because of some off-by-one processing error. Therefore look for wrong buffer address/size and flaws in processing code.