Two single ended ADC inputs to read a differential analog input

[MEHRANPOUR]

Hello

I Want to use ST F7 microcontroller to read a differential analog input I could not find differential input support in the datasheet.

Other than that I want to know if we read differential inputs with two single ended input does it attenuate the common mode noises in digital level.

Those ADCs that support differential or pesudo can eliminate noises during sample and hold progress in hardware level but I want to know if I can have the same performance on the software level.

I can not use front end signal conditioning with opamps.

Please consider a situation that my ADC does not have differential feature.

regards,
MM

 

[KlausST]

Hi,

ST F7 microcontroller

Which one exactly? If you want more detailed answers you need to give more exact informations.

I could not find differential input support in the datasheet

Some STM32Fxx microcontrollers have a "simultaneous sampling" feature. Then just convert two channels at the same time.
For "differential result" just subtract one channel conversion result from the other channel conversion result with software.

Klaus

 

[stenzer]

Hi,

is it possible to sample both ADC inputs simultaneous?
If so, and both signals are DC biased (or even DC signals) it should work, as you will reconstruct your differential signal in the digital domain as following:

V_diff = (V_ADC1 + V_CMM) - (V_ADC2 + V_CMM) = V_ADC1 + V_CMM - V_ADC2 - V_CMM = V_ADC1 - V_ADC2

greets

 

[danadakk]

Some micros, if they have an input G stage, may have production line
trimming to insure CMR is achieved.

You can run an experiment, tie both single ended inputs together, and
feed that with a ramp and look at A/D output to see if it is handling the
CM properly, eg. largely rejecting it. Simultaneous sampling is not the
entire fix for this type of part, but also needed.


Regards, Dana.