I am looking for some guidance in designing the common mode and differential mode filter for the ADC input of the ADS1263. An example from the EVM is such:
I'm comfortable with selecting the components for given cut-off frequencies, but I'm unsure about how to select these cut-off frequencies for my application.
I am using the circuit as differential, and the maximum frequency of interest is approximately 20 Hz. Would it be sensible to select components for the differential mode filter to have a cut-off near 20 Hz (likely 25 Hz to account for roll-off)? Is there any reason that I might choose a higher frequency?
Then, what is the purpose of the common mode filter in this case? I understand that this might cancel out noise external to the sensing circuit (RF noise for example). Would it be sensible to make the common mode frequency cut-off all the expected RF and digital voltage frequencies?
Lawrence (Embedded Software Engineer)