I know that true differential SAR ADCs usually have narrow common mode input range around VREF. However, someADCs e. g. AD7641, AD7643, AD7644 do not specify the common mode range. Does this mean they don't have this limitation?
And in fact are there any SAR ADCs that don't have this limitation or I can save the effort to study them (and go straight for sigma-delta ADCs)?
None of the current differential input SAR allow for unrestricted VCM. I would recommend to keep the VCM wthin +/-100mV of Vref/2.