I'm searching through digikey right now and see many ADCs with the input counts listed as "1, 2" or "2, 4". What does this number convention mean?
For example, this Microchip ADC has its input count listed as "2, 4". Looking through the data sheet, I see that it has 4 inputs. What does the 2 in "2, 4" mean?
The first page of data sheet for the linked device is fairly clear: -
And you configure those inputs as follows: -
Other vendors of similar devices use similar techniques and methods. The devil is in the data sheet.
It means, there are totally four inputs for ADC in which you can use these inputs as four single-ended inputs or two pseudo-differential inputs. In single-ended mode, an analog signal that needs to be converted is converted with reference to the ground or reference voltage.
If the need arises to sense the signal ground or decouple the relative measurement result from the current carrying ground plane, you may need to move to a pseudo differential input ADC. In this mode, a device is performing a differential measurement, but the differential that is sensed is a single-ended input signal measured with respect to the input signal ground level.
