Other Parts Discussed in Thread: ADS8881
This part is useful for my particular application due to the differential input, 18-bit resolution, throughput and parallel data output. However, I also have a strange use case where I plan to mux two measurements into this A/D:
- The first is a fully-differential signal centered around VREF/2 that may span the full input range of the A/D. This signal meets all of the guidelines in the ADS8482 datasheet.
- The second is a single-ended signal that can range between 0.5V and VREF-0.5V. I want to supply this signal to the IN+ pin and VREF/2 to the IN- pin of the A/D. In this case my input signals fall outside of the recommended common-mode input range for the part.
The common-mode input range for the part is specified as 200mV above or below VREF/2. In the "Analog Input" section of the datasheet there is a paragraph that states "Care must be taken regarding the absolute analog input voltage. To maintain the linearity of the converter, the +IN and –IN inputs and the span [+IN – (–IN)] must be within the limits specified. Outside of these ranges, the converter's linearity may not meet specifications."
Can you provide any more clarification on what might happen if I try to measure single-ended signals that fall outside of the recommended common-mode input range? Is it a just a hit to linearity or will the part function incorrectly? Are there any changes in the small signal measurement bandwidth if my common mode input is moving in and out of the specified range? Thanks for your help!