The AD7606 shows what appear to be differential amplifiers at each of the analog inputs. There is no mention of a common-mode voltage limit between VxIN and VxGND for any of the inputs.
My application has four inputs with a +2.5V offset and four other inputs with -2.5V offset. The positive offset signals only go more positive (+2.5V to +7.1V) and the negative signals only go more negative (-2.5V to -7.1V). I have to use the 10V range but only get about 5V of useful information.
Can I use my +2.5V bias on the VxGND pins for the positive inputs and the -2.5V bias for the negative inputs to cancel the offset?
This would give me a 5V range and double my effective resolution. I could accomplish the same thing with eight op-amps on the inputs to subtract out the bias, but this is expensive, uses more real estate and may introduce more noise and linearity errors, negating the improved resolution.