I'm using the ADS1675 ADC in a project of mine. It has a differential input which is +/- 3V. I'm confused by the datasheet that says the recommended common mode voltage is 2.5V. Why would you want a common mode voltage in a differential signal? And this is essentially just a DC offset right, so the actual input range relative to the ADC ground will be between -.5V and +5.5V?
So essentially I will need to add a 2.5V supply or reference and use that as ground for the input stage as in the picture below?
Also they use -4V and 9V as the amplifier rails. I get that this is like +/- 6.5V raised by 2.5V.. So would I just use the 2.5V reference as ground for a +/- 6.5V supply?