We use an AD7192 24 Bit 4.8kHz Sigma Delta ADC in our low noise design. the input mode is differential. Our external 2.5V reference produces a 0.1 to 20Hz noise of 240uV rms..
Empirically it has been found that the refernce noise is only prominent at FSD eg when the DC supplied to the differential inputs is close to 2.5V and pratically insignificant for diffenetial inputs near zero.
Disregarding ADC conversion noise, input noise etc, would it be a safe assumption to make that the ADC EXTERNAL REFERENCE noise component is proportional to differential voltage applied to the ADC inputs?
we look forward to your comments.