I bought AD7175-2 Evaluation Board(EVAL-AD717x-2SDZ(Rev-E)) and carried out Noise test with two different configurations as below and observed Signal variation
ADC ODR - 250 KSPS
My K20 SPI Clock - 6.25 MHZ
ADC Read / data - 10.4 uSec
1. Differential mode: Two inputs from same on board Reference source (ADR4450).
Test Set up as shown below
2. Differential mode: same signal feed to two inputs
why signal variation is 250uV in differential mode ? Please Explain.