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FAQ. In AD7124-4/AD7124-8, Can I use a single AIN pin as analog input pin and shared this pin as output of Internal Excitation Current Source (IOUT) pin?

Answer: Yes, that should work and the number of AIN pins per sensors is minimized. However, sharing pins will add error to the overall conversion as there will be a voltage drop across the R of the RC anti-aliasing filter/EMC filtering which in series with the RTD, thus limited R values can be used. It is recommended for EMC/anti-aliasing optimum performance; it is a good practice to enable IOUT on a dedicated pin and applied to the RTD outside of the AIN input filters. In this case, only leakage current goes through the R value of the external filter so the impact of the R value on overall accuracy is minimize. This implementation uses one extra AIN pin versus the shared implementation.