The ADS111x-Q1 have an integrated voltage reference. An external reference cannot be used with these devices.

The ADS111x-Q1 does not use a traditional band-gap reference to generate the internal voltage reference. For that reason, the reference does not have an actual specified voltage value. Instead of using the reference voltage value and the gain setting to derive the full-scale range of the ADC, use the FSR values provided in Table 8-1 directly.

Errors associated with the initial voltage reference accuracy and the reference drift with temperature are included in the gain error and gain drift specifications in the Section 6.5 table.