SBAS894A April 2018 – October 2018 ADS112C04
The device provides some means for monitoring the analog power supply and the external voltage reference. To select a monitoring voltage, the internal multiplexer (MUX[3:0]) must be configured accordingly in the configuration register. The device automatically bypasses the PGA and sets the gain to 1, irrespective of the configuration register settings when the monitoring feature is used. The system monitor function only provides a coarse result and is not meant to be a precision measurement.
When measuring the analog power supply (MUX[3:0] = 1101), the resulting conversion is approximately (AVDD – AVSS) / 4. The device uses the internal 2.048-V reference for the measurement regardless of what reference source is selected in the configuration register (VREF[1:0]).
When monitoring the external reference voltage source (MUX[3:0] = 1100), the result is approximately (V(REFP) – V(REFN)) / 4. The device automatically uses the internal reference for the measurement.