SLAU723A October 2017 – October 2018 MSP432E401Y , MSP432E411Y
The ADC uses internal signals VREFP and VREFN as references to produce a conversion value from the selected analog input. VREFP can be connected to either VREFA+ or VDDA and VREFN can be connected to either VREFA- or GNDA as configured by the VREF bit in the ADC Control (ADCCTL) register, as shown in Figure 10-8.
The range of this conversion value is from 0x000 to 0xFFF. In single-ended-input mode, the 0x000 value corresponds to the voltage level on VREFN; the 0xFFF value corresponds to the voltage level on VREFP. This configuration results in a resolution that can be calculated using the following equation:
mV per ADC code = (VREFP - VREFN) / 4096
While the analog input pads can handle voltages beyond this range, the analog input voltages must remain within the specification limits in the device-specific data sheet to produce accurate results. The VREFA+ and VREFA– specifications define the useful range for the external voltage references on VREFA+ and VREFA-. Care must be taken to supply a reference voltage of acceptable quality. Figure 10-9shows the ADC conversion function of the analog inputs.