ADC Input Configuration

The ADC Input Configuration (IC) bit is used to determine whether the ADC uses both positive and negative input channels in differential operations, or only the positive input channel in single-ended operations.

When IC is set (IC = 1), the ADC operates in Differential mode. In Differential mode, the ADC calculates the difference between a positive analog input signal and a negative analog input signal with respect to the ADC reference voltage (VREF), and the conversion result may be a positive or negative value. The positive input signal is selected by the ADC Positive Channel Selection (ADPCH) register, and the negative input signal is selected by the ADC Negative Channel Selection (ADNCH) register. The ADC reference voltage (VREF) is the difference between the ADC Positive Voltage Reference (VREF+) input and VSS.

Figure 1. Differential Conversion Result
Conversionresult=INADPCHINADNCHVREF+VREF

When IC is clear (IC = 0), the ADC operates in Single-Ended mode. In Single-Ended mode, the ADC converts the positive input signal with respect to VREF, and the conversion result will be a positive value. The positive input is selected by ADPCH, similar to Differential mode; however, in Single-Ended mode, ADC hardware ignores any negative input selections selected by ADNCH. In Single-Ended mode, VREF is the difference between VREF+ and VSS.

Figure 2. Single-Ended Conversion Result
Conversionresult=INADPCHVREF+VSS