The ADC uses VREFP and VREFN as reference voltages to produce a conversion value from the selected analog input. The reference voltages can be supplied from within the IC, or from an external voltage source. VREFP can be connected to either VDDA or VREFA+ and VREFN can be connected to either GNDA or VREFA-. This can be configured by setting the VREF bit in the ADC Control register. In single-ended mode, the ADC resolution can be expressed as a difference of the positive and negative reference voltages over the maximum number of ADC steps. This is mathematically represented in the form of the equation shown on this slide. The diagram on this slide shows the conversion range of the ADC in the single-ended mode. The conversation result will vary from 0 hex to FFF hex for the input voltage range starting from the negative reference voltage of the ADC to the positive reference voltage of the ADC.