Datasheet

Figure 18-8. ADC Voltage Reference
Voltage reference
selected using the
VREF field in the
ADCCTL register
VREFP
VREFN
ADC
VDDA
GNDA
VREFA+
VREFA-
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 limits prescribed by Table 32-44 on page 2136 to produce accurate results. The
V
REFA+
and V
REFA-
specifications define the useful range for the external voltage references on
VREFA+ and VREFA-, see Table 32-44 on page 2136. Care must be taken to supply a reference
voltage of acceptable quality. Figure 18-9 on page 1213 shows the ADC conversion function of the
analog inputs.
December 13, 20131212
Texas Instruments-Advance Information
Analog-to-Digital Converter (ADC)