0xFFF
0xC00
0x800
0x400
- Input Saturation
VR
EF
N
¼
(VR
EF
P
±
VR
EF
N
)
½
(VR
EF
P
±
VR
EF
N
)
¾
(VR
EF
P
±
VR
EF
N
)
VR
EF
P
V
IN
VDDA
GNDA
VREFA+
VREFA-
Voltage reference
selected using the
VREF field in the
ADCCTL register
VREFP
VREFN
ADC
Functional Description
711
SLAU723A – October 2017 – Revised October 2018
Copyright © 2017–2018, Texas Instruments Incorporated
Analog-to-Digital Converter (ADC)
10.3.4.1 Voltage Reference
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. ADC Voltage Reference
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
V
REFA+
and V
REFA–
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.
shows
the ADC conversion function of the analog inputs.
Figure 10-9. ADC Conversion Result