Figure 15-7. ADC Input Equivalency
Rs
Cs
C
ADC
Pin
V
S
I
L
Zs
Clamp
R
ADC
Input PAD
Equivalent
Circuit
Z
ADC
Input PAD
Equivalent
Circuit
R
ADC
Input PAD
Equivalent
Circuit
R
ADC
12-bit
SAR ADC
Converter
Pin
Pin
Tiva™ Microcontroller
12-bit
Word
V
ADCIN
ESD
V
DD
The ADC operates from both the 3.3-V analog and 1.2-V digital power supplies. The ADC clock can
be configured to reduce power consumption when ADC conversions are not required (see “System
Control” on page 239). The analog inputs are connected to the ADC through specially balanced input
paths to minimize the distortion and cross-talk on the inputs. Detailed information on the ADC power
supplies and analog inputs can be found in “Analog-to-Digital Converter (ADC)” on page 1861.
15.3.4.1
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
is connected to
GNDA
as configured by the
VREF
bit in the
ADC Control (ADCCTL)
register, as
shown in Figure 15-8.
Figure 15-8. ADC Voltage Reference
Voltage reference
selected using the
VREF field in the
ADCCTL register
VREFP
ADC
VDDA
GNDA
VREFA+
VREFN
GNDA
June 18, 2014
1064
Texas Instruments-Production Data
Analog-to-Digital Converter (ADC)