LM4F112C4QC Datasheet, PDF (789/1189 Pages) Texas Instruments – Microcontroller

Figure 13-7. ADC Input Equivalency Diagram
Stellaris^® LM4F112C4QC Microcontroller
Zs
Rs
Pin
V_S
Cs
V_ADCIN
ESD clamps
to GND only
Input PAD
Equivalent
Circuit
Z_ADC
R_ADC
5V ESD
Clamp
I_L
Stellaris® Microcontroller
12‐bit
SAR ADC
Converter
12‐bit
Word
Pin
Input PAD
R_ADC
Equivalent
Circuit
Pin
Input PAD
R_ADC
Equivalent
Circuit
C_ADC
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 217). 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 1137.
13.3.4.1
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 13-8.
April 25, 2012
789
Texas Instruments-Advance Information