LM3S9997_15 Datasheet, PDF (564/1337 Pages) Texas Instruments – Stellaris LM3S9997 Microcontroller

Analog-to-Digital Converter (ADC)
Figure 12-7. ADC Input Equivalency Diagram
VDD
ESD
Clamp
R_ADC
V_IN
ESD
Clamp
I_L
Stellaris® Microcontroller
10-bit
converter
C_ADC
Sample and hold
ADC converter
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 212). 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 1259.
12.3.4.1
Internal Voltage Reference
The band-gap circuitry generates an internal 3.0 V reference that can be used by the ADC to produce
a conversion value from the selected analog input. The range of this conversion value is from 0x000
to 0x3FF. This configuration results in a resolution of approximately 2.9 mV per ADC code. While
the analog input pads can handle voltages beyond this range, the analog input voltages must remain
within the limits prescribed by “Electrical Characteristics” on page 1248 to produce accurate results.
Figure 12-8 on page 565 shows the ADC conversion function of the analog inputs.
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July 03, 2014
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