LM3S5C36 Datasheet, PDF (548/1068 Pages) Texas Instruments – Stellaris® LM3S5C36 Microcontroller

Analog-to-Digital Converter (ADC)
Figure 12-14. Internal Temperature Sensor Characteristic
Sensor = 2.7 V – ^(T+55)
75
Sensor
2.7 V
1.633 V
0.3 V
-55° C
25° C
125° C Temp
The temperature sensor reading can be sampled in a sample sequence by setting the TSn bit in
the ADCSSCTLn register. The temperature reading from the temperature sensor can also be given
as a function of the ADC value. The following formula calculates temperature (in ℃) based on the
ADC reading:
Temperature = 147.5 - ((225 × ADC) / 4095)
12.3.7
Digital Comparator Unit
An ADC is commonly used to sample an external signal and to monitor its value to ensure that it
remains in a given range. To automate this monitoring procedure and reduce the amount of processor
overhead that is required, each module provides eight digital comparators. Conversions from the
ADC that are sent to the digital comparators are compared against the user programmable limits
in the ADC Digital Comparator Range (ADCDCCMPn) registers. If the observed signal moves
out of the acceptable range, a processor interrupt can be generated and/or a trigger can be sent to
the PWM module. The digital comparators four operational modes (Once, Always, Hysteresis Once,
Hysteresis Always) can be applied to three separate regions (low band, mid band, high band) as
defined by the user.
12.3.7.1
Output Functions
ADC conversions can either be stored in the ADC Sample Sequence FIFOs or compared using the
digital comparator resources as defined by the SnDCOP bits in the ADC Sample Sequence n
Operation (ADCSSOPn) register. These selected ADC conversions are used by their respective
digital comparator to monitor the external signal. Each comparator has two possible output functions:
processor interrupts and triggers.
548
January 23, 2012
Texas Instruments-Production Data