TM4C1297NCZAD Datasheet, PDF (1064/1750 Pages) Texas Instruments – Tiva Microcontroller

Analog-to-Digital Converter (ADC)
■ The maximum possible differential input swing, or the maximum differential range, is: -VREF_Dto
+VREF_D, so the maximum peak-to-peak input differential signal is (+VREF_D - -VREF_D) = 2 *
VREF_D= 2 * (VREFP - VREFN)
■ In order to take advantage of the maximum possible differential input swing, VIN_CM should be
very close to VREF_CM, see Table 27-44 on page 1709.
If VIN_CM is not equal to VREF_CM, the differential input signal may clip at either maximum or minimum
voltage, because either single ended input can never be larger than VREFP or smaller than VREFN,
and it is not possible to achieve full swing. Thus any difference in common mode between the input
voltage and the reference voltage limits the differential dynamic range of the ADC.
Because the maximum peak-to-peak differential signal voltage is 2 * (VREFP - VREFN), the ADC
codes are interpreted as:
mV per ADC code = (2 *(VREFP - VREFN)) / 4096
Figure 15-10 shows how the differential voltage, ∆V, is represented in ADC codes.
Figure 15-10. Differential Voltage Representation
0xFFF
0x800
-(VREFP - VREFN)
0
V
- Input Saturation
VREFP - VREFN
15.3.6
Internal Temperature Sensor
The temperature sensor serves two primary purposes: 1) to notify the system that internal temperature
is too high or low for reliable operation and 2) to provide temperature measurements for calibration
of the Hibernate module RTC trim value.
The temperature sensor does not have a separate enable, because it also contains the bandgap
reference and must always be enabled. The reference is supplied to other analog modules; not just
the ADC. In addition, the temperature sensor has a second power-down input in the 3.3 V domain
which provides control by the Hibernation module.
The internal temperature sensor converts a temperature measurement into a voltage. This voltage
value, V_TSENS, is given by the following equation (where TEMP is the temperature in °C):
1064
Texas Instruments-Production Data
June 18, 2014