Datasheet

u

225 ADCCODE
T 147.5
4095
 

u  
 
u
5
OUT
5
2.19262 10 1.8639 V
T 1481.96
3.88 10
   
 
 u u   u u 
5 2 2
OUT
V 3.88 10 T 1.15 10 T 1.8639V
www.ti.com Data Logger, Motion Sensor, Temperature Sensors, CAN Transceiver, OLED, and SD Card (Schematic page 2)
2.2.4 Temperature Sensors
Temperature can be measured by the Texas Instruments TMP20 Analog Temperature Sensor (U3) and/or
the internal microcontroller temperature sensor.
2.2.4.1 External TMP20 Temperature Sensor
The output of the sensor is connected directly to the microcontroller’s ADC. Table 2-5 shows the signal
used by the temperature sensor.
Table 2-5. Temperature Sensor Signals
GPIO Pin Pin Function Temp. Sensor
PE7 AIN20 V
OUT
The sensor's analog output over the -55°C to +130°C temperature range corresponds to the parabolic
transfer function (taken from the TMP20 data sheet):
where
• the temperature T is in °C (5)
Solving for temperature results in the following equation:
(6)
When only concerned with a narrow temperature range, a linear transfer function can be calculated. See
the ±2.5°C Low-Power, Analog Out Temperature Sensor Data Sheet (TMP20) for these calculations.
Table 2-6 shows the linear transfer functions for a common selection of temperature ranges.
Table 2-6. Linear Transfer Functions for Common Temperature Ranges
Temperature Range
Maximum Deviation from
Linear Equation (V)
Parabolic Equation (°C)
T
MIN
(°C) T
MAX
(°C)
-55 130 V
OUT
= –11.79mV/°C x T + 1.8528 ±1.41
-40 110 V
OUT
= –11.77mV/°C x T + 1.8577 ±0.93
-30 100 V
OUT
= –11.77mV/°C x T + 1.8605 ±0.70
-40 85 V
OUT
= –11.67mV/°C x T + 1.8583 ±0.65
-10 65 V
OUT
= –11.71mV/°C x T + 1.8641 ±0.23
35 45 V
OUT
= –11.81mV/°C x T + 1.8701 ±0.004
20 30 V
OUT
= –11.69mV/°C x T + 1.8663 ±0.004
2.2.4.2 Internal Microcontroller Temperature Sensor
The TM4C123GH6PGE microcontroller has an internal temperature sensor that can be used to notify the
system that the internal temperature is too high or low for reliable operation. The temperature sensor can
be sampled internally by the ADC. Given the ADC reading, the internal temperature, T in °C, can be
calculated as follows (taken from the TM4C123GH6PGE data sheet):
(7)
See the TM4C123GH6PGE data sheet for more information on the internal microcontroller temperature
sensor.
11
SPMU357B–August 2013–Revised March 2014 Hardware Description
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