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Application Report
SBOA138A–September 2015–Revised October 2015
Easy-to-use Cabling Interface for Measuring Temperature
with the TMP107
Mihail Gurevitch..................................................................................................... HPA Sensing Group
ABSTRACT
This application note provides recommendations on how to design a robust temperature measuring
cabling system based on the TMP107 temperature sensor. Design considerations and helpful hints are
provided for this UART-based system as well as initialization procedures and debugging suggestions. By
following the recommendations provided, the user can design a long-distance temperature measuring
chain while achieving the performance as stated in the data sheet specifications.
Contents
1 Introduction ................................................................................................................... 2
2 Overview...................................................................................................................... 2
2.1 TMP107 Mode of Operation ...................................................................................... 2
2.2 Distance to the Object, Number of Measuring Points.......................................................... 4
2.3 Desired Measurement Precision.................................................................................. 4
2.4 Sampling Rate....................................................................................................... 4
2.5 SMAART Bus Communication Speed ........................................................................... 5
2.6 Chain Supply Voltage .............................................................................................. 7
2.7 Chain Implementation.............................................................................................. 7
2.8 Host Control Board ................................................................................................. 8
3 Working With Alert Pins..................................................................................................... 9
4 Self-Heating Effect ......................................................................................................... 10
5 Chain Initialization.......................................................................................................... 11
6 Fixing Chain Problems..................................................................................................... 12
7 Conclusion .................................................................................................................. 13
List of Figures
1 Oscilloscope of Global Read Command in Continuous Conversion Mode .......................................... 3
2 Oscilloscope of Temperature Data Collection in One Shot Mode for 4 Parts Chain ............................... 3
3 Oscilloscope of 32 Device Chain Global Temperature Data Read Event ........................................... 5
4 Oscilloscope of 32 Device Chain Global EEPROM Cell-1 Data Read Event........................................ 6
5 Example of Host Control Board Based on PC USB Port and Coupon Board With TMP107 ...................... 7
6 Example USB Port-Based Control Board................................................................................. 8
7 Example Microcontroller-Based Control Board .......................................................................... 9
8 Alert Pin Output Voltage vs Sink Current: Temperature = 25°C....................................................... 9
9 TMP107 Self-Heating Effect vs Supply Voltages: Temperature = 25°C ............................................ 10
10 TMP107 Self Heating Effect vs Alert Pin Sink Current. V+ = 3.3 V ................................................. 11
11 Oscilloscope of 4 Parts Chain Initialization Signal..................................................................... 12
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SBOA138A–September 2015–Revised October 2015 Easy-to-use Cabling Interface for Measuring Temperature with the TMP107
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