TIDUFD0 August   2025

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Wireless Hardware Configurations
      2. 2.2.2 Auxiliary Power Strategy
      3. 2.2.3 Thermistor Multiplexer
      4. 2.2.4 Cell Balancing
    3. 2.3 Highlighted Products
      1. 2.3.1 CC2662R-Q1
      2. 2.3.2 BQ78706
      3. 2.3.3 TMUX1308
      4. 2.3.4 LM5168
      5. 2.3.5 TMP61
  9. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Software Requirements
    3. 3.3 Test Setup
    4. 3.4 Test Results
      1. 3.4.1 Network Performance
        1. 3.4.1.1 Network Initiation
        2. 3.4.1.2 Network Latency
        3. 3.4.1.3 PDR, PS
        4. 3.4.1.4 Low-Power Mode
      2. 3.4.2 Cell Voltage Accuracy
      3. 3.4.3 Temperature Sensing Using TMP61
      4. 3.4.4 Thermistor Multiplexer Timing
      5. 3.4.5 Current Consumption
  10. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
      3. 4.1.3 Layout Prints
    2. 4.2 Tools and Software
    3. 4.3 Documentation Support
    4. 4.4 Support Resources
    5. 4.5 Trademarks
  11. 5About the Author

3.4.3 Temperature Sensing Using TMP61

Four TMP61 thermistors are used to verify the BMU temperature sensing function. This section focuses on how to use TMP61 to measuring the temperature with BQ78706.

In this design, GPIO3 to GPIO8 are configured as ADC and OTUT inputs (ratiometric). GPIO3 to GPIO6 are directly connected to TMP61 with 10kΩ pullup resistors. Using GPIO3 as an example, RT3 is the resistance of the TMP61 connected to GPIO3, RATIO3 is the GPIO3_RATIO reading data, Rpull is the 10kΩ pullup resistor, T3 is the temperature sensing by TMP61. Calculate RT3 using Equation 3.

Equation 3. RT3=RATIO31-RATIO3×Rpull

TMP61 provides the fourth order polynomial TMP. Calculate T3 using Equation 4.

Equation 4. T3=A4×RT34+A3×RT33+A2×RT32+A1×RT3+A0

where

  • A0 = –2.691712E+02, A1 = 5.062889E–02, A2 = –3.099051E–06,
    A3 = 1.153395E–10, A4 = –1.746912E-15

In the test, the BQ78706 GPIO3 reading data is 50.46%. The corresponding RT3 is 10185.71Ω. The temperature T3 is 28.1°C. To improve the temperature measurement accuracy of the TMP61, refer to the steps outlined in the How to Achieve ±1°C Accuracy or Better Across Temperature With Low-Cost TMP6x Linear Thermistors application note.