TIDUFB6 December   2024

 

  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 Multiplexer Network and Switch Strategy
      2. 2.2.2 Cell Balancing
      3. 2.2.3 Stacked AFE Communication
      4. 2.2.4 MCU and CAN Interface
    3. 2.3 Highlighted Products
      1. 2.3.1 BQ78706
      2. 2.3.2 TMUX1308
      3. 2.3.3 TCAN1044-Q1
      4. 2.3.4 MSPM0G3519
      5. 2.3.5 LMR51406
      6. 2.3.6 ISO7731
      7. 2.3.7 UCC33420
      8. 2.3.8 UCC33421
      9. 2.3.9 TMP61
  9. 3Hardware, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Test Setup
    3. 3.3 Test Results
      1. 3.3.1 Daisy Chain
      2. 3.3.2 Cell Voltage Accuracy
      3. 3.3.3 Temperature Sensing Using TMP61
      4. 3.3.4 Temperature Sensing Timings
      5. 3.3.5 Cell Balancing and Thermal Performance
      6. 3.3.6 Current Consumption
  10. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
    2. 4.2 Tools and Software
    3. 4.3 Documentation Support
    4. 4.4 Support Resources
    5. 4.5 Trademarks
  11. 5About the Author

3.3.4 Temperature Sensing Timings

This test uses one BMU and the BQ79600 EVM. The test points for BQ78706#1 are found in Figure 3-3 including GPIO7, GPIO9, GPIO10, GPIO11, and COMLP. The temperature sensing test software follows the steps in Figure 2-2.

TIDA-010279 Test Setup for Temperature Sensing Figure 3-3 Test Setup for Temperature Sensing

Figure 3-4 shows the temperature sensing timings with MUX.

TIDA-010279 Temperature Sensing Timings With MUX Figure 3-4 Temperature Sensing Timings With MUX

The test needs eight steps to read all the thermistor and voltages. Each step contains a broadcast write to set TMUX1308 and a broadcast read of GPIO7 and GPIO8 from all the BQ78706 devices in the stacked BMUs. To clearly show the process of each step, the reading command is not used. Only the write command is used to select TMUX1308 channels from S0 to S8. The RS_R2 is connected in channel S3 and has a small resistance of 1kΩ that a logic analyzer can recognize as a signal 0. In Figure 3-5, eight steps transfer one by one and the duration from step 0 to step 7 is 27.07ms. This process demonstrates that eight TMUX1308 status transfers work correctly.

When the MUX channel is switched, a settling time must be considered. In this design, the filter capacitor is 0.1μF and the pullup resistor is 10kΩ. When channel S3 switches to S4, the voltage of GPIO7 changes from 0.455V to 5V. The constant time of circuit is 1ms and at least 9ms is needed for the GPIO7 voltage to be stable within 1mV of change. Figure 3-3 shows the GPIO7 MUX voltage settling waveform.

TIDA-010279 MUX Voltage Settling Waveform Figure 3-5 MUX Voltage Settling Waveform