TIDUF20 December   2022

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5.   5
  6. 1System Description
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Auxiliary Power Strategy
      2. 2.2.2 High-Side N-Channel MOSFET
      3. 2.2.3 Stacked AFE Communication
    3. 2.3 Highlighted Products
      1. 2.3.1 BQ76942
      2. 2.3.2 LM5168
      3. 2.3.3 ISO1640
      4. 2.3.4 TCAN1042HV
      5. 2.3.5 THVD2410
      6. 2.3.6 TPS7A25
      7. 2.3.7 MSP430FR2155
      8. 2.3.8 TMP61
      9. 2.3.9 TPD2E007
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Test Setup
    3. 3.3 Test Results
      1. 3.3.1 Cell Voltage Accuracy
      2. 3.3.2 Pack Current Accuracy
      3. 3.3.3 Auxiliary Power and System Current Consumption
      4. 3.3.4 Protection
      5. 3.3.5 Working Modes Transition
      6. 3.3.6 ESD Performance
  9. 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
  10. 5About the Author

3.3.2 Pack Current Accuracy

This design uses four 2-mΩ, 2-W, 50-PPM shunt resisters in parallel to measure pack current. The board offset was calibrated using the guidance of the Calibration section of the BQ76942 Evaluation Module user's guide. Then current gain was calibrated with 5-A discharging current and also followed the guidance of the Calibration section of the BQ76942 Evaluation Module. Write the board offset and current gain values with one-time-programmable (OTP) to the bottom BQ76942, otherwise the MCU has to store such data and write to the bottom BQ76942 every time the device wakes up from shutdown mode. Figure 3-3 shows the pack current accuracy data under room temperature. The maximum current error is below ±30 mA when the discharging current is below 5 A and ±0.5% when the discharging current is above 5 A.

Figure 3-3 Pack Current Accuracy