TIDUF44 January   2024

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Highlighted Products
      1. 2.2.1 BQ76907
      2. 2.2.2 BQ76905
      3. 2.2.3 BQ77207
      4. 2.2.4 MSPM0L1106
      5. 2.2.5 TCAN1042
      6. 2.2.6 TPSM365R6V5
      7. 2.2.7 TLV704
      8. 2.2.8 TMP61
  9. 3System Design Theory
    1. 3.1 Primary Protection Design
    2. 3.2 Secondary Protection
    3. 3.3 Other Circuit Design
  10. 4Hardware, Software, Testing Requirements, and Test Results
    1. 4.1 Hardware Requirements
    2. 4.2 Software Requirements
    3. 4.3 Test Setup
    4. 4.4 Test Results
      1. 4.4.1 Cell Voltage Accuracy
      2. 4.4.2 Pack Current Accuracy
      3. 4.4.3 Protection
      4. 4.4.4 Cell Balancing
      5. 4.4.5 Working Modes Transition
      6. 4.4.6 Thermal Performance
  11. 5Design and Documentation Support
    1. 5.1 Design Files
      1. 5.1.1 Schematics
      2. 5.1.2 BOM
    2. 5.2 Tools and Software
    3. 5.3 Documentation Support
    4. 5.4 Support Resources
    5. 5.5 Trademarks
  12. 6About the Author

3.1 Primary Protection Design

For the design of primary protection (BQ7690x), follow the design recommendations in the data sheet.

In addition, D2 and D16 were added to prevent the voltage drop of BAT and REGOUT after short circuit.

A wake-up circuit for the TS pin was added, because the TS pin maximum withstand voltage is 2.1 V. D7 and D8 was added as voltage regulator and protection. The voltage of cell1 fluctuates the moment S1 is triggered. After wake-up, voltage monitoring returns to normal.

A balancing circuit was also designed in this design. In this design, 100 Ω and 220 nF are selected for the input of VC0 to VC7. (Limit the external cell input resistance times external input capacity to 200 μs or below,and note that the recommended value of the input resistance is 10 Ω, too large an input resistance affects the sampling accuracy.) For external balancing circuit design detail, see the Cell Balancing With BQ769x2 Battery Monitors application note.

GUID-20230907-SS0I-M8S2-DGRC-RVMQCLKH6JK1-low.svgFigure 3-1 Primary Protection Design Circuit