TIDUF32 December   2024 ADC128S102QML-SP , INA901-SP , LM117QML-SP , LM193QML-SP , LM4050QML-SP , LMP7704-SP , MSP430FR5969-SP , TMP9R00-SP , TPS7A4501-SP , TPS7H2211-SP , TPS7H5001-SP , TPS7H6003-SP

 

  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 System Control and Processing
      2. 2.2.2 Battery Cell Monitoring
      3. 2.2.3 Temperature Sensing
      4. 2.2.4 Battery Stack Control
      5. 2.2.5 Battery Balancing
      6. 2.2.6 Power Tree and Power Sequencing
    3. 2.3 Highlighted Products
      1. 2.3.1  MSP430FR5969-SP
      2. 2.3.2  ADC128S102QML-SP
      3. 2.3.3  TLV1H103-SEP
      4. 2.3.4  TPS7H2211-SP
      5. 2.3.5  TPS7A4501-SP
      6. 2.3.6  INA901-SP
      7. 2.3.7  INA1H94-SP
      8. 2.3.8  LMP7704-SP
      9. 2.3.9  TMP9R00-SP
      10. 2.3.10 LM117QML-SP
      11. 2.3.11 LM4050QML-SP
  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
  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

2.2.2 Battery Cell Monitoring

This reference design was created to support eight standard Lithium-Ion 4.2V batteries. The LM117QML-SP linear regulator is used in the reference design to step down a 33.6V battery output to 12V. LM117QML-SP has a maximum input rating of 40V. If more battery cells are desired, a different step-down buck is required.

The battery cell monitoring is designed to monitor battery cell voltages in the range of 3V to 4.2V. A wider range can be accommodated by changing the gain of the LMP7704-SP amplifier circuit following the INA1H94-SP. This resistor change also needs to be reflected in the BMS GUI through the SCISwitchValueChanged function.

The battery-monitoring circuit (see Figure 2-2) functions by first utilizing the INA1H94-SP, a precision unity-gain difference amplifier, to accurately measure the voltage from two batteries. The INA1H94-SP can measure small differential voltages in the presence of common-mode signal up to 150V. The R97 resistor functions to change the gain. The LMP7704-SP is used to adjust the common mode and range of the signals to maximize the dynamic range of the ADC input. The output is sent to the MCU and displayed on the GUI.

The INA1H94-SP is in a single-supply operation for this design, leading to the addition of a 2.5V reference. This IC does not have a rail-to-rail input or output, requiring a reference to satisfy the common-mode range. The data sheet specifies that the voltages at the internal amplifier are within 1.5V of the supply voltage. A 2.5V reference was chosen to satisfy this, but a reference as low as 1.5V is acceptable.

TIDA-010931 Battery Monitoring Figure 2-2 Battery Monitoring