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

2.1 Block Diagram

Figure 2-1 shows the system block diagram.

Figure 2-1 TIDA-010247 Block Diagram

The design uses two stacked high-accuracy battery monitor and protector BQ769x2 devices from TI to monitor up to 32 series battery cells voltage, pack current and temperature data, and protect the battery pack from all unusual situations, including: COV, CUV, OT, OCD, OCC, and SCD. This BQ769x2 family has three devices: BQ76942 to cover 3s to 10s applications, BQ769142 to cover up to 14s applications, and the BQ76952 to cover up to 16s applications. These are pin-to-pin devices, so updating the design to match different battery cell applications with a limited number of component changes is easy. This design used the BQ76942 for tests.

There is a lower-power MSP430™ MCU MSP430FR2155 which communicates with both BQ76942 devices, deals with all system control strategies, and uploads all the requested information to the system side. Since the top BQ76942 references the top battery group as ground which is not the same ground with the MCU, isolation is required in the communication between the MCU and the top BQ76942. The ISO164x, a hot swappable, low-power, bidirectional isolated I2C interface, supports the stable isolated I2C communication.

This design has both an RS-485 transceiver and a CAN transceiver. The CAN transceiver TCAN1042HV integrates level translation via the VIO terminal to allow for interfacing the transceiver I/Os directly to 1.8-V, 2.5-V, 3.3-V, or 5-V logic I/Os. The TCAN1042HV has ±70-V bus fault protection which is good enough to cover 60-V battery packs for light e-motorcycle. Since the MSP430FR2155 does not have an integrated CAN controller, CAN communication is not supported by this design. The THVD2410 is a half-duplex RS485 transceiver supporting a single 3-V to 5.5-V supply and designed for both 3.3-V and 5-V MCUs. The THVD2410 also supports ±70-V fault protection. This design uses a 120-V input, 0.3-A, ultra-low IQ synchronous buck DC/DC converter LM5168 with a low IQ, 18-V, 300-mA LDO TPS7A25 as the auxiliary power. A ±1%, 10-kΩ linear thermistor with positive temperature coefficient and 0603 package TMP61 is utilized to monitor the MOSFET temperature and is measured by the MCU ADC.