TIDUF46 October   2023

 

  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 Isolated UART Interface to MCU
    3. 2.3 Highlighted Products
      1. 2.3.1 BQ79616
      2. 2.3.2 TMUX1308
      3. 2.3.3 TMUX1574
      4. 2.3.4 TMUX1102
      5. 2.3.5 TPS22810
      6. 2.3.6 ISO7742
      7. 2.3.7 TSD05C
      8. 2.3.8 ESD441
      9. 2.3.9 ESD2CAN24-Q1
  9. 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 Temperature Sensing Accuracy
      3. 3.3.3 Cell Voltage and Temperature Sensing Timings
      4. 3.3.4 Cell Balancing and Thermal Performance
      5. 3.3.5 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

2.2.4 Isolated UART Interface to MCU

The design reserves an isolated UART interface to the MCU for a CAN structure. The ISO7742 is used to connect the UART interface of the BQ79616 and the MCU. Since the CVDD and TX pins of the BQ79616 supply a constant voltage in both SHUTDOWN and ACTIVE modes, the ISO7742 is powered from the VCC (CVDD) and input (TX) when the BQ79616 SHUTDOWN mode of the ISO7742 is directly connected to BQ79616.

Figure 3-14 shows the ISO7742 circuit directly connected to the BQ79616.

GUID-20230925-SS0I-S3WQ-SDCX-KNS3KSDX4LGJ-low.svgFigure 2-5 ISO7742 Circuit Directly Connected to BQ79616

The TMUX1102 is used to block the current from the TX pin. The TMUX1102 has a powered-off protection feature and high bandwidth of 300 MHz, which is suitable for the TX signal transmit path. A PMOS is used to block the CVDD pin connection from the BQ79616 to the ISO7742 unidirectionally. Both the TMUX1102 and PMOS are enabled by an optocoupler pulldown signal controlled by the MCU.

Figure 3-14 shows the ISO7742 circuit connected to TMUX and PMOS.

GUID-20230925-SS0I-3T5G-JXBZ-GJKBQ9DZNNFN-low.svgFigure 2-6 ISO7742 Circuit Connected to TMUX and PMOS