TIDUF55 November   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 Power Tree and Wakeup
      2. 2.2.2 Insulation Requirement for Isolated Interface
      3. 2.2.3 Robust Relay Driver
      4. 2.2.4 Stackable Daisy Chain Communication
    3. 2.3 Highlighted Products
      1. 2.3.1  TMDSCNCD263
      2. 2.3.2  LMR51440
      3. 2.3.3  TPS7A16
      4. 2.3.4  TPS7B81
      5. 2.3.5  TPS62913
      6. 2.3.6  TPS4H160-Q1
      7. 2.3.7  ULN2803C
      8. 2.3.8  ISO1042
      9. 2.3.9  UCC12050
      10. 2.3.10 ISO1410
      11. 2.3.11 SN6505B
      12. 2.3.12 BQ32002
      13. 2.3.13 HDC3020
      14. 2.3.14 TPS3823
      15. 2.3.15 DP83826E
      16. 2.3.16 TPS763
      17. 2.3.17 LM74701-Q1
  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
      1. 3.4.1 Power Supply Testing
      2. 3.4.2 Daisy Chain Signal Quality
      3. 3.4.3 Relay Driving
      4. 3.4.4 Isolated CAN Transceiver Operation
  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

2.2.1 Power Tree and Wakeup

Figure 3-17 shows the BCU power tree.

GUID-20231019-SS0I-K1F9-BZS8-C55WN9QDGVZM-low.svg Figure 2-2 BCU Power Tree

The BCU is supplied in a rated 24 V with a range of 18 V to 32 V. The 24-V power supply can be from AC-DC module or DC-DC module with 70-W minimum power.

There are two 24-V input supply paths (LV_24V and RY_24V). LV_24V is used to supply all the control functions of the devices. The LM51440 is used to convert the LV_24V to 5 V with 4-A maximum current. The 5-V power rails are used to provide the supply voltage to the TMDCNCD263, UCC12050, and SN6505B. The UCC12050 provides transceiver-side supply 5-V voltage for the isolated CAN. The SN6505B, transformer and TPS76350 provides transceiver-side supply 5-V voltage for the isolated RS-485. The low-dropout (LDO) TPS7A1601 converts LV_24V to 12 V. The 12-V power rails can enable the reverse wakeup feature of the BQ79600. The LDO TPS7B8133 converts 5 V to 3.3 V. The 3.3-V power rail is used to provide the digital-side supply voltage of the isolated CAN or isolated RS-485, BQ32002, HDC3020, and TPS3823. RY_24V is used to supply the relay coils independently from LV_24V.

There are two wakeup paths to wake LMR51440 through the EN pin. One is a button trigger using LV_24V, another is a reverse wakeup from BQ79600-Q1. The BQ79600-Q1 supports automatic host wakeup through the INH pin when an unmask fault is detected in the battery pack. The MCU gives an IO voltage to the LMR51440, holds the LMR51440 through the EN pin when the wakeup trigger voltage fluctuates.