TIDUFB5A December   2024  – January 2026

 

  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 Redundant Input Supplies
      2. 2.2.2 Ethernet Ring
      3. 2.2.3 Audio Video Bridging (AVB)
      4. 2.2.4 Low-Power Mode and Wake
      5. 2.2.5 Limp Home Mode
      6. 2.2.6 SPI Daisy Chain
      7. 2.2.7 Reset Aggregation
    3. 2.3 Highlighted Products
      1. 2.3.1  AM263P4-Q1
      2. 2.3.2  DP83TG721S-Q1
      3. 2.3.3  DP83TD555J-Q1
      4. 2.3.4  TPS653860-Q1
      5. 2.3.5  TPS2HCS10-Q1
      6. 2.3.6  TPS2HCS05-Q1
      7. 2.3.7  DRV8245S-Q1
      8. 2.3.8  TIC12400-Q1
      9. 2.3.9  LM74900-Q1
      10. 2.3.10 LM74703-Q1
      11. 2.3.11 INA186-Q1
      12. 2.3.12 TPS7B81-Q1
      13. 2.3.13 TPS3762-Q1
      14. 2.3.14 TPS62903-Q1
      15. 2.3.15 TPS62902-Q1
      16. 2.3.16 TPS7B4256-Q1
      17. 2.3.17 TPS1211-Q1
      18. 2.3.18 TPS1HC30-Q1
      19. 2.3.19 TPS4HC120-Q1
      20. 2.3.20 TPS2HC08-Q1
      21. 2.3.21 TPS1HC04-Q1
      22. 2.3.22 DRV8714S-Q1
      23. 2.3.23 DRV8145S-Q1
      24. 2.3.24 DRV81602-Q1
      25. 2.3.25 TPS1214-Q1
      26. 2.3.26 TCAN1043A-Q1
      27. 2.3.27 TCAN1044-Q1
      28. 2.3.28 TCAN1046V-Q1
      29. 2.3.29 SN3257-Q1
      30. 2.3.30 TLIN1021A-Q1
      31. 2.3.31 TLIN1024A-Q1
      32. 2.3.32 TAS6754-Q1
      33. 2.3.33 TMUX1308-Q1
      34. 2.3.34 TPLD1201-Q1
      35. 2.3.35 SN74CBTLV3861-Q1
      36. 2.3.36 TXE8124-Q1
      37. 2.3.37 TCAL9539-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 Redundant Input Supply
      2. 3.4.2 Power Sequence
      3. 3.4.3 Reset Aggregation
      4. 3.4.4 Low Power Mode Tests
        1. 3.4.4.1 Low Power Mode Quiescent Current
        2. 3.4.4.2 Wake Measurement Results
        3. 3.4.4.3 CAN Wake
        4. 3.4.4.4 LIN Wake
        5. 3.4.4.5 High-Side Switch Controller Wake
        6. 3.4.4.6 Smart eFuse Wake
        7. 3.4.4.7 High-Side Switch Wake
  10. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 Layout
      3. 4.1.3 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
  12. 6Revision History

2.2.1 Redundant Input Supplies

This design features two ideal diode controllers for the redundant 12V inputs, the LM74704-Q1 and LM74900-Q1. The LM74704-Q1 drives an external N-channel MOSFET to regulate forward voltage drop and turns off the MOSFET when a reverse current event is detected. The LM74900-Q1 behaves similarly, but drives back-to-back N-channel MOSFETs to emulate an ideal diode rectifier and has integrated current sense. The first MOSFET provides reverse input protection and output voltage holdup, and the second MOSFET allows load disconnect in case of an overcurrent or overvoltage event. In this system, the drain of the N-channel MOSFET driven by LM74704-Q1 is connected to the drain of the first N-channel MOSFET driven by LM74900-Q1 to create a 12V always-on rail. The second MOSFET of LM74900-Q1 provides power to load drivers to allow for load disconnect in the case of overcurrent or overvoltage and to disconnect the supply during a low-power state to reduce quiescent current.