TIDUEX8 September   2020

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5.   5
  6. 1System Description
    1. 1.1 Key System Specifications
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Highlighted Products
      1. 2.2.1 TPS23730
      2. 2.2.2 TLV431
    3. 2.3 System Design Theory
      1. 2.3.1 IEEE802.3bt Introduction
  8. 3Hardware, Testing Requirements, and Test Results
    1. 3.1 Required Hardware
      1. 3.1.1 Hardware
    2. 3.2 Testing and Results
      1. 3.2.1 Test Setup
      2. 3.2.2 Test Results
        1. 3.2.2.1 Efficiency
        2. 3.2.2.2 Control Loop Gain/Stability
        3. 3.2.2.3 Load Transient
        4. 3.2.2.4 Input and Output Ripple
        5. 3.2.2.5 Switching Waveforms
        6. 3.2.2.6 Start Up Response
        7. 3.2.2.7 Soft-Stop Response
        8. 3.2.2.8 Output Short Circuit Response
        9. 3.2.2.9 Thermal Performance
  9. 4Design Files
    1. 4.1 Schematics
    2. 4.2 Bill of Materials
    3. 4.3 PCB Layout Recommendations
      1. 4.3.1 Layout Prints
    4. 4.4 Altium Project
    5. 4.5 Gerber Files
    6. 4.6 Assembly Drawings
  10. 5Related Documentation
    1. 5.1 Trademarks
  11. 6Terminology
  12. 7About the Author

1 System Description

The IEEE802.3bt standard allows the implementation of >25-W PoE designs on a compliant, uniform standard over all four data pairs of the Ethernet connector. This Type-3, 50-W PoE flyback converter design is intended for users to develop such end products for various cost sensitive communication and industrial applications that require over 25 W of power on a 5-V rail. The design files include Schematics, Bill of Materials (BOMs), Altium files, Gerber Files and Fabrication Files.

This isolated active clamp forward design has an input voltage range of 37 V - 57 V for PoE and an optional auxiliary 37-V to 57-V power supply path which will be prioritized if enabled. The output of this design is 5-V at 10-A (50 W) which provides higher power than the previous sub-25-W IEEE802.3at standard allowed.

The TPS23730 soft-stop feature minimizes stress on switching power FETs and predictability of the shutdown procedure, allowing FET BOM cost reduction. Programmable spread spectrum frequency dithering (SSFD) is provided to minimize the size and cost of EMI filter. This design also has hiccup mode protection enabled, which provides excellent thermal protection during faults.