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

2.3.1 IEEE802.3bt Introduction

PoE hardware classification allows the Power Sourcing Equipment (PSE) to determine the power requirements of a Powered Device (PD) before supplying power. This classification processes assists with power budgeting and efficiency. Prior to the IEEE802.3bt standard, the IEEE802.3at standard allowed up to 30 W of power sourced at the PSE and 25.5 W of power at the PD for Class 4 across two pairs of the Ethernet cable.

Table 2-1 IEEE802.3at Power Types and Classes
CLASSTYPENUMBER OF PAIRSPOWER SOURCED AT PSEMINIMUM POWER AT PD
01215.4 W13.0 W
1124 W3.84 W
2127 W6.49 W
31215.4 W13.0 W
42230 W25.5 W

The IEEE802.3bt standard utilizes all four pairs of the Ethernet connector and increases the maximum power the load can consume as well as the power the PSE can supply. Two new types are established under the IEEE802.3.bt standard: Type 3 (60-W PSE) and Type 4 (90-W PSE). With this increased power rating, various end equipment's such as surveillance cameras and access points can incorporate more features such as analytics, rotation and heaters. Table 2-2 highlights the IEEE802.3bt types and classes.

Table 2-2 IEEE802.3bt Power Types and Classes
CLASSTYPENUMBER OF PAIRSPOWER SOURCED AT PSEMINIMUM POWER AT PD
01 or 3215.4 W13.0 W
11 or 32 or 44 W3.84 W
21 or 32 or 47 W6.49 W
31 or 32 or 415.4 W13.0 W
42 or 32 or 430 W25.5 W
53445 W40.0 W
63460 W51.0 W
74475 W62.0 W
84490 W71.3 W