SLVSG51A April   2021  – February 2022 TPS23882B

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
    1. 6.1 Detailed Pin Description
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Typical Characteristics
  8. 8 Parameter Measurement Information
    1. 8.1 Timing Diagrams
  9. 9 Detailed Description
    1. 9.1 Overview
      1. 9.1.1 Operating Modes
        1. 9.1.1.1 Auto
        2. 9.1.1.2 Autonomous
        3. 9.1.1.3 Semiauto
        4. 9.1.1.4 Manual and Diagnostic
        5. 9.1.1.5 Power Off
      2. 9.1.2 PoE Compliance Terminology
      3. 9.1.3 PoE 2 Type-3 2-Pair PoE
      4. 9.1.4 Requested Class Versus Assigned Class
      5. 9.1.5 Power Allocation and Power Demotion
      6. 9.1.6 Programmable SRAM
    2. 9.2 Functional Block Diagram
    3. 9.3 Feature Description
      1. 9.3.1 Port Remapping
      2. 9.3.2 Port Power Priority
      3. 9.3.3 Analog-to-Digital Converters (ADC)
      4. 9.3.4 I2C Watchdog
      5. 9.3.5 Current Foldback Protection
    4. 9.4 Device Functional Modes
      1. 9.4.1 Detection
      2. 9.4.2 Classification
      3. 9.4.3 DC Disconnect
    5. 9.5 I2C Programming
      1. 9.5.1 I2C Serial Interface
    6. 9.6 Register Maps
      1. 9.6.1 Complete Register Set
      2. 9.6.2 Detailed Register Descriptions
        1. 9.6.2.1  INTERRUPT Register
        2. 9.6.2.2  INTERRUPT MASK Register
        3. 9.6.2.3  POWER EVENT Register
        4. 9.6.2.4  DETECTION EVENT Register
        5. 9.6.2.5  FAULT EVENT Register
        6. 9.6.2.6  START/ILIM EVENT Register
        7. 9.6.2.7  SUPPLY and FAULT EVENT Register
          1. 9.6.2.7.1 Detected SRAM Faults and "Safe Mode"
        8. 9.6.2.8  CHANNEL 1 DISCOVERY Register
        9. 9.6.2.9  CHANNEL 2 DISCOVERY Register
        10. 9.6.2.10 CHANNEL 3 DISCOVERY Register
        11. 9.6.2.11 CHANNEL 4 DISCOVERY Register
        12. 9.6.2.12 POWER STATUS Register
        13. 9.6.2.13 PIN STATUS Register
          1. 9.6.2.13.1 AUTONOMOUS MODE
        14. 9.6.2.14 OPERATING MODE Register
        15. 9.6.2.15 DISCONNECT ENABLE Register
        16. 9.6.2.16 DETECT/CLASS ENABLE Register
        17. 9.6.2.17 Power Priority / 2Pair PCUT Disable Register Name
        18. 9.6.2.18 TIMING CONFIGURATION Register
        19. 9.6.2.19 GENERAL MASK Register
        20. 9.6.2.20 DETECT/CLASS RESTART Register
        21. 9.6.2.21 POWER ENABLE Register
        22. 9.6.2.22 RESET Register
        23. 9.6.2.23 ID Register
        24. 9.6.2.24 Connection Check and Auto Class Status Register
        25. 9.6.2.25 2-Pair Police Ch-1 Configuration Register
        26. 9.6.2.26 2-Pair Police Ch-2 Configuration Register
        27. 9.6.2.27 2-Pair Police Ch-3 Configuration Register
        28. 9.6.2.28 2-Pair Police Ch-4 Configuration Register
        29. 9.6.2.29 Capacitance (Legacy PD) Detection
        30. 9.6.2.30 Power-on Fault Register
        31. 9.6.2.31 PORT RE-MAPPING Register
        32. 9.6.2.32 Channels 1 and 2 Multi Bit Priority Register
        33. 9.6.2.33 Channels 3 and 4 Multi Bit Priority Register
        34. 9.6.2.34 Port Power Allocation Register
        35. 9.6.2.35 TEMPERATURE Register
        36. 9.6.2.36 INPUT VOLTAGE Register
        37. 9.6.2.37 CHANNEL 1 CURRENT Register
        38. 9.6.2.38 CHANNEL 2 CURRENT Register
        39. 9.6.2.39 CHANNEL 3 CURRENT Register
        40. 9.6.2.40 CHANNEL 4 CURRENT Register
        41. 9.6.2.41 CHANNEL 1 VOLTAGE Register
        42. 9.6.2.42 CHANNEL 2 VOLTAGE Register
        43. 9.6.2.43 CHANNEL 3 VOLTAGE Register
        44. 9.6.2.44 CHANNEL 4 VOLTAGE Register
        45. 9.6.2.45 2x FOLDBACK SELECTION Register
        46.       93
        47. 9.6.2.46 FIRMWARE REVISION Register
        48. 9.6.2.47 I2C WATCHDOG Register
        49. 9.6.2.48 DEVICE ID Register
        50. 9.6.2.49 CHANNEL 1 DETECT RESISTANCE Register
        51. 9.6.2.50 CHANNEL 2 DETECT RESISTANCE Register
        52. 9.6.2.51 CHANNEL 3 DETECT RESISTANCE Register
        53. 9.6.2.52 CHANNEL 4 DETECT RESISTANCE Register
        54. 9.6.2.53 CHANNEL 1 DETECT CAPACITANCE Register
        55. 9.6.2.54 CHANNEL 2 DETECT CAPACITANCE Register
        56. 9.6.2.55 CHANNEL 3 DETECT CAPACITANCE Register
        57. 9.6.2.56 CHANNEL 4 DETECT CAPACITANCE Register
        58. 9.6.2.57 CHANNEL 1 ASSIGNED CLASS Register
        59. 9.6.2.58 CHANNEL 2 ASSIGNED CLASS Register
        60. 9.6.2.59 CHANNEL 3 ASSIGNED CLASS Register
        61. 9.6.2.60 CHANNEL 4 ASSIGNED CLASS Register
        62. 9.6.2.61 AUTO CLASS CONTROL Register
        63. 9.6.2.62 CHANNEL 1 AUTO CLASS POWER Register
        64. 9.6.2.63 CHANNEL 2 AUTO CLASS POWER Register
        65. 9.6.2.64 CHANNEL 3 AUTO CLASS POWER Register
        66. 9.6.2.65 CHANNEL 4 AUTO CLASS POWER Register
        67. 9.6.2.66 ALTERNATIVE FOLDBACK Register
        68. 9.6.2.67 SRAM CONTROL Register
          1. 9.6.2.67.1 SRAM START ADDRESS (LSB) Register
          2. 9.6.2.67.2 SRAM START ADDRESS (MSB) Register
          3. 9.6.2.67.3 118
  10. 10Application and Implementation
    1. 10.1 Application Information
      1. 10.1.1 Autonomous Operation
      2. 10.1.2 Introduction to PoE
        1. 10.1.2.1 2-Pair Versus 4-Pair Power and the New IEEE802.3bt Standard
    2. 10.2 Typical Application
      1. 10.2.1 Design Requirements
      2. 10.2.2 Detailed Design Procedure
        1. 10.2.2.1 Connections on Unused Channels
        2. 10.2.2.2 Power Pin Bypass Capacitors
        3. 10.2.2.3 Per Port Components
        4. 10.2.2.4 System Level Components (not Shown in the Schematic Diagrams)
      3. 10.2.3 Application Curves
  11. 11Power Supply Recommendations
    1. 11.1 VDD
    2. 11.2 VPWR
  12. 12Layout
    1. 12.1 Layout Guidelines
      1. 12.1.1 Kelvin Current Sensing Resistors
      2.      138
    2. 12.2 Layout Example
      1. 12.2.1 Component Placement and Routing Guidelines
        1. 12.2.1.1 Power Pin Bypass Capacitors
        2. 12.2.1.2 Per-Port Components
  13. 13Device and Documentation Support
    1. 13.1 Documentation Support
      1. 13.1.1 Related Documentation
    2. 13.2 Receiving Notification of Documentation Updates
    3. 13.3 Support Resources
    4. 13.4 Trademarks
    5. 13.5 Electrostatic Discharge Caution
    6. 13.6 Glossary
  14. 14Mechanical, Packaging, and Orderable Information

9.1.5 Power Allocation and Power Demotion

The Power Allocation settings in register 0x29 sets the maximum power level a port powers on. Settings for each class level from 2-pair 4 W (Class 1) up to 2-pair 30 W (Class 4) have been provided to maximize system design flexibility.

Note:

The Power Allocation settings in register 0x29 do not set the power limit for a given port. The port and channel power limiting is configured with the 2P (registers 0x1E- x 21) policing registers

During a turn-on attempt, if a PD presents a classification level greater than the power allocation setting for a port, the TPS23882B limits the number of classification fingers presented to the PD prior to turn on based on the power allocation settings in register 0x29. This behavior is called Power Demotion as it is the number of fingers presented to the PD that sets the maximum level of power the PD is allowed to draw before the PSE is allowed to disable it.

Note:

The IEEE 802.3 standard requires PDs that are power demoted by a PSE to limit their total power draw below the Type/class level set by the number of fingers presented by the PSE during mutual identification.

In a 2-pair system, Power demotion is limited to either 30 W (3-fingers) or 15.4 W (1-finger) as there is no other physical means of indicating to a PD over the physical layer that less than 15.4 W is available.

If register 0x29 is configured for either 4 W (class 1) or 7 W (Class 2), and a class 3 or higher device is connected, the port is not powered and a Start Fault is reported along with an "Insufficient Power" indication provided in register 0x24.

Table 9-2 2-Pair Power Demotion Table
Power Allocation
Register 0x29		Assigned Class Value (Based on the PD Connected at the Port)
Class 1 PDClass 2 PDClass 3 PDClass 4 PDClass 5+ PDs
2-Pair 4 WClass 1Start Fault
Insufficient Power		Start Fault
Insufficient Power		Start Fault
Insufficient Power		Start Fault
Insufficient Power
2-Pair 7 WClass 1Class 2Start Fault
Insufficient Power		Start Fault
Insufficient Power		Start Fault
Insufficient Power
2-Pair 15.5 WClass 1Class 2Class 3Class 3Class 3
2-Pair 30 WClass 1Class 2Class 3Class 4Class 4