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  • TPS2378 IEEE 802.3at PoE High-Power PD Interface

    • SLVSB99C March   2012  – July 2015 TPS2378

      PRODUCTION DATA.  

  • CONTENTS
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  • TPS2378 IEEE 802.3at PoE High-Power PD Interface
  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1  APD Auxiliary Power Detect
      2. 7.3.2  CDB Converter Disable Bar Pin Interface
      3. 7.3.3  CLS Classification
      4. 7.3.4  DEN Detection and Enable
      5. 7.3.5  Internal Pass MOSFET
      6. 7.3.6  T2P Type-2 PSE Indicator
      7. 7.3.7  VDD Supply Voltage
      8. 7.3.8  VSS
      9. 7.3.9  PowerPAD
      10. 7.3.10 Forced, Four-Pair, High Power PoE
    4. 7.4 Device Functional Modes
      1. 7.4.1  PoE Overview
      2. 7.4.2  Threshold Voltages
      3. 7.4.3  PoE Start-up Sequence
      4. 7.4.4  Detection
      5. 7.4.5  Hardware Classification
      6. 7.4.6  Inrush and Start-up
      7. 7.4.7  Maintain Power Signature
      8. 7.4.8  Start-up and Converter Operation
      9. 7.4.9  PD Hotswap Operation
      10. 7.4.10 Start-up and Power Management, CDB and T2P
      11. 7.4.11 Adapter ORing
      12. 7.4.12 Using DEN to Disable PoE
      13. 7.4.13 ORing Challenges
  8. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Requirements
        1. 8.2.2.1 Input Bridges and Schottky Diodes
        2. 8.2.2.2 Protection, D1
        3. 8.2.2.3 Capacitor, C1
        4. 8.2.2.4 Detection Resistor, RDEN
        5. 8.2.2.5 Classification Resistor, RCLS
        6. 8.2.2.6 APD Pin Divider Network RAPD1, RAPD2
      3. 8.2.3 Application Curves
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Example
    3. 10.3 EMI Containment
    4. 10.4 Thermal Considerations and OTSD
    5. 10.5 ESD
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Community Resources
    3. 11.3 Trademarks
    4. 11.4 Electrostatic Discharge Caution
    5. 11.5 Glossary
  12. 12Mechanical, Packaging, and Orderable Information
  13. IMPORTANT NOTICE

Package Options

Mechanical Data (Package|Pins)
  • DDA|8
    • MPDS092F
Thermal pad, mechanical data (Package|Pins)
  • DDA|8
    • PPTD058I
Orderable Information
  • slvsb99c_oa
  • slvsb99c_pm
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    • Full reading width
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DATA SHEET

TPS2378 IEEE 802.3at PoE High-Power PD Interface

1 Features

  • IEEE 802.3at Type-2 Hardware Classification with Status Flag
  • Adapter Priority Input
  • DC/DC Converter Enable
  • Robust 100 V, 0.5-Ω Hotswap MOSFET
  • Operating Current up to 850 mA
  • 1-A (Typical) Operating Current Limit
  • 15 kV and 8 kV System-level ESD Capability
  • PowerPAD™ HSOP Package

2 Applications

  • IEEE 802.3at-compliant Devices
  • Video and VoIP Telephones
  • Multiband Access Points
  • Security Cameras
  • Pico-base Stations
  • Forced, Four-Pair, High Power Devices (SLVA625)

3 Description

This 8-pin integrated circuit contains all of the features needed to implement an IEEE802.3at type-2 powered device (PD). The low 0.5-Ω internal switch resistance, combined with the enhanced thermal dissipation of the PowerPAD™ package, enables this controller to continuously handle up to 0.85 A. The TPS2378 features an auxiliary power detect (APD) input, providing priority for an external power adapter. It also features a 100-V pass transistor, 140-mA inrush current limiting, type-2 indication, auto-retry fault protection, and an open-drain power-good output.

Device Information(1)

PART NUMBER PACKAGE BODY SIZE (NOM)
TPS2378 HSOP (8) 4.89 mm × 3.90 mm
  1. For all available packages, see the orderable addendum at the end of the data sheet.

Typical Application Circuit

TPS2378 typ_app_lvsb99.gif

4 Revision History

Changes from B Revision (November 2012) to C Revision

  • Added ESD Ratings table, Feature Description section, Device Functional Modes, Application and Implementation section, Power Supply Recommendations section, Layout section, Device and Documentation Support section, and Mechanical, Packaging, and Orderable Information section Go
  • Deleted Detailed Pin Description section. Go
  • Deleted CBD Pin Interface sectionGo
  • Deleted APD Pin Divider Network, RAPD1, RAPD2 sectionGo

Changes from A Revision (March 2012) to B Revision

  • Added Application: Forced, Four-Pair, High Power Devices (SLVA625)Go
  • Added Note 1 to the ELECTRICAL CHARACTERISTICS tableGo
  • Added section: Forced, Four-Pair, High Power PoE Go
  • Changed Table 2, From: POWER ≤ 12.95W To: POWER ≤ 13W, From: POWER > 12.95W To POWER > 13W, and PD INPUT POWER (max) From: 12.95 W To 13W Go
  • Changed Table 2, PSE Output Power for 802.3at (Type 2) From: 36W to 30WGo
  • Changed text in the Detection section From: "( ΔV / ΔI ) between 23.75 kΩ and 26.25 kΩ at the PI." To: "( ΔV / ΔI ) between 23.7 kΩ and 26.3 kΩ at the PI." Go
  • Added text to the Startup and Converter Operation section: "Additional loading applied between VVDD and VRTN during the inrush state may prevent successful PD and subsequent converter start up."Go
  • Changed text in the Detection Resistor, RDEN section From: "RDEN between 23.75 kΩ and 26.25 kΩ, or 25 kΩ ± 5%. " To: "RDEN between 23.7 kΩ and 26.3 kΩ, or 25 kΩ ± 5%."Go

Changes from * Revision (March 2012) to A Revision

  • Changed the Inrush termination MAX value From: 100% To: 99%Go

5 Pin Configuration and Functions

DDA Package
8-Pin HSOP
Top View
TPS2378 po_lvsb99.gif

Pin Functions

PIN I/O DESCRIPTION
NAME NO.
VDD 1 I Connect to positive PoE input power rail. Bypass with 0.1 µF to VSS.
DEN 2 I/O Connect 24.9 kΩ to VDD for detection. Pull to VSS disable pass MOSFET.
CLS 3 O Connect resistor from CLS to VSS to program classification current.
VSS 4 — Connect to negative power rail derived from PoE source.
RTN 5 — Drain of PoE pass MOSFET.
CDB 6 O Active low, open-drain converter disable output, referenced to RTN.
T2P 7 O Active low indicates type 2 PSE connected or APD active.
APD 8 I Raise 1.5 V above RTN to disable pass MOSFET and force T2P active.
Pad — — The PowerPad™ must be connected to VSS. A large fill area is required to assist in heat dissipation.

 
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