SNOSDG3 December   2024 LM74681

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 Switching Characteristics
    7. 5.7 Typical Characteristics
  7. 6 Parameter Measurement Information
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Input and Output Voltage
      2. 7.3.2 Charge Pump
      3. 7.3.3 Gate Driver
      4. 7.3.4 Enable
    4. 7.4 Device Functional Modes
      1. 7.4.1 Conduction Mode
        1. 7.4.1.1 Regulated Conduction Mode
        2. 7.4.1.2 Full Conduction Mode
      2. 7.4.2 Reverse Current Protection Mode
  9. 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 Procedure
        1. 8.2.2.1 Design Considerations
        2. 8.2.2.2 MOSFET Selection
        3. 8.2.2.3 Output capacitance
      3. 8.2.3 Application Curves
    3. 8.3 Powered Device for IEEE 802.3bt Class 5-8 (45W-90W) Systems
    4. 8.4 Power Supply Recommendations
      1. 8.4.1 Transient Protection
    5. 8.5 Layout
      1. 8.5.1 Layout Guidelines
      2. 8.5.2 Layout Example
  10. 9 Device and Documentation Support
    1. 9.1 Receiving Notification of Documentation Updates
    2. 9.2 Support Resources
    3. 9.3 Trademarks
    4. 9.4 Electrostatic Discharge Caution
    5. 9.5 Glossary
  11. 10Revision History
  12. 11Mechanical, Packaging, and Orderable Information

パッケージ・オプション

メカニカル・データ（パッケージ｜ピン）
サーマルパッド・メカニカル・データ
発注情報

3 Description

The LM74681 is a 100V ideal diode bridge controller capable of driving a MOSFET bridge, enabling efficient low-loss bridge rectifier solutions in Power over Ethernet (PoE) applications. It allows a Power over Ethernet, powered device (PD) to receive power from RJ-45 data pairs, spare pairs, or any combination of the two, regardless of voltage polarity. The integrated charge pump allows use of N-channel MOSFETs, which are smaller and more cost effective than P-channel MOSFETs for the same power level. The LM74681 along with N-channel MOSFET bridge can replace the conventional diode bridge and can be conveniently implemented in both 2-pair and 4-pair PoE PD systems. In the event of a power source failure or short circuit, a rapid turn-off feature reduces reverse current spikes. The device also features an ultra-low quiescent current of 0.27µA, which ensures that there is no data corruption during the PoE PD detection and classification phase. This device is characterized for operation over a junction temperature range of –40°C to +125°C.
Package Information
PART NUMBER PACKAGE(1) PACKAGE SIZE(2)
LM74681 DRR (WSON, 12) 3mm × 3mm
(1) For all available packages, see the orderable addendum at the end of the data sheet.
(2) The package size (length × width) is a nominal value and includes pins, where applicable.
LM74681 Typical Application SchematicTypical Application Schematic
LM74681 –48V DC Input, Startup With Vin Ramp–48V DC Input, Startup With Vin Ramp