LT4321 - PoE Ideal Diode Bridge Controller

Features

  • Reduces Heat, Eliminates Thermal Design Problems
  • Maximizes Power Efficiency
  • Less than 800μA Quiescent Operating Current
  • Fully Compatible with IEEE 802.3 Detection and Classification
  • IEEE 802.3 Compliant When Paired with a Powered Device (PD) Controller
  • Works with 2-Pair and 4-Pair PoE Applications
  • Compatible with PoE, PoE+, and LTPoE++™
  • 100V Absolute Maximum Voltage
  • H-Grade Version Operates Up to 125°C
  • 16-Lead 4mm × 4mm QFN Package

Typical Application

LT4321 Typical Application

Description

The LT®4321 is a dual ideal diode bridge controller that enables a Power over Ethernet (PoE) powered device (PD) to receive power in either voltage polarity from RJ-45 data pairs, spare pairs, or both. The LT4321 and eight N-channel MOSFETs replace the eight diodes in a passive PoE rectifier bridge. The LT4321 eases thermal design and increases delivered power.

An internal charge pump allows an all-NMOS bridge eliminating larger and more costly PMOS switches. The LT4321 works with 2-pair and 4-pair applications. High impedance input sense pins prevent reverse current on unused pairs. If the power source fails or is shorted, a fast turn-off minimizes reverse current transients. Unlike discrete ideal bridge solutions, the LT4321 will operate through transients without enabling the MOSFETs on unpowered pairs.

Packaging

For complete and up to date package information and drawings, please refer to our packaging page

QFN-16

LT4321 Package Drawing

Order Info

Package Variations and Pricing

Part Number Package Pins Temp Price (1-99) Price (1k)* RoHS Data
LT4321HUF#PBF QFN 16 H $4.85 $3.39 View
LT4321HUF#TRPBF QFN 16 H $3.45 View
LT4321IUF#PBF QFN 16 I $4.21 $2.95 View
LT4321IUF#TRPBF QFN 16 I $3.01 View
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* The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Linear Technology sales office or authorized distributor.

Demo Boards

Linear Technology offers many demo boards free of charge to qualified customers. Contact your local sales office or distributor to inquire about a demo board. Certain demo boards are also available for sale via credit card on this website. Demo boards are for evaluation purposes only. It remains the customer’s responsibility to verify proper and reliable operation in the actual end application.

Part Number Description Price Documentation
DC2093A-A LT4275/LT4321 LTPoE++/PoE+/PoE PD Demo Board $95.00
DC2093A-B LT4275B/LT4321 PoE+/PoE PD Demo Board $95.00
DC2093A-C LT4275C/LT4321 PoE PD Demo Board $95.00
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Companion Boards

Part Number Description Price Documentation
DC1814A-A DC1814A-A LTC4274A-1: LTPoE++ (38.7W) PSE (req. DC2093) $100.00
DC1815A-A LTC4266A-1: 4-Port 38.7W LTPoE++ PSE (req. DC2093 & DC590) $200.00
DC1814A-B DC1814A-B LTC4274A-2: LTPoE++ (52.7W) PSE (req. DC2093) $100.00
DC1815A-B LTC4266A-2: 4-Port 52.7W LTPoE++ PSE (req. DC2093 & DC590) $200.00
DC1814A-C DC1814A-C LTC4274A-3: LTPoE++ (70W) PSE (req. DC2093) $100.00
DC1815A-C LTC4266A-3 4-Port 70W LTPoE++ PSE (req. DC2093 & DC590) $200.00
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Click here to view our complete list of demo boards

Applications

  • PoE/PoE+/ LTPoE++ Powered Devices
  • DC Polarity Correction and Ideal Diode-ORing of Telecom Supplies

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Design Tools

Linear Technology provides a variety of custom design simulation tools and device models to allow even novice designers to quickly and easily evaluate circuits using high performance switching regulators, amplifiers, data converters, filters and more. Please visit our Design Tools page to view and download:

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