LT4321

RECOMMENDED FOR NEW DESIGNS

PoE Ideal Diode Bridge Controller

Data Sheet (Rev. A) Product Selection Table
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Overview

  • 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
LT4321
PoE Ideal Diode Bridge Controller
Powered Device tor PoE (to 13W), PoE+ (to 25.5w), or Linear LTPoE++ (to 90W) Systems LT4321 Pin Configuration
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Documentation

Data Sheet 1

User Guide 16

Technical Articles 2

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Software Resources

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Hardware Ecosystem

Parts Product Life Cycle Description
Ideal Diodes and PowerPath Controllers 1
LT4320
LT4320-1
Ideal Diode Bridge Controller
Power-over-Ethernet (PoE) Controllers 2
LT4275
PRODUCTION LTPoE++/PoE+/PoE PD Controller
LT4276
PRODUCTION LTPoE++/PoE+/PoE PD Forward/Flyback Controller
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Tools & Simulations

LTspice

Models for the following parts are available in LTspice:

  • LT4321
LTspice

LTspice® is a powerful, fast and free simulation software, schematic capture and waveform viewer with enhancements and models for improving the simulation of analog circuits.

Evaluation Kits

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DC2046A-A

LT4276B/LT4321 Demo Board | PoE+ (25W, 3.3V/6.8A) PD with DC/DC and Ideal Diode Bridge

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Product Details

Demonstration circuit 2046A-A is an Ethernet Alliance™ certified PoE powered device (PD) with an isolated power supply using synchronous flyback topology, featuring the LT4276 and ideal diode bridge controller (LT4321).

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DC2475A-A

LT4295/LT4321 Demo Board | PoE++ (40W, 12V/3A) PD with Flyback DC/DC and Ideal Diode Bridge

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Product Details

Demonstration circuit 2475A-A is an Ethernet Alliance™ certified IEEE802.3bt compliant Power over Ethernet (PoE) powered device (PD). It features the LT4295 PD interface and switching regulator controller with the LT4321 PoE ideal diode bridge controller.

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DC2093A-A

LT4275A/LT4321 LTPoE++/PoE+/PoE PD Demo Board

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Product Details

DC2093A-A Demo Board for:
LT4275 LTPoE++/PoE+/PoE PD Controller
LT4321 PoE Ideal Diode Bridge Controller

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DC2046A-B

LT4276B/LT4321 Demo Board | PoE+ (25W, 5V/4.7A) PD with DC/DC and Ideal Diode Bridge

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Product Details

Demonstration circuit 2046A-B is a PoE powered device (PD) with an isolated power supply using synchronous flyback topology, featuring the LT4276 and ideal diode bridge controller (LT4321)



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DC2046A-F

LT4276C/LT4321 Demo Board | PoE (13W, 5V/2.3A) PD with DC/DC and Ideal Diode Bridge

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Product Details

Demonstration circuit 2046A-F is an Ethernet Alliance™ certified PoE Powered Device (PD) with an isolated power supply using synchronous flyback topology, featuring the LT4276 and ideal diode bridge controller (LT4321).

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DC2046A-C

LT4276B/LT4321 Demo Board | PoE+ (25W, 12V/1.9A) PD with DC/DC and Ideal Diode Bridge

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Product Details

Demonstration circuit 2046A-C is a PoE powered device (PD) with an isolated power supply using synchronous flyback topology, featuring the LT4276 and ideal diode bridge controller (LT4321).



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DC2093A-B

LT4275B/LT4321 PoE+/PoE PD Demo Board

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Product Details

DC2093A-B Demo Board for:
LT4275 LTPoE++/PoE+/PoE PD Controller
LT4321 PoE Ideal Diode Bridge Controller

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DC2093A-C

LT4275C/LT4321 PoE PD Demo Board

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Product Details

DC2093A-C Demo Board for:
LT4275 LTPoE++/PoE+/PoE PD Controller
LT4321 PoE Ideal Diode Bridge Controller

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DC2125A

LT4275/LT4321/LTM8027 Demo Board | LTPoE++ PD Plus Diode Bridge and DC/DC Controller

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Product Details

Demonstration circuit 2125 is a small, highly-integrated, non-isolated PoE Powered Device (PD) solution. It features a PD Interface Controller (LT4275), which interfaces with a PoE Power Sourcing Equipment (PSE), an ideal diode bridge controller (LT4321), which minimizes bridge losses, and a DC/DC μModule® regulator (LTM8027).

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DC2046A-D

LT4276B/LT4321 Demo Board | PoE+(25W, 24V/1A) PD with DC/DC and Ideal Diode Bridge

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Product Details

Demonstration circuit 2046A-D is a PoE powered device (PD) with an isolated power supply using synchronous flyback topology, featuring the LT4276 and ideal diode bridge controller (LT4321).



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DC2047A-A

LT4276B/LT4321 Demo Board | PoE+ (25W, 12V/1.9A) PD with DC/DC, Ideal Diode Bridge and 9V-57V AUX

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Product Details

Demonstration circuit 2047A-A is an IEEE802.3at compliant Power over Ethernet (PoE) Powered Device (PD) with support for 9-57VDC and 24VAC auxiliary supply input. It features the LT4276 PD interface and switching regulator controller, the LT4321 PoE ideal diode bridge controller, and the LT4320 ideal diode bridge controller.

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DC2046A-E

LT4276A/LT4321 Demo Board | LTPoE++ (38.7W, 5V/7A) PD with DC/DC and Ideal Diode Bridge

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Product Details

Demonstration circuit 2046A-E is a PoE powered device (PD) with an isolated power supply using synchronous flyback topology, featuring the LT4276 and ideal diode bridge controller (LT4321).



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AD-PS3803-RD

PoE+ with Ideal Diode Bridge to Isolated Flyback DC/DC (12V, 2A)

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Features and Benefits

  • Galvanically isolated 12V flyback DC output with up to 24 W of output power capability
  • No Transformer third winding or Opto-Isolator for output regulation
  • Supports IEEE802.3at (PoE+, Type 2) and IEEE802.3bt (PoE++, Type 3 and 4) interfacing and power supply control via a configurable jumper array
  • Supports a wide input DC auxiliary power of 37V to 57V

Product Details

The AD-PS3803-RD reference design is a power converter capable of harnessing any IEEE802.3at (PoE+, Type 2) compliant downstream Power-Over-Ethernet (PoE) supply to provide a galvanically isolated DC power.

At the core of this solution is the LT8306 60V No-Opto Flyback controller, stepping down the 37V to 57V PoE input voltage to a 12V, 24W DC output.

The on-board LT4275 LTPoE++/PoE+/PoE power delivery (PD) controller handles interfacing and power delivery to any PoE supply.

The LT4321 ideal diode bridge controller is used for improved end-to-end power delivery efficiency and eased thermal design by utilizing low RDS(ON) N-Channel FETs, replacing the eight-diode configuration typically found in passive PoE rectifier bridge.

The AD-PS3803-RD also has auxiliary DC power support for a wide input range of 37V to 57V.

APPLICATIONS

  • Industrial Automation
  • Surveillance Camera Systems
  • VoIP Phones
  • Payment Terminal Systems
  • Wireless Access Points

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DC2584A-A

LT4295/LT4321 Demo Board | PoE++ (71W/12V/5.5A) PD with Forward DC/DC and Ideal Diode Bridge

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Product Details

Demonstration circuit 2584A is an IEEE 802.3bt (Draft 2.1) compliant Power over Ethernet (PoE) Powered Device (PD). It features the LT4295 PD interface and switching regulator controller and the LT4321 PoE ideal diode bridge controller.

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DC2583A

LT4294/LT4321 Demo Board | PoE++ (71W/37V to 57V) PD and Ideal Diode Bridge

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Product Details

Demonstration circuit 2583 is an Ethernet Alliance™ certified IEEE 802.3bt compliant Power over Ethernet (PoE) powered device (PD). It features the LT4294 PD interface controller and the LT4321 PoE ideal diode bridge controller.

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EVAL-LTC9105-AZ

EVAL-LTC9105-AZ: LTC9105, MAX5974C, LT4321, and ADuM1252 IEEE 802.3bt Powered Device with I2C Telemetry

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Features and Benefits

  • IEEE 802.3bt-compliant Class 6 PD
  • Port telemetry with an isolated I2C interface
  • 5V/9.2A isolated synchronous forward converter

Product Details

The EVAL-LTC9105-AZ is an IEEE 802.3bt-compliant Type 3, Class 6 Power over Ethernet (PoE) powered device (PD) with port telemetry via I2C. The evaluation board features the LTC9105 PD interface controller, MAX5974C switching regulator controller, the LT4321 PoE ideal diode bridge controller, and the ADuM1252 I2C isolator.

The LTC9105 provides IEEE 802.3af-, IEEE 802.3at-, and IEEE 802.3bt-compliant interfacing with port voltage and current telemetry via I2C. It utilizes an external, low channel resistance, RDS(ON) (34mΩ typical), N-channel, hot-swap metal-oxide semiconductor, field-effect transistor (MOSFET), and 50mΩ sense resistor. Automatic maintain power signature (MPS) keeps the port connected when the current drops to a low level.

The MAX5974C controls a DC/DC converter utilizing a highly efficient active-clamp forward converter topology with synchronous rectification and provides an isolated 5V/9.2A output. The LT4321 controls eight low RDS(ON) (57mΩ typical), N-channel MOSFETs to further improve end-to-end power delivery efficiency and ease thermal design. The ADuM1252 isolates I2C data between the LTC9105 and a host controller on a nonisolated ground domain.

The EVAL-LTC9105-AZ is configured as a Class 6 PD and accepts up to 51W of delivered power from a power sourcing equipment (PSE) via its RJ45 connector (J1). The EVAL-LTC9105-AZ can be powered by a local 55V DC power supply using the auxiliary supply input terminals. With the DC590B I2C interface board connected to the EVAL-LTC9105-AZ, the EVAL-LTC9105-AZ graphical user interface (GUI) displays port telemetry and configuration options.

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DC2911A

LT4293, LT4321 IEEE 802.3bt and LTPoE++ Interoperable Powered Device

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Product Details

Demonstration circuit 2911A is an IEEE 802.3bt compliant and LTPoE++ interoperable Power over Ethernet (PoE) Powered Device (PD). It features the LT4293 PD interface controller and the LT4321 PoE ideal diode bridge controller.

The LT4293 provides LTPoE++, IEEE 802.3af (PoE, Type 1), IEEE 802.3at (PoE+, Type 2), and IEEE 802.3bt (PoE++, Type 3 and 4) compliant interfacing. It utilizes an external, low RDS(ON) (30mΩ typical) N-channel MOSFET for the Hot Swap function to improve efficiency.

Power good (PWRGD) output indicates the PD controller is ready to provide power to the downstream load. This signal can be used to enable an isolated power supply. The T2P output indicates the available power from the Power Sourcing Equipment (PSE). This signal communicates allocated power from either LTPoE++ or IEEE 802.3bt-compliant PSEs to the downstream PD circuitry.

The LT4321 controls eight low RDS(ON) (57mΩ typical) N-channel MOSFETs to further improve end-to-end power delivery efficiency and ease thermal design. This solution replaces the eight diodes typically found in a passive PoE rectifier bridge.

The DC2911A accepts up to 90W of delivered power from a PSE via the RJ45 connector (J1) or a local 48V DC power supply using the auxiliary supply input. When both supplies are connected, the auxiliary supply input has priority over the PoE input.

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DC2539A-A

LT4295/LT4321 Demo Board | PoE++ (51W, 12V/3.9A) PD with Flyback DC/DC and Ideal Diode Bridge

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Product Details

Demonstration circuit 2539A is an IEEE802.3bt (Draft 2.1) compliant Power over Ethernet (PoE) Powered Device (PD). It features the LT4295 PD interface and switching regulator controller and the LT4321 PoE ideal diode bridge controller.

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DC2476A-A

LT4295/LT4321 Demo Board | PoE++ (71W/24V/2.7A or 62W/24V/2.3A) PD with Flyback DC/DC and Ideal Diode Bridge

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Product Details

Demonstration Circuit 2476A is an Ethernet Alliance™ Gen 2 PoE certified IEEE 802.3bt compliant power over ethernet (PoE) powered device (PD). It features the LT4295 PD interface and switching regulator controller and the LT4321 PoE ideal diode bridge controller.

The LT4295 provides IEEE 802.3af (PoE, Type 1), IEEE 802.3at (PoE+, Type 2), and IEEE 802.3bt (PoE++, Type 3 and 4) compliant interfacing and power supply control. It utilizes an external, low RDS(on) (30mΩ typical) N-channel FET for the hot swap function to improve efficiency. The LT4295 controls a DC/DC converter that utilizes a highly efficient flyback topology with synchronous rectification.

The LT4321 controls eight low RDS(on) (30mΩ typical) N-channel FETs to further improve end-to-end power delivery efficiency and ease thermal design. This solution replaces the eight diodes typically found in a passive PoE rectifier bridge.

The DC2476A-A accepts up to 71.3W of delivered power from a power sourcing equipment (PSE) via the RJ45 connector (J1) or a local 48V DC power supply using the auxiliary supply input. When both supplies are connected, the auxiliary supply input has priority over the PoE input. The DC2476A-A supplies a 24V output at up to 2.7A as a Class 8 (71.3W) PD and up to 2.4A as a Class 7 (62W) PD application.
DC2046A-A
LT4276B/LT4321 Demo Board | PoE+ (25W, 3.3V/6.8A) PD with DC/DC and Ideal Diode Bridge
DC2046A-A Application Circuit DC2046A-A Application Circuit DC2046A-A Application Circuit DC2046A-A Application Circuit DC2046A-A Application Circuit EA Certified 4
DC2475A-A
LT4295/LT4321 Demo Board | PoE++ (40W, 12V/3A) PD with Flyback DC/DC and Ideal Diode Bridge
DC2475A-A Demo Board DC2475A-A Demo Board DC2475A-A Demo Board DC2475A-A Demo Board DC2475A-A Demo Board DC2475A-A Application Circuit DC2475A-A Application Circuit DC2475A-A Application Circuit EA Certified 4
DC2093A-A
LT4275A/LT4321 LTPoE++/PoE+/PoE PD Demo Board
DC2093A-A Demo Board DC2093A-A Demo Board DC2093A-A Demo Board DC2093A-A Demo Board DC2093A-A Demo Board DC2093A-A - Schematic
DC2046A-B
LT4276B/LT4321 Demo Board | PoE+ (25W, 5V/4.7A) PD with DC/DC and Ideal Diode Bridge
DC2046A-B Demo Board DC2046A-B Demo Board DC2046A-B Demo Board DC2046A-B Demo Board DC2046A-B Demo Board DC2046A-B - Schematic
DC2046A-F
LT4276C/LT4321 Demo Board | PoE (13W, 5V/2.3A) PD with DC/DC and Ideal Diode Bridge
DC2046A-F Demo Board DC2046A-F Demo Board DC2046A-F Demo Board DC2046A-F Demo Board DC2046A-F Application Circuit DC2046A-F Application Circuit DC2046A-F Application Circuit DC2046A-F Application Circuit DC2046A-F Application Circuit EA Certified 3
DC2046A-C
LT4276B/LT4321 Demo Board | PoE+ (25W, 12V/1.9A) PD with DC/DC and Ideal Diode Bridge
DC2046A-C Demo Board DC2046A-C Demo Board DC2046A-C Demo Board DC2046A-C Demo Board DC2046A-C Demo Board DC2046A-C - Schematic
DC2093A-B
LT4275B/LT4321 PoE+/PoE PD Demo Board
DC2093A-B Demo Board DC2093A-B Demo Board DC2093A-B Demo Board DC2093A-B Demo Board DC2093A-B Demo Board DC2093A-A - Schematic
DC2093A-C
LT4275C/LT4321 PoE PD Demo Board
DC2093A-A - Schematic
DC2125A
LT4275/LT4321/LTM8027 Demo Board | LTPoE++ PD Plus Diode Bridge and DC/DC Controller
DC2125A Demo Board DC2125A Demo Board DC2125A Demo Board DC2125A Demo Board DC2125A Demo Board DC2125A - Schematic
DC2046A-D
LT4276B/LT4321 Demo Board | PoE+(25W, 24V/1A) PD with DC/DC and Ideal Diode Bridge
DC2046A-D Demo Board DC2046A-D Demo Board DC2046A-D Demo Board DC2046A-D Demo Board DC2046A-D Demo Board DC2046A-D - Schematic
DC2047A-A
LT4276B/LT4321 Demo Board | PoE+ (25W, 12V/1.9A) PD with DC/DC, Ideal Diode Bridge and 9V-57V AUX
DC2047A-A Evaluation Board DC2047A-A Evaluation Board - Top View DC2047A-A Evaluation Board - Bottom View DC2047A-A - Schematic
DC2046A-E
LT4276A/LT4321 Demo Board | LTPoE++ (38.7W, 5V/7A) PD with DC/DC and Ideal Diode Bridge
DC2046A-E Demo Board DC2046A-E Demo Board DC2046A-E Demo Board DC2046A-E Demo Board DC2046A-E Demo Board DC2046A-E - Schematic
AD-PS3803-RD
PoE+ with Ideal Diode Bridge to Isolated Flyback DC/DC (12V, 2A)
AD-PS3803-RD Board Photo Angle View AD-PS3803-RD Board Photo Top View AD-PS3803-RD Board Photo Bottom View AD-PS3803-RD Block Diagram
DC2584A-A
LT4295/LT4321 Demo Board | PoE++ (71W/12V/5.5A) PD with Forward DC/DC and Ideal Diode Bridge
DC2584A-A Demo Board DC2584A-A Demo Board DC2584A-A Demo Board DC2584A-A Demo Board DC2584A-A Demo Board
DC2583A
LT4294/LT4321 Demo Board | PoE++ (71W/37V to 57V) PD and Ideal Diode Bridge
DC2583A Application Circuit DC2583A Application Circuit DC2583A Application Circuit DC2583A Application Circuit EA Certified 3 EA Certified 4
EVAL-LTC9105-AZ
EVAL-LTC9105-AZ: LTC9105, MAX5974C, LT4321, and ADuM1252 IEEE 802.3bt Powered Device with I2C Telemetry
EVAL-LTC9105-AZ Board Photo Angle View EVAL-LTC9105-AZ Board Photo Top View EVAL-LTC9105-AZ Board Photo Bottom View EA PoE PD 6
DC2911A
LT4293, LT4321 IEEE 802.3bt and LTPoE++ Interoperable Powered Device
DC2911A Application Circuit DC2911A Application Circuit
DC2539A-A
LT4295/LT4321 Demo Board | PoE++ (51W, 12V/3.9A) PD with Flyback DC/DC and Ideal Diode Bridge
DC2539A-A Demo Board DC2539A-A Demo Board DC2539A-A Demo Board DC2539A-A Demo Board DC2539A-A Demo Board DC2539A-A - Schematic
DC2476A-A
LT4295/LT4321 Demo Board | PoE++ (71W/24V/2.7A or 62W/24V/2.3A) PD with Flyback DC/DC and Ideal Diode Bridge
DC2476A-A Demo Board DC2476A-A Demo Board DC2476A-A Demo Board DC2476A-A Demo Board DC2476A-A Demo Board Ethernet Alliance Certified 2.0 Power over Ethernet (PoE)

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