LT4321
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LT4321

PoE Ideal Diode Bridge Controller

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Info : RECOMMENDED FOR NEW DESIGNS tooltip
Info : RECOMMENDED FOR NEW DESIGNS tooltip
Part Details
Part Models 4
1ku List Price Starting From $1.74
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
Additional Details
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The LT4321 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.

Applications

  • PoE/PoE+/ LTPoE++ Powered Devices
  • DC Polarity Correction and Ideal Diode-ORing of Telecom Supplies
Part Models 4
1ku List Price Starting From $1.74

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Documentation

Documentation

Video

Part Model Pin/Package Drawing Documentation CAD Symbols, Footprints, and 3D Models
LT4321HUF#PBF
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LT4321HUF#TRPBF
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LT4321IUF#PBF
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LT4321IUF#TRPBF
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Software & Part Ecosystem

Software & Part Ecosystem

Evaluation Kit

Evaluation Kits 17

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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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DC2046A-A

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

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

Product Detail

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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DC2475A-A

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

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

Product Detail

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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DC2046A-B

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

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DC2046A-B

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

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

Product Detail

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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DC2046A-F

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

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

Product Detail

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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DC2046A-C

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

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

Product Detail

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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DC2093A-C

LT4275C/LT4321 PoE PD Demo Board

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DC2125A

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

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DC2125A

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

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

Product Detail

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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DC2584A-A

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

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DC2584A-A

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

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

Product Detail

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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DC2583A

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

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

Product Detail

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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DC2539A-A

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

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DC2539A-A

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

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

Product Detail

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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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

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

Product Detail

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.

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DC2911A

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

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DC2911A

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

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

Product Detail

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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DC2046A-E

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

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DC2046A-E

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

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

Product Detail

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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DC2046A-D

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

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DC2046A-D

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

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

Product Detail

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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DC2047A-A

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

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

Product Detail

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.

Evaluation Kits17

Tools & Simulations

Tools & Simulations 1

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.

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