Analog Devices LT4294 | Demoboard DC2583A

Description

Demonstration circuit 2583 is an IEEE 802.3bt (Draft 2.3)compliant Power over Ethernet (PoE) powered device(PD). It features the LT®4294 PD interface controller andthe LT4321 PoE ideal diode bridge controller.The LT4294 provides 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) (57mΩ typical) N-channel FET for the hotswap function to improve efficiency. Additional featuresinclude power good (PWRGD) and T2P output indicatorsfor interfacing with downstream electronics. ThePWRGD output indicates the PD controller is ready toprovide power to the downstream load. This signal can beused to enable an isolated power supply. The T2P outputindicates the available power from the power sourcingL, LT, LTC, LTM, Linear Technology, LTPoE++ and the Linear logo are registered trademarks ofAnalog Devices, Inc. All other trademarks are the property of their respective owners.Board Photoequipment (PSE) to the downstream load. This signal canbe used to limit the load and prevent overloading the PSE.The LT4321 controls eight low RDS(ON) (57mΩ typical)N-channel FETs to further improve end-to-end powerdelivery efficiency and ease thermal design. This solutionreplaces the eight diodes typically found in a passivePoE rectifier bridge.The DC2583A accepts up to 71W of delivered power froma PSE via the RJ45 connector (J1) or a local 48V DCpower supply using the auxiliary supply input. When bothsupplies are connected, the auxiliary supply input haspriority over the PoE input.

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