Analog Devices LT4276 | Demoboard DC2047A-A

Description

Demonstration circuit 2047A-A is an IEEE802.3at compliantPower over Ethernet (PoE) Powered Device (PD) withsupport for 9-57VDC and 24VAC auxiliary supply input. Itfeatures the LT®4276 PD interface and switching regulatorcontroller, the LT4321 PoE ideal diode bridge controller,and the LT4320 ideal diode bridge controller.The LT4276 provides IEEE802.3af (PoE, Type 1) andIEEE802.3at (PoE+, Type 2) compliant interfacing andpower supply control. It utilizes an external, low RDS(ON)(57mΩ typical) N-channel FET for the hot swap functionto improve efficiency. The LT4276 also provides a DC-DCconverter configured as a highly efficient flyback topologywith synchronous rectification.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 passive PoErectifier bridge. The LT4320 controls four N-channel FETs (9.6mΩ typical)to replace a diode bridge typically found at the auxiliarysupply input. AC rectification and DC polarity correctionare provided. This solution reduces voltage drop associatedwith the diode bridge and enables the power supplyoperation as low as 9VDC at the auxiliary supply input.This improves end-to-end efficiency and reduces heat.The DC2047A-A accepts up to 25.5W of delivered powerfrom a Power Sourcing Equipment (PSE) via the RJ45connector (J1) or a local AC/DC power supply using theauxiliary supply input. When both supplies are connected,the auxiliary supply input has priority over the PoE input.The DC2047A-A supplies a 12V output at up to 1.9A.

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