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dc2475aafb

DEMO MANUAL

DC2475A-A

Description

LT4295, LT4321

High Efficiency IEEE802.3bt (PoE++, Type 3,

40W) PD with PoE Ideal Diode Bridge

Demonstrationcircuit2475A-AisanIEEE802.3bt(Draft2.0)

compliant Power over Ethernet (PoE) powered device (PD).

ItfeaturestheLT®4295PDinterfaceandswitchingregulator

controllerwiththeLT4321PoEidealdiodebridgecontroller.

The LT4295 provides IEEE802.3af (PoE, Type 1),

IEEE802.3at (PoE+, Type 2), and IEEE802.3bt (PoE++,

Type 3 and 4) compliant interfacing and power supply

cal) 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 synchro-

nous rectification.

N-channel FETs to further improve end-to-end power

L

, LT, LTC, LTM, Linear Technology, the Linear logo and LTPoE++ are registered trademarks of

Analog Devices, Inc. All other trademarks are the property of their respective owners.

performance summary

BoarD photo

delivery efficiency and ease thermal design. This solution

replaces the eight diodes typically found in a passive PoE

rectifier bridge.

The DC2475A-A accepts up to 40W of delivered power

from a power sourcing equipment (PSE) via the RJ45

connector (J1) or a local 48VDC power supply using the

auxiliary supply input. When both supplies are connected,

the auxiliary supply input has priority over the PoE input.

The DC2475A-A supplies a 12V output at up to 3A.

Design files for this circuit board are available at

http://www.linear.com/demo/DC2475A-A

Top Side

PARAMETER

CONDITIONS

VALUE

At RJ45

37V to 57V

Auxiliary Voltage

37V to 57V

12V (Typical)

3A (Max)

Output Voltage Ripple

Load Regulation

±0.1% (Typical)

Efficiency

92% (Typical)

Switching Frequency

250kHz (Typical)

Bottom Side