Texas Instruments AN-1574 LM5073 User Manual

1 Introduction
The LM5073 evaluation board is designed as a low cost solution for both IEEE802.3af fully compliant and
non-compliant Power over Ethernet (PoE) PD applications. The board also supports PD operation with
auxiliary power sources like AC wall adaptors, solar cells, and so on. The maximum intake power of the
PD interface can be programmed up to 25W. In order to facilitate an overall PD evaluation, the board also
includes integrated Ethernet RX and TX magnetics, an RJ45 interface to user's PHY circuit, and an
LM5576 buck regulator. The board can be conveniently reconfigured with built-in jumpers to realize an
optimal solution for a particular application.
For detailed information on the LM5073 and LM5576, refer to the device data sheets.
2 Features of the Evaluation Board
• IEEE 802.3af fully compliant
• Programmable maximum input dc current through PD interface: 800mA
• Input voltage ranges:
– PoE input voltage range at startup: 40 to 57V
– PoE input voltage range with normal operation: 33 to 57V
– Front Aux voltage range: 20 to 57V
– Rear Aux input voltage range: 10 to 57V
• Flexible selection of external DC-DC converter for optimal solution
• On board DC-DC converter:
– Output voltage: 3.3V
– Maximum output current: 3.0A
– Switching frequency: 150kHz
• Easily reconfigurable for different applications
• Complete PD interface including Ethernet magnetics and RJ45 connector interface to PHY
• Two layer PCB with single side component placement
3 Precautions
Before powering up the evaluation board, please carefully read this article. As seen below, the evaluation
board is easily reconfigurable to realize optimal solutions for various applications, while the factory original
configuration of the board is Configuration 1.
4 An Important Note About the Maximum Power Capability and Cable Usage
The LM5073 PD interface supports a maximum intake power of 25W. The user must make sure that the
Power Sourcing Equipment (PSE) in use can provide at least 30W.
Important: Please note that the CAT-5 cable may not support the maximum power over two pairs of
twisted wires under strict safety considerations. Users shall select the proper cable wires to support the
design power level without compromising the applicable safety standards. Using an improper cable at
such power levels may violate various safety regulations and may cause damage.
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SNVA214A – April 2007 – Revised April 2013
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AN-1574 LM5073 Evaluation Board
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User's Guide
SNVA214A – April 2007 – Revised April 2013
AN-1574 LM5073 Evaluation Board
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