Hi.
I'm normally not designing power-related circuitry, but now I'm considering the using the TPS23754 in a design. I have tried to read the spec, but I'm still not sure about the output levels and how it's adjusted.
I need to generate a +24V system voltage (1A max current), from the ethernet cable. Is this voltage level achievable, and what transformer should I use?
I'm planning on implementing this feature on a Gigabit LAN. Do you seee any problems with that?
In general, power supply design is very difficult for novices, so I would caution this information is of limited usefulness to you.
The TPS23754 is a combination PoE+ interface and dc/dc controller. The actual output voltage is the result of the rest of the power supply and is not restricted by the TPS23754.
IEEE 802.3at is compatible with 1000baseT.
The power available to the PD per IEEE 802.3at is 25.5W. assume that you will get an efficiency on the order of 88% (just a guess) to estimate the available output power.
In short, I suggest that you look at http://focus.ti.com/docs/toolsw/folders/print/tps23754evm-420.html (or search the TI webpage for slvu301) and http://www.coilcraft.com/poe300.cfm . Coilcraft has a verision of the transformer designed for 24V.
There are lots of other changes to the SLVU301 circuit that are required apart from the transformer. You might look at SLVA305 for some design hints, and search the TI website as well for past Unitrode and TI papers on flyback design.
ALL CONTENT AND MATERIALS ON THIS SITE ARE PROVIDED "AS IS". TI AND ITS RESPECTIVE SUPPLIERS MAKE NO REPRESENTATIONS ABOUT THE SUITABILITY OF THESE MATERIALS FOR ANY PURPOSE AND DISCLAIM ALL WARRANTIES AND CONDITIONS WITH REGARD TO THESE MATERIALS, INCLUDING BUT NOT LIMITED TO, ALL IMPLIED WARRANTIES AND CONDITIONS OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT OF ANY THIRD PARTY INTELLECTUAL PROPERTY RIGHT. NO LICENSE, EITHER EXPRESS OR IMPLIED, BY ESTOPPEL OR OTHERWISE, IS GRANTED BY TI. USE OF THE INFORMATION ON THIS SITE MAY REQUIRE A LICENSE FROM A THIRD PARTY, OR A LICENSE FROM TI.
Content on this site may contain or be subject to specific guidelines or limitations on use. All postings and use of the content on this site are subject to the Terms of Use of the site; third parties using this content agree to abide by any limitations or guidelines and to comply with the Terms of Use of this site. TI and its suppliers reserve the right to make corrections, deletions, modifications, enhancements, improvements and other changes to the content and materials, its products, programs and services at any time or to move or discontinue any content, products, programs, or services without notice.