PD POWER OVER ETHERENET (POE) WITH 5V TO 12V AUXILLARY INPUT

WhiteHorse

Other Parts Discussed in Thread: TPS23753, TPS23751, TPS23756

I need a PD Power Over Ethernet Solution 15W output with an auxillary input of 5V to 12V. I see evaluation boards with aux input voltages much higher than 5V, but I need 5V to 12V. Please provide a solution.

John

over 13 years ago

0 Eric Wright over 13 years ago

TI__Mastermind 42795 points

The lowest practical auxiliary voltage our devices support is 10V.

0 WhiteHorse over 13 years ago in reply to Eric Wright

Genius 4430 points

That is certainly helpful, but for others that have the same question I thing it is important to let them know there are at least 3 methods to provide auxillary power to a PD. One of the methods diode ORs an AUX power source with the PD's output so that the AUX voltage could actually be less than the PDs output which is typically 5V. Here is a link to the document that describes the three methods of implementing AUX power in a PD.

Advanced Adapter ORing Solutions using the TPS23753 (Rev. A)
Application Reports: http://www.ti.com/litv/pdf/slva306a

0 Eric Wright over 13 years ago in reply to WhiteHorse

TI__Mastermind 42795 points

Sorry, that I didn't completely comprehend the question. Some of our datasheets have a link to this app note on the front page and most have links in the apps section where the adapter solutions are discussed. Let me know if further detail is req'd.

0 Mark Latham over 9 years ago in reply to Eric Wright

Intellectual 275 points

Hi Eric (if you're still there!),

I have an PoE+ application with 12VDC aux input that must be isolated on-board, so for convenience I'm planning to use two TPS23751 and OR the converter outputs with power switches. For the 12VDC input (non-PoE) section, I don't imagine an OTS xfmr will provide adequate Vc auxiliary bias voltage. Since the bias current is so small, do you see any issue to just supply that with an LDO?

0 Darwin Fernandez over 9 years ago in reply to Mark Latham

TI__Mastermind 41790 points

Hi Mark,

Yes, I have also seen solutions that diode OR the VC rail with the aux input or an LDO powered by aux input.

Also, we do have a 12V adapter solution that uses the TPS23756 to output Class 4 power. It's transformer was designed for a wide input voltage range. Please see below link to its user's guide for your reference.

www.ti.com/.../slvu329a.pdf

0 Mark Latham over 9 years ago in reply to Darwin Fernandez

Intellectual 275 points

Thank you Darwin, that was the answer I needed.

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PD POWER OVER ETHERENET (POE) WITH 5V TO 12V AUXILLARY INPUT