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Dirty PoE

VforVendetta
Prodigy 170 points
Other Parts Discussed in Thread: TPS23753A, TPS23861

Is anybody familiar with non-spec compliant PoE PSE?

Generically speaking the term is "dirty PoE". So far as I can tell it is a class of products that exists that provides 12-24VDC over either the primary or spare pairs of an RJ-45. This voltage is provided continuously. No negotiation, no recognition of classification resistors. Not much to do with the PoE spec. Just a DC supply cabled over RJ45. Here is an example:

At any rate I'm working on a design with TPS23753A. Anyone have insight on how to accommodate this type of PSE? The best idea I have thus far is somehow route the dirty PoE over to the auxiliary power input and properly OR the device to have PoE preference. This way if a valid PSE is hooked up it will use it and show up correctly on network configuration tools. If the voltage is only 12-24VDC, the auxiliary input should take over and work.

Any thoughts? Anyone else looking into dirty PoE?

Thanks,
V

  • 0
    TI__Genius 15685 points

    Hi V,

    Yes. We do have some customers asking something like you proposed. From the PSE side, our TPS23861 has a manual mode, you can just turn on the power without detection and classification.  The output would be ~48V. On the PD side, it receives the power from the PSE and it can output at different voltage level through DCDC converter.

    We have a couple of PD reference designs. Please visit www.ti.com/poe 

    So is there any data transmitting through the Ethernet cable? Do you use the Ethernet cable only for power delivering?

    Best regards,

    Penny

  • 0 in reply to Penny Xu
    Prodigy 170 points

    Penny!!

    Thanks for responding so fast!

    The application has no need for data. It is a dead-ended "dumb" PD. It also will not support data pass-through. The PD only needs the Ethernet cable for power.

    I'm using the TPS23753A. This has a UVLO of ~35V. Is there any way to wire it up so it will still function with dirty PoE bringing in only 12V or 24V? The TPS23753A supports auxiliary power in of 12V-56V. I'm thinking there might some way to utilize this feature to make use of a dirty PoE of 12V or 24V.

    Thanks!

    V