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TPS2379: an extensibility for PoE++ and IEEE 802.3bt

Shinichi Inoue
Guru 20486 points
Part Number: TPS2379

Dear Specialists,

My customer is confirming TPS2379 circuit.

And he has questions about the result.

Could you please advise?

---questions from the customer---

I have confirmed the operation of IEEE 802.3af PoE (15.4 W) and IEEE 802.3 at PoE + (25.5 W) with TPS2379.

By adding external FET, I have also confirmed the operation of  PoE++（4 pairs 60W）

(1) By adding external FEt, is it possible to use IEEE802.3bt with TPS2379?

(2) Or it is not supported some PD classes of IEEE 802.3bt, does it not work at all?

(3) In case of TPS2373-4 does it work both IEEE 802.3af PoE（15.4W）and IEEE 802.3at PoE+（25.5W）.　

The datasheet described it is possible to use IEEE802.3at, but not described about IEEE802.3af? 

How about IEEE802.3af?

---

I appreciate your great help.

Best regards,

Shinichi

  • 0
    TI__Expert 5615 points
    Shinichi,

    Greetings and thank you for your interest in Texas Instruments and our growing portfolio of IEEE802.3bt controllers! Answers to your questions are below:

    (1) By adding external FEt, is it possible to use IEEE802.3bt with TPS2379?
    (2) Or it is not supported some PD classes of IEEE 802.3bt, does it not work at all?

    The best/easiest way to achieve IEEE802.3bt compatibility is with our new TPS2373-4. The TPS2379 does not have the ability to support .bt detection and classification in the physical layer (without software development on the load side). Further, it can not support the other big change coming with the new standard - different maintain power signature (MPS) timing. In short, no, the TPS2379 can not achieve IEEE802.3bt compatibility. This is why our product folder suggests the TPS2373-4 if that is required.

    You can learn more about the new MPS timing by reading our blog on the topic --> e2e.ti.com/.../ieee802-3bt-a-guide-to-understanding-the-current-spec


    (3) In case of TPS2373-4 does it work both IEEE 802.3af PoE（15.4W）and IEEE 802.3at PoE+（25.5W）.　
    The datasheet described it is possible to use IEEE802.3at, but not described about IEEE802.3af? How about IEEE802.3af?

    The new standard supersedes, and replaces, the older '.at' and '.af' standards. This means, if one claims "IEEE802.3bt compliance", they are saying it is backward compatible, and inter-operable, with parts released under the older standards (including .af). In short, yes, the TPS2373-4 can be powered by PSE which is compliant to the IEEE802.3af standard. Upon detection and classification, in this case, it will start up under a Type 1 maximum power of 12.95W (received at end of 100m of CAT-5 cable).

    In addition to being backward compatible with older standard PSE ICs, the TPS2373-4 can also receive power from some non-compliant PSEs already deployed in the marketplace today - including the suite of Linear Tech (ADI) PSEs which go by the name PoE++.

    You can learn more about this new standard by visiting our FAQ page --> e2e.ti.com/.../3487.poe-general-faqs

    or viewing our latest videos --> training.ti.com/ieee8023bt-new-features

    Please let me know if needing any additional information.

    Best Regards, Thomas
  • 0 in reply to Thomas Lewis
    Guru 20486 points
    Hi Thomas

    Thank you for your reply.

    I'll send your answer to the customer.

    If he has an additional question, I consult you.

    I appreciate your great help.

    Best regards,
    Shinichi