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TPS2378: Requirement of DLL classification

Shinichi Inoue
Guru 21696 points
Part Number: TPS2378

Dear Specialists,

My customer is considering TPS2378 and has a question.

I would be grateful if you could advise.

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According to the datasheetP.13 7.4.1 PoE Overview, type 2 PSEs are required to do type 1 hardware classification plus a (new) data-layer classification, or an enhanced type 2 hardware classification.

In this case, if using a DLL, where is the function installed?

When using TPS2378 to supply class 4 power for PD, does the PD side need to support DLL in addition to select RCLS?

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I appreciate your great help in advance.

Best regards,

Shinichi

  • 0
    TI__Mastermind 41770 points

    Hi Shinichi-san,

    The TPS2378 PD controller, as an IC itself, is able to do classification through the physical layer (hardware classification). DLL is done through the data layer and NOT the physical layer which means you will need a micro controller on your PD system (PD load) to implement DLL and negotiate with the PSE (through the data lines) that the PD is requesting higher than Type 1 power.

    Please note on page 16 of the TPS2378 datasheet:
    "DLL communication is implemented by the ethernet communication system in the PD and is not implemented by the TPS2378."

    Since a PD is still required to do hardware classification for Type 2 applications, it must still present a Class 4 resistor on RCLS.

    Regards,

    Darwin

  • 0 in reply to Darwin Fernandez
    Guru 21696 points

    Hi Darwin,

    Thank you for your reply.

    I understand when using DLL, MCU is necessary.

    I'll share your information with the customer.

    I appreciate your great help.

    Best regards,

    Shinichi