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TPS2372: Non Standard PSEs with TI BT PDs

Prodigy 220 points

Replies: 6

Views: 196

Part Number: TPS2372

 Hi All,

I have watched  the video called TPS2372/3 working with no compliant high power injector and I have  few questions:

UPOE:

In order to connect a TI's BT PD to a UPOE PSE, the PD needs to have its first class resistor as a class 4. That means that on a TPS2372 PD the Class Signature resistor A must have a value of 63.4Ω in order to be powered by an UPOE PSE regardless what value is set for Class Signature B?.

POE++:

Using a POE++ PSE with a TI BT PD doesn't require any specific instruction to be classified and powered up by a POE++ PSE, it should be classified and powered as a BT PSE would do, is this correct?.

If a POE++ PSE of 120w is connected to a TI BT PD Class 8, the PD application  will have to make sure that it doesn't exceed 71w at the PD, as the PSE will be able to supply up to 120w violating the IEEE and UL standard, is this statement correct?

POH:

POH PSE will just turn on a TI BT PD if it is classified as a class 4. If the TI BT PD is classified Class 5 or above the POH PSE won't turn on the TI BT PD, is this correct?.

Thanks in advance.

Regards,

Daniel.

  • Hi Daniel,

    If using Forced UPOE, the UPOE switch would not do a 3 finger. This means CLSB can be any resistance for the TPS2372.

    For POE++, the TPS2372 can distinguish between a POE++ PSE and a BT PSE through the TPH/TPL/BT output pins. A microprocessor can then take these signals and adjust the output power as necessary.

    For POH, you are correct, a POH PSE will only turn ON if the TPS2372 is connected as Class 4 and Class 4 for CLSA and CLSB. Anything higher (Class 5,6,7,8) the PSE will turn ON but will shutoff shortly after (not interoperable).

  • In reply to Darwin Fernandez:

    Hi Darwin,

    Thanks for your answers, they are very useful but I would just like to clarify some of the points.

    UPOE:

    It is clear now that the value or existence of a resistor in CLSB is irrelevant because a UPOE will just send two class finger as it just look for a class 4 PD.  In order to be recognized by an UPOE injector, the TPS2372 needs to have a class 4 resistor in CLSA, is this statement correct?.

    Thanks in advance.

    Regards,

    Daniel.

  • In reply to Daniel Campano:

    Hi Daniel,

    That's correct, CLSA need to be Class 4.

    Note that a UPOE injector will be a forced UPOE configuration. This means you will need two PDs (at Class 4 each) to interoperate. I recommend looking at the UPOE training below. Thanks!

    training.ti.com/high-power-poe-design-considerations

  • In reply to Darwin Fernandez:

    Thanks Darwin

  • In reply to Daniel Campano:

    Daniel, Does this resolve this thread?

    If so, we would appreciate it if you signaled by clicking on the "Resolved" button.

    Thank you for your interest in PoE products from Texas Instruments,

    Thomas Lewis

    PoE Applications & Marketing Manager

    www.ti.com/poe

  • In reply to Thomas Lewis:

    Thanks, It resolve the issue.

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