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TPS23754: TPS23754 with two RJ45

Kuan Wei Chen (Kevin Chen)
Genius 9710 points
Part Number: TPS23754
Other Parts Discussed in Thread: TPS2372, PMP20859, TPS2378

Dear Team,

My customer wants to use TPS23754 for two RJ45 port for the redundant application.

Here is some question from the customer:

1. If both of the RJ45 port supply power will cause a short circuit or handshaking issue?

    What is the issue need to be careful with two RJ45 port?

2. Can we setup priority for two RJ45 port?

3. If one of the RJ45 remove, can another port suppourt directly?

    Both Ethernet ports must support 802.3at PD with automatic failover with zero downtime.

BR

Kevin

  • 0
    TI__Genius 9230 points

    Hi Kevin,

    We have recently published PMP20859 to the web. It uses dual TPS2372 PD controllers in order to do hitless (zero down time) transition between redundant PoE inputs and/or an adapter. When both PoE inputs are connected, power is shared, but not a perfect 50/50 split. PMP20859 is a class 5 .bt solution (40W input), but it can be easily reconfigured for .at power level (25W input).

    If the customer is interested in 50/50 power sharing or another type of PoE redundancy, we have several reference designs & collateral we can share with you, offline.

    With that said, I will address your questions, directly:

    1. If using dual PoE inputs, the main issue is allowing each PoE input to finish detection, class, and inrush independently with two ports of the same PSE or different PSEs. This can be accomplished most easily by having two separate PD controllers & a single power stage so that delay circuitry can be used to manage the separate startups (detection, class, inrush). We used TPS2372-3 in PMP20859 specifically because Auto MPS allows the 2nd PoE port to be in standby to allow for hitless transition between the 2 ports. Also, having 2 PWM controllers is unnecessary.

    2. Are you asking about dual PoE priority over an adapter or power sharing between both PoE ports? We can take this question offline after I send hitless transition collateral.

    3. PMP20859 is designed to allow hitless transition from dual to single port.

    Regards,
    Tom Amlee
    PoE PD Apps Engineer

  • 0 in reply to Thomas Amlee
    TI__Genius 9710 points
    Dear Amlee,
    Thanks for the information.
    If customer want to use .at TPS2378 to achieve hitless transition , can we achieve it?
    Since TPS2378 don't have auto MPS, do you have any comments?
    BR
    Kevin
  • 0 in reply to Kuan Wei Chen (Kevin Chen)
    TI__Genius 9230 points

    Hi Kevin,

    If TPS2378 were to be used, an external circuit would need to be designed to achieve auto MPS, anyways. It saves complexity & associated BOM costs to use TPS2372.

    Thanks,
    Tom Amlee
    PoE PD Apps Engineer