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TPS23756: Powering a board with the TPS23756 part using a Cisco Catalyst 2960.

Shashi Ramamurthy41
Prodigy 40 points
Part Number: TPS23756

Hi,

We are having a issue with the POE part TPS23756 on our boards. The T2P pin on the part is  a Active low output that indicates a PSE has performed the IEEE 802.3at type 2 hardware classification. This pin does not go low when connecting to a endspan CISCO Catalyst 2960 even though the Cisco device does detect that our device which has the TPS23756 is Type 2 Class 4 device. We have set the power on the Cisco device to the highest possible of 29W to the device. We do not have this problem with other POE injectors like PowerDSine 9001. Any help would be great.

  • 0
    TI__Mastermind 40720 points
    Hi Shashi,

    A PSE can choose to do either physical layer classification (hardware classification) or data layer classification. I find that endspans do either one, while injectors do hardware classification.

    I'm not too familiar with this endspan but sometimes you can configure the endspan to do hardware classification rather than data layer class. If the end span is doing data layer classification, the PSE will not send 2 class fingers. Rather, the PD must have a micro on it load to negotiate through the data lines that the PSE can deliver Type 2 power. In this case the load doesn't need the T2P signal and will know the PSE power level through this communication.
  • 0 in reply to Darwin Fernandez
    TI__Mastermind 40720 points
    Hi Shashi,

    Has this thread be resolved? If so, please click the resolved button so we can close this thread. You can also post a new thread if having further questions. Thanks!