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System with TPS2378 not working properly in LLDP mode

Cornelius Vollbrecht
Prodigy 10 points
Part Number: TPS2378

Hello,

currently, we are using the TPS2378 chip for PoE+ negotation in our system, but we can not get it it to work properly. To be more precise, the negotiation for the different power classes fails, the device is not recognized as a device with a power class higher than 0. We implemented the recommended layout in the datasheet, set up the configuration with LLDP and tried different PoE+-switches, all to no avail. Can you provide us with additional information how to debug this problem, or can you send us the name of the Ethernet switch your company used for the testing/manufacturing of the TPS2378? Especially the last part would be very helpful for us in order to understand the behaviour of the chip. Thank you in advance!

Best regards,

Cornelius

  • 0
    TI__Expert 5615 points

    Cornelius,

    Our PoE PD (load) solutions are all designed for IEEE compliance and high interoperability.  If you test our TPS2378 EVM with the PSE switches you are already have on hand, it will pass (in physical, not LLDP, layer testing...as our demo boards do not include the data path) and properly classify as a Type 2 / Class 4 load.

    Does your board pass when tested in the physical layer?  My first instinct given the limited information here is that something is wrong in the data path...not the power path.  What value resistor have you populated on pin #3 (CLS)?

    Thank you for considering PoE products from Texas Instruments,

  • 0 in reply to Thomas Lewis
    TI__Expert 5615 points

    It's been a week since hearing from you Cornelius. I am going to go ahead and close this thread but feel free to reply if still needing some help from us.

    Thanks,