• State TI Thinks Resolved
  • Locked Locked
  • Replies 6 replies
  • Answers 4 answers
  • Subscribers 64 subscribers
  • Views 730 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS2388: The TPS2388's open circuit detection voltage

Chen Pang Chang
Prodigy 50 points
Part Number: TPS2388

I would like to know in the TPS2388's SPEC Figure15 which shows there is around 25V on this condition. but, in other brand's PSE chip normally just around 12V. What's the different with your and others?

  • 0
    TI__Genius 15685 points

    Hi Chen Pang,

    It is just different design specification. IEEE standard specifies the max open circuit detection voltage at 30V. So both TI and other vendors' open circuit detection voltage is compliant to standard. Thanks.

    Best regards,

    Penny

  • 0 in reply to Penny Xu
    TI__Expert 5615 points
    Chen Pang, Has this answered your question?

    We think it is resolved but would appreciate your agreement.

    Thank you for interest in PoE products from Texas Instruments,
  • 0 in reply to Thomas Lewis
    Prodigy 50 points
    Hi Penny & Thomas

    We got one issue about the 2388 connect to Spirent and it would cause the Spirent's PHY damaged. We measured the Spirent impedance on the center-tap is about 1.8 Ohm. There is 6V on the PHY side mdi signal when 2388 connect to Spirent. We through your open circuit voltage is too high ,also if you meet the short center-tap DUT that will probably cause the PHY damaged. it is a big issue for you. Don't you think that?
  • 0 in reply to Chen Pang Chang
    TI__Genius 15685 points

    Hi Chen Pang,

    If the port only has 1.8ohm, TPS2388 sees as short circuit and we don't apply open circuit detection voltage on the port. For our open circuit detection voltage, we are compliant to the standard. Thanks. 

    Best regards,

    Penny

  • 0 in reply to Penny Xu
    Prodigy 50 points

    Hi, Penny

    You mention that is steady state, but have you measure the transient response ? There will have around 6 voltage pulse while you plug in the RJ cable in the DUT PHY side's MDI signal. it's over any PHY's SPEC. The point is the other brand's PoE IC will not have this huge pulse.

  • 0 in reply to Chen Pang Chang
    TI__Genius 15685 points

    Hi Pang Chang,

    We haven't heard from other customer about this issue on TPS2388 and we don't have the equipment to reproduce your issue.Maybe you can reduce the port capacitance to reduce the energy during open circuit detection. Thanks.

    Best regards,

    Penny