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two Pcie redriver SN65LVPE504 in serie

Daniel Wintsch
Other Parts Discussed in Thread: SN65LVPE504

Hi

We have a design where we put two of your pcie redriver SN65LVPE504 in serie with 3m cable between. We randomly have startup problem where we don't get the link up. If the startup works, we have the full performance for several hours.


Does someone did the same? Or is there any app note for such an application?


thanks

daniel

  • 0
    TI__Mastermind 23815 points

    Hi Daniel,

    This behavior could be due to Rx detect feature, have you tried setting EN_RXD=LOW?

    Regards

  • 0 in reply to Moises Garcia
    Hi, thanks for your answer. We build our design with setting EN_RXD to low. But we also tested with setting it to high without any difference. I saw in the datasheet that there is also an "electricle idle state". Is it possible to disable that state? Or is it somehow possible to see if the device is in a power low state? Or do you have other ideas for me to test?

    reagards
    daniel
  • 0 in reply to Daniel Wintsch
    TI__Mastermind 23815 points

    Hi Daniel,

    Besides EN_RXD=Low, could you confirm PS0=Low too?

    Could you share the settings for EQ, DE, OS, SQ_TH for each device? Could you share schematics and layout?

    Unfortunately this device doesn't have status pin, you would need to monitor high speed signals

    IN datasheet page 2 you can find electrical idle support and power save features, another option is to see how much current the device is consuming when it works vs when it doesn't work.

    Regards

  • 0 in reply to Moises Garcia
    Hi Moises

    I hope you got the schematic and overview from my email. Do you have any updates?

    daniel
  • 0 in reply to Moises Garcia
    Hi Moises

    I've got an update. I measured the current of both redriver U103 and U104. If everything works U103 need 174mA, U104 170mA. If it wan't work, U104 just need 1mA. After a reset, not power cycle, the current goes up again to 170mA and everything is fine again. Does this make sense for you?

    regards
    daniel
  • 0 in reply to Daniel Wintsch
    TI__Mastermind 23815 points
    Hi Daniel,

    Thank you so much for taking the measurements.
    If power consumption is so low, it means the device is not working at all, this current is close to the Icc for no connect, datasheet page 7.
    Besides, from the datapath diagram you sent there are descriptions to reproduce failing scenarios, if when the link is working it cotinues to work all the time the problem should come from Rx detection.

    There may be problems with CPU, ADQ14 and LVPE504 Rx detection
    SH_ENABLE handle other device apart from LVPE504, when this signal is off it shutdowns the system?
    In that case, starting from CPU, LVPE504 and ADQ14 powered off, or reset.
    Power up CPU side,
    Power up ADQ14
    Power up LVPE504 at the end

    Does it makes any change?

    Could you measure differential impedance on LVPE504 pins?

    Regards