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DP83848I: DP83848/49 RX_CLK clock recovery error

Iwata Etsuji
Expert 6400 points
Part Number: DP83848I

Hi team,

The recovery clock of DP83848 or 49 seem to be suddenly unlocked during sending idle pattern from Tx.
This phenomena seems to be depending on the cables.
What kind of parameters should we focus on the S-parameter analysis of the system in order to investigate the root cause of this issue? crosstalk, reflection, etc.?

Best regards,
Iwata Etsuji

  • 0
    TI__Mastermind 18425 points
    Hello Iwata-san,

    Is the RX_CLK turning off during data communication? Can you elaborate how this phenomena is dependent on the cables?

    -Regards
    Aniruddha
  • 0 in reply to Aniruddha Khadye
    TI__Mastermind 18425 points
    Hello Iwata-san,

    Based on our offline communication, it looks like the problem is observed on RX_CLK. Also this issue is observed only with a certain type of cable at long lengths, correct? Maybe the insertion loss and return loss of this particular cable is not as good as the other cables tested which is causing some link instabilities. RX_CLK frequency is directly related to the speed at which the PHY links up so any kind of link instability can affect the RX_CLK performance.
    Can you ask customer to monitor the LED_LINK (pin 28) and LED_SPEED (pin 27) using a oscilloscope to check if the link is stable at 100Mbps?

    -Regards
    Aniruddha