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Original question:

DS250DF810: DS250DF810 rx over equalization problem

DS250DF810: DS250DF810 RX eye diagram problem

user4838693
Prodigy 190 points

Part Number: DS250DF810

I found that the eye diagram read by Rx is relatively small.

The eye width is 0.375ui and the eye height is 250mv.

So what parameters should I adjust to make the eye diagram better? Thank you!

  • 0
    TI__Mastermind 19235 points

    Hi,

    These eye opening values meet TI recommended minimum thresholds for error free operation. But I think we can improve them.

    Have you tried using DFE enabled with adapt mode 2? See below.

    Table. Adapt mode 2, Enable the DFE

    　

    STEP

    SHARED/ CHANNEL REGISTER SET

    OPERATION

    REGISTER ADDRESS [HEX]

    REGISTER VALUE [HEX]

    WRITE MASK [HEX]

    COMMENT

    1

    Channel

    Write

    31

    40

    60

    Adapt Mode = 2

    2

    Channel

    Write

    23

    40

    40

    Enable DFE Override

    3

    Channel

    Write

    1E

    02

    0A

    Enable DFE (DFE_PD=0) and enable DFE taps 3-5 (EN_PARTIAL_DFE=1)

    Note: A CDR reset and release operation is recommended after applying above settings 

    Cordially,

    Rodrigo Natal

    HSSC Applications Engineer

  • 0 in reply to Rodrigo Natal
    Prodigy 190 points

    Yes, I tried to adjust these parameters, but the eye diagram parameters did not improve

  • 0 in reply to user4838693
    TI__Mastermind 19235 points

    Hi,

    Try enabling the CTLE limiting output mode, by setting channel register 0x13[2]=1. In addition ensure that EQ_HI_GAIN is enabled i.e. 0x13[5] is set to 1.

    Regards,

    Rodrigo Natal