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Original question:

DS280MB810: DS280MB810 Schematic Review

DS280MB810: DS280MB810 Schematic Review

Gowtham M P
Prodigy 50 points
Part Number: DS280MB810
Other Parts Discussed in Thread: DS280DF810

Tool/software:

Hi TI Team,

Thank you for the schematic review.

Could you please clarify the following

   

  1. In MUX1_2 and MUX2, RX7_P/N, RX6_P/N, RX5_P/N, and RX4_P/N are configured as DeMUX, while RX3_P/N, RX2_P/N, RX1_P/N, and RX0_P/N are configured as MUX. Could you confirm if this configuration is achievable?
  2. All DS280MB810 repeaters are configured in SMBUS slave mode on our card. Could you advise on the method for initial programming of these devices?
  • 0
    TI__Mastermind 27800 points

    Hi Gowtham,

    An engineer has been assigned to your thread. He will get back to you soon.

    Best,

    Lucas

  • 0 in reply to Lucas Wolter
    TI__Mastermind 36153 points

    Hi Gowtham,

    Good to hear from you.

    1) This configuration is fine.  Each crosspoint can be configured independently.

    2) You can reference the DS280MB810 programming guide.  We have tables for front port egress, front port ingress, and backplane configuration sequences that can be used to get you started.  You will need to adjust the CTLE setting to your application.  See section "Adjust Equalization Level".  You'll also need to configure the crosspoint.  The "Select Crosspoint Mode" section has more information on configuring the crosspoint.

    Please let us know if you have any more questions.

    Thanks,

    Drew

  • 0 in reply to Drew Miller1
    Prodigy 50 points

    Hi Drew Miller / TI Team,

    In the updated schematic, we are planning to use 6 retimer ICs (DS280DF810) in place of the redriver IC (DS280MB810). We have configured a daisy chain from the Calibration Clock Out (CAL_CLK_OUT) of one IC to the Calibration Clock In (CAL_CLK_IN) of the next.

    1. Do you foresee any concerns with having 6 retimer ICs in a daisy chain for the calibration clock?

    2. Please let us know if the 25 MHz clock can be sourced from a free-running clock source or if it should be sourced from a reference clock.

    Regards,

    Gowtham M P

  • 0 in reply to Gowtham M P
    TI__Mastermind 27800 points

    Hi Gowtham,

    1. I don't have any concern with daisy chaining the calibration clock to 6 retimers. According to the datasheet, up to 20 retimers' calibration clocks can be daisy chained.

    2. The 25 MHz clock should be sourced from an external oscillator.

    Note that Thursday and Friday are US holidays. We will resume monitoring E2E threads on Monday, 12/2.

    Best,

    Lucas

  • 0 in reply to Lucas Wolter
    Prodigy 50 points

    Hi Lucas / TI team,

    Thank you for answering our queries.

    Could you please elaborate on Query 2 by addressing the following question:

    In our card, we are using this retimer for the CPRI datapath. Can you confirm whether the calibration clock fed to the retimer should be locked to the CPRI clock, or if it's acceptable to use a free-running clock source?

    Thank you for your assistance.

    Regards,
    Gowtham M P

  • 0 in reply to Gowtham M P
    TI__Mastermind 36153 points

    Hi Gowtham,

    It is fine to use a free-running clock source for the 25 MHz clock.

    Please also note that DS280DF810 has a high minimum CTLE boost.  We recommend having at least 3 dB of insertion loss between source TX and DS280DF810 in order to help avoid over-equalization.

    Thanks,

    Drew