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Original question:

CDCM6208: About output format.

  • TI Thinks Resolved

CDCM6208: LVPECL output matching network

Intellectual 2880 points
Lacey Lin

Replies: 5

Views: 403

Part Number: CDCM6208

Hi team,

For the LVPECL output, does the CDCM6208 only support the AC coupling?

If I use the DC coupling to connect the CDCM6208 output to a LVPECL receiver, will this cause issue?

Lacey

Thanks a lot!

Intellectual 2880 points
Lacey Lin
  • Genius 9155 points
    Lane Boyd
    Hi Lacey,

    Yes, the output only supports AC-coupling for LVDS or LVPECL outputs. DC coupling can cause issues.

    Kind regards,
    Lane

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  • Intellectual 2880 points
    Lacey Lin

    In reply to Lane Boyd:

    Hi Lane，
    Can you help to share the detail structure or reason for why the DC coupling will cause issue?
    And what's the issue?
    Customer need the detail information to evaluate the solution.
    Lacey
    Thanks a lot!
  • Expert 4400 points
    Madhu Balasubramanian

    In reply to Lacey Lin:

    Hi Lacey, there is no device issue with DC coupling but we need to recommend the right interface if customer prefer to DC couple in order to support both the output common mode voltage for CDCM6208 as well as the input common mode voltage for the LVPECL receiver. Can you share the specifications of the LVPECL receiver, like Vicm, Vid etc so that we can look into the correct recommendation. AC coupling will always be the easiest.
  • Intellectual 2880 points
    Lacey Lin

    In reply to Madhu Balasubramanian:

    Hi Madhu，
    For my understanding, the CDCM6208 can support DC LVPECL, because the common mode voltage of the CDCM6208 in LVPECL-Like is not the same as the standard LVPECL. right?
    So what's the common mode voltage of CDCM6208 in the LVPECL-Like output?
    Customer said they need to double check with the receiver vendor to make sure the LVPECL receiver specs.
    Lacey
    Thanks a lot!
  • Expert 8270 points
    Shawn Han

    In reply to Lacey Lin:

    Hi Lacey,

    Datasheet shows it as below. Notice it is a CML driver internal for this LVPECL-like output.

    Best Regards,

    Shawn

    ____________________________________________________________________________________

    To design your own Clock Tree solution, visit WEBENCH Clock Architect ! ​​​​

    More information Clock and Timing System products: http://www.ti.com/clock-and-timing/overview.html

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