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Compact connector (and cable) for screened 50 ohm diff pair.

Discussion in 'Electronic Design' started by Nial Stewart, Feb 4, 2010.

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  1. Nial Stewart

    Nial Stewart Guest

    I'm looking for a connector which mounts on a board in a PC104+
    stack and am stumped. I need something which meets the following

    PCB mounted header <13mm high, and associated cable connector.

    Terminates screened cable suitable for 50 ohm diff pair.

    Reasonably compact, I only have one diff-pair per header.

    Reasonably robust, used in an industrial environment, but by professionals.

    BTW, it's feeding an ADC which is sampling at 200Msps so I don't
    need a bandwidth of GHz.

    All the requirements spec states is...
    "The ADC differential inputs are connected via 33R series resistors
    (at the chip) direct to a miniature shielded input connector"

    The other end of the cable doesn't exist yet, my contact mentioned
    tri-ax cables but these don't seem to fit in the space I've got.

    I suggested something like an HDMI or mini USB connector but
    they've come back saying they want a "generic non-specific" connector.

    I'm stalled on this so any suggestions are very welcome.

  2. Nial Stewart

    Nial Stewart Guest

    In situations like this, my policy is "make it their problem." Tell
    That's what I thought, but they want non application specific

    I think I might put a bit of effort into talking them round here,
    something like this is probably the best solution.

    There's provision for 50 ohms between the pair at the ADC (not fitted).

    I don't know if they want to experiment here, I'm just following the spec.

    As someone said, things would be great if it wasn't for clients (and

    Thanks for the feedback John, that's another pint I owe you (proper
    UK pint, ie 568ml)!

  3. Nial Stewart

    Nial Stewart Guest

    If it would be indelicate for you to tell them that they're idiots, I

    He who pays the piper doesn't get called an idiot.

    They are worked on slowly so they decide that it's their idea in the first


  4. Nemo

    Nemo Guest

    I'm looking for a connector which mounts on a board in a PC104+
    How about a... stereo audio jack? And for the cable, screened twisted

    (Though I've read in this NG, and other places that twisted pair's
    fields extend outside the cable, the implication being you should not
    use it near lots of metal objects.)

    Such a cheap connector might not meet the following requirement:
    But if they are asking for 33 ohm resistors, instead of... what is it...
    two 37.5 ohms normally? perhaps they're not too worried about ideal
    It sounds like they have partial knowledge of the subject, or have not
    had time to think through the entire system, and are in a
    blame-avoidance culture and want you to tell them what will work.
  5. Nial Stewart

    Nial Stewart Guest

    I'm stalled on this so any suggestions are very welcome.

    Thanks Bill,

    That looks like another possible solution, I'll look into it.

  6. Nial Stewart

    Nial Stewart Guest

    Careful: the coax-insert D-subs are very expensive.

    The client has said he's past experience with these and doesn't like them,
    he thinks they aren't reliable enough.
    Most RJ45 sockets are tight height wise but I agree with USB / SATA.

    I'm working on them.

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