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EMI, Cross Talk, Ground Bounce

Discussion in 'CAD' started by samiam, Apr 24, 2007.

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  1. samiam

    samiam Guest

    I am sure you all know the myriad of problems that can plague a digital
    circuit on a PCB, most through the fault of that phenomenon called
    INDUCTANCE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

    I am trying to change the way I lay out circuits on double sided PCB's
    that I build at home.

    I have reading up on signal integrity issues and learning that perhaps
    the way I have been doing things are flawed - ok TERRIBLY flawed.

    The question I have for the gurus on here is this?:
    assuming a situation where I dont go with the ideal layout method of
    seperate ground and power planes (a 3 - 4 layer board minimum) is there
    a way to get some of those sort of benefits on a two layer design?

    I can only build double sided boards at home, so any suggestions on
    optimal ways/methods of laying out signal/power/gnd tracks and vias to
    best defeat the voltage drops between traces and the noise and cross
    talk effects would be SINCERELY appreciated
     
  2. Hal Murray

    Hal Murray Guest

    I'd start by making the bottom layer a ground plane.

    That probably works OK for simple board. You have to find
    some way to get decent power distribution.

    You can get more "layers" by using wires, including helpers
    for the power.
     
  3. Fred Bartoli

    Fred Bartoli Guest

    samiam a écrit :
    Make your bottom layer a GND plane.
    Use SMDs as much as possible, and work hard on placing the components.
    Route the supplies with tracks and have a good bypass policy. If you
    have the possibility to place the bypass caps on bottom side (and for
    hobbyist boards you can) then do it.
    That should, for reasonable hobbyists project, leave few tracks to run
    on the bottom side and when you have to, do this on the shortest
    possible distance. If you have some difficult case, still for hobbyist
    use, you can easily live with a few additionnal jumpers, wires,...

    I've made some moderately complex (~400 SMDs) high volume boards that
    way and they were plain success.
     
  4. Joerg

    Joerg Guest

    In a pinch you can also buy jumpers in SMT. Often they are called "zero
    ohms resistors". They come in the popular SMT resistors sizes and
    probaby 1210 would be nice for hobby projects because that leaves a bit
    more space to route underneath. My layouter would close his eyes and
    tunnel a 0603 without breaking a sweat but don't do that for hobbyist
    boards.
     
  5. Marra

    Marra Guest

  6. JeffM

    JeffM Guest

    Marra wrote WITHOUT CONTEXT[1]:
    Full disclosure would be nice:
    http://groups.google.com/groups/sea...9-orUyGBN00G0sVMjw&scoring=d&filter=0&num=100

    ....perhaps a proper sig:
    http://www.google.com/search?q=two-hyphens-and-a-space+-stripped+-FWIW+-Suspensive
    ..
    ..
    [1]
    http://www.google.com/search?q=cach...up+before.the.original.*.*+*-for-your-readers
     
  7. Fred Bartoli

    Fred Bartoli Guest

    Marra a écrit :
    Almost always a sure receipt for disaster.
     
  8. Marra

    Marra Guest

    Well it works for me !!!!
     
  9. Marra

    Marra Guest


    You can use the power of the computer to move components around until
    the optimum layout is achieved.
    I leave mine on overnight processing.
     
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