Isolating Pins and track from noise

Discussion in 'Embedded Systems and Microcontrollers' started by Tera-Scale, May 15, 2012.

  1. Tera-Scale

    Thread Starter Active Member

    Jan 1, 2011
    164
    5
    I have a PIC24F microcontroller which will be running on an external 32Mhz crystal. The space of the final product will be slightly restriced while sensitive analog circuitry is a must to be close to the micro controller as some pins are analog with low voltage signals.

    What are the best practices to isolate and ground any noise from the crystal and if its possible from the same uC? are there any PCB design techniques?
    It is important that two of the tracks from analog pins (in uC) have the least stray capacitance if it is possible. Schematic is attached.

    thanks
     
  2. BillO

    Well-Known Member

    Nov 24, 2008
    985
    136
    Perhaps grounding the can of the crystal will help. Mount it flat to the PCB, not vertical, and make sure there is a ground plane under and around it and actually solder the can (via a small wire or tab) to the ground plane.

    [​IMG]




    An alternative might be to use a crystal oscillator. They are usually 4 pin devices that lay flat against the PCB and the can will have a grounding pin. Again, be sure that there is a ground plane under and around it.

    [​IMG]
     
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  3. coldpenguin

    Active Member

    Apr 18, 2010
    165
    9
    I don't know, but is there an advantage to using a 4 layer pcb, but having the outer layers as ground (apart from the placement of components of course)?
     
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