"Jack C. Olson" wrote:
>
> snip <
> If I have impedance controlled signals that are part of
> a circuit that is being run on +2.6V or +3.3V, but there
> is a closer plane available, like +5V, the signal returns
> will snap to the closer one, right?

        The return path will "snap" to the nearest hunk of
        metal available, regardless of what its DC function
        is.  This is an AC path - the return is seeking the
        lowest inductance way back, or the tightest possible
        loop.

        This can lead to all sorts of discussion in the EE
        and SI community, but the principles are fundamental
        to EMC (EMI).

--

      Jeff Seeger                         Applied CAD Knowledge Inc
      Chief Technical Officer                  Tyngsboro, MA  01879
      jseeger "at" appliedcad "dot" com                978 649 9800

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