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Using PSpice's DigStim for Analog Signals

Discussion in 'CAD' started by Bob Penoyer, Aug 3, 2006.

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  1. Bob Penoyer

    Bob Penoyer Guest

    I'm having trouble using/understanding the use of DigStim.

    DigStim1 under Capture appears to offer analog functions (EXP, PULSE,
    PWL, SFFM, and SIN) as well as digital functions (Clock, Signal, Bus)
    options in the New Stimulus window. But when I create an analog
    stimulus and run PSpice, I get meaningless output.

    For example, if I create a PULSE stimulus and simply connect a probe
    to the output, I get a digital probe output (with a black probe at the
    output) in which the logical output appears to be indeterminate. If I
    connect the DigStim1 output to a resistor to ground, the probe is then
    green (i.e., analog) but the result is a constant voltage of about
    1.35V for a set of 3.5V pulses.

    PULSE, EXP, etc. plot out in the DigStim1 editor as expected after
    completing the Attributes assignments. But I don't see these
    characteristics when I run PSpice.

    What, if anything, am I doing wrong?
     
  2. Jim Thompson

    Jim Thompson Guest

    Using Capture.

    Seriously, read up on A/D interface selection.

    ...Jim Thompson
     
  3. Bob,
    the DigStim1 is a stimulus editor part, something that Jim doesn't fool
    with. He used traditional stim1(or 4, or 8, etc.) parts when he needs a
    digital stimulus. He also uses a Vpulse when he needs a pulse waveform,
    and other basic parts. For an old master, they are much easier to set
    up, and are a lot less confusing.

    In your case, you opened the stimulus editor, and added a new stimulus
    to the file. You also gave it a name. If you look at the digstim1
    part, you will notice an IMPLEMENTATION property. This would be the
    name of the stimulus you just created. However, it need to be digital,
    not analog, since this is a digital part. If you want an analog pulse
    waveform, use a VSTIM part.

    Charlie
     
  4. Bob Penoyer

    Bob Penoyer Guest

    On Thu, 03 Aug 2006 09:10:08 -0700, Charlie Edmondson

    Thanks for your response. Apparently, Cadence provides both the
    digital and analog stimulus selections in one window, the New Stimulus
    window. It would have made a lot more sense to provide digital choices
    for the digital stimulus and analog for analog.

    Thanks again for your help.
     
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