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Using PSpice's DigStim for Analog Signals

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?

Reply to
Bob Penoyer
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Using Capture.

Seriously, read up on A/D interface selection.

...Jim Thompson

--
|  James E.Thompson, P.E.                           |    mens     |
|  Analog Innovations, Inc.                         |     et      |
|  Analog/Mixed-Signal ASIC\'s and Discrete Systems  |    manus    |
|  Phoenix, Arizona            Voice:(480)460-2350  |             |
|  E-mail Address at Website     Fax:(480)460-2142  |  Brass Rat  |
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Reply to
Jim Thompson

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

Reply to
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.

Reply to
Bob Penoyer

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