[SI-LIST] Re: Spice PULSE parameters (was: hspice field solver question)
- From: "Ingraham, Andrew" <a.ingraham@xxxxxxxx>
- To: <si-list@xxxxxxxxxxxxx>
- Date: Mon, 22 Dec 2003 12:48:15 -0500
This question wasn't really about the Hspice field solver; it was about the
PULSE independent source.
> Vin in1 0 pulse 3.3 0 5n 0.5n 0.5n 25ns
...
> I wonder how do we determine the frequency, rise/fall time of this pulse
> function??
Assuming that I am remembering the order of PULSE parameters correctly:
The waveform alternates between 3.3 and 0 volts.
It has an initial delay of 5ns, where the voltage remains steady at 3.3V,
before it starts to change toward 0V.
The rise time is 0.5ns, measured from 0% (= 3.3V) to 100% (= 0.0V). Note
that "rise" means going from the initial voltage (3.3V) to the second
voltage (0V), which in this case is toward a less positive voltage so the
voltage is actually falling!
The fall time is 0.5ns, measured from 100% (0.0V) to 0% (3.3V).
The period is 25ns, so the frequency is 40MHz.
Since the PULSE function uses straight-line edges, you can calculate the
rise and fall times for other percentages. For example, the 10-90% rise and
fall times are 80% * 0.5ns = 0.4ns; the 20-80% rise time is 0.3ns.
Regards,
Andy
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