[SI-LIST] Re: Spice PULSE parameters (was: hspice field solver question)

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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