Re: [SI-LIST] : Transmission Line Thy Applied to short interconnects

[email protected]
Tue, 23 Mar 1999 13:49:44 EST


Since your original inquiry was on the 18th, you may have dispensed with this
problem; however, here's my two cents.... and don't take it negatively, as
it's meant as constructive criticism.

If you don't have a circuit simulator, GET ONE. The questions you posed could
be answered with confidence in a couple of hours. Go ahead and generate the
model(s) to include transmission lines, as that's what they are. The T-lines
will simulate properly for low- and high-frequency AC simulations as well as
time domain (transient) simulations. You could easily alter the driver
rise/fall times, driving impedance, and voltage swings to bound worst-case
conditions. Current modeling programs allow you to step one or more
parameters simultaneously, so you can quickly optimize the design using a set
of preferred (or perhaps dictated) parts by trial and error simulations.

You may find no terminations are required, or that perhaps diode terminations
are superior to R (or RC) terminations for the intended application. But all
of these options could be evaluated in short order, and confident decisions
made to speed the design. Plots of stepped parameter runs could be used to
document (and justify) your design selections.

If your management has refused funding for a simulation package, their head is
in the sand. With the posture that requires, a swift kick is in order.

Mike Conn
Owner/Principal Consultant
Mikon Consulting

PS: If I seem a little testy, the stock market is doing badly today.

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