Re: FW: FW: Spice Model of IBIS

Well, I just couldn't resist.

I certainly wouldn't argue with anyone that SPICE (actually some SPICE
commercial derivative) is the premier circuit simulation technology that
is currently publically available. I also wouldn't argue with anyone who
said that IBIS has some problems that need to be addressed.

However, the market has shown that there is a need for a PCB SI
simulation technology that offers features that transcend the current
SPICE node based syntax. Think of the bigger problem. You need to
simulate the SI and Crosstalk effects of every net on a PCB. You need
MIN MAX timing from every driver to every receiver. You need SI and
Noise margin numbers for every net. And you need them quickly enough so
that you can use the data to turn the design a couple of times. I
believe these issues are difficult to solve using SPICE as it (they)
exists on the market today.

Of course, I use SPICE every day. I think it is great. I just believe in
using the right tool for the right job and I have more than one job to
do.

Here is a conceptual example:
you have a 32 wire bus. Each wire couples to it's neighbors. You need to
simulate every wire and the effects on that wire by it's immediate
neighbors. You do not want to waste simulation time by simulating
effects of the wires that are more than a couple of conductors away.

How would you solve this problem using SPICE?
Can it be solved automatically?
How would spice represent the names of the different nets? (ie. what is
the crosstalk on D13?).

As for accuracy:
Leave the argument of which approach is more accurate for the moment.
what is the accuracy of your inputs? (PCB stack-up, SPICE model data,
Dielectric constant, trace width).
If you are simulating to a higher accuracy than your data inputs then
you are wasting time and deceiving yourself. I think that a teacher told
me this in 5th grade but I never really believed it until I started
doing SI simulation.
Received on Tue Mar 31 09:05:50 1998