[SI-LIST] Re: HyperLynx vs Hspice

  • From: Ekkehard Miersch <miersch@xxxxxxxxxxxxxxxxx>
  • To: naveenr@xxxxxxxxxxxxxxx
  • Date: Thu, 02 Oct 2003 16:37:18 +0200

Hi all,

let’s assume a circuit is switching with 210psec and the signal 
propagation speed = energy propagation speed is 70psec/cm.
The access of the switching device to charges needed for the switching 
is restricted to a circle (sphere) of 3cm.
Beyond 3cm a thing like (ideal?) ground is not defined anymore (!), 
which means none of the electrons outside the 3cm circle can reach the 
switching device during the switching event of 210psec. And the 
electrons outside the 2cm circle reach the device only after 140psec, 
which means pretty delayed.
Just looking at this, I have understanding problems with modelling 
techniques, assuming e.g. Ideal Ground.
At high speed conditions on a PCB, I have problems with ECAD systems, 
which use TEM ( e.g. 2D solver), with quasi static TEM solutions, with 
PEEC without retardation, which ignore losses and/or and the frequency 
dependence of R,L,C, with algorithms, which approximate  the Maxwell 
Equations, with the assumption of ideal ground. Even Spice is such a 
tool, if non ideal ground assumptions are left out in the applied Spice 
model.  I call these tools conventional tools with which it is however 
possible to handle large complex structure in acceptable computer 
running times. But these tools ignore also via- via coupling and via 
–ground plane structures and just miss with their answers the boat at 
high speed.

Especially when it is claimed that those conventional tools are High 
Speed PCB analysis tools. But most of the traditional tools on the 
market do this. Did the guys, who claim the high speed modelling 
capabilities of  conventional tools forget all the nice things they 
learned at the university ?
Some ways around this dilemma are shown under 
www.mentor.com/germany/veranstaltungen/hsconf/ in the paper “High-Speed 
Design Analyse: Vergleich von Messung und Simulation“.

I am very interested to learn more about the opinion, that Hyperlynx is 
a 3GHz analysis tool or that Hspice can analyze 10GB/sec nets without 
having the precise information within that Hspice run about all the net 
discontinuities and the interaction of these nets with their power 
system through the net vias? The 2 examples Hyperlynx and the straight 
forward used Hspice are only examples representing the other 
conventional tools using similar techniques.

Ekkehard



Naveen Reddy wrote:
> Hi Everybody:
> I need to perform some high speed simulations (over 3GHz) for my
> backplane and I currently have the Mentor HyperLynx tool. I have run
> into a little problem. HyperLynx needs IBIS models for simulation
> purposes, whereas most of the vendors provide only spice models and not
> IBIS. Although HyperLynx can convert Spice models to IBIS, it does need
> a Spice simulator to do that.
> 
> I am a little confused here and am hoping I can have these questions
> answered.
> 
> 1. Can I use just Hspice to perform all my high speed simulations or is
> HyperLynx a better tool for this application?
> 2. Has anyone had experience with converting 3D spice models to IBIS?
> What are the tradeoffs?
> 3. HyperLynx has three levels of licenses - regular, EXT and GHZ. Which
> one should I be using?
> 
> Thanks in advance.
> 
> -Naveen.
> 
> 
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-- 
EFM Consulting
Dr. Ekkehard Miersch
Dresdener Str.6
D-71101 Schoenaich
Germany
Tel.        +49 (0)7031-6571-13
Fax/Tel. +49 (0)7031-6571-14
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EFM.Miersch@xxxxxxxxxxx


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