FreeLists / si-list / [SI-LIST] Re: How accurate is HSPICE's field solver?

["Scott McMorrow" <scott@xxxxxxxxxxxxx>]

Pat,

No, I did mean 1 victim and 4 aggressors.  With this configuration with 
most simulators you can perform two types of simulations, crosstalk and ISI.

A crosstalk simualtion is performed with all 4 aggressors driven with a 
pattern and the victim in a quiescent logic state, either active high, 
active low, or both.

An ISI simulation is performed with the 4 aggressors and the victim 
driven with patterns. Choosing different patterns to stimulate all 
possible crosstalk and signalling modes is always an interesting exercise.

best regards,

scott


-- 
Scott McMorrow
Teraspeed Consulting Group LLC
2926 SE Yamhill St.
Portland, OR 97214
(503) 239-5536
http://www.teraspeed.com


Pat Diao wrote:

>Scott,
>
>Did you mean 1 aggressor and 4 victims below?  It won't change the coupling
>coefficient either way, but physically in most simulators the aggressor is
>the one that carries the active voltage.
>
>Just want to clarify...
>
>Pat  
>
>
>
>Pat Diao
>ASAT Inc.
>Fremont, CA
>phone: (510) 249-1227
>
>
>-----Original Message-----
>From: Scott McMorrow [mailto:scott@xxxxxxxxxxxxx]
>Sent: Thursday, February 06, 2003 12:48 PM
>To: mherndon@xxxxxxxxx
>Cc: si-list@xxxxxxxxxxxxx
>Subject: [SI-LIST] Re: How accurate is HSPICE's field solver?
>
>
>Matt,
>
>For single ended simulations I most always use 5 coupled lines, 1 victim 
>and 4 aggressors.  And for differential simulations I use 6 or 10 
>coupled lines (3 or 5 differential pairs)  There are several reasons why 
>I do this:
>
>1) By extending the simulation trace geometry out to 2 aggressors on 
>either side, I guarantee that the adjacent aggressors are operating in 
>their normal electromagnetic field configuration, with their impedance 
>altered correctly by the adjacent aggressors traces.  This reduces some 
>errors in the overall crosstalk and eye pattern simulations.  Although 
>neighbors that are 2 conductors away from the victim have very little 
>direct influence upon the victim, they do have an indirect influence due 
>to their coupling to the nearest crosstalk neighbor, having a tendency 
>to alter the dynamic impedance of the nearest neighbors, and therefore 
>the amount of energy available for crosstalk on the victim.
>
>2) Signals always travel through packages and often travel through 
>connectors.  In both cases, coupling is almost always much stronger than 
>it is on the PCB. (Unless the PCB stackup is poorly designed.)  It is 
>often necessary to simulate many neighbors in packages and connectors. 
> In order to keep the simulations symmetric and not induce artifacts due 
>to different driven phases, I find it useful to extract as many 
>conductors in the PCB as will be simulated through the package and 
>connectors.  For packages that are designed with poor power/ground 
>structures, I find that there are additional modes of propagation 
>between the signal conductors and package power conductors that cannot 
>be accounted for if all of the signal conductors are not driven.  This 
>will sometimes require a large number of conductors to be extracted from 
>the PCB, in order to include all of the system effects.  Oftentimes I 
>find that for non perfectly terminated busses the crosstalk will 
>saturate in the package before ever reaching the PCB.
>
>3) At high frequencies fine pitch BGA via breakouts can introduce a 
>large amount of crosstalk, similar to that caused by connectors. Since 
>these patterns are square arrays, I will use a 3x3 array of vias, 
>extract them using a full wave field solver, convert the s-parameters 
>into a spice circuit with BroadBand Spice, and then assign the signals 
>and grounds based upon the ball-out pattern of the BGA. This will often 
>cause the simulation to need quite a few parallel lines to be extracted 
>from the PCB.
>
>I hope this answers your question,  Matt.
>
>Best regards,
>
>scott
>
>
>  
>


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