[SI-LIST] Re: How accurate is HSPICE's field solver?
- From: "Scott McMorrow" <scott@xxxxxxxxxxxxx>
- To: Pat_Diao@xxxxxxxx, "silist" <si-list@xxxxxxxxxxxxx>
- Date: Thu, 06 Feb 2003 15:23:34 -0800
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
>
>
>
>
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List archives are viewable at:
//www.freelists.org/archives/si-list
or at our remote archives:
http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
