[SI-LIST] Re: local and global ground

Andy:

Thank you for sharing your experience on this. I rechecked the 2 models from
2 vendors. I did not find any .Global statements in either of them. But in
one of the model, I do find node 0 inside the model, which may be the reason
that give me "inductor/voltage loop" error.

In the case of the second model, there is no 0 node inside the model and the
vendor claim that they run this type of simulation without any problem in
another SPICE tool. I have sent the HSPICE deck to the vendor and ask them
to try it out. This is case where I see big spike on ground (amplitude even
a few times bigger than my incident voltage swing).

Regards

Perry

"Ingraham, Andrew" wrote:

> I have done what you are trying to do ... use a local non-ground
> reference in HSPICE ... and it can work if done right.
>
> Sometimes you run into problems where some vendor's model has hidden
> connections to ground, either because it is encrypted so you can't tell
> what the heck is in it, or because they did something incredibly
> un-user-friendly like having .GLOBAL node statements within their
> subcircuits.  I have spent hours un-doing this kind of junk in vendor
> models.
>
> But in your case the daughter card side is so simple, that I suspect the
> connector models are at fault.
>
> Are you sure the connector models were created to include what one might
> call "common mode" effects, when the two sides are unhinged?  If it only
> models local effects between neighboring pins, or if it was intended to
> have reference node 0 on both sides, it might have completely missed the
> effects between the two boards.  Getting a totally "correct" model that
> really behaves just like the real connector, under all conditions, isn't
> something that just automatically pops out of the modeling process.
> Just like SPICE's transmission line model ignores the common-mode
> (unless we explicitly include it, which takes some effort), the
> connector models might have done the same.
>
> What you are seeing is probably not "numerical noise", but rather "real"
> noise from the point of view of the simulator, but due to poor modeling.
> There's a difference.
>
> I am puzzled why the second vendor's model gives you an
> "inductor/voltage loop" error message, which is fixed by connecting the
> daughter card side to node 0.  Usually that error means there is a
> connection that shouldn't be there, like maybe you unintentionally
> re-used a node number.  I might have expected a "floating node" or "no
> DC path to ground" error message, in your case.  Track down exactly
> where that inductor/voltage loop is, it might tell you something.
>
> Andy
>
> ------------------------------------------------------------------
> 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:
> http://www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
> List archives are viewable at:
>                 http://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
>

--
Perry Qu

Product Integrity         |      600 March Road
Alcatel Canada            |      Ottawa, ON K2K 2E6, Canada

DID: (613) 7846720        |      FAX: (613) 5993642


------------------------------------------------------------------
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:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field

List archives are viewable at:     
                http://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: