[SI-LIST] Re: Decoupling capacitors
- From: Ray Anderson <raymond.anderson@xxxxxxx>
- To: RJatou@xxxxxxxxxx
- Date: Thu, 23 May 2002 13:25:54 -0700
Ross Jatou wrote:
>
> Ray,
>
> We have SQPI as well and have been trying to correlate it to measurements.
> My question is: how do you incorporate chip capacitance ?
> The capacitance is in two forms:
> 1) package and die capacitance between power and ground
> 2) integrated caps that are placed in the package.
>
> Ross
>
Ross-
The present incarnation/version of SQPI (14.1 or 14.2) doesn't have
the capability for including capacitance inside a package, except
by very indirect, labor intensive and undesireable means
You need to manually generate a special capacitor model which
contains a subcircuit that describes your package and whatever
capacitances you want to include. This involves editing the .dml,
.txt, and .dcl files. Your subcircuit will probably have a
noise source embedded in it, in which case you will need to
reset the mandatory noise sources in the SQPI generated spectre deck
to near zero values.Quite involved, inconvenient and error
prone as there several steps that must be accomplished outside
of the SQPI environment.
You can't just put a capacitor down and call it chip capacitance,
(well you could, but it wouldn't be accurate) because you need
to get the capacitance onto the other side of the package
parasistics to make it work right.
However, this issue has been raised, and as I understand it,
means to do such things as you've just identified are scheduled
as enhancements in an upcoming release.
Check the following URL:
http://www.specctraquest.com/Contribute/ToolsUtilities.asp
for a Perl script developed by a SQPI user at Intel that automates
a lot of the stuff required to model all the way up to the die.
I haven't tried it, but it looks like it does all the right stuff.
Contact you rep to register your request. The more people
asking for a particular feature, the better, as it may get
it done faster :)
-Ray
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