RE: [IBIS-Users] Per-Pin Distributed RLC Support

Radovan,
 
I suspect the reason people are asking for this data is because at the
speeds we're dealing with, large packages are really acting like
transmission lines.  We can clearly see the effects in the lab - measure
the input pin of a large device where the driver is serially terminated
and you'll see the "ledging" characteristic associated with a
transmission line.  Lumped RLC parasitics, whether in per-pin or matrix
form, won't necessarily reproduce this behavior.
 
I use the term "necessarily" on purpose - some simulators convert
package RLC parasitics into their transmission line equivalents - so
you'll see transmission line behavior in all cases - but that is
implementation-dependent.  Explicitly expressing the parasitics as a
transmission line should force the simulator to model it that way [or so
one would hope].
 
This isn't an issue for all devices - but it's an issue for devices that
are, say, more than 1" square with signaling edge rates less than 250ps.
You can take the same rules of thumb for evaluating line length vs. edge
rate and distributed/lumped line behavior at the board level and apply
them to packages - the problem is the same.
 
Fork/endfork statements are used to describe branches in package
routing.  Not that common anymore, I grant you - but once upon a time,
plating bars and associated package stubs were common, and the
fork/endfork statements were used to describe the stub.  They're also
common in the few cases where discrete devices are part of the package
routing.
 
Todd.
 
Todd Westerhoff
High Speed Design Group Manager
Cisco Systems
1414 Massachusetts Ave - Boxboro, MA - 01719 email:twesterh@cisco.com
ph: 978-936-2149
============================================
 
"Always do right.
 This will gratify some people and astonish the rest."
 
- Mark Twain

 

________________________________

From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On
Behalf Of Radovan.Vuletic@infineon.com
Sent: Tuesday, October 18, 2005 2:42 AM
To: tom@teraspeed.com; ray.anderson@xilinx.com; ibis-users@eda.org
Subject: RE: [IBIS-Users] Per-Pin Distributed RLC Support


Hi,
 
Tom, I think that you put the right question, so let me elaborate this
little bit further:
 
1. are there any available tools that generate/extract such RLC data out
of package data?
 
2. before I submit the request to package experts to extract one more
package format (they will crucify me anyway :-)  I would like to know
how many people would like/intend to use it
 
3. I know that the next question is not fair and that I compare here
apples and oranges, but if you have one one side such RLC data and on
the other side Sparse Matrix data what would you prefer to use? - My
choice will be always Sparse Matrix - unless there is some very specific
request
 
4. last but not least, quiet honestly, for me it is still little bit
unclear what is meant to describe with "fork" and "endfork"  branches
... Is it meant to indicate that for example 2 or more pads are sharing
the same pin/ball or something similar - or I am missing the point
totally? I thing that one picture (perhaps also in specs) could help on
this place.
 
Regards,
Radovan

	-----Original Message-----
	From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org]
On Behalf Of Tom Dagostino
	Sent: Tuesday, October 18, 2005 2:39 AM
	To: Ray Anderson; ibis-users@eda.org
	Subject: RE: [IBIS-Users] Per-Pin Distributed RLC Support
	
	
	Ray
	 
	Do any of the simulators support this?
	 

	Tom Dagostino
	Teraspeed(R) Labs
	13610 SW Harness Lane
	Beaverton, OR 97008
	503-430-1065
	tom@teraspeed.com
	www.teraspeed.com
	
	Teraspeed Consulting Group LLC
	121 North River Drive
	Narragansett, RI 02882
	401-284-1827 

		-----Original Message-----
		From: owner-ibis-users@eda.org
[mailto:owner-ibis-users@eda.org]On Behalf Of Ray Anderson
		Sent: Monday, October 17, 2005 4:14 PM
		To: ibis-users@eda.org
		Cc: Ray Anderson
		Subject: [IBIS-Users] Per-Pin Distributed RLC Support
		
		

		In reviewing a large sampling of IBIS models from
numerous vendors I have yet to find any that implement the distributed
RLC format as described in the [Pin Numbers] section of the IBIS spec.
(pages 117-120 in the 4.1 spec)

		 

		I was wondering if anyone is aware of any published
models that take advantage of this method of describing package
parasitics.

		 

		Regards,

		 

		-Ray

		 

		 

		Raymond Anderson

		Senior Signal Integrity Staff Engineer

		Product Technology Department

		Advanced Package R&D

		Xilinx Inc.

		 

		 


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