Walter,
I am not sure I can answer your Yes/No question at the end with a yes or no.
I will have to think about this some more (so anyone feel free to correct
me if I say something wrong), but to me the problem seems to be putting
statements into the specification about where the reference terminal should
be connected to. As soon as we make statements like that, we are putting
restrictions/assumptions into the spec on how the model should be made and/or
used which may not support everyone's needs or goals. That's why we need to
be extremely careful about making such statements, or how we make such
statements in the spec...
But Brad was also correct with his comment last time that a shortcut, by its
nature cannot and shouldn't be expected to be a general solution...
So then if we define this shortcut as a subset of the general solution, we
need to decide which subset would be most useful.
Thanks,
Arpad
==============================================================================
From: ibis-editorial-bounce@xxxxxxxxxxxxx
[mailto:ibis-editorial-bounce@xxxxxxxxxxxxx] On Behalf Of Walter Katz
Sent: Monday, March 14, 2016 11:37 AM
To: Muranyi, Arpad <Arpad_Muranyi@xxxxxxxxxx>; IBIS-ATM
<ibis-macro@xxxxxxxxxxxxx>; ibis-interconn@xxxxxxxxxxxxx;
ibis-editorial@xxxxxxxxxxxxx
Subject: [ibis-editorial] Re: According to Scott McMorrow the Node 0 ground
assumption can be valid!
Arpad,
Precisely so. The important statement is
"but a package designer maybe serious about wanting to know how good the GND
traces are in his/her package..."
I would like to state this in a different way:
1. What does the system designer want:
a. Does not care about power delivery at all
b. Cares about power delivery but does not care about GND bounce
c. Cares about power delivery and cares about GND bounce
2. What does the package designer want.
a. Does not care about power delivery at all
b. Cares about power delivery but does not care about GND bounce
c. Cares about power delivery and cares about GND bounce
And then the important questions:
When is the package interconnect model created for the package designer?
Does the system designer want this model, or a simpler model that considers
power delivery and not GND bounce.
My answer to these questions is that there is nothing in what we have proposed
from preventing a model maker from created the most complex package models that
will support the package designer. He probably will not be able to use the
Touchstone shortcut, so be it.
But we should also allow the model maker do deliver models that support 1a and
1b above. Based on what Scott has said, and you agree with, then we should
allow Node 0 in both Touchstone shortcut and IBIS-ISS subckts and making it
clear that such models require that simulations use a "ground referenced system
where node 0 ground is applied to every element in the path".
Is there a compromise here that can satisfy everyone's requirements. Do we
solve this by having a package modeling sub-parameter [Ground Referenced
System] Yes|No.
Walter
From:
ibis-editorial-bounce@xxxxxxxxxxxxx<mailto:ibis-editorial-bounce@xxxxxxxxxxxxx>
[mailto:ibis-editorial-bounce@xxxxxxxxxxxxx] On Behalf Of Muranyi, Arpad
Sent: Monday, March 14, 2016 12:14 PM
To: IBIS-ATM <ibis-macro@xxxxxxxxxxxxx<mailto:ibis-macro@xxxxxxxxxxxxx>>;
ibis-interconn@xxxxxxxxxxxxx<mailto:ibis-interconn@xxxxxxxxxxxxx>;
ibis-editorial@xxxxxxxxxxxxx<mailto:ibis-editorial@xxxxxxxxxxxxx>
Subject: [ibis-editorial] Re: According to Scott McMorrow the Node 0 ground
assumption can be valid!
Walter,
Scott is absolutely correct. The catch is this statement:
"But, ground bounce inductance and resistance is then lumped into power
circuit and signal path circuits, and the discrimination between the these is
lost."
With that, the question becomes, how do we want to visualize
the results, and I feel that the answer is related to the
relativity theory. Do we want to see the dog wiggle its tail,
or the tail wiggle the dog... :)
More seriously, if we only care about how the receiver sees
the signal, we really don't need to know whether the receiver's
"GND" (i.e. reference) was rock steady or bouncing like crazy.
But if we want to make sure that the receiver's "GND" is not
bouncing like crazy, we will most likely want to see what it
does. But then the question becomes: "with respect to what?"...
Perhaps a better "GND" under the chip (GND plane of the PCB),
or the VRM half a mile away, or the ground stake at the utility
service entrance two miles away... :) I am trying to be funny
with some of this, but a package designer maybe serious about
wanting to know how good the GND traces are in his/her package...
Thanks,
Arpad
================================================================
From:
ibis-editorial-bounce@xxxxxxxxxxxxx<mailto:ibis-editorial-bounce@xxxxxxxxxxxxx>
[mailto:ibis-editorial-bounce@xxxxxxxxxxxxx] On Behalf Of Walter Katz
Sent: Sunday, March 13, 2016 7:06 PM
To: IBIS-ATM <ibis-macro@xxxxxxxxxxxxx<mailto:ibis-macro@xxxxxxxxxxxxx>>;
ibis-interconn@xxxxxxxxxxxxx<mailto:ibis-interconn@xxxxxxxxxxxxx>;
ibis-editorial@xxxxxxxxxxxxx<mailto:ibis-editorial@xxxxxxxxxxxxx>
Subject: [ibis-editorial] According to Scott McMorrow the Node 0 ground
assumption can be valid!
All, (and Radek, Brad and Vladimir in particular)
Scott McMorrow writes:
Circuit theory says that we can go from a partial element system where ground
and power loops are fully modeled to a ground referenced system where node 0
ground is applied to every element in the path. But, ground bounce inductance
and resistance is then lumped into power circuit and signal path circuits, and
the discrimination between the these is lost. From a differential node voltage
perspective at the receiver, the result is the same. The voltage between the
signal and ground will remain the same. If there is a difference, then
somewhere in the circuit, the ground partial inductance has not been reduced
into the loop inductance for the signal path and power paths.
It is a pretty standard transformation from partial inductance/resistance
matrices to loop inductance/resistance matrices, and is covered quite
extensively in Brian Young's book, which is still the best on the subject. He's
been at Motorola and TI. I believe he's at TI now running their ASIC packaging
group.
http://www.amazon.com/Digital-Signal-Integrity-Simulation-Interconnects/dp/0130289043
Walter
Walter Katz
wkatz@xxxxxxxxxx<mailto:wkatz@xxxxxxxxxx>
Phone 303.449-2308
Mobile 303.335-6156