Walter,
I believe "Signal Reference" may be too restrictive for our purpose.
IBIS does support power aware simulations, and as a consequence we
might be looking at the power lines as well (not only signal lines).
For that reason, I think we should use "Reference", which can be a
reference for whatever you are observing.
Thanks,
Arpad
====================================================================
From: ibis-macro-bounce@xxxxxxxxxxxxx [mailto:ibis-macro-bounce@xxxxxxxxxxxxx] ;
On Behalf Of Walter Katz
Sent: Tuesday, January 17, 2017 4:26 PM
To: Scott@xxxxxxxxxxxxx; msteinb@xxxxxxxxxx; ibis-macro@xxxxxxxxxxxxx
Subject: [ibis-macro] Re: What is "Signal Ground", "Signal Return", "Signal
Reference" how are all voltage measurements made
All,
Here is a site that tries to distinguish Ground, Return and Reference. I hope
no one objects if we use the term "Signal Reference", and in my example when
[GND Clamp Reference] =0.0V, then all voltage measurements at the terminals of
an I/O buffer be really V(<terminal>,gnd_clamp_ref) using SPICE voltage probe
nomenclature.
http://electronics.stackexchange.com/questions/240311/what-is-the-difference-in-the-terms-signal-return-signal-reference-and-si
"Signal ground" is the most generic of these terms. It is used primarily when
you want to distinguish it from other kinds of ground, such as safety ground or
power supply return paths.
"Signal return" means that the speaker is thinking particularly about how the
signal current is flowing. This would come up when thinking about EMC in terms
of loop area (magnetic coupling). This could apply to cables or PCB designs,
and primarily in low-impedance circuits.
"Signal reference" means that the speaker is thinking particularly about
distinguishing the signal voltage from any kind of common-mode interference.
This would apply primarily in high-impedance circuits.
But they all mean "ground" in one sense or another, and the specific nuance
depends very much on context.
These nuances come up when you realize that, in real-world designs, you have to
treat "ground" not as a single, universal reference node, but rather as a
network of nodes connected by various parasitic impedances (resistance,
inductance) to each other and to other circuit nodes (capacitively or
inductively).
Walter
From: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx>
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Scott McMorrow
Sent: Tuesday, January 17, 2017 5:08 PM
To: msteinb@xxxxxxxxxx<mailto:msteinb@xxxxxxxxxx>;
ibis-macro@xxxxxxxxxxxxx<mailto:ibis-macro@xxxxxxxxxxxxx>
Subject: [ibis-macro] Re: What is "Local Ground", how are all voltage
measurements made
Agreed, Mike.
Return node
Reference node
Anything but Ground
Scott McMorrow, CTO Signal Integrity Group
Samtec
Office 401-284-1827 | +1-800-726-8329
www.samtec.com<http://www.samtec.com/>
From: ibis-macro-bounce@xxxxxxxxxxxxx<mailto:ibis-macro-bounce@xxxxxxxxxxxxx>
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Mike Steinberger
Sent: Tuesday, January 17, 2017 5:04 PM
To: ibis-macro@xxxxxxxxxxxxx<mailto:ibis-macro@xxxxxxxxxxxxx>
Subject: [ibis-macro] Re: What is "Local Ground", how are all voltage
measurements made
All-
To quote Heidi Barnes (and possibly others) "ground" is for potatoes and
carrots.
Rather than referring to "Local Ground", I request that you refer to a "local
return node" as a single point on the current return path for a given circuit
node. Even this concept is an engineering approximation; however this
approximation can at least be rigorously defined. Given a signal node and its
corresponding local return node, the only voltage that is defined is the
voltage difference between the signal node and the local return node; and
that's enough information to solve even a complex high frequency circuit.
Tautologically speaking, it is true that the voltage difference between the
local return node and itself is 0.0V; however, that isn't a very useful
observation.
Mike Steinberger
On 1/17/2017 4:13 PM, Walter Katz wrote:
All,
I think that IBIS should simply state:
All voltage measurements at a buffer shall be made relative to a "Local Ground"
node.
The "Local Ground" is defined as any Rail Terminal that has a value of 0.0
volts in DUT conditions.
* If there is no Rail Terminal that has a value of 0.0 volts in DUT
conditions, then
o A component pin rail signal name that has a 0.0V DUT value, then that
signal name shall be "Local Ground".
? If there is no component pin that has a DUT value of 0.0V, then simulator
Node 0 shall be the reference voltage for all voltage measurements.
Walter
Walter Katz
wkatz@xxxxxxxxxx<mailto:wkatz@xxxxxxxxxx>
Phone 303.449-2308
Mobile 303.335-6156
