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-differen
ce-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] On Behalf Of Scott McMorrow
Sent: Tuesday, January 17, 2017 5:08 PM
To: msteinb@xxxxxxxxxx; 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
<http://www.samtec.com/> 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
<mailto:wkatz@xxxxxxxxxx> wkatz@xxxxxxxxxx
Phone 303.449-2308
Mobile 303.335-6156
