Walter,
I agree with your first proposed sentence. However, not to be pedantic, how
can a Rail Terminal "have" a voltage "value"? The original IBIS text was
murky on this point, but some of our more recent changes are slowly fixing
this to refer only to voltages with respect to defined reference points.
The bullets below may end up conflating the concept of a Rail Terminal as a
(reference) point and a Rail Terminal as a supply having a voltage with
respect to. another point.
I think what is intended in the bulleted lines is:
'The "Local Ground" may be defined as a Rail Terminal. However, the value
of any voltage measurements associated with that Rail Terminal shall be, by
definition, 0.0 (e.g., a Local Ground defined as gnd_clamp_ref for a given
[Model] means that the voltage value entry for [GND Clamp Reference] shall
and must be 0.0).'
This may be a little difficult to enforce and we could end up with some
ambiguous cases, but it's worth testing on existing models.
Also, the additional language you use implies that any rail (e.g. [GND Clamp
Reference]) with voltage value entry 0.0 automatically becomes the
reference. Does that prevent AC voltage noise measurements on those rails?
In other words, does this erase any distinction between the reference and a
rail like [Pulldown Reference] or [GND Clamp Reference] which may be
nominally 0.0 V vs. an unstated Node 0, but may experience noise effect of
interest during operation?
- MM
From: ibis-macro-bounce@xxxxxxxxxxxxx
[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Walter Katz
Sent: Tuesday, January 17, 2017 1:14 PM
To: IBIS-ATM <ibis-macro@xxxxxxxxxxxxx>
Subject: [ibis-macro] What is "Local Ground", how are all voltage
measurements made
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
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