Radek,
Re
What about the other buffer rail terminals? How do they fit into the
topology of BIRD 158. My question was whether that needs to be clarified
somewhere between the two BIRDs.
They do not. There is no clarification to be made between the two BIRDs.
The fundemental point of describing the buffer between the differential
input to the on-die S-Parameter and the die pads as an s4p says to ignore
all of the affects with all of the rail voltages other than the test
fixture reference voltage and it local point at the buffer which is the [*
Reference] whose value is 0.0V. Since almost always IBIS models are
described with [Voltage Range], then both the [Pulldown Reference] and the
[GND Clamp Reference] are 0.0V, and the only thing that the EDA tool needs
to do is reference the s4p to the rail voltage applied to Pulldown_Ref or
GND_Clamp_Ref.
Walter
Walter Katz
<mailto:wkatz@xxxxxxxxxx> wkatz@xxxxxxxxxx
Phone 303.449-2308
Mobile 303.335-6156
From: ibis-interconn-bounce@xxxxxxxxxxxxx
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radek_biernacki@xxxxxxxxxxxx
Sent: Tuesday, August 29, 2017 4:10 PM
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Subject: [ibis-interconn] Re: reconciling BIRDs 158 and 189
Walter,
First, that was discussed many times but let's not dispute it and simply
assume that there is a "buffer rail terminal whose value of [Pulldown
Reference], [GND Clamp Reference], [Pullup Reference], [Power Clamp
Reference] is zero". That resolves the signal reference node. What about
the other buffer rail terminals? How do they fit into the topology of BIRD
158. My question was whether that needs to be clarified somewhere between
the two BIRDs.
Radek
From: ibis-interconn-bounce@xxxxxxxxxxxxx
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[mailto:ibis-interconn-bounce@xxxxxxxxxxxxx] On Behalf Of Muranyi, Arpad
Sent: Tuesday, August 29, 2017 11:39 AM
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Subject: [ibis-interconn] Re: reconciling BIRDs 158 and 189
All,
Radek raises an interesting question and this is related to the LTI
requirement / assumption in IBIS-AMI.
If the analog front end of the buffer is a power aware model, the
fluctuations on the power lines will modulate the buffer's drive
characteristics. This is a time varying behavior, which we can't have
according to the LTI requirement.
If this time variance is short lived and caused by the same buffer
which is involved in the AMI analysis, it could be captured in a step
response, which is one way of generating the channel impulse
response for the AMI models. But long term variations, extending
beyond a step response will not be captured this way. Also power
variations due to other effects on the die, such as SSO caused by
other buffers can't be captured this way, because they are more
random in nature.
Another complication is that BIRD158 models may not be used in
channel characterizations using a time domain step response. I
don't know how power effects could be included if the analysis is
done in the frequency domain.
So the short answer in my mind is that for AMI simulations we should
not attempt to include power delivery effects. But this seems to be
a model maker problem, not a spec problem. Just because the spec
allows you to do it, it doesn't mean that you have to do it.
Thanks,
Arpad
========================================================
From: ibis-macro-bounce@xxxxxxxxxxxxx
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[mailto:ibis-macro-bounce@xxxxxxxxxxxxx] On Behalf Of Walter Katz
Sent: Tuesday, August 29, 2017 12:58 PM
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Subject: [ibis-macro] Re: [ibis-interconn] reconciling BIRDs 158 and 189
Radek,
What specific question relevant to power supply terminals of BIRD 189.x
models?
The only possible relevant question is what node in my simulation deck
needs to be hooked up to the reference terminal of the Ts4file. Since BIRD
158 represents differential s-parameters, this reference voltage is only
important in power aware simulations, and in that case should use the
reference node of the I/O buffer it is connected to. This reference node
is the buffer rail terminal whose value of [Pulldown Reference], [GND
Clamp Reference], [Pullup Reference], [Power Clamp Reference] is zero.
Walter
Walter Katz
<mailto:wkatz@xxxxxxxxxx> wkatz@xxxxxxxxxx
Phone 303.449-2308
Mobile 303.335-6156
From: ibis-interconn-bounce@xxxxxxxxxxxxx
<mailto:ibis-interconn-bounce@xxxxxxxxxxxxx>
[mailto:ibis-interconn-bounce@xxxxxxxxxxxxx] On Behalf Of
radek_biernacki@xxxxxxxxxxxx <mailto:radek_biernacki@xxxxxxxxxxxx>
Sent: Tuesday, August 29, 2017 1:36 PM
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Subject: [ibis-interconn] reconciling BIRDs 158 and 189
Hi All,
With the coming interconnect/package modeling via BIRD 189.x and the
specific package modeling needs of BIRD 158.x I have a question. Do we
need to provide specific guidance, or even restrict BIRD 189.x generality
of the package modeling for the needs of BIRD 158.x? In particular, the
question is how the general interconnect/package model of BIRD 189.x is to
be hooked up to the schematic of BIRD 158.x. Specifically, the question is
relevant to power supply terminals of BIRD 189.x models.
Radek
