RE: [IBIS-Users] A question about the ibis simulation.

First, I had a typo in my last message, it should have read
“spike” instead of “spice”.

Second, since I received a private reply on this topic attributing
the spikes to magical parasitics, I want to make it absolutely
clear that the debated waveforms can be reproduced with a very
simple experiment. Please try the following HSPICE netlist in
your favorite SPICE simulator:


**********************************************************************
.TRAN 10.0ps 60.0ns
.OPTIONS POST=2 PROBE
.PRINT TRAN Pls = V(pls)
+ Drv = V(drv)
+ Rcv = V(rcv)
**********************************************************************
V1 pls 0 PULSE (0.0V 5.0V 0.1ns 1.0ps 1.0ps 25.0ns 50.0ns)
Rdrv pls drv R=65
*Cdrv drv 0 C=2.0pF
*
T1 drv 0 rcv 0 Zo=50 Td=1ns
*
*Crcv rcv 0 C=2.0pF
**********************************************************************
.END
**********************************************************************


Try it once as it is shown here, and then try it again with the
two capacitors commented in. You should be able to reproduce
the following waveforms:

[cid:image005.png@01CC3C19.BD0608C0]


Note that the blue waveform on the lower plot (which was
generated with the two capacitors enabled) is pretty close
to what the original question was all about, and note that
the above netlist has absolutely nothing magical in it.

It consists of a simple Thevenin driver model (voltage
source and a resistor) with or without the die capacitance,
an ideal T-line, and a receiver model which is either empty
or nothing more than a simple capacitor. There are no
package models or inductors in this circuit and the T-line
is also ideal (lossless), so there is nothing magical in
the netlist, yet it pretty accurately reproduces the
original waveforms.

I would like to take this opportunity to encourage anyone
new to signal integrity to try to answer your own questions
first with simple experiments like this, because you can
learn a lot more by doing it on your own, and you can also
reduce unnecessary traffic on email lists like this one...

Thanks,

Arpad
============================================================


From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf Of Muranyi, Arpad
Sent: Wednesday, July 06, 2011 8:46 AM
To: 'ibis-users'
Subject: RE: [IBIS-Users] A question about the ibis simulation.

The reason for the spice is most likely
the capacitance in the receiver.

Arpad
========================================

From: Zhanggezi [mailto:gezi.zhang@huawei.com]
Sent: Wednesday, July 06, 2011 5:35 AM
To: Muranyi, Arpad; 'ibis-users'
Cc: 'yang@huawei.com'
Subject: 答复: [IBIS-Users] A question about the ibis simulation.

Hi All,

The topology is below. And ibis file is very large, I will share with you if needed after deleting unnecessary information.
[cid:image002.png@01CC3C17.2328C2D0]

And the probe is on the receiver, three simulation outputs are different corners for one model(fast,typical and slow corners), and I
Want to the reason for the spike. Any one can help?
[cid:image003.jpg@01CC3C17.2328C2D0]

发件人: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] 代表 Muranyi, Arpad
发送时间: 2011年7月5日 23:52
收件人: 'ibis-users'
主题: RE: [IBIS-Users] A question about the ibis simulation.

Naftali,

I am not sure I understand what the “The topology is one on one” is
referring to in the original question. So I am not sure what
you mean by “set a very same length to both T branches” either. Please
clarify your question.

Thanks,

Arpad
==============================================================

From: naftali refaeli [mailto:Naftali.Refaeli@ecitele.com]
Sent: Tuesday, July 05, 2011 10:49 AM
To: Muranyi, Arpad; 'ibis-users'
Subject: RE: [IBIS-Users] A question about the ibis simulation.

Do you mean that If he will set a very same length to both T branches – then the phenomenon will disappear?


Naftali Refaeli
CAE Engineer
ITO
HP Enterprise Services
Telephone +972 3.9266973
Mobile +972 52.3542043
Email Naftali.Refaeli@ecitele.com<mailto:Naftali.Refaeli@ecitele.com>

From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf Of Muranyi, Arpad
Sent: Tuesday, July 05, 2011 6:45 PM
To: 'ibis-users'
Subject: RE: [IBIS-Users] A question about the ibis simulation.

Grace,

It looks like that the first ledge is the voltage that the
driver can drive with the load imposed on it by the T-line.
Once the reflection comes back to the driver the voltage
steps up to the full swing levels. This is basic T-line
theory.

Arpad
============================================================

From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org] On Behalf Of Zhanggezi
Sent: Monday, July 04, 2011 8:54 PM
To: 'ibis-users'
Subject: [IBIS-Users] A question about the ibis simulation.




Hi All,



  The topology is one on one. The simulation result is below. I am curious about the simulation circled



by red pink. What’s the cause? Could someone give me any hint?



  [cid:image004.png@01CC3C17.2328C2D0]



Thank you.



Grace

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