[SI-LIST] Re: SSN and Crosstalk in Package
- From: Zhangkun <zhang_kun@xxxxxxxxxx>
- To: rich.evans@xxxxxx, weirsi@xxxxxxxxxx, lgreen22@xxxxxxxxxxxxxx, James Church <jchurch@xxxxxxxx>, wbecker@xxxxxxxxxx
- Date: Wed, 20 Apr 2005 09:21:52 +0800
Dear all
Maybe I am making some mistake. I would check the spice deck again. Sorry for
reply so later.
Best Regards
Zhangkun
2005.4.20
----- Original Message -----
From: "Richard P EVANS" <rich.evans@xxxxxx>
To: "'si-list'" <si-list@xxxxxxxxxxxxx>
Sent: Friday, April 15, 2005 8:57 PM
Subject: [SI-LIST] Re: SSN and Crosstalk in Package
> Remember too, when you make the power/ground supplies "perfect",
> the output drivers will be able to switch much faster, so the rise/fall
> times will be shorter and cause more crosstalk.
>
> ---Rich
>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
> Behalf Of steve weir
> Sent: Friday, April 15, 2005 5:55 AM
> To: zhang_kun@xxxxxxxxxx; si-list
> Subject: [SI-LIST] Re: SSN and Crosstalk in Package
>
>
> Zhangkun, your results are very unexpected. For most packages the common
> return inductance is dominant over line to line coupling. I think there
> is a flaw in your method. Can you explain further how in your simulation
> you eliminated the parasitics of the power distribution network but
> retained the signal return parasitics?
>
> I think we should wait to discuss your observations and conclusions until
> we are satisfied that your model is valid. Respectfully, right now I have
> grave doubts about your model.
>
> Regards,
>
>
> Steve
>
>
> At 04:48 PM 4/15/2005 +0800, Zhangkun wrote:
> >Dear all
> >Recently, I was simulating SSN in package. I found out that in the
> >"SSN"
> >noise, there are two parts:
> > 1. The noise because of the inductance of power or ground net.
> > 2. The crosstalk between signals.
> >
> >Moreover, I noticed that the second part is much larger than the first
> >one. The verification method is to simulate twice:
> > 1.Regular simulation.
> > 2.Simulation with perfect power supply. Therefore the inductance of
> > power or ground net is eliminated.
> >
> >Comparing these two SSN simulaiton results, I notice that the
> >difference
> >is not great. Therefore, I concluded that the main source of "SSN" is the
> >crosstalk in package.
> >
> >
> >
> >Let the above conclusion be correct. I think that the SSN would be not
> >very critical. My explanation is following. Based on the "SSN" waveform,
> >it is clear that the crosstalk is mainly inductive and the capacitive
> >coupling is small. When the inductive and capacitive coupling is not
> >equal, the farend crosstalk is very large. The nearend crosstalk would be
> >very small for the trace in package is very short.
> >
> >Now let us consider several SSN situation. There are N IO ports in the
> >IC.
> >
> > 1.(N-1) net is output and aggressive. Victim net is output and quiet.
> > Because the crosstalk is inductive, there would be great "SSN"
> > in
> > the victim net. However, the "SSN" is of high frequency. When the "SSN"
> > is transfered along the transmission line, it would be damped and would
> > not damage the signal integrity of victim net.
> >
> > 2.(N-1) net is output and agressive. Victim net is input and quiet.
> > Because the nearend crosstalk is small, there would be no
> > great
> > damage for the input net.
> >
> > 3.(N-1) net is input and aggressive. One net is input/outpu,
> > quiet,
> > and victim.
> > Normally, the risetime and falltime at input buffer is large for
> > the damp of transmission line or loading effect. Therefore, there would
> > be no critical crosstalk.
> >
> >At last, there would be no critical "SSN" problem if the crosstalk in
> >package is dominating.
> >
> >
> >The above is my viewpoint about SSN in package. Any comment is welcome.
> >The basic is that crosstalk in package is much larger that the noise
> >because of inductance of power supply system.
> >
> >Best Regards
> >
> >Zhangkun
> >2005.4.15
> >
> >
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