[SI-LIST] Re: SSN and Crosstalk in Package

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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