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Forums > Silicon-package-board > Signal Integrity and Modeling

Subject: SSN warning and ugly waveform at AP SI 15.7
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imsong
Posts: 18
Online: User is Offline
12/05/2006 9:30 PM  
The warning message is "Only one DC plane was found, cann't mesh ground."
Sometimes the warning message is "No voltage source pin is found for Ground Bounce"

The waveform is attched.

What is the problem?

But at "comprehensive" simulation, I could see the SSN at same environment.

Please let me know.





Donald Telian
Posts: 42
Online: User is Offline
12/27/2006 3:05 PM  
You've succeeded in getting noisy power and ground busses, so it seems the question/warnings are related to the quality of the waveforms. WARNINGs draw your attention to something that may not be setup quite right, even though you still achieved some result. In your case, you may need to "Identify DC Nets" so that the tool knows which planes to mesh. For example, you may need to apply 0V to your ground planes.

Either way, the non-ideal power is modifying your signal performance so it would be interesting/valuable to compare how much change you see as compared with using ideal power. And if the dark blue waveform is your receiver, I'd be concerned about its Vswing and the loss incurred from the driver (which I'm guessing is brown?).

Hope that helps. It's a bit difficult to understand the question. Also, it's helpful to vary the colors in your waveforms.
Donald Telian
SI Consultant
telian@sti.net
559-760-5793
imsong
Posts: 18
Online: User is Offline
2/14/2007 6:08 PM  
Thank you for your reply.

I had already set the DC voltage.

In the waveform the black wave and low voltage swing is driver component pin, the other black wave is receiver part.
The power and ground bouce wave is that of receiver component pin.

It is hard to understand how I set the simulation to SSN even if I read the manual.
Donald Telian
Posts: 42
Online: User is Offline
2/16/2007 9:21 AM  
Start by unchecking "Plane Modeling" under Preferences>InterconnectModels. Then you'll just be using the RLC package parasitcs in the SSN simulation. You likely know how to change the RLC values, and you can also change/correct how the power busses are setup under "Edit Model" -> "Assign Power/GND Pins". This is a good way to add non-ideal power effects to your sims as it will pushout/pullin some of the important timing edges and skews.

Once you succeed with that, you could then try to add in "Plane Modeling". However, I'd expect the more interesting effects to come from the package parasitics.

Give it a try.

Donald
Donald Telian
SI Consultant
telian@sti.net
559-760-5793
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Forums > Silicon-package-board > Signal Integrity and Modeling > SSN warning and ugly waveform at AP SI 15.7


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