BeTheSignal
New techniques for PDN modeling promise more accurate power noise predictions
Eric Bogatin
9/3/2010 5:13 AM EDT
Accurate model critical
The initial voltage sag on the chip, occurring in the first few hundred picoseconds of the clock edge, is controlled by the amount of on-die capacitance and the total charge that switches. The overshoot occurring 15 nanoseconds later is the inductive response of the package, resonating with the on-die capacitance.
He identified three design features to reduce this noise: more on-die capacitance, lower package inductance and more on-package decoupling capacitors. As all of these solutions add cost, it is critical to have an accurate model to predict the expected “bang for the buck.”
The approach Smith’s team developed for modeling on-die transient currents and their interaction with the impedance model of the system’s PDN is a step in this direction.
For more information, see:
http://www.altera.com/literature/cp/cp-01060-pdn-noise.pdf
Eric Bogatin is a Signal Integrity Evangelist with Bogatin Enterprises, a world leader in signal integrity training. Many of his papers and columns are available on the www.BeTheSignal.com website.
The initial voltage sag on the chip, occurring in the first few hundred picoseconds of the clock edge, is controlled by the amount of on-die capacitance and the total charge that switches. The overshoot occurring 15 nanoseconds later is the inductive response of the package, resonating with the on-die capacitance.
He identified three design features to reduce this noise: more on-die capacitance, lower package inductance and more on-package decoupling capacitors. As all of these solutions add cost, it is critical to have an accurate model to predict the expected “bang for the buck.”
The approach Smith’s team developed for modeling on-die transient currents and their interaction with the impedance model of the system’s PDN is a step in this direction.
For more information, see:
http://www.altera.com/literature/cp/cp-01060-pdn-noise.pdf
Eric Bogatin is a Signal Integrity Evangelist with Bogatin Enterprises, a world leader in signal integrity training. Many of his papers and columns are available on the www.BeTheSignal.com website.
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http://www.lulu.com/spotlight/poconoarmchairreview
9/7/2010 1:31 AM EDT
I LOVE the way this article begins!
It starts with a dramatic punch, right out of nowhere, worthy of a Dashiell Hammett novel: "The bad news is that power distribution noise requirements will be getting more difficult to meet." That is bad news.
Then, it immediately escalates the conflict, in the very next sentence, with the really bad news. "And the really bad news is that the actual on-die power noise you currently have is probably much larger than you think."
What can I do? I'm on my feet now, tearing my hair.
Before I catch my breath, the messenger of this pronouncement--as solemn as death, heavy with gravitas, yet, tinged with a promise of desperate hope--is revealed: "This is the message from Larry Smith, signal and power integrity architect at Altera Corp."
I stop. For a moment, all is silent. I imagine the name on the door. It's not Sam Spade. It's Larry Smith. And Shishuang Sun, too, it turns out. Close enough.
Actually, this is a good article. Learned something about catching on-die noise from it. I can't wait for the movie version to come out.
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junko.yoshida
9/7/2010 1:50 AM EDT
So, Rich, you, too, are a Dashiell Hammett fan! I laughed out loud reading your comment. It was gripping!
Your post made me go back to read the whole contributed article, which turned out very informative.
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http://www.lulu.com/spotlight/poconoarmchairreview
9/13/2010 10:43 PM EDT
Thank you for your kind words. I'm happy and touched that anyone found them to be of any interest.
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iniewski
9/13/2010 8:56 PM EDT
Love your sense of humor Rich! Interesting article, I have spent months of my life struggling with on-chip power supply noise issues. Will be happy to share once the current project is finished...Kris
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http://www.lulu.com/spotlight/poconoarmchairreview
9/13/2010 10:44 PM EDT
Thank you, too, for your kind words. It's also nice of you to offer to share.
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ReneCardenas
11/9/2010 11:12 AM EST
Rich, & Eric
I enjoyed reading this article, but even more the play by play dissection of the author writing style. It confirms some suspicion that was previously only theoretically formulated.
Again Eric, and Rich, I really enjoy both of your writings, keep on doing what you are doing, you do it very well and it is a pleasure reading you, and thank you gentlemen!
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