[SI-LIST] Re: PI resonance test

  • From: Cristian Filip <cris_filip2002@xxxxxxxx>
  • To: "weirsi@xxxxxxxxxx" <weirsi@xxxxxxxxxx>
  • Date: Thu, 16 Jan 2014 17:07:27 -0800 (PST)

Hi Steve,
Could you please clarify here what is the excitation mechanism of the cavity at 
600 MHz? I would expect that the on-package and on-die capacitors would 
suppress the high frequency content of the noise, so only low frequency noise 
would reach the ports of the cavity. 
Thank you,
Cristian


________________________________
From: steve weir <weirsi@xxxxxxxxxx>
To: Cristian Filip <cris_filip2002@xxxxxxxx> 
Cc: "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx> 
Sent: Wednesday, January 15, 2014 11:33:02 PM
Subject: [SI-LIST] Re: PI resonance test


Cristian, the problem is that the statements are both right and wrong 
simultaneously.  Those citations mostly refer to either the crossover of 
Xc of the cavity versus Xl of the discrete capacitor network, and / or 
the LPF between the power cavity and the IC die.
Back at the power cavity, individual discrete bypass caps can exhibit 
practical mounted ESLs anywhere from around 100pH to 3nH or more.    3nH 
works out to about 12 Ohms @ 600MHz, but 100pH is only about 0.4 Ohms.  
Undamped cavity resonances can be many Ohms.  It only takes a few 
carefully chosen capacitors to damp resonances that could otherwise make 
nightmares for EMI and/or fast interfaces.

The mantra of PI/SI is:  It depends.

Steve.

On 1/15/2014 4:46 PM, Cristian Filip wrote:
>
> Hi Steve,
> Thank you for replay. The upper limit of the frequency range where the 
> PCB and mounted MLCC are still effective is that kind of information 
> that shows up on nearly every PI book or article. Although there are 
> variations from one author to the other most of them agree on 
> 80/100MHz. Here are few examples:
> 1.Dr. Eric Bogatin, “Signal and Power Integrity Simplified”, Second 
> Edition, page 632
> ------------------------------------------------------------------------------------------------------------
> TIPThe frequency region that board level PDN design can influence is 
> roughly from the 100 kHz range up to about 100 MHz. This is where the 
> planes of the board and the multilayer ceramic capacitors (MLCC) can 
> play a role.
> ------------------------------------------------------------------------------------------------------------
> 2.Vishram S. Pandit, Woong Hwan Ryu, Myoung Joon Choi, “Power 
> Integrity for I/O Interfaces: With Signal Integrity/Power Integrity 
> Co-Design”, page 148 and Figure 5.19
> ------------------------------------------------------------------------------------------------------------
> The effective frequency range of the board ceramic (edge) capacitor is 
> from 1 MHz to tens of MHz, and the package capacitor is from tens of 
> MHz to a few hundreds MHz. The chip capacitor can be effective all the 
> way to a very high frequency range.
> ------------------------------------------------------------------------------------------------------------
> 3.Madhavan Swaminathan, A. Ege Engin, “Power Integrity Modeling and 
> Design for Semiconductors and Systems”, please see Figure 1-40 at page 
> 65 and the explanation at page 64
> ------------------------------------------------------------------------------------------------------------
> Between 10 and 100 MHz, the interaction between the package and board 
> becomes important.
> ------------------------------------------------------------------------------------------------------------
> You seem to disagree with all of those authors, so could you please 
> provide us your number along with explanations? Is this number typical 
> for most of the industry designs or it is just the result of an 
> experimental prototype meant to push the technology towards its limits?
> Thank you,
> Cristian
>
> *From:* steve weir <weirsi@xxxxxxxxxx>
> *To:* si-list@xxxxxxxxxxxxx
> *Sent:* Tuesday, January 14, 2014 9:05:45 PM
> *Subject:* [SI-LIST] Re: PI resonance test
>
> Cristian, 600MHz is still a low enough frequency that capacitors can
> usually be used to damp PDN resonance, especially if the power cavity is
> close to the same PCB surface as the capacitors.
>
> Steve.
> On 1/14/2014 4:16 PM, Cristian Filip wrote:
> > Hi Ravi,
> > As I know that you are using HyperLynx for PDN characterization, I 
> want to remind you that the simulator is not accounting for the 
> on-package and on-die capacitance, or for the package inductance. 
> Consequently the resonance that you see on your plot is not what the 
> IC power pins will see. The 600 MHz frequency resonance is quite high 
> and the capacitors mounted on the PCB are not effective due to the 
> loop inductance. This being said you should either be worried only 
> about resonances that occur at lower frequencies (typically less than 
> 100 MHz) or even better, perform transient simulations that include 
> beside the PCB PDN, power aware models (IBIS 5.0 or newer, Spice, CPM).
> > Cheers,
> > Cristian
> > Â
> > ________________________________
> > From: çŽ‹ç´ åŽ <star_wang1@xxxxxxxxxxx 
> > <mailto:star_wang1@xxxxxxxxxxx>>
> > To: si-list@xxxxxxxxxxxxx <mailto:si-list@xxxxxxxxxxxxx>
> > Sent: Tuesday, January 14, 2014 7:37:45 AM
> > Subject: [SI-LIST] PI resonance test
> >
> >
> > Dear all
> >   I have a problem about how to test power plane resonance.
> >
> > I did a simulation of a 1.0v power plane(12v turn 1.0v) and the 
> resonance is
> > high at 600mhz,how can I verify my simulation through test?
> >
> > Thanks
> >
> >
> >
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> -- 
> Steve Weir
> IPBLOX, LLC
> 1580 Grand Point Way
> MS 34689
> Reno, NV  89523-9998
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-- 
Steve Weir
IPBLOX, LLC
1580 Grand Point Way
MS 34689
Reno, NV  89523-9998
www.ipblox.com

(775) 299-4236 Business
(866) 675-4630 Toll-free
(707) 780-1951 Fax

All contents Copyright (c)2013 IPBLOX, LLC.  All Rights Reserved.
This e-mail may contain confidential material.
If you are not the intended recipient, please destroy all records
and notify the sender.



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