[SI-LIST] Re: Self Impedance Analysis of Power Distribution Network
- From: Siddharth Rajagopalan <maxsidhu@xxxxxxxxx>
- To: mgreim001@xxxxxxxxx
- Date: Tue, 27 Nov 2012 10:43:59 +0530
HI bala,
In the book that you read which was written by eric bogatin,
he suggested that effect of ceramic capacitors on AC coupling will be upto
100 MHZ and not that the simulation has to be done upto 100 MHz. it has to
be done till the I/0's operating frequency. Hope this helps
Regards,
Siddharth Rajagopalan
Cisco systems
On Mon, Nov 26, 2012 at 6:51 PM, Michael Greim <mgreim001@xxxxxxxxx> wrote:
> Oh,
> At the end of the paper there are also references to a number
> of other papers that will help with your PDN design challenges.
> Enjoy.
>
> -Michael.
>
> On Mon, Nov 26, 2012 at 8:19 AM, Michael Greim <mgreim001@xxxxxxxxx>
> wrote:
>
> > Hi All,
> >
> > This is a shameless promotion of Lee's site and my paper, but
> > the paper should give a bunch of you a great starting point for
> > circuit board issues like the following. Istvan has fantastic content
> > on all things PDN on his site. If folks have any other questions,
> > feel free to throw questions directly to me or out on the reflector.
> > I will give you a response and in many cases it will not be "it depends".
> >
> > http://www.speedingedge.com/PDF-Files/ednpds_0600MikeGreim.pdf
> >
> > Bala, to answer you question, for things to work properly, you need
> > to keep your PDN impedance below mark or you run into problems
> > with anti resonant PDN impedance peaks. When you run into these
> > via various data patterns, the bad behavior will often times manifest
> > itself as bit errors, data errors because of the simple math that Steve
> > (think it was him) brought up. Sometimes SI and PI gets back to
> > really simple math of V= IR.
> >
> > I am still not a fan of rules of thumb. Guess I need to talk to
> > Eric.....;-)
> > If you do something and you don't know why (specially PDN) then
> > odds are you have problems and just don't know it yet.....and again,
> > or why. 2amps is less of a problem than 20amps or 100amps.
> >
> > How about that for a starting point?
> >
> > -Michael.
> >
> > We will either find a way or make one - Hannibal
> >
> > In the middle of every difficulty lies opportunity - Al Einstein
> >
> > If you think you can do something or you think
> > you can't, in both cases you are probably right - H Ford
> >
> > If you're not getting the results you want with the
> > current approach, move on and try something else. - A. Fleischmann
> >
> >
> > On Mon, Nov 26, 2012 at 4:24 AM, bala <balaseven@xxxxxxxxx> wrote:
> >
> >> @Michael Greim
> >> I am considering PDN from source to PCB.I am okay with IR drop and
> density
> >> concept..
> >> While doing Ac analysis(Self impedance vs Frequency) plot,i have no clue
> >> on
> >> upto what frequency it has to be done?Eric bogatin suggestive,it should
> be
> >> atleast 100MHZ for all PDN.For the device operating at KHZ
> frequencies,why
> >> should i have to run this upto 100MHZ?
> >>
> >> Say for example,I just wanted to know my self impedance curve of
> ARRIA-2's
> >> 2.5V LVCMOS supply which will consumes 2Amps maximum,and the operating
> >> frequency is 125MHZ.And my target impedance is 0.0625ohms..My question
> >> is;Should self impedance of my PDN be below this target impedance till
> >> 125MHZ?Why?
> >>
> >> Regards
> >> bala
> >>
> >>
> >>
> >>
> >> On Sun, Nov 25, 2012 at 10:09 AM, steve weir <weirsi@xxxxxxxxxx> wrote:
> >>
> >> > The required frequency range depends on what one is doing. For
> >> > single-ended logic the 5th harmonic is a practical rule of thumb.
> For a
> >> > 28Gbps channel the 5th harmonic is excessive. The fundamental issue
> is
> >> > that for just power delivery this is pretty much an issue of Ohm's
> Law:
> >> > The voltage launched into the Tx line launch will approximate
> >> > |Zlaunch|/(|Zlaunch + Zdriver + Zpdn|). The grid assumption works to
> >> > the extent that the PDN impedance variation of any of the drivers
> >> > looking into the grid is small compared to the load.
> >> >
> >> > Steve.
> >> >
> >> >
> >> > On 11/24/2012 8:16 PM, Brendan Simpson wrote:
> >> > > Bala,
> >> > >
> >> > > I believe you need to simulate not up to the operating frequency,
> but
> >> to
> >> > at least the 5th harmonic as the 5th and above will give you a
> reliable
> >> > square wave. You should be able to reliably simulate a power
> >> distribution
> >> > network as a grid of discrete components with current sources
> switching
> >> in
> >> > the general region that the current drawing elements reside. My
> >> experience
> >> > is with PCBs, but my understanding is that a similar approach is taken
> >> at
> >> > the chip level. Also of note is that the grid analysis method only
> works
> >> > correctly when you have whole planes for power distro, such as in a
> PCB.
> >> > >
> >> > > Best Regards,
> >> > > Brendan
> >> > >
> >> > > On Nov 23, 2012, at 6:37 2800AM, bala wrote:
> >> > >
> >> > >> Hi all,
> >> > >> Why self impedance analysis of Power Distribution Network has to be
> >> done
> >> > >> upto IO's operating frequency?
> >> > >>
> >> > >> --
> >> > >> bala
> >> > >>
> >> > >>
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> >> > --
> >> > Steve Weir
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> >> --
> >> bala
> >>
> >>
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> >>
> >
> >
> > --
> >
> >
>
>
> --
> -Michael.
>
> We will either find a way or make one - Hannibal
>
> In the middle of every difficulty lies opportunity - Al Einstein
>
> If you think you can do something or you think
> you can't, in both cases you are probably right - H Ford
>
> If you're not getting the results you want with the
> current approach, move on and try something else. - A. Fleischmann
>
>
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