[SI-LIST] Re: Is Impedance Enough for Describing the PDS?
- From: Zhangkun <zhang_kun@xxxxxxxxxx>
- To: amahajan@xxxxxxxxxxxx, weirsp@xxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Fri, 09 Jul 2004 19:23:11 +0800
Dear Abhijit
This kind of problem has been talked about several month ago : ). I do not
agree the "star topology". In high frequency domain, if there is no plane
capacitance, the power integrity is bad.
Best Regards
Zhangkun
2004.7.9
----- Original Message -----
From: "Abhijit Mahajan" <amahajan@xxxxxxxxxxxx>
To: <weirsp@xxxxxxxxxx>; <si-list@xxxxxxxxxxxxx>
Sent: Friday, July 09, 2004 3:36 PM
Subject: [SI-LIST] Re: Is Impedance Enough for Describing the PDS?
> Steve/Others.
>
> Would it be better then to reduce the area of power planes as much as
> possible(by
> localizing the power planes to only cover the pins that need it) and pack
> the decoupling there?
> islands of same voltage can be then connected with wide traces to the
> nearest bulk cap
> And finally brought together at the regulator.
>
> This can be vaguely be described as a "star topology" for power
> distribution.
>
> Does anyone think there is any value in this appproach? Has it been
> discussed before?
>
>
> ##I am assuming all signal routing is over a common ground plane.
>
>
> Thanks!
>
> Abhijit.
>
>
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On
> Behalf Of steve weir
> Sent: Friday, July 09, 2004 6:04 AM
> To: zhang_kun@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Is Impedance Enough for Describing the PDS?
>
>
> Zhangkun, the problem is that the PDS overlaps both signal integrity and
> EMC compliance. If the system rules are done right, then the PDS
> decoupling problem will eventually reduce to an impedance profile. But
> that profile is both spatial and frequency dependent. If I shove all the
> decoupling capacitors into one corner of the board I get a very different
> result than if I distribute them.
>
> Steve.
> At 08:04 AM 7/9/2004 +0800, zhangkun 29902 wrote:
> >Dear all
> >
> >When talking about power delivery system with other engineer, there are
> >a
> >lot of element to describe the PDS, such as energy storage, decoupling,
> >bypassing, and so on. I think all these parameter could be described by
> >one element, impedance of PDS.
> >
> >Is my point right? Is impedance enough for describing the PDS?
> >
> >Best Regards
> >
> >Zhangkun
> >2004.7.9
> >
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