[SI-LIST] Re: How can I simulate the influence of power plane noise on the signal trace ?
- From: steve weir <weirsi@xxxxxxxxxx>
- To: zhangkun 29902 <zhang_kun@xxxxxxxxxx>
- Date: Fri, 13 May 2005 23:14:08 -0700
Zhangkun, what will and will not work is always a matter of coefficients
not absolutes in the topology. While there are conditions where
referencing a plane other than the power common can work just fine, there
are those where it will not work reliably at all.
If the noise on the other plane be a voltage plane, floating piece of metal
or what have you is sufficiently low to remain within the common mode range
of the receiver amplifier then we get past the first and most severe hurdle
which is my point #2. Beyond that, the degradation of the signal quality
and timing depends on the circumstances. But there can be no doubt that
once the common mode range of the receive amplifier is violated, there is
no reliable data transfer. This is a well demonstrated phenomenon that
routinely burns designers whether they are using isolated or non-isolated
links.
Best Regards,
Steve.
At 08:21 AM 5/14/2005 +0800, zhangkun 29902 wrote:
>Steve
>
>In the realistic, there have to be some signal refered to power plane.
>Moreover, I do not think it is very cirtical if the decoupling for the
>power delivery system.
>
>I have use 3D field solver to simulate this kind of situation. There is
>displacement current between planes, which gives rise to problem. If the
>displacement current could be lessen, I think it is no critical for the
>signal to refer to any plane.
>
>Best Regards
>
>Zhangkun
>2005.5.14
>
>----- Original Message -----
>From: steve weir <weirsi@xxxxxxxxxx>
>Date: Saturday, May 14, 2005 1:43 am
>Subject: [SI-LIST] Re: How can I simulate the influence of power
>plane noise on the signal trace ?
>
> > Jia, if you assume that:
> >
> > 1. The geometry of each line is identical
> > 2. The noise does not violate the CM range of the receiver,
> > 3. The CM rejection of the receiver is perfect
> >
> > Then you will not see any effects whatsoever. Put in more
> > realistic models
> > for each point above and you will find:
> >
> > 1. Differential noise injection
> > 2. Very bad if this happens, don't let it!
> > 3. Increased jitter
> >
> > For these reasons, it is a poor idea to reference high performance
> > links
> > against multiple voltage rails. It doesn't mean that you cannot
> > do it
> > successfully, but it does mean that you have a lot of additional
> > homework
> > to do, and may not be able to meet a given performance target.
> >
> > Steve.
> > 11:47 AM 5/13/2005 +0800, Jia Gongxian wrote:
> > >Dear all,
> > >
> > >I'd like to simulate the influence of power plane noise on the
> > signal
> > >traces, which are differential stripline, using the power plane
> > as one
> > >reference plane.That is,
> > >
> > > ----------------------------------- ground plane
> > >
> > > --- --- differential traces
> > >
> > > ----------------------------------- power plane + noise
> > >
> > > Any suggestions will be welcome.
> > >
> > >Thanks.
> > >
> > >Jia Gongxian
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