[SI-LIST] Re: Reference Plane
- From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
- To: "Loyer, Jeff" <jeff.loyer@xxxxxxxxx>,"Zhangkun" <zhang_kun@xxxxxxxxxx>
- Date: Mon, 8 Sep 2003 15:06:02 -0700
Jeff,
I agree with you that the typical power delivery system is likely to do a
poor job of addressing this problem. The fix I try to get people to work
is fix the power delivery system. There are other reasons to do this, such
as EMI.
Lee
> [Original Message]
> From: Loyer, Jeff <jeff.loyer@xxxxxxxxx>
> To: <leeritchey@xxxxxxxxxxxxx>; Zhangkun <zhang_kun@xxxxxxxxxx>
> Cc: si-list <si-list@xxxxxxxxxxxxx>
> Date: 9/8/2003 11:30:47 AM
> Subject: RE: [SI-LIST] Re: Reference Plane
>
> Hi Lee,
> The problem appears to be how we're interpreting the original question.
As I understood it, the issue being raised is the effect of a trace
transitioning between different reference planes, which is a different
issue than coupling of power supply noise onto that trace.
>
> I contend that the issue of transitions between reference planes may or
may not be adequately addressed by the typical power-delivery subsystem.
Providing a proper path for return current is a different (but possibly
overlapping) issue than keeping noise off VCC. I think Ray Anderson did a
great job of articulating the difference between the two in an earlier
posting.
>
> I've posted my thoughts (based on theory, measurements, and experience)
on this contention earlier, and they should be available on the archives.
If you have issues with those, please let me know.
>
> Jeff Loyer
>
> -----Original Message-----
> From: Lee Ritchey [mailto:leeritchey@xxxxxxxxxxxxx]
> Sent: Monday, September 08, 2003 10:57 AM
> To: Loyer, Jeff; Zhangkun
> Cc: si-list
> Subject: [SI-LIST] Re: Reference Plane
>
>
> Jeff,
>
> I am aware there has been lots of discussion and that's just what it is.
> There is also plenty of science that supports my statements. It is true
> that whatever ripple there is on Vcc or Vdd will couple onto any signal
> that runs over that plane. Nothing wrong with that as long as the ripple
> voltage is within limits. This condition is satisfied by doing a good job
> of designing the power supply system. I've designed hundreds of
> supercomputer PCBs just this way. Does Cray Research ring a bell? How
> about Amdahl?
>
> Lee
>
>
> > [Original Message]
> > From: Loyer, Jeff <jeff.loyer@xxxxxxxxx>
> > To: Zhangkun <zhang_kun@xxxxxxxxxx>
> > Cc: <leeritchey@xxxxxxxxxxxxx>; si-list <si-list@xxxxxxxxxxxxx>
> > Date: 9/8/2003 8:53:20 AM
> > Subject: [SI-LIST] Re: Reference Plane
> >
> > Eeks! I would not agree with Lee's statement. There has been a LOT of
=
> > discussion on this issue, and I would strongly suggest you work to =
> > understand the issues as they can have considerable impact.
> >
> > Searching through the archives for "reference plane" should give you =
> > tons of information on the subject.
> >
> > Jeff Loyer
> >
> > -----Original Message-----
> > From: Lee Ritchey [mailto:leeritchey@xxxxxxxxxxxxx]
> > Sent: Monday, September 08, 2003 8:08 AM
> > To: Zhangkun; si-list
> > Subject: [SI-LIST] Re: Reference Plane
> >
> >
> > Zhangkun,
> >
> > If you have designed your power subsystem correctly, the Vcc and ground
> > planes of you power supply will be tied to each other through less than
=
> > 10
> > milliohms at all of the frequencies that are in you signal, so you don't
> > haveto worry about a disconnect.
> >
> > Lee
> >
> >
> > > [Original Message]
> > > From: Zhangkun <zhang_kun@xxxxxxxxxx>
> > > To: si-list <si-list@xxxxxxxxxxxxx>
> > > Date: 9/8/2003 9:50:26 PM
> > > Subject: [SI-LIST] Reference Plane
> > >
> > > Dear All:
> > > There are one driver and one receiver, which is connected by one =
> > trace.
> > The driver and receiver use GND as their reference. The trace use VCC as
> > its reference plane. As shown in power integrity, there is impedance
> > between power and ground. Therefore, there are one disconnection at the
> > driver and one disconnection at the receiver. Would these two =
> > disconnection
> > disgrade signal integrity?
> > >
> > > Best Regards
> > >
> > > Zhangkun
> > > 2003.09.08
> > >
> > >
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