FreeLists / si-list / [SI-LIST] Re: risetime effects of plane breaks

[Dan Bostan <dbostan@xxxxxxxxx>]

You can cross the break as long as you provide a close
path for the return current also.
/dan


--- "Muranyi, Arpad" <arpad.muranyi@xxxxxxxxx> wrote:

> Even though I was just speed reading this
> thread, I didn't see this mentioned yet:
> 
> You can also get by with plane breaks if the
> traces going over it are closely coupled
> differential pairs...
> 
> Arpad
>
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
>
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=20
> 
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx] =
> On Behalf Of steve weir
> Sent: Monday, January 10, 2005 11:21 AM
> To: emcesd2000@xxxxxxxxx; SI-List
> Subject: [SI-LIST] Re: risetime effects of plane
> breaks
> 
> Oscar, yes, it is quite a dramatic effect isn't it? 
> I suspect that  =
> when=20
> Lee says "it depends on how you do it" he has
> another contiguous plane, =
> ie=20
> ground underneath the split as opposed to a split on
> all planes as in=20
> Doug's experiment.  Assuming lots of decoupling
> between each of the =
> islands=20
> and the common ground plane the jump in coupling
> between lines  would be =
> 
> greatly suppressed.
> 
> Regards,
> 
> 
> Steve.
> 
> At 11:00 AM 1/10/2005 -0800, Ahmad Fallah wrote:
> >Hi Steve,
> >
> >I have repeated Doug's experiment with a modified
> fixture where an=20
> >additional trace (victim) was added near (~1 cm)
> the "signal" line for=20
> >X-talk measurements.  I have measured a 10-fold
> increase in x-talk=20
> >amplitude in going from Case 1 to Case 2.
> >
> >Case 1: the offending and victim lines are both
> drawn over a solid =
> return=20
> >plane.
> >Case 2: the offending and victim lines are both
> drawn over the cut in =
> the=20
> >return plane
> >
> >Regards,
> >
> >Oscar
> >
> >
> >
> >steve weir <weirsp@xxxxxxxxxx> wrote:
> >
> >Lee, the 5cm is the length of the break. The break
> is only about =
> 20-50mils
> >wide. Hit the link and scroll to Figure 3. In
> Doug's test set-up, both =
> of
> >the two planes have been broken. Now, If one cares
> to do a crosstalk =
> test,
> >it looks like Doug could modify his fixture rather
> easily to do that. =
> In
> >the vicinity of the break, the multiple line
> coupling, including =
> between
> >members of a diff pair jumps.
> >
> >
> >
> >
> >
> >If you want to perform an entertaining experiment,
> take a diff pair, or
> >just one active driver and a quiet line and route
> them over a narrow, =
> and
> >short break, say 0.25" by 0.02" and take four port
> S parameter
> >measurements. Take another pair and do likewise,
> but keep extending the
> >length of the slot, ie perpendicular to the traces
> by a factor of 2 =
> with
> >each test. Even though the width of the gap is
> short, by the time that
> >slot becomes an inch or two long the band of
> frequencies where coupling =
> is
> >fairly strong will be pretty wide.
> >
> >http://emcesd.com/tt2005/tt010105.htm
> >
> >Regards,
> >
> >Steve
> >
> >
> >At 04:30 PM 1/9/2005 -0800, Lee Ritchey wrote:
> > >Just noticed that you call a 5 cm break
> relatively small. Does that =
> mean
> > >5 cm in width?
> > >
> > >Lee W. Ritchey
> > >Speeding Edge
> > >P. O. Box 2194
> > >Glen Ellen, CA 95442
> > >Phone- 707-568-3983
> > >FAX- 707-568-3504
> > >
> > >I just used the energy it took to be angry to
> write some blues.
> > >Count Basie
> > >
> > >
> > > > [Original Message]
> > > > From: Doug Smith
> > > > To: SI-List
> > > > Date: 1/8/2005 5:23:26 PM
> > > > Subject: [SI-LIST] risetime effects of plane
> breaks
> > > >
> > > > I think most of us know not to route signals
> over plane breaks on =
> PWBs
> > > > as all kinds of bad things can happen when
> this occurs in a =
> layout.
> > > > But, how do you convince co-workers or your
> boss that a new design
> > > > needs to avoid doing this even if added
> expense or project delay =
> is
> > > > required? Experimental data can be the key and
> this month my =
> Technical
> > > > Tidbit shows what happens to signal risetime
> if the signal crosses =
> a
> > > > plane break.
> > > >
> > > > Crossing Ground Plane Breaks - Part 4
> > > > Risetime Effects on Signals
> > > >
> > > > Abstract: Signals that cross ground plane
> breaks on printed wiring
> > > > boards (PWBs) experience degradation as well
> as cause EMI =
> problems.
> > > > Significant degradation of signal risetime is
> shown to occur, even
> > > > with a relatively small ground break of five
> cm at risetimes on =
> the
> > > > order of 300 ps.
> > > >
> > > > The link to the article is the picture of the
> experimental test =
> setup
> > > > at the bottom of the home page at
> http://emcesd.com .
> > > >
> > > > Doug
> > > > --
> > > >
>
-------------------------------------------------------
> > > > ___ _ Doug Smith
> > > > \ / ) P.O. Box 1457
> > > > =3D=3D=3D=3D=3D=3D=3D=3D=3D Los Gatos, CA
> 95031-1457
> > > > _ / \ / \ _ TEL/FAX: 408-356-4186/358-3799
> > > > / /\ \ ] / /\ \ Mobile: 408-858-4528
> > > > | q-----( ) | o | Email: doug@xxxxxxxxxx
> > > > \ _ / ] \ _ / Website: http://www.dsmith.org
> > > >
>
-------------------------------------------------------
> > > >
> > > >
>
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> > > > To unsubscribe from si-list:
> > > > si-list-request@xxxxxxxxxxxxx with
> 'unsubscribe' in the Subject =
> 
=== message truncated ===



        
                
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