[SI-LIST] Re: risetime effects of plane breaks
- From: "Grasso, Charles" <Charles.Grasso@xxxxxxxxxxxx>
- To: "'Chris.Cheng@xxxxxxxxxxxx'" <Chris.Cheng@xxxxxxxxxxxx>, 'SI-List ' <si-list@xxxxxxxxxxxxx>
- Date: Tue, 11 Jan 2005 11:28:35 -0700
Hi Chris - The simulation was very similar to Dougs
that is: a trace over a ground with a partial break
under the trace. I did not study the stripline case.
Best Regards
Charles Grasso
Senior Compliance Engineer
Echostar Communications Corp.
Tel: 303-706-5467
Fax: 303-799-6222
Cell: 303-204-2974
Pager/Short Message: 3032042974@xxxxxxxx
Email: charles.grasso@xxxxxxxxxxxx;
Email Alternate: chasgrasso@xxxxxxxx
-----Original Message-----
From: Chris Cheng [mailto:Chris.Cheng@xxxxxxxxxxxx]
Sent: Monday, January 10, 2005 9:04 PM
To: 'SI-List '
Subject: [SI-LIST] Re: risetime effects of plane breaks
Thanks Charles,
However, when you say it get worst, is it for the stripline case or
microstrip like Doug did ? In the later case, we seem to agree no one will
or should do it in real life. Are saying the EMI still get worst in
stripline case with a solid ground on one side ?
-----Original Message-----
From: Charles Grasso
To: cpad@xxxxxxxxx; SI-List
Sent: 1/10/2005 8:47 PM
Subject: [SI-LIST] Re: risetime effects of plane breaks
In another life I ran such a simulation based on a trace crossing a split
and looked at the radiated profile. The radiated profile was *significantly*
worse. I added a capacitor and found that although most of the emissions
dropped dramatically there was always one resonance peak that was an
absolute screamer. This resonance varied
with
the inductance seen by the signal due to the split and the capacitance
across the split.
Cross splits with caution.
On Mon, 10 Jan 2005 19:20:01 -0800, Chris Padilla <cpad@xxxxxxxxx>
wrote:
> I'd like to see the EMI implications (radiation) of crossing a split
in a
> plane. What is okay for SI may not be so for EMI....
>
> ----->Chris
>
> At 07:05 PM 1/10/2005 -0800, Chris Cheng wrote:
>> I see, but I will be more interested in real life application where
>> there is
>> a stripline crossing a cut power plane with a solid ground on the
other
>> side. They exit in really world and I for one would like to know at
what
>> point it will degrade the performance to an unacceptable level. 300ps
>> edge ?
>> 100ps edge ? 20 mil gap ? 100 mil gap ? etc. My experience suggest
they
>> can
>> work up to a reasonable speed (at least to the point where you start
>> thinking maybe differential signal makes more sense due to other
design
>> considerations).
>>
>> -----Original Message-----
>> From: steve weir [mailto:weirsp@xxxxxxxxxx]
>> Sent: Monday, January 10, 2005 6:56 PM
>> To: Chris.Cheng@xxxxxxxxxxxx; SI-List
>> Subject: Re: [SI-LIST] Re: risetime effects of plane breaks
>>
>>
>> Chris, because Zontar is listening.
>>
>> Doug set-up a nice physics experiment that nicely demonstrates the
bad
>> things that happen when crossing a split with no other solid plane in
>> the
>> vicinity. For my money, it aptly demonstrates several important
effects
>> and precisely why it would be a bad idea to put into practice.
>>
>> Various people from Lee to Dan, Arpad, and yourself have pointed-out
>> that
>> under appropriate circumstances crossing a cut is not automatically
the
>> end
>> of the world. I don't think anyone proposes that crossing cuts like
>> Doug
>> has set-up comes without substantial consequences.
>>
>> Best Regards,
>>
>>
>> Steve.
>>
>> At 06:30 PM 1/10/2005 -0800, Chris Cheng wrote:
>> >Sorry but I have to ask, why would anyone will run a single edge
>> signal at
>> >300ps as microstrip across a cut ground reference plane ? I can
>> understand
>> >if it is a stripline with a solid ground on one reference and cut
power
>> >planes on the other (which I have do a lot, not by choice though).
What
>> >application will call for such routing ?
>> >
>> >-----Original Message-----
>> >From: steve weir [mailto:weirsp@xxxxxxxxxx]
>> >Sent: Monday, January 10, 2005 12:28 PM
>> >To: arpad.muranyi@xxxxxxxxx; SI-List
>> >Subject: [SI-LIST] Re: risetime effects of plane breaks
>> >
>> >
>> >Arpad, a jump from 10-14% coupling up to 30% or so is still very
>> >significant. Phase match and other common mode issues should not be
>> >dismissed when attempting to cross a split. The first choice should
be
>> >don't do it. But if one must, then do so with care.
>> >
>> >Regards,
>> >
>> >
>> >Steve.
>> >At 11:41 AM 1/10/2005 -0800, Muranyi, Arpad 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=3
D=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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