[SI-LIST] Re: Coupling Between Adjacent Capacitors
- From: "Brad Brim" <bradb@xxxxxxxxxxx>
- To: "'steve weir'" <weirsi@xxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Tue, 12 Jul 2011 16:00:36 -0700
hey Steve,
Isn't most of the coupling through the mounting structure and not the
components themselves?
One should expect more coupling if the caps for a diff pair channel are two
adjacent devices in a cap array component. More coupling from closer
proximity of mounting structures as well as more coupling between the two
more closely spaced devices.
cheers,
-Brad
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of steve weir
> Sent: Tuesday, July 12, 2011 3:45 PM
> To: si-list@xxxxxxxxxxxxx
> Subject: [SI-LIST] Re: Coupling Between Adjacent Capacitors
>
> Coupling between DC blocking capacitors can be significant,
> and for any high speed link the coupling is almost all
> magnetic. Play with a field solver and you can see that
> turning one capacitor 90 degrees greatly reduces this
> coupling. It also screws up the path symmetry, and burns up
> usually precious PCB real-estate. If you turn both
> capacitors by 90 degrees so that the forward signal paths
> point away from each other, you get low coupling and retain
> path symmetry, but burn-up even more real-estate than turning
> just the one.
>
> Steve.
> On 7/12/2011 9:42 AM, Brian Rautio wrote:
> > I agree with Rick, but want to point out that it's also a
> function of the potential on the capacitors. If we imagine
> two parallel plate capacitors side by side, with the planes
> of the plates co-linear, there is going to be significantly
> more coupling between them in odd mode than even mode, and
> conversely, even mode is more likely to couple with the rest
> of the circuit.
> >
> > As far as the role orientation plays, it's no more
> complicated than e-fields going from high potential to low
> potential. If you know the geometry and potentials, the best
> position and orientation should be self evident. If you only
> know the geometry, there's a number of electromagnetic
> simulators that can plot e-field lines directly.
> >
> > Brian
> >
> >
> > -----Original Message-----
> > From: si-list-bounce@xxxxxxxxxxxxx
> [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of Rick Collins
> > Sent: Tuesday, July 12, 2011 11:43 AM
> > To: si-list@xxxxxxxxxxxxx
> > Subject: [SI-LIST] Re: Coupling Between Adjacent Capacitors
> >
> > If capacitors were just simple plates separated by large air gaps,
> > the parasitic effects might be more noticeable, but any cap you buy
> > is either a series of plates with very small spacings like
> > multi-layer ceramic caps, or made of layers rolled up. The fringe
> > effects would be very small indeed and likely no more than the stray
> > capacitance of any components or traces on the board.
> >
> > That said, I'm sure you can find some situations where this could be
> > significant. For example radial ceramic caps are just one layer and
> > not very thin if I remember correctly. I expect they might have a
> > significant fringe field. But I haven't used one of those
> in over 15 years.
> >
> > Rick
> >
> >
> > At 11:22 AM 7/12/2011, Scuteri, Jeremy wrote:
> >> I have a question about coupling between adjacent
> capacitors and the
> >> sensitivity to their orientation. I have heard of turning
> inductors
> >> 90degrees to avoid magnetic coupling, but I did not think such a
> >> thing applied to capacitors. Maybe there could be some coupling of
> >> the fringe field if the caps are very close to each other. Has
> >> anyone experienced a sensitivity to the orientation of capacitors?
> >>
> >> Thanks,
> >> Jeremy Scuteri
> >>
> >>
> >> ------------------------------------------------------------------
> >> To unsubscribe from si-list:
> >> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the
> Subject field
> >>
> >> or to administer your membership from a web page, go to:
> >> //www.freelists.org/webpage/si-list
> >>
> >> For help:
> >> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> >>
> >>
> >> List technical documents are available at:
> >> http://www.si-list.net
> >>
> >> List archives are viewable at:
> >> //www.freelists.org/archives/si-list
> >>
> >> Old (prior to June 6, 2001) list archives are viewable at:
> >> http://www.qsl.net/wb6tpu
> >>
> > ------------------------------------------------------------------
> > To unsubscribe from si-list:
> > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the
> Subject field
> >
> > or to administer your membership from a web page, go to:
> > //www.freelists.org/webpage/si-list
> >
> > For help:
> > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> >
> >
> > List technical documents are available at:
> > http://www.si-list.net
> >
> > List archives are viewable at:
> > //www.freelists.org/archives/si-list
> >
> > Old (prior to June 6, 2001) list archives are viewable at:
> > http://www.qsl.net/wb6tpu
> >
> >
> >
> > -----
> > No virus found in this message.
> > Checked by AVG - www.avg.com
> > Version: 10.0.1390 / Virus Database: 1516/3760 - Release
> Date: 07/12/11
> > ------------------------------------------------------------------
> > To unsubscribe from si-list:
> > si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the
> Subject field
> >
> > or to administer your membership from a web page, go to:
> > //www.freelists.org/webpage/si-list
> >
> > For help:
> > si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
> >
> >
> > List technical documents are available at:
> > http://www.si-list.net
> >
> > List archives are viewable at:
> > //www.freelists.org/archives/si-list
> >
> > Old (prior to June 6, 2001) list archives are viewable at:
> > http://www.qsl.net/wb6tpu
> >
> >
> >
>
>
> --
> Steve Weir
> IPBLOX, LLC
> 150 N. Center St. #211
> Reno, NV 89501
> www.ipblox.com
>
> (775) 299-4236 Business
> (866) 675-4630 Toll-free
> (707) 780-1951 Fax
>
>
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
> or to administer your membership from a web page, go to:
> //www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>
> List technical documents are available at:
> http://www.si-list.net
>
> List archives are viewable at:
> //www.freelists.org/archives/si-list
>
> Old (prior to June 6, 2001) list archives are viewable at:
> http://www.qsl.net/wb6tpu
>
>
>
------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
or to administer your membership from a web page, go to:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List technical documents are available at:
http://www.si-list.net
List archives are viewable at:
//www.freelists.org/archives/si-list
Old (prior to June 6, 2001) list archives are viewable at:
http://www.qsl.net/wb6tpu
Other related posts:
