[SI-LIST] Re: Routing Signals Between PWB Layers - Part 2
- From: "Nima Lotfi" <lnima@xxxxxxxxxx>
- To: <istvan.novak@xxxxxxx>
- Date: Thu, 4 May 2006 12:34:06 -0400
Istvan,
I'm looking for a tool to simulate board resonance. Did you use
simulation software to confirm the frequency of modal resonance of the
PCB planes? If so can tell me what tool you've used.
Thanks,=20
______________________=20
Nima Lotfi, P. Eng=20
Digital Hardware Design Engineer=20
Nortel
758-7786 ESN=20
(403) 769-7786 Direct=20
(403) 769-5350 Fax=20
LNima@xxxxxxxxxxxxxxxxxx=20
> -----Original Message-----
> From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
> On Behalf Of Istvan Novak
> Sent: Thursday, May 04, 2006 7:10 AM
> To: GStokes@xxxxxxxxx
> Cc: SI-List
> Subject: [SI-LIST] Re: Routing Signals Between PWB Layers - Part 2
>=20
> Geoff, Doug,
>=20
> This example nicely shows the importance of proper power distribution
> design.
>=20
> The emission peaks correspond to the modal resonances of the PCB
planes.
> As Doug points out in the article, moving the planes closer would
reduce
> the
> emission about proportionally. However, if one wants to stay with a
> four-layer
> construction, reducing the plane separation is not a viable solution:
it
> would
> either result in an unmanageably thin board, or if we add the
tickhness
> back to
> the top/bottom dielectrics, in a dramatically reduced routing density.
>=20
> Nearby grounding vias would help, but in practical cases the two
planes
> are at
> different DC potentials, so it must be a bypass capacitor rather than
a
> stitching
> via. A single bypass capacitor will do little in the hundreds of MHz
> frequency range,
> even if it serves only one signal. Also, if we have wide busses
instead
> of a single
> trace, trying to provide a return path locally to all of the layer
> transitions becomes
> much harder to implement.
>=20
> A more realistic and straightforward solution is to design the
> power-distribution
> network in such a way that it does not exhibit large resonances. In
> multi-layer
> boards, where we may also have ground-ground planes creating such
> cavities, the
> solution is stitching vias, but not necessarily near the layer
> transitions. We would
> just need to make sure that the large resonating cavity is broken up
to
> sufficiently
> small blocks such that the lowest resonance frequency is safely above
> the highest
> frequency of excitation.
>=20
> Regards,
>=20
> Istvan Novak
> SUN Microsystems
>=20
>=20
>=20
> Geoff Stokes wrote:
>=20
> >Hi Doug
> >
> >In this experiment, you appear to have no plane vias adjacent to the
> >signal vias. What would happen if a few plane vias were added around
> >the transitions and fairly close by?
> >
> >Geoff Stokes
> >Systems Engineer
> >Zetex Semiconductors plc
> >Zetex Technology Park
> >Chadderton
> >Oldham
> >OL9 9LL
> >UK
> >=3D20
> >+44-161-622-4857
> >www.zetex.com
> >www.zetex.cn
> >=3D20
> >
> >=3D20
> >-----Original Message-----
> >From: si-list-bounce@xxxxxxxxxxxxx
[mailto:si-list-bounce@xxxxxxxxxxxxx]
> >On Behalf Of Doug Smith
> >Sent: 03 May 2006 21:41
> >To: SI-List
> >Subject: [SI-LIST] Routing Signals Between PWB Layers - Part 2
> >
> >Hi All,
> >
> >I have been writing and recording again and have posted part 2 of
my=3D20
> >article on signals that change layers in a PWB.
> >
> >Abstract: Printed wiring board, PWB, signal paths must often
change=3D20
> >layers in a board stackup. Under some conditions this can cause=3D20
> >problems. An emissions example is used to illustrate the
conditions=3D20
> >where changing layers can cause problems.
> >
> >The link to the article is the picture of the emissions plot at
the=3D20
> >bottom of the home page at http://emcesd.com .
> >
> >There is also an audio discussion of this article on my podcast
site:=3D20
> >http://emcesd-podcast.com where the direct link to the article is:
> >
> >http://emcesd-podcast.com/2006/may/2006-0503.mp3
> >
> >Can't download mp3 files? Download the following instead:
> >
> >http://emcesd-podcast.com/2006/may/2006-0503.dcs
> >
> >After download, change the extension from .dcs to .mp3 and the
file=3D20
> >will then be able to play on most computers. Since the last =
HFNews=3D20
> >there have been two new podcasts posted.
> >
> >Doug
> >--=3D20
> >-------------------------------------------------------
> > ___ _ Doug Smith
> > \ / ) P.O. Box 1457
> > =3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D=3D3D 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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