RE: [SI-LIST] : Stack up

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From: Ronald E. Nikel (renikel@tricn.com)
Date: Thu Feb 24 2000 - 11:21:56 PST


Hmmm,

Well I would suggest developing a set of routing rules that constrain the
spacing between different groups and pairs of signals such that crosstalk
does not occur and for those instances when spacing must be violated write
crosstalk checking rules so that the router gets a DRC rule once the voltage
induced exceeds a threshold limit set by you.

I routinely do this on systems in which I am running around hundreds of
diffpairs running at lvds type levels running greater than a 2Gb/s and PECL
and LVTTL signals are running around on the same layer. CCT has a great set
of crosstalk checking DRC's which allow the autorouter to go off and
correct/check crosstalk violations if spacing is reduced in areas of
connectors and BGA's.

Ron.

-----Original Message-----
From: owner-si-list@silab.eng.sun.com
[mailto:owner-si-list@silab.eng.sun.com]On Behalf Of Scott McMorrow
Sent: Wednesday, February 23, 2000 10:24 AM
To: renikel@ix.netcom.com
Subject: Re: [SI-LIST] : Stack up

Lee is correct. A simulator with the ability to perform
crosstalk checks on these layers would be of great
benefit.

regards,

scott

--
Scott McMorrow
Principal Engineer
SiQual, Signal Quality Engineering
18735 SW Boones Ferry Road
Tualatin, OR  97062-3090
(503) 885-1231
http://www.siqual.com

Lee Ritchey wrote:

> I'm trying to say that PECL and LVDS can be routed on the same layer and achieve adequate isolation. Forcing separate layers for each technology complicates the design and potentially raises the cost > unnecessarily. > > Lee > > sweir wrote: > > > Lee, > > > > Agreed. But moving the PECL away from a layer adjacent to the LVDS > > guarantees the separation. Are you suggesting a better stackup, or more > > questions before making a recommendation? > > > > Regards, > > > > Steve. > > At 07:46 AM 2/22/00 -0800, you wrote: > > >The PECL clocks don't need their own layer. Just make sure that the > > >spacing between them and LVDS is large enough that the coupling is within spec. > > > > > >sweir wrote: > > > > > > > Iulian, > > > > > > > > If you need Sig5 for LVDS, get the PECL clocks out of Sig6. Also, do you > > > > have a substantial number or single-ended signals? If so, you need to take > > > > proper care to avoid crosstalk between those and the LVDS signals as well. > > > > > > > > Will the PECL clocks fit on signal bottom? If so, then I suggest the > > > > following as a symmetric stack-up that will reduce your crosstalk problems > > > > between the PECL clocks and LVDS: > > > > > > > > Signal top > > > > 1.8 > > > > Gnd > > > > S1 > > > > S2 > > > > Gnd > > > > S3 > > > > S4 > > > > Gnd > > > > S5 > > > > S6 > > > > Gnd > > > > 3v3 > > > > Signal Bottom -Pecl clocks > > > > > > > > Regards, > > > > > > > > Steve. > > > > At 11:23 AM 2/21/00 -0800, you wrote: > > > > > > > > >Hi > > > > > > > > > >I'm listening to this list for some time now and I would like to ask your > > > > >opinion on a stack-up I'm working on. > > > > > It is a board with 4x64 pairs of LVDS signals, 77.76 MHz > > > clock, high > > > > >speed(777.6 Hb/s). > > > > > > > > > > I came up with a 14 layers that looks like that: > > > > > > > > > >Signal top fanout, some analog power > > > > >1.8V > > > > >Gnd > > > > >Sig1 LVDS > > > > >Sig2 LVDS > > > > >Gnd > > > > >Sig3 LVDS > > > > >Sig4 LVDS > > > > >Gnd > > > > >Sig5 LVDS > > > > >Sig6 PECL clocks > > > > >3.3V > > > > >Gnd > > > > >Signal bottom fanout > > > > > > > > > > I'll be using 1.6 mil core for my high speed cap. > > > > > I would gladly use less layers, but I'm being forced by the HS3 > > > > >connectors. > > > > > > > > > > I would really appreciate your opinion. > > > > > > > > > > > > > > > > > > > >Thanks, > > > > > > > > > >Iulian Ungureanu > > > > >PCB Designer > > > > >PMC-Sierra,Inc. > > > > >Iulian_Ungureanu@pmc-sierra.com > > > > >http://www.pmc-sierra.com > > > > >Voice:(604)415-6053 Ext.2586 > > > > >Fax:(604)415-6206 > > > > > > > > > > > > > > > > > > > >**** To unsubscribe from si-list or si-list-digest: send e-mail to > > > > >majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE > > > > >si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. > > > > >si-list archives are accessible at http://www.qsl.net/wb6tpu > > > > >**** > > > > > > > > **** To unsubscribe from si-list or si-list-digest: send e-mail to > > > majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE > > > si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. > > > > si-list archives are accessible at http://www.qsl.net/wb6tpu > > > > **** > > > > > > > > > > > > > > >**** To unsubscribe from si-list or si-list-digest: send e-mail to > > >majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE > > >si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. > > >si-list archives are accessible at http://www.qsl.net/wb6tpu > > >**** > > > > **** To unsubscribe from si-list or si-list-digest: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. > > si-list archives are accessible at http://www.qsl.net/wb6tpu > > **** > > **** To unsubscribe from si-list or si-list-digest: send e-mail to majordomo@silab.eng.sun.com. In the BODY of message put: UNSUBSCRIBE si-list or UNSUBSCRIBE si-list-digest, for more help, put HELP. > si-list archives are accessible at http://www.qsl.net/wb6tpu > ****

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