+/- 10% of what nominal baseline impedance? Scott McMorrow Teraspeed Consulting Group LLC 121 North River Drive Narragansett, RI 02882 (401) 284-1827 Business (401) 284-1840 Fax http://www.teraspeed.com Teraspeed® is the registered service mark of Teraspeed Consulting Group LLC On 1/6/2012 2:45 AM, Rajan Hansa wrote: > guys don't you think that if impedance variation is under 10 % then we > shouldn't worry much about it. > My analogy is that for 10 % impedance variation return loss is more than > -20 db and effect of this return loss is less than 0.5 db on insertion loss > which is quite acceptable when we compare it with losses due to attenuation > on insertion loss. > > Correct me if i am wrong or am I missing something ??? > > > On Fri, Jan 6, 2012 at 3:51 AM, David Siadat > (dsiadat)<dsiadat@xxxxxxxxx>wrote: > >> I agree with Aubrey's statement. >> If you do not specify Impedance Control design (possibly for each >> layer), then traces on the layer with not enough copper material will >> have more than +/-10% impedance variations even if you specified its >> characteristic impedance in your request! >> >> -David >> >> -----Original Message----- >> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] >> On Behalf Of Aubrey K Sparkman >> Sent: Thursday, January 05, 2012 11:49 AM >> To: Michael Greim >> Cc: Ken Cantrell; Mikhail Matusov; si-list@xxxxxxxxxxxxx >> Subject: [SI-LIST] Re: Impedance Controlled Board Production Vs Normal >> Board Production >> >> Michael, >> >> A fab house only has to meet the specifications in the contract. I >> would >> say the company got what they specified. >> >> My point was that an impedance only specification is often inadequate. >> >> >> Aubrey >> >> On 1/5/12 1:16 PM, "Michael Greim"<mgreim001@xxxxxxxxx> wrote: >> >>> There needs to be an interlock between the fab house and >>> design team. If different construction methods are employed >>> and they aren't checked then offending engineer is really getting >>> what they deserve. Check twice, or more, and cut once is >>> a lesson often learned quite painfully. >>> -Michael >>> >>> On Thu, Jan 5, 2012 at 10:27 AM, Aubrey K Sparkman< >>> asparky@xxxxxxxxxxxxxxxxxxxxxxxx> wrote: >>> >>>> Ken, >>>> >>>> What you say is true. What hasn't been mentioned is the risk behind >>>> specifying only the impedance. >>>> >>>> Mikhail makes a good point about specifying the board stackup >>>> CONSTRUCTION. I have seen failures when impedance only was >> specified. >>>> The design went out as a dual stripline with 4 mil cores between the >>>> signals and their respective reference planes and a 12 mil prepreg >>>> between >>>> the two signal layers. The pcb house was given permission to use 5 >> mil >>>> cores since they didn't have 4 mil cores in stock. For the 2nd >> build, >>>> the >>>> pcb house outsourced the design to another house which used 8 mil >> cores. >>>> Trace widths and prepreg thickness were adjusted appropriately so >> that >>>> both board thickness and impedance specifications were met. >>>> >>>> Any guesses about the performance of the boards in the 2nd build? >>>> >>>> Aubrey Sparkman >>>> SparkRight Solutions >>>> >>>> On 1/5/12 10:36 AM, "Ken Cantrell"<Ken.Cantrell@xxxxxxxxxxxxxxxx> >>>> wrote: >>>> >>>>> Mikhail, >>>>> I'm not disputing anything that you said, just pointing out that: >>>>> "If I, as a designer, know the process and materials used by the >>>>> particular >>>>> manufacturer >>>>> well enough" is a big If. That's a mature designer talking. Not >>>>> something >>>>> a relative beginner would know or even be able to accomplish. >>>>> >>>>> 2cents >>>>> Ken >>>>> >>>>> -----Original Message----- >>>>> From: si-list-bounce@xxxxxxxxxxxxx >>>>> [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Mikhail Matusov >>>>> Sent: Thursday, January 05, 2012 9:05 AM >>>>> To: si-list@xxxxxxxxxxxxx >>>>> Subject: [SI-LIST] Re: Impedance Controlled Board Production Vs >> Normal >>>>> Board Production >>>>> >>>>> >>>>> I don't think those who responded understood the question correctly. >> I >>>>> think >>>>> the OP was asking whether some degree of impedance control can be >>>> achieved >>>>> by precisely specifying the board's stackup, width of the traces, >> and >>>>> process tolerances without explicitly asking the manufacturer to >>>> control >>>>> impedance. For some applications it just boils down to the cost. If >> I, >>>> as >>>>> a >>>>> designer, know the process and materials used by the particular >>>>> manufacturer >>>>> well enough I should be able to specify the board in such a way that >>>> the >>>>> impedance will end up in the right ballpark. In fact, I use this >>>> method >>>>> for >>>>> non-critical designs. >>>>> >>>>> ======================= >>>>> Mikhail Matusov >>>>> Senior Hardware Design Engineer >>>>> Square Peg Communications >>>>> Tel.: +1 (613) 271-0044 ext.231 >>>>> Fax: +1 (613) 271-3007 >>>>> http://www.squarepeg.ca >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> >>>>> ----- Original Message ----- >>>>> From: "Loyer, Jeff"<jeff.loyer@xxxxxxxxx> >>>>> To:<si-list@xxxxxxxxxxxxx> >>>>> Sent: Thursday, January 05, 2012 10:22 AM >>>>> Subject: [SI-LIST] Re: Impedance Controlled Board Production Vs >> Normal >>>>> Board >>>>> Production >>>>> >>>>> >>>>>> Perhaps I'm the only one who is finding it ironic that, on a >> "Signal >>>>>> Integrity" reflector list, "Impedance Controlled" isn't considered >>>>>> "Normal". I haven't had the luxury of not specifying impedance >>>> control >>>>>> since a small 33MHz PCI card design, many years ago. >>>>>> >>>>>> I'm afraid Jayasuryan that you won't find the answer you're >> looking >>>> for >>>>>> on >>>>>> an e-mail thread, or it is going to be a long, drawn out, painful >>>>>> affair. >>>>>> You have a lot of work to do to understand what impedance control >> is >>>> and >>>>>> how it relates to signal integrity. I would recommend starting >> with >>>> the >>>>>> books that have been listed many times on this list. You can also >>>>>> search >>>>>> the archives for "impedance control" to find discussions about >>>> different >>>>>> opinions on how much is enough. >>>>>> >>>>>> Good luck in the new year, >>>>>> Jeff Loyer >>>>>> >>>>>> -----Original Message----- >>>>>> From: si-list-bounce@xxxxxxxxxxxxx >>>> [mailto:si-list-bounce@xxxxxxxxxxxxx >>>> ] >>>>>> On Behalf Of steve weir >>>>>> Sent: Monday, January 02, 2012 6:23 AM >>>>>> To: si-list@xxxxxxxxxxxxx >>>>>> Subject: [SI-LIST] Re: Impedance Controlled Board Production Vs >>>> Normal >>>>>> Board Production >>>>>> >>>>>> Suppose as you like. Hope as you might. What you don't contract >> is >>>> not >>>>>> guaranteed. >>>>>> >>>>>> Steve. >>>>>> On 1/2/2012 5:56 AM, Jayasuryan KG wrote: >>>>>>> Dear Experts, >>>>>>> >>>>>>> >>>>>>> >>>>>>> Happy New Year!! >>>>>>> >>>>>>> >>>>>>> >>>>>>> I have question regarding the impedance controlled board >> production! >>>>>>> Is there any special process to produce impedance controlled >> board >>>>>>> rather than the normal production? >>>>>>> >>>>>>> >>>>>>> >>>>>>> Suppose if I go with normal production for a impedance >> controlled >>>>>>> board >>>>>>> (the design has been done to meet the impedance) what are the >>>> possible >>>>>>> issues can happen? >>>>>>> >>>>>>> >>>>>>> >>>>>>> Looking for your immediate response. Thanks in advance. >>>>>>> >>>>>>> >>>>>>> >>>>>>> Best Regards, >>>>>>> >>>>>>> - Jayasuryan >>>>>>> >>>>>>> >> ------------------------------------------------------------------ >>>>>>> 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. 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All Rights Reserved. >>>>>> This e-mail may contain confidential material. >>>>>> If you are not the intended recipient, please destroy all records >> and >>>>>> notify the sender. >>>>>> >>>>>> ------------------------------------------------------------------ >>>>>> 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 >>>>>> >>>>>> >>>>>> >>>>> ------------------------------------------------------------------ >>>>> 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 >>>>> >>>>> >>>>> >>>> >>>> ------------------------------------------------------------------ >>>> 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 >>>> >>>> >>>> >>> >>> -- >>> -Michael. >>> >>> We will either find a way or make one - Hannibal >>> >>> In the middle of every difficulty lies opportunity - Al Einstein >>> >>> If you think you can do something or you think >>> you can't, in both cases you are probably right - H Ford >>> >>> If you're not getting the results you want with the >>> current approach, move on and try something else. - A. Fleischmann >>> >>> >>> ------------------------------------------------------------------ >>> 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 >> >> >> ------------------------------------------------------------------ >> 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 > > ------------------------------------------------------------------ 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