... which is the fundamental point, isn't it? <rant> "How much impedance variance is acceptable?" is not an answerable question, if the circuit isn't specified and the analysis isn't done. Let me say that again - the original question is not answerable, based on the data provided. You want a rule of thumb for average situations? Sure - here you go. You want to know if this rule will work in your situation? No one knows. And while I'm on a rant, allow me to pose a few more unanswerable questions: 1. What's 2 + ? 2. Which came first, the chicken or the egg? 3. Why does the helicopter? 4. What do you get when you cross an elephant with a rhinoceros? I maintain that each of those questions is just as answerable as the impedance tolerance question, with the exception of #4, which can be answered. The answer to that question is "elephino" (pronounced "elef eye no"). </rant> Todd. -- Todd Westerhoff VP, Software Products SiSoft 6 Clock Tower Place, Suite 250 Maynard, MA 01754 (978) 461-0449 x24 twesterh@xxxxxxxxxx www.sisoft.com "It doesn't matter what you've heard Impossible is not a word It's just a reason For someone not to try" -Kutless -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On Behalf Of DAVID CUTHBERT Sent: Thursday, January 05, 2012 10:37 AM To: Loyer, Jeff Cc: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Impedance Controlled Board Production Vs Normal Board Production And you can simulate your circuit to explore how much T-line impedance mismatch it can tolerate. Dave Cuthbert On Jan 5, 2012 8:24 AM, "Loyer, Jeff" <jeff.loyer@xxxxxxxxx> wrote: > 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. Center St. #211 > Reno, NV 89501 > www.ipblox.com > > (775) 299-4236 Business > (866) 675-4630 Toll-free > (707) 780-1951 Fax > > All contents Copyright (c)2012 IPBLOX, LLC. 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