De nada! -------------------------------------------------- From: "Grasso, Charles" <Charles.Grasso@xxxxxxxxxxxx> Sent: Tuesday, September 27, 2011 3:10 PM To: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>; "steve weir" <weirsi@xxxxxxxxxx>; <si-list@xxxxxxxxxxxxx> Subject: [SI-LIST] Re: Routing differential lines as single ended traces ? > Thank you Lee! > > Best Regards > Charles Grasso > Compliance Engineer > Echostar Communications > (w) 303-706-5467 > (c) 303-204-2974 > (t) 3032042974@xxxxxxxxx > (e) charles.grasso@xxxxxxxxxxxx > (e2) chasgrasso@xxxxxxxxx > > > -----Original Message----- > From: Lee Ritchey [mailto:leeritchey@xxxxxxxxxxxxx] > Sent: Monday, September 26, 2011 4:50 PM > To: Grasso, Charles; steve weir; si-list@xxxxxxxxxxxxx > Subject: Re: [SI-LIST] Re: Routing differential lines as single ended > traces ? > > Charles, > > I knew someone would ask that question! I usually design stackups with 4 > mils of laminate between the stripline layer and its plane. When I do > that, > a 10 mil edge to edge separation results in one trace diminishing the > impedance of its neighbor by about 1%. That's not a big drop and 10 mil > separation has not turned out to be a problem for routing the board. > > As you can see, there is a judgment call to be made here. > > 5% would be half the entire impedance error budget we allow and 10% would > be > all of it. > > Hope this helps. > > lee > > -------------------------------------------------- > From: "Grasso, Charles" <Charles.Grasso@xxxxxxxxxxxx> > Sent: Monday, September 26, 2011 1:04 PM > To: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>; "steve weir" > <weirsi@xxxxxxxxxx>; <si-list@xxxxxxxxxxxxx> > Subject: [SI-LIST] Re: Routing differential lines as single ended traces ? > >> Hello Lee - How much interaction is too much? 1% 5% - 10%?? >> >> >> Best Regards >> Charles Grasso >> Compliance Engineer >> Echostar Communications >> (w) 303-706-5467 >> (c) 303-204-2974 >> (t) 3032042974@xxxxxxxxx >> (e) charles.grasso@xxxxxxxxxxxx >> (e2) chasgrasso@xxxxxxxxx >> >> -----Original Message----- >> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] >> On Behalf Of Lee Ritchey >> Sent: Monday, September 26, 2011 10:11 AM >> To: steve weir; si-list@xxxxxxxxxxxxx >> Subject: [SI-LIST] Re: Routing differential lines as single ended traces >> ? >> >> I always route differential pairs to a "not closer than" rule. This >> guarantees that there will be no unwanted interaction such as one line >> driving the impedance of the other down. I have seen no cases where this >> has resulted in a lack of board space for routing. Perhaps there are >> some >> somewhere. >> >> >> I arrive at the "not closer than" rule by using a field solver to >> determine >> how close the two lines can be without adversely affecting the impedance >> of >> either one. >> >> When you use the "not closer than" rule all traces are single ended and >> usually 50 ohm. That means you don't need to add complexity to bare >> board >> test by insisting on a 100 ohm diff pair measurement. Makes life much >> easier. The drivers always wanted to see 50 ohm lines any way. >> >> Lee >> >> -------------------------------------------------- >> From: "steve weir" <weirsi@xxxxxxxxxx> >> Sent: Sunday, September 25, 2011 7:22 PM >> To: <si-list@xxxxxxxxxxxxx> >> Subject: [SI-LIST] Re: Routing differential lines as single ended traces >> ? >> >>> On 9/25/2011 6:57 PM, Low Jerry wrote: >>>> Hi, >>>> I recently came across a validation platform where the LVDS >>>> differential >>>> lines are routed as single ended traces traces instead of tightly >>>> coupled >>>> differential pairs. The motivation I found was so that they could use >>>> each >>>> of the pairs as single ended traces when needed as well. When I probed >>>> deeper it seems like the person who proposed this scheme has left. So I >>>> would like to seek help here on some clarification >>>> >>>> - Will a scheme like this impact the performance of the >>>> differential >>>> pair >>> The scheme itself will not. >>>> ? Since I understand that differential routing is more immune to >>>> noise. >>> That is largely a myth. There are only a few very special circumstances >>> where tightly coupled pairs exhibit better noise rejection to PCB trace >>> noise aggressors than reasonably routed, loosely coupled pairs. >>>> - What are the considerations/feasiblity studies that need to be >>>> done >>>> before implementing a scheme like this ? >>> They are the same as with any signal integrity requirements. The scheme >>> doesn't impose anything extra. It does remove some headaches. >>>> - Since this is a validation platform what measures can be taken >>>> ensure >>>> that the performance seen are similar to a production platform if >>>> the >>>> production platform is routed in differential. >>> Homework gets done or it doesn't. >>> >>> Steve >>>> >>>> Thanks in advance for the feedbacks. Have a great day. >>>> >>>> >>>> ------------------------------------------------------------------ >>>> 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 >> >> >> >> >> ------------------------------------------------------------------ >> 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