Here is a DesignCon2013 paper on the effect of nearby gnd via placement on HS SE and Diff Signals by: A. Jaze; B. Archambeault; and S. Connor. http://e.ubmelectronics.com/images/DesignCon2014/12-WA2_Paper_EffectofNearbyGroundVia.pdf Bert Simonovich > On Sep 8, 2014, at 3:35 AM, Leeyuyun <lee.home.61@xxxxxxxxx> wrote: > > Hi, Steve > Could you help explain >> I think that you are considering a high frequency problem in low >> frequency terms > I do not understand "in low frequency terms", could you help clarify it? > How to roughly evaluate cavity effect when stitching via close to signal vias? > Any white paper or material to show stitching via effect? > When I ask two parties to run two kinds of simulation, including only one > stitching vias and more stitching vias, the result from two parties is > different. One shows only one stitching is better, but another shows more > stitching vias better. How do I make decision which one is correct? > Thank you > Lee > >> steve weir <weirsi@xxxxxxxxxx> æ¼ 2014/9/8 ä¸å11:57 寫éï¼ >> >> It is neither. It is a description of the physics. Real engineering >> accounts for pertinent physics. >> >> Best Regards, >> >> >> Steve >>> On 9/7/2014 6:41 PM, leeritchey@xxxxxxxxxxxxx wrote: >>> This sounds like a bit of supposiition rather than real engineering. >>> >>> Sent from my HTC One⢠X, an AT&T 4G LTE smartphone >>> >>> ----- Reply message ----- >>> From: "steve weir" <weirsi@xxxxxxxxxx> >>> To: "Leeyuyun" <lee.home.61@xxxxxxxxx> >>> Cc: "si-list@xxxxxxxxxxxxx" <si-list@xxxxxxxxxxxxx> >>> Subject: [SI-LIST] Re: One stitching via or more vias is better for 25Gbps >>> application??? >>> Date: Sun, Sep 7, 2014 10:43 AM >>> >>> >>> I think that you are considering a high frequency problem in low >>> frequency terms. Stitch vias impact the cavity, and when they are in >>> close proximity to signal vias and traces, they affect wave modes near >>> those structures. Thinking about stitch vias and the cavities that they >>> traverse as though they are continuations of the TEM path that breaks at >>> a Z axis transition is not a good approximation. The Z axis signal >>> transition injects the signal energy into the cavity. The various >>> properties of the cavity: material, and geometry, including what vias >>> stitch the cavity surfaces together and where affects how that signal >>> energy propagates through the cavity in all directions. >>> >>> Steve >>>> On 9/7/2014 5:31 AM, Leeyuyun wrote: >>>> Hi, Steve >>>> But IL and RL should depend upon the distance / via pad size of signal via >>>> and gnd stitching via >>>> If only depend on capacitor vsd via, is the return path loop larger to >>>> create large inductance? >>>> Does it fit into 25Gbps application? >>>> Could you advise what is the benefit of case 1 and case 2? >>>> Thanks >>>> Lee >>>> >>>> >>>>> steve weir <weirsi@xxxxxxxxxx> æ¼ 2014/9/7 ä¸å6:11 寫éï¼ >>>>> >>>>> The statement is based on the idea that Vss stitching from bypass >>>>> capacitor Vss vias and IC Vss vias is adequate. The idea concludes that >>>>> explicit vias corresponding to signal or signal pair transitions are not >>>>> necessary. >>>>> >>>>> Steve >>>>>> On 9/7/2014 2:46 AM, Leeyuyun wrote: >>>>>> Stitching should be needed when gnd reference plane change >>>>>> I do not know why you said do not need any stitching vias >>>>>> I want to clarify my question as below >>>>>> # means stitching vias, * means signal vias, + means positive signal, - >>>>>> means negative signal >>>>>> 1. Only on stitching vias >>>>>> +++++++++++++++++*++++++++++ >>>>>> # >>>>>> --------------------------*---------------- >>>>>> 2. At least two stitching vias >>>>>> # >>>>>> ++++++++++++++++*+++++++++++ >>>>>> >>>>>> ------------------------*------------------ >>>>>> # >>>>>> For each structure, what is theory behind? What is your recommendation >>>>>> for stitching via structure in the 25Gbps structure? >>>>>> >>>>>>> "Lee " <leeritchey@xxxxxxxxxxxxx> æ¼ 2014/9/7 ä¸å3:17 寫éï¼ >>>>>>> >>>>>>> No stitching vias are needed. Where did this idea get started? >>>>>>> >>>>>>> -----Original Message----- From: Leeyuyun >>>>>>> Sent: Saturday, September 06, 2014 4:25 AM >>>>>>> To: si-list@xxxxxxxxxxxxx >>>>>>> Cc: lee.home.61@xxxxxxxxx >>>>>>> Subject: [SI-LIST] One stitching via or more vias is better for 25Gbps >>>>>>> application??? >>>>>>> >>>>>>> Hi, all >>>>>>> I am doing 100Gbps (4x25Gps) product now >>>>>>> How do we put stitching vias when high speed signal change the layer? >>>>>>> This is a differential pair, which has P and N >>>>>>> Someone told me that one stitching vias is better because P and N share >>>>>>> the common return >>>>>>> Someone told me that more stitching vias is better because loop >>>>>>> inductance could be reduced more >>>>>>> I am confused which one is better? >>>>>>> Can anyone help me? >>>>>>> Thanks, >>>>>>> Lee------------------------------------------------------------------ >>>>>>> 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 forum is accessible at: >>>>>>> http://tech.groups.yahoo.com/group/si-list >>>>>>> >>>>>>> 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 >>>>>>> >>>>>>> >>>>>>> >>>>>>> >>>>>>> ----- >>>>>>> No virus found in this message. >>>>>>> Checked by AVG - www.avg.com >>>>>>> Version: 2014.0.4765 / Virus Database: 4015/8162 - Release Date: >>>>>>> 09/05/14 >>>>>> ------------------------------------------------------------------ >>>>>> 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 forum is accessible at: >>>>>> http://tech.groups.yahoo.com/group/si-list >>>>>> >>>>>> 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 >>>>> 1580 Grand Point Way >>>>> MS 34689 >>>>> Reno, NV 89523-9998 >>>>> www.ipblox.com >>>>> >>>>> (775) 299-4236 Business >>>>> (866) 675-4630 Toll-free >>>>> (707) 780-1951 Fax >>>>> >>>>> All contents Copyright (c)2013 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 forum is accessible at: >>>>> http://tech.groups.yahoo.com/group/si-list >>>>> >>>>> 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 >>> 1580 Grand Point Way >>> MS 34689 >>> Reno, NV 89523-9998 >>> www.ipblox.com >>> >>> (775) 299-4236 Business >>> (866) 675-4630 Toll-free >>> (707) 780-1951 Fax >>> >>> All contents Copyright (c)2013 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 forum is accessible at: >>> http://tech.groups.yahoo.com/group/si-list >>> >>> 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 >> 1580 Grand Point Way >> MS 34689 >> Reno, NV 89523-9998 >> www.ipblox.com >> >> (775) 299-4236 Business >> (866) 675-4630 Toll-free >> (707) 780-1951 Fax >> >> All contents Copyright (c)2013 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 forum is accessible at: > http://tech.groups.yahoo.com/group/si-list > > 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 forum is accessible at: http://tech.groups.yahoo.com/group/si-list 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