Just as a point of clarification, device manufacturers are not the only ones that can add decoupling on the chip or package. For example, designers using IBM standard cell in CCGA packages can, and do, add decoupling capacitance in various amounts they choose (within limits) to both the silicon and on the package. The package decoupling can be targeted to any of the several power forms (core, I/O) by the user. I'm sure some other vendors allow something similar. I agree that the subtleties of this discussion are interesting. respectfully, Brad Henson Raytheon (no affiliation with IBM) "Fabrizio Zanella" To: <bhenson@xxxxxxxxxxxx>, <Ken.Cantrell@xxxxxxxxxxx> <fzanella@broadb cc: <bill.panos@xxxxxxxxxxxxxxx>, "Chris Cheng" us.com> <chris.cheng@xxxxxxxxxxxx>, <scott@xxxxxxxxxxxxx>, <si-list@xxxxxxxxxxxxx> 07/15/2003 05:54 Subject: RE: [SI-LIST] Re: Reducing SSO noise in an FPGA AM This discussion has turned quite interesting. There have been several comments which imply that the only way to reduce SSO noise in an FPGA/ASIC is to add decoupling at the die or inside the package. These are fixes which only the device manufacturers can make. Does anyone have measurement/simulation data on what effect adding many decoupling capacitors under the BGA package, between VCC and ground balls, will have on the SSO noise? Thanks and regards, Fabrizio -----Original Message----- From: Bradley S Henson [mailto:bhenson@xxxxxxxxxxxx] Sent: Monday, July 14, 2003 12:23 PM To: Ken.Cantrell@xxxxxxxxxxx Cc: bill.panos@xxxxxxxxxxxxxxx; Chris Cheng; scott@xxxxxxxxxxxxx; si-list@xxxxxxxxxxxxx; si-list-bounce@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Reducing SSO noise in an FPGA I think Ken provides a good summary that I generally agree with also. There is an interesting side note to the on-package decoupling that is not always clear. On-chip/package decoupling helps the SSO noise problem by paralleling the local I/O power and ground inductance during the switching event. This lowers the effective inductance. However, without decoupling there is often a degenerative feedback that takes place, essentially turning off the output driver a tad as a result of the SSO noise. Sometimes we see this covered in specs as SSO timing pushout. The subtle point about on package (or on chip) decoupling is that it not only parallels the I/O power and ground pins in the area, but it also stiffens the local rails to the offending driver. Less rail lift or droop means less degenerative feedback and more noise generation. Because of this, you will not always see the expected improvement in SSO noise with the application of on-package I/O power decoupling. I'm not advocating neglecting this important design detail, but rather explaining a subtle 2nd order impact. Regards, Brad Henson Raytheon "Ken Cantrell" <Ken.Cantrell@src To: <scott@xxxxxxxxxxxxx>, <bill.panos@xxxxxxxxxxxxxxx> comp.com> cc: "Chris Cheng" <chris.cheng@xxxxxxxxxxxx>, Sent by: <si-list@xxxxxxxxxxxxx> si-list-bounce@fr Subject: [SI-LIST] Re: Reducing SSO noise in an FPGA eelists.org 07/14/2003 08:13 AM Please respond to Ken.Cantrell Scott, My lab measurements(anything else is speculation)are in agreement with your statements. It is a package problem, and all the BC in the world won't change it. I have varied the noise levels going into the chip from 2% to >10% with no significant measured change in SSO, with Zo vs Frequency running 2x to 3x the calculated target value. I am increasing the BC via diameters and break out trace widths from ball to via as general improvements, but don't expect that it will make any difference. Layering and loop size are already optimized. There's a joke for you, minimizing loop size in dense, thick boards. Do you have data on any board geometry changes that produce a positive effect? Ken -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of Scott McMorrow Sent: Friday, July 11, 2003 4:45 PM To: bill.panos@xxxxxxxxxxxxxxx Cc: Chris Cheng; si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: Reducing SSO noise in an FPGA Bill, I respectfully disagree with you and agree with Chris. The SSO problem wrt. to a device driver is a chip and package problem. The round trip time from the driver, through the package and out to a BC layer is longer than the risetime for almost all packages and devices where this is a problem. SSO is generally a loop inductance issue. No amount of capacitance at the end of a large loop inductance in a power delivery system can effect the problem. For the capacitance to be effect, it has to be in the package or on the die. As a result, the PCB has no effect on instantaneous SSO problems. You can make the problem worse, but if the package and silicon are already hosed, their ain't much you can do to make it better. SSO problems are almost always I/O power issues. This is a region of silicon and package design where there are many tradeoffs, quite a few of them wrong. If this portion of the design is already broken (and it is in quite a few FPGA, ASICs and even in custom devices) then all the BC in the world will not fix it. BC can deal with lower frequency noise components and lower the overall noise floor for a PCB power delivery system. BC can reduce the power impedance profile. BC can even be used to change the resonant frequency of a board, if the dielectric constant is higher than FR4. But BC cannot help the classical SSO problem. If you have real engineering data that shows differently, I would enjoy seeing it. best regards, scott -- Scott McMorrow Teraspeed Consulting Group LLC 2926 SE Yamhill St. Portland, OR 97214 (503) 239-5536 http://www.teraspeed.com bpanos wrote: >Chris >I think it's "guest" not "guess", (might want to check your syntax) >I disagree with your notion that BC is useless in an SSO applications, Even with >as you say with good reference pane placement. SSO problems may be manifested by >supply bounce or ground. Concerning supply bounce in the presence of bypass caps >and issues with ESL (low ESL caps are not always provided or an option), BC >could be entertained. To what degree BC would be of a benefit is up to debate. >Bill > > > > >Chris Cheng wrote: > > > >>BC is useless to solve packaging SSO or any SSO problem for that matter if >>you manage your signal reference plane correctly on the PCB. If you choose >>to use the wrong reference plane for your I/O and then decided to throw >>money to fix it with BC, be my guess. >> >>Chris >> >>-----Original Message----- >>From: bpanos [mailto:bill.panos@xxxxxxxxxxxxxxx] >>Sent: Friday, June 27, 2003 4:05 PM >>To: perry.qu@xxxxxxxxxxx >>Cc: zhang_kun@xxxxxxxxxx; fzanella@xxxxxxxxxxxx; si-list@xxxxxxxxxxxxx >>Subject: [SI-LIST] Re: Reducing SSO noise in an FPGA >> >>I personally have not tried implementing this particular application, in >>this fashion, but I wonder how well using BC (buried capacitance) material >>would work with SSO issues with an FPGA. >>Granted, there may not be enough capacitance / sq, though with 0.5mil BC it >>might be an option.. >>Regards, >>Bill >> >>Perry Qu wrote: >> >> >> >>>Hi, Zhangkun: >>> >>>We have been using 100nF cap extensively in our high speed design (> >>> >>> >>100MHz) and so far so good. In my understanding, small ESL is the key to >>make a flat impedance curve in frequency >> >> >>>range, as explained here many times by Larry Smith and Istvan Novak. Small >>> >>> >>caps such as NPO 1nF will normally give us high Q since resonance factor >>increase when ESL increase, and when >> >> >>>ESR and C decrease. For NPO cap, it has very small ESR and small C, so if >>> >>> >>we do not control ESL to very small value, we will end up with high Q. Such >>high Q cap may cause strong >> >> >>>anti-resonance when mixed with other cap and/or plane pairs. In our >>> >>> >>designs, since we can't control ESL very well with special stackup/routing, >>we use 1nF very carefully. >> >> >>>Regards >>> >>>Perry >>> >>>Zhangkun wrote: >>> >>> >>> >>>>Dear Zanella >>>> >>>>I think 0.1uF and 0.22uF is too large for decoupling. When the frequency >>>> >>>> >>goes up to 100MHz, these two kind of caps will be of no use. Istvan has >>writen one paper about measuring caps. >> >> >>>>Best Regards >>>> >>>>Zhangkun >>>>2003.06.26 >>>>----- Original Message ----- >>>>From: "Fabrizio Zanella" <fzanella@xxxxxxxxxxxx> >>>>To: <si-list@xxxxxxxxxxxxx> >>>>Sent: Thursday, June 26, 2003 12:01 AM >>>>Subject: [SI-LIST] Reducing SSO noise in an FPGA >>>> >>>> >>>> >>>>>I would like to hear about experiences regarding methods of reducing >>>>>simultaneous switching noise in a large FPGA, BGA package. Let's >>>>> >>>>> >>assume >> >> >>>>>a 128bit bus, with a signal frequency of 100MHz. >>>>>How effective is adding ground planes 2 mils from the VCC planes in >>>>>reducing SSN? If one uses BC, does every VCC pin in the FPGA require >>>>>decoupling? And should the caps be tied to the BGA pins with blind >>>>> >>>>> >>vias >> >> >>>>>so they can be placed directly under the BGA? What are the optimal >>>>>values for the decoupling capacitors, 0.1uf, 0.22uF? >>>>> >>>>>Thanks very much and regards, >>>>> >>>>> >>>>>Fabrizio Zanella >>>>>Principal Hardware Design Engineer >>>>>Broadbus Technologies >>>>>fzanella@xxxxxxxxxxxx >>>>>=20 >>>>>-------------------------------------------------------- >>>>> >>>>>=20 >>>>>This email message and any files transmitted with it contain = >>>>>confidential information intended only for the person(s) to whom this >>>>> >>>>> >>= >> >> >>>>>email message is addressed. If you have received this email message >>>>> >>>>> >>in = >> >> >>>>>error, please notify the sender immediately by telephone or email and >>>>> >>>>> >>= >> >> >>>>>destroy the original message without making a copy. Thank you.=20 >>>>>=20 >>>>>------------------------------------------------------------------ >>>>>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 archives are viewable at: >>>>>//www.freelists.org/archives/si-list >>>>>or at our remote archives: >>>>>http://groups.yahoo.com/group/si-list/messages >>>>>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 archives are viewable at: >>>> //www.freelists.org/archives/si-list >>>>or at our remote archives: >>>> http://groups.yahoo.com/group/si-list/messages >>>>Old (prior to June 6, 2001) list archives are viewable at: >>>> http://www.qsl.net/wb6tpu >>>> >>>> >>>> >>>-- >>>Perry Qu >>> >>>Design & Qualification | 600 March Road >>>Alcatel Canada | Ottawa, ON K2K 2E6, Canada >>> >>>DID: (613) 7846720 | FAX: (613) 5993642 >>> >>>------------------------------------------------------------------ >>>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 archives are viewable at: >>> //www.freelists.org/archives/si-list >>>or at our remote archives: >>> http://groups.yahoo.com/group/si-list/messages >>>Old (prior to June 6, 2001) list archives are viewable at: >>> http://www.qsl.net/wb6tpu >>> >>> >>> >>-- Binary/unsupported file stripped by Ecartis -- >>-- Type: text/x-vcard >>-- File: bill.panos.vcf >>-- Desc: Card for bpanos >> >>------------------------------------------------------------------ >>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 archives are viewable at: >> //www.freelists.org/archives/si-list >>or at our remote archives: >> http://groups.yahoo.com/group/si-list/messages >>Old (prior to June 6, 2001) list archives are viewable at: >> http://www.qsl.net/wb6tpu >> >> >> > > >-- Binary/unsupported file stripped by Ecartis -- >-- Type: text/x-vcard >-- File: bill.panos.vcf >-- Desc: Card for bpanos > > >------------------------------------------------------------------ >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 archives are viewable at: > //www.freelists.org/archives/si-list >or at our remote archives: > http://groups.yahoo.com/group/si-list/messages >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 archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages 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 archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages 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 archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu -------------------------------------------------------- This email message and any files transmitted with it contain confidential information intended only for the person(s) to whom this email message is addressed. If you have received this email message in error, please notify the sender immediately by telephone or email and destroy the original message without making a copy. Thank you. ------------------------------------------------------------------ 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 archives are viewable at: //www.freelists.org/archives/si-list or at our remote archives: http://groups.yahoo.com/group/si-list/messages Old (prior to June 6, 2001) list archives are viewable at: http://www.qsl.net/wb6tpu