I find that when EMI is this far out of compliance the problem is usually a basic ground return path issue. Possible sources are: Insufficient ground pins/balls Perforated planes in PCB or package Uncontrolled DDR power or ground plane resonance. These problems can sometimes be found by inspection by an expert. A full wave package/PCB solver can be used to perform an eigenmode analysis for power/ground plane issues. A solver like Ansoft SIwave can be useful for these analysis. Happy hunting. Scott On Jan 7, 2012 7:26 PM, "Ken Wyatt" <ken@xxxxxxxxxxxxxxxx> wrote: > Great reply Alfred - lots of good troubleshooting tips. > > Your comment on the PSA2701T caught my eye, as I've been using one of > these for several years. However, few people have heard of the TTi Spectrum > Analyzer, which is too bad. It's an incredible handheld (truly handheld!) > instrument manufactured in the UK and distributed by Newark Electronics and > Saelig Co. here in the US. Saelig actually has a slightly better price at > $1,887. If anyone is interested in additional info on the TTi PSA2701T > spectrum analyzer, I posted a comprehensive review on my web site: > http://www.emc-seminars.com/Technical_Articles/files/TTi_PSA2701T_Spectrum_Analyzer_Wyatt.pdf > . > > I'm also glad you referenced Doug Smith's web site. It's chock-full of > high-frequency, EMC and ESD measurement techniques and tips. He's at: > http://emcesd.com/ > > By the way, anyone who registers for my free quarterly EMC newsletter will > receive a link to a free list of troubleshooting tips, as well as all past > newsletters. Click on the link below... > > References: > > Newark: > http://www.newark.com/aim-tti-instruments/psa2701t/analyzer-spectrum-1mhz-to-2700mhz/dp/54M5938 > > Saelig: http://www.saelig.com/category/TEEMCEE.htm > > Cheers, Ken > _______________________ > Kenneth Wyatt > Wyatt Technical Services LLC > Woodland Park, CO > Email Me! | Web Site | Blog > Subscribe to Newsletter > Connect with me on LinkedIn > > On Jan 7, 2012, at 1:16 PM, alfred1520list wrote: > > > Guess one more post does not alter the SNR significantly:) > > > > Quarter wave of 513 MHz in free space is 5.76", and roughly > > half that in FR4. I guess you don't happen to have a 3" tall > > metal standoff that's mounted close to the ASIC to act as > > an antenna, right? Any way, controlled impedance traces aren't > > efficient antenna compare to other physically large structure. > > As some one else pointed out, common mode current can > > couple to other physically large structures and they become > > efficient radiator. I find Doug has a few excellent papers > > on EMI on his site: > > > > http://emcesd.com > > > > I find this particular interesting: > > > > "Current Probes, More Useful Than You Think": > > http://emcesd.com/pdf/iprobe98.pdf > > > > One other suggestion from experience. When you have 20 suspects > > areas, it might be easier trying to make it worst to see which one > > of them is the dominant source. Even though all 20 suspects can all > > radiate, probably only one of them is order of magnitude higher > > than others. If you can find that one and knock it down, you made > > significant progress. Since at 513 MHz it still needs significant > physical > > dimension (like an 1" long???) to radiate efficiently, use a piece of > metal > > like X-Acto knife, to touch everything and see if it make it worst. Any > > where you touch and made it worst is worth a closer look, especially > > places where you don't expect, e.g. power supply, etc. > > > > Speaking of sniffing radiation, I have used PSA2701T: > > http://www.tti-test.com/products-tti/rf/spectrum-analyzer.htm > > > > It's a great piece of gear and low enough in cost (a couple of US dollar > as > > I recall). Since you aren't making certification measurement, you can > > simply use any length of wire that register a reading at the frequency of > > interest and make relative measurement. I used a cheap US$30 discone > > antenna. If you make the spike smaller, you have made it better. > > > > > > Best Regards, > > Alfred Lee > > > > Web: www.mds.com > > > > ----- Original Message ----- > > From: "Eric Steimle" <eric.steimle@xxxxxxxxxx> > > To: "vinod ah" <ah.vinod@xxxxxxxxx>; "SI-LIST" <si-list@xxxxxxxxxxxxx> > > Sent: Saturday, January 07, 2012 11:27 AM > > Subject: [SI-LIST] Re: DDR3 clock failing radiation Tests > > > > > >> I agree that seeing the most emissions coming out of the ASIC is pretty > common, especially if it's your ASIC ;), and unless you > >> have some kind of crazy expensive (possible magic) software, simulation > can't save you now. I don't know what your application is > >> but in the past I did a lot of unshielded consumer designs that used > DDR2/3, and most of them would not have made it through scan > >> without spread spectrum. I also agree that going to an expert EMI > consultant could be well worth it, if your in NC I know a good > >> one. > >> Anyway I like to tackle emi problems by cutting everything into smaller > and smaller pieces. I don't know what your production > >> options are but here's one thing to try. If you want to narrow things > down you could build yourself a shield for your ASIC as a > >> test. Just get some Kapton tape, and some copper tape. Kapton tape > all around the ASIC, then copper tape over that. Then ground > >> the heck out of that copper tape, I usually do that by taking an exacto > knife and cutting down to my gnd plane, but do what you > >> can do. After that sniff it again, or go pre-scan it if you can afford > it. > >> > >> If that does nothing, at least you know you have additional problems > elsewhere. If it cleans it up, hurray just ship everything > >> with copper tape. Kidding but you could re-spin the board to > accommodate a shield, and get the product out the door. > >> > >> This is just one of hundreds of things to try, but you asked for help > finding the source. The best advice I can give is to start > >> eliminating things, by shielding / pulling parts off the board, > changing clock frequencies, anything you can think of to narrow > >> down the problem. Keep track of how each change affects your > emissions. One time we ripped 12 ASICs off a large board and still > >> had the problem! It was a lot easier to find without all those extra > parts to question though. > >> > >> Good luck. > >> > >> > >> Eric F. Steimle > >> Hardware Engineering Manager > >> > >> +1 732-440-1280 x210 Office > >> +1 732-212-9424 Fax > >> > >> 444 Route 35 South > >> Building B > >> Eatontown, NJ 07724 USA > >> > >> eric.steimle@xxxxxxxxxx > >> www.altior.com > >> > >> > >> > >> ****Confidentiality Statement**** > >> This message (including any attachments) contains confidential > information > >> intended for a specific individual and purpose, and is protected by > law. If > >> you are not the intended recipient, you should delete this message and > are > >> hereby notified that any disclosure, copying, or distribution of this > message, > >> or the taking of any action based on it, is strictly prohibited. > >> > >> Please consider the environment before printing this e-mail. > >> > >> ________________________________________ > >> From: si-list-bounce@xxxxxxxxxxxxx [si-list-bounce@xxxxxxxxxxxxx] On > Behalf Of vinod ah [ah.vinod@xxxxxxxxx] > >> Sent: Saturday, January 07, 2012 12:27 AM > >> To: SI-LIST > >> Subject: [SI-LIST] DDR3 clock failing radiation Tests > >> > >> Hi all, > >> I am facing problems related to EMI. I am having a ASIC with 2 DDR3 > >> controllers running at 513MHz clock. I am interfacing 2 memories to > each of > >> the controller. So totally 4 memory chips on board, all running at > 513MHz > >> clock. During pre-compliance radiation testing in FCC certified lab, we > >> observed 513MHz in the spectrum with 15dB above the CISPR class B limits > >> i.e. test failing by 15dB !!!!! > >> > >> I tried to corelate this result with Hyperlynx spectrum analyzer > simulation > >> and SI simulation. The waveforms and radiation level looks fine in > >> Hyperlynx i.e. no issues seen. Initially i had suspected the layout, but > >> hyperlynx SI simulation looks fine and also the clock & dqs waveforms in > >> CRO looks fine i.e. no ringing/overshoot etc. The DDR3 clock is routed > in > >> inner layer 3 of six layer stack up of the board. > >> > >> I have tried using EMI shield, but still i am failing by 8dB. Only > thing i > >> have not yet tried is spread spectrum clocking. But I am unable to find > the > >> source of problem. Can you please help me out in finding the sourceto > this > >> problem. > >> > >> I understand that it is very tuff to provide solution to this problem > >> without seeing the layout, but i am expecting some tips so that i can > move > >> ahead in debugging the problem. > >> > >> Regards > >> Vinod A H > >> > >> > >> ------------------------------------------------------------------ > >> 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