What Scott said. Determine if it's diff or common on the cables first. Design input filtering to supply accoringly. However, it's usually a chassis grounding issue. You need to measure with a 4-lead and get 1.5 - 3.0 mOhms, max. Ken -----Original Message----- From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]On Behalf Of steve weir Sent: Sunday, January 08, 2012 6:42 AM To: si-list@xxxxxxxxxxxxx Subject: [SI-LIST] Re: DDR3 clock failing radiation Tests No, Steve. On 1/7/2012 9:35 PM, vinod ah wrote: > Hi all, > After going through the all the answers provided, i went ahead suspecting > the power supply. I find that the 1.5V switching regulator which powers the > DDR3 controller and memories is sometimes operating in discontinuous mode > due to lesser current drawn by the controllers& memories (by seeing the > voltage waveforms at the inductor of the switching regulator). So this > discontinuous mode of operation is the reason for EMI issue i am facing? > > Regards > Vinod A H > > On Sun, Jan 8, 2012 at 8:29 AM, steve weir<weirsi@xxxxxxxxxx> wrote: > >> Ken, another really good alternative is the Signal Hound USB based >> analyzer for $919. From 100Hz to 3.3GHz it goes down to -135dB, and it >> is usable from 1Hz to 4.4GHz. >> >> http://www.signalhound.com/ >> >> Best Regards, >> >> >> Steve >> On 1/7/2012 4:23 PM, Ken Wyatt 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_A nalyzer_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 >>> >>> >>> >> >> -- >> 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 > > > -- 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