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