[SI-LIST] Re: DDR3 clock failing radiation Tests

  • From: steve weir <weirsi@xxxxxxxxxx>
  • To: si-list@xxxxxxxxxxxxx
  • Date: Sun, 08 Jan 2012 05:41:40 -0800

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_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
>>>
>>>
>>>
>>
>> --
>> 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
  

Other related posts: