[SI-LIST] Re: AC coupling capacitors (SATA, PCIe)

  • From: Tesla <emcesd@xxxxxxx>
  • To: weirsi@xxxxxxxxxx
  • Date: Mon, 24 Sep 2012 10:50:28 +0800 (CST)

Hi, Steve
 
"forcing us into ridiculously large coupling caps, and VCO stability 
requirements"
Do you mean PCI-SIG defines too large capacitor?
If so, can we use small coupling caps for better performance?
 
Thanks.
 
Regards.







At 2012-09-18 05:23:46,"steve weir" <weirsi@xxxxxxxxxx> wrote:
>For most current generation SERDES applications many ordinary MLCCs do 
>just fine provided that you optimize the transition, pad, and anti-pad 
>geometries for maximum transparency.  There are differing schools of 
>thought with regard to whether or not one is better off choosing a 
>capacitor that is filled-out resulting in a thin cover layer, or one 
>uses a capacitor that has a relatively thick cover layer.  Arguments for 
>the former concentrate on the electrical superiority of that choice, 
>while arguments for the latter concentrate on the supply source 
>stability of the latter.  Economics dictate that today's thin cover 
>layer capacitor, is tomorrow's thick cover layer capacitor.
>
>If I had a time machine I would go back and beat the engineering 
>ramifications of channel percentage bandwidth into the PC-SIG folks who 
>designed PCI-Express, forcing us into ridiculously large coupling caps, 
>and VCO stability requirements.  The time for that is far behind us, so 
>we have to live with these things.  0201s are now available in large 
>enough capacitances to meet the spec.
>
>Steve.
>
>On 9/17/2012 1:20 PM, Hermann Ruckerbauer wrote:
>> Hello Rohit,
>>
>> thanks for the answer, and sorry for my bad description.
>>
>> I hope to clarify what I ment:
>>   Any kind of Capacitor that is specially designed for AC-Coupling
>> (DC-Blocking) for a specific application (PCIe, SATA, ...) e.g. :
>> - low ESR/ESL caps / high Q caps / controlled ESR caps
>> - Special material
>> - size other than 0402 (e. g. 0201 or reverse geometry)
>> - Special designed to have the impdeance minimum fitting to the
>> application (I have no idea how to fit 10MHz from plot in the link below
>> to e.g. 3GHz of a SATA interface).
>> - ... ????
>>
>> I found a lot of documents dealing with Capacitors for PDN, but not too
>> much for Capacitors used as AC-coupling in serial link applications.
>> e. g.     www.murata.com/products/article/pdf/ta1082.pdf
>>
>> Currently I can optimize my board e. g. in order to avoid the
>> Capacitance of the pads, but I have somehow no idea whether I can use
>> some optimized capacitors as AC-Coupling of a SATA or PCIe interface ..
>>
>> Any feedback welcome ..
>>
>> Hermann
>>
>>
>>
>> Our next Events:
>> ================
>>
>> "Open the Black Box of Memory"
>> Seminar on 08/09. November 2012
>>
>> Check our website or contact us for details
>>
>> EKH - EyeKnowHow
>> Hermann Ruckerbauer
>> www.EyeKnowHow.de
>> Hermann.Ruckerbauer@xxxxxxxxxxxxx
>> Veilchenstrasse 1
>> 94554 Moos
>> Tel.:        +49 (0)9938 / 902 083
>> Mobile:      +49 (0)176  / 787 787 77
>> Fax: +49 (0)3212 / 121 9008
>>
>> Am 13.09.2012 12:38, schrieb Rohit MISHRA:
>>> Hello Hermann,
>>>
>>> I don't know what do you mean by "special AC coupling capacitors" but there 
>>> was a paper from Yaochao Yang & his team in DesignCon 2012, Titled " 
>>> Embedded DC Blocking Capacitors in Connectors - Study of Impacts on PCB 
>>> Design"
>>>
>>> You can have a look, May be you can find what you are looking for.
>>>
>>> Rgds,
>>> Rohit
>>>
>>>
>>>
>>> -----Original Message-----
>>> From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] On 
>>> Behalf Of Hermann Ruckerbauer
>>> Sent: Thursday, September 13, 2012 2:34 PM
>>> Cc: SI LIST
>>> Subject: [SI-LIST] AC coupling capacitors (SATA, PCIe)
>>>
>>> Hi,
>>>
>>> i have done a short search on special AC coupling capacitors for serial
>>> interfaces  (PCIe, SATA, .. ) , but found nothing really special.
>>> I have found Steves DesignCon 2012 presentation, but this deals more
>>> with characterization than performance requirements.
>>>
>>> Is there something better available, than a standard C0G/X7R  capacitors ?
>>>
>>> Thanks for any feedback ..
>>>
>>> Hermann
>>>
>>> Our next Events:
>>> ================
>>>
>>> "Open the Black Box of Memory"
>>> Seminar on 08/09. November 2012
>>>
>>> Check our website or contact us for details
>>>
>>> EKH - EyeKnowHow
>>> Hermann Ruckerbauer
>>> www.EyeKnowHow.de
>>> Hermann.Ruckerbauer@xxxxxxxxxxxxx
>>> Veilchenstrasse 1
>>> 94554 Moos
>>> Tel.:       +49 (0)9938 / 902 083
>>> Mobile:     +49 (0)176  / 787 787 77
>>> Fax:        +49 (0)3212 / 121 9008
>>>
>>>
>>> ------------------------------------------------------------------
>>> 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 forum  is accessible at:
>>>                 http://tech.groups.yahoo.com/group/si-list
>>>
>>> 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 forum  is accessible at:
>>>                 http://tech.groups.yahoo.com/group/si-list
>>>
>>> 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 forum  is accessible at:
>>                 http://tech.groups.yahoo.com/group/si-list
>>
>> 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 forum  is accessible at:
>               http://tech.groups.yahoo.com/group/si-list
>
>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 forum  is accessible at:
               http://tech.groups.yahoo.com/group/si-list

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:

  1. Home
  2. si-list
  3. Archive
  4. 09-2012