[SI-LIST] Re: AC Coupled Signals

Except, of course, for PCIE, where the nets go to a different board and
the spec says that the CAP belongs to the TX.



-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Stephen Zinck
Sent: Monday, September 24, 2007 4:47 PM
To: jory_mckinley@xxxxxxxxx; leeritchey@xxxxxxxxxxxxx;
npatel@xxxxxxxxxx; si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Re: AC Coupled Signals

Hi Jory,

I have simulated this at length and concur with your experience that the

capacitor is best placed at the receiver...

In effect, the attenuation associated with the capacitor placement at
the=20
receiver (parasitics/pads/vias) is lost in the rise-time degradation of
the=20
system.
The classic "don't break it until you have to" rule is applicable... OK
this=20
is my rule... :-)

All the best,
Steve

Stephen P. Zinck
Interconnect Engineering Inc.
P.O. Box 577
South Berwick, ME 03908
Phone - (207) 384-8280
Email - szinck@xxxxxxxxxxxxxxxxxxxxxxxxxxx
Web - www.interconnectengineering.com

----- Original Message -----=20
From: "Jory McKinley" <jory_mckinley@xxxxxxxxx>
To: <leeritchey@xxxxxxxxxxxxx>; <npatel@xxxxxxxxxx>;
<si-list@xxxxxxxxxxxxx>
Sent: Monday, September 24, 2007 5:31 PM
Subject: [SI-LIST] Re: AC Coupled Signals


>I will elaborate a bit on what I have seen. I have measured (time
domain)=20
>in the lab some effects that appears to be location specific in the=20
>placement of the AC coupling caps at the rcvr.  Now this may be due in
part=20
>to the fact that I am using 50-ohm resistor termination in each lead as

>well and the combination (cap plus rcvr reflection) is giving some=20
>imbalance depending on distance.  The best rcvr eye that I am seeing is

>when I can move the AC/term as close to the rcvr as I can.  By the way=20
>these are 5Gb/s signals.
> If I have time I will try and isolate what I am seeing and even
simulate=20
> it, has anyone else seen or simulated this?
> -Jory
>
> ----- Original Message ----
> From: Lee Ritchey <leeritchey@xxxxxxxxxxxxx>
> To: "npatel@xxxxxxxxxx" <npatel@xxxxxxxxxx>; si-list@xxxxxxxxxxxxx
> Sent: Monday, September 24, 2007 1:06:06 PM
> Subject: [SI-LIST] Re: AC Coupled Signals
>
> Nikil,
>
> I have made measurements on test PCBs and the location is not all that
> important.  In identical pairs, one with AC coupling capacitors and
the
> other without, the loss vs. frequency is virtually identical at leas
out=20
> to
> 6 GHz.  That would be 12 Mb/S.
>
> Lee Ritchey
>
>
>> [Original Message]
>> From: <npatel@xxxxxxxxxx>
>> To: <si-list@xxxxxxxxxxxxx>
>> Date: 9/24/2007 10:21:37 AM
>> Subject: [SI-LIST] AC Coupled Signals
>>
>> Hi all,
>> In case of AC coupled signals does anyone know of an optimum
placement
>> for the caps? I mean should they be placed near the source, receiver,
>> middle of  the transmission line?
>> How much difference does it make in the opening of the eye?
>> The signals are differential CML running at 3.0Gbps
>>
>> Thanks,
>> Nikhil
>>
>>
>> ------------------------------------------------------------------
>> 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:
>> http://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:
>>         http://www.freelists.org/archives/si-list
>> or at our remote archives:
>>         http://groups.yahoo.com/group/si-list/messages
>> 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:
> http://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:
>        http://www.freelists.org/archives/si-list
> or at our remote archives:
>        http://groups.yahoo.com/group/si-list/messages
> Old (prior to June 6, 2001) list archives are viewable at:
>         http://www.qsl.net/wb6tpu
>
>
>
>
>
>
>
>
>
>
>
________________________________________________________________________
____________
> Moody friends. Drama queens. Your life? Nope! - their life, your
story.=20
> Play Sims Stories at Yahoo! Games.
> http://sims.yahoo.com/
> ------------------------------------------------------------------
> 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:
> http://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:
> http://www.freelists.org/archives/si-list
> or at our remote archives:
> http://groups.yahoo.com/group/si-list/messages
> Old (prior to June 6, 2001) list archives are viewable at:
>  http://www.qsl.net/wb6tpu
>
>
>=20


------------------------------------------------------------------
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:
http://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:    =20
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu
 =20
------------------------------------------------------------------
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:
http://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:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu

Other related posts: