[SI-LIST] Re: delay tuning method of differential pair
- From: "Stefan Milnor" <stefan.milnor@xxxxxxxxxxxxxx>
- To: <rhaller@xxxxxxxxxxxxx>, <shlepnev@xxxxxxxxxxxxx>, <pcbtime@xxxxxxxx>, "si-list" <si-list@xxxxxxxxxxxxx>
- Date: Tue, 19 Nov 2013 12:43:37 -0800
The nicely-done paper states that serpentines may do more harm than
good, but offers no alternative (that I noticed). Do you advocate a
single big length compensating loop at one end of a pair, as you
sometimes see in layouts?
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Robert Haller
Sent: Tuesday, November 19, 2013 12:20 PM
To: shlepnev@xxxxxxxxxxxxx; pcbtime@xxxxxxxx; si-list
Subject: [SI-LIST] Re: delay tuning method of differential pair
Yuriy,
Nice paper. I have never liked serpentine, and prefer to correct
skew at ends, with appropriate corroborating 3D simulations.
The challenge I see is simulating thousands of links (in a timely
manner) and getting all of them right.
Regards
Bob Haller
Architect
Extreme Networks
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On Behalf Of Yuriy Shlepnev
Sent: Tuesday, November 19, 2013 1:04 PM
To: pcbtime@xxxxxxxx; 'si-list'
Subject: [SI-LIST] Re: delay tuning method of differential pair
When estimating different skew compensation structures, in addition to
comparison of SDD11 and SDD21, you have to compare the mode
transformation parameters SDC11, SDC22 (near-end mode transformation)
and SDC12, SDC21 (far-end mode transformation). In general, skew
compensation for coupled differential pairs must be formulated not in
terms of the length matching, but rather as minimization of the
differential reflection and near and far end mode transformation
parameters. See example at this presentation
www.simberian.com/AppNotes/Shlepnev_DesignInsights_FRSI_Oct3_2013.pdf
(starting from slide 29). As you can see, addition of serpentines for
some structures may not improve the "skew" and make things worse. Do
comprehensive analysis with the tools that capture the relevant effects.
Best regards,
Yuriy
Yuriy Shlepnev, Ph.D.
President, Simberian Inc.
3030 S Torrey Pines Dr. Las Vegas, NV 89146, USA Office +1-702-876-2882;
Fax +1-702-482-7903 Cell +1-206-409-2368; Virtual +1-408-627-7706
Skype: shlepnev
www.simberian.com
Simbeor - Accurate, Fast, Easy and Affordable Electromagnetic Signal
Integrity Software
2010 and 2011 DesignVision Award Winner
-----Original Message-----
From: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx]
On
Behalf Of pcbtime
Sent: Tuesday, November 19, 2013 2:33 AM
To: si-list
Subject: [SI-LIST] delay tuning method of differential pair
Hi Expert
I was confuse about the delay tuning method. We have two choice: Single
loop or small serpentines Single loop can match the length quickly then
small serpentines. That's mean:
Single loop has big different when tuning but short time.
small serpentines has small different when tuning but takes long time.
We try to simulation the result is below 12.5GHZ. We can't find any
different in SDD21 and SDD11 That's mean Single loop and small
serpentines is almost same when signal is below 8GBps Why most the
design guide force to use small serpentines
And I am so sorry for send two mail with unreadable code
Best Regards
pcbtime-----------------------------------------------------------------
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