[SI-LIST] Re: Choice of routing layers
- From: steve weir <weirsp@xxxxxxxxxx>
- To: maheshkrish@xxxxxxxxxxx, si-list@xxxxxxxxxxxxx
- Date: Thu, 29 Apr 2004 16:24:14 -0700
Mahesh, the correct answer lies in what the IC vendor used as the reference
in the package. The key thing to remember is that the power / ground entry
to the package each compose a formidable impedance in the path of any high
speed signal. The way that signals get out of a package is through a
transmission line where the input port is the signal and one of the voltage
rails. You want the PCB to simply be a continuation of that transmission line.
Taking advantage of Jon's neat sidraw tool:
* The following text constitutes a picture drawn using the SI Draw
(v1.11) tool.
* Simply copy this text to a file, save the file with a .OUT extension, and
* open the file with the SI Draw tool. Or you can use the standard UNIX
(esc w)(cntrl-k) or WINDOWS CUT and PASTE
* commands to paste in sidraw. All spurious text should be ignored so
you can use SELECT ALL from
* The edit menu pulldown in your email if applicable. You can download
the SI Draw tool
* from http://www.si-list.org/files/tools/.
*
LINE: blue 105.0 90.0 120.0 90.0 120.0 85.0 125.0 80.0 130.0 80.0 135.0
85.0 135.0 90.0 135.0 85.0 140.0 80.0 145.0 80.0 150.0 85.0 150.0 90.0
150.0 85.0 155.0 80.0 160.0 80.0 165.0 85.0 165.0 90.0 180.0 90.0
PRIMITIVE: 1
LINE: blue 120.0 300.0 135.0 300.0 135.0 295.0 140.0 290.0 145.0 290.0
150.0 295.0 150.0 300.0 150.0 295.0 155.0 290.0 160.0 290.0 165.0 295.0
165.0 300.0 165.0 295.0 170.0 290.0 175.0 290.0 180.0 295.0 180.0 300.0
195.0 300.0
PRIMITIVE: 3
LINE: blue 45.0 115.0 85.0 145.0 45.0 175.0 45.0 115.0
POLY: black none 120.0 130.0 120.0 185.0 200.0 185.0 200.0 130.0 120.0 130.0
LINE: black 105.0 90.0 60.0 90.0 60.0 125.0
POLY: black none 120.0 215.0 120.0 270.0 200.0 270.0 200.0 215.0 120.0 215.0
LINE: blue 50.0 200.0 90.0 230.0 50.0 260.0 50.0 200.0
LINE: black 120.0 300.0 70.0 300.0 70.0 245.0 70.0 155.0
LINE: black 60.0 125.0 60.0 210.0
LINE: black 20.0 175.0 20.0 185.0 30.0 185.0 10.0 185.0
PRIMITIVE: 6
LINE: black 30.0 195.0 10.0 195.0 20.0 195.0 20.0 205.0
PRIMITIVE: 6
LINE: black 70.0 300.0 20.0 300.0 20.0 200.0
LINE: black 55.0 90.0 20.0 90.0 20.0 175.0
LINE: black 55.0 90.0 60.0 90.0
LINE: black 80.0 145.0 120.0 145.0
LINE: black 90.0 230.0 115.0 230.0
LINE: black 110.0 230.0 115.0 225.0
LINE: black 110.0 230.0 120.0 230.0 120.0 230.0
LINE: black 120.0 170.0 100.0 170.0 100.0 300.0
LINE: black 100.0 250.0 115.0 250.0
LINE: black 265.0 45.0 265.0 85.0
LINE: black 265.0 115.0 265.0 155.0 265.0 155.0
LINE: black 265.0 185.0 265.0 225.0
LINE: black 265.0 250.0 265.0 295.0
LINE: black 265.0 310.0 265.0 355.0
LINE: black 195.0 300.0 260.0 300.0
LINE: black 180.0 90.0 265.0 90.0
LINE: black 200.0 140.0 290.0 140.0
LINE: black 200.0 170.0 240.0 170.0 240.0 300.0
LINE: black 200.0 255.0 235.0 255.0
LINE: black 200.0 225.0 290.0 225.0
TEXT: black 140.0 145.0 w TX LINE
TEXT: black 140.0 230.0 w TX LINE
TEXT: black 80.0 395.0 w PWB reference should match package reference
POLY: black none 290.0 125.0 290.0 275.0 465.0 275.0 465.0 120.0 290.0
120.0 290.0 125.0
LINE: black 260.0 300.0 495.0 300.0
LINE: black 375.0 275.0 375.0 300.0
TEXT: black 330.0 180.0 w Diff TX LINE
TEXT: black 85.0 40.0 w Package
TEXT: black 375.0 55.0 w PCB
END:
Steve.
At 11:34 PM 4/29/2004 +0100, Mahesh Krishnan wrote:
>Hello Everyone,
>I had question related to the choice of routing layer for the differential
>10Gbps Ethernet signals. The 10G interface signals are referenced to 1.2V.
>Which of the following routing options would be better from the point of
>view of reducing emissions?
>
>Option1: Routing on signaling layers sandwiched by ground on either side
>(stripline formed by 2 ground planes)
>
>Option2: Routing on signalling layers sandwiched by a ground and 1.2V on
>either side (stripline formed by a ground and 1.2V plane)
>
>Please let me know your thoughts.
>
>Thanks,
>--mahe.
>
>
>
>---------------------------------
> Yahoo! Messenger - Communicate instantly..."Ping" your friends today!
> Download Messenger Now
>
>------------------------------------------------------------------
>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 FAQ wiki page is located at:
> http://si-list.org/wiki/wiki.pl?Si-List_FAQ
>
>List technical documents are available at:
> http://www.si-list.org
>
>List archives are viewable at:
> //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:
//www.freelists.org/webpage/si-list
For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
List FAQ wiki page is located at:
http://si-list.org/wiki/wiki.pl?Si-List_FAQ
List technical documents are available at:
http://www.si-list.org
List archives are viewable at:
//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:
