Browse si-list: This Month's Archive • Main Archive Page • Related posts • Previous by Date • Next by Date
[SI-LIST] Re: Serpentine Traces

From: Adam.Tambone@xxxxxxxxxxxxxxxxx
To: rhaller@xxxxxxxxxx
Date: Tue, 10 Sep 2002 14:43:33 -0400

Hello Bob,

When applying the 2D field solver to the serpentine geometry, how do you
account for the bends perpendicular to the coupled t-lines?  If you create
separate models for the bends are you still able to couple them with the
'straight' lengths of t-lines?

Thanks,
Adam




|---------+---------------------------->
|         |           Robert Haller    |
|         |           <rhaller@xxxxxxxx|
|         |           om>              |
|         |           Sent by:         |
|         |           si-list-bounce@fr|
|         |           eelists.org      |
|         |                            |
|         |                            |
|         |           09/10/02 02:19 PM|
|         |           Please respond to|
|         |           rhaller          |
|         |                            |
|---------+---------------------------->
  
>-------------------------------------------------------------------------------------------------------------------------------|
  |                                                                             
                                                  |
  |        To:      ericg@xxxxxxxxxxx                                           
                                                  |
  |        cc:      si-list@xxxxxxxxxxxxx                                       
                                                  |
  |        Subject: [SI-LIST] Re: Serpentine Traces                             
                                                  |
  
>-------------------------------------------------------------------------------------------------------------------------------|





Eric ,
             For the example given, 176 ps/in -> 170 ps/in the difference
was
between 5/50 and 5/20 (Line width, /Line Spacing). The delay variations
were even more dramatic at tighter spacings.

To answer Andy's question, I click Info in Allegro - which I believe
measures the center of the line.

Regards,
Bob
--
Robert J. Haller (rhaller@xxxxxxxxxx)
Principal Consultant
Signal Integrity Software Inc.
6 Clock Tower Place, Suite 250
Maynard, MA 01754
Phone: (978) 461-0449, ext 15


Eric Goodill wrote:
> Bob,
>
> What is 'close' in your test board?
>
> -Eric
>
> Robert Haller wrote:
>
>
>>Praveen,
>>           This is a good question and has been raised before on the
SI-LIST.
>>Serpentine etch is often done to match clock lines or source syncronous
>>data lines.
>>
>>I did bench testing of serpentine lines, in conjuction with simulations.
>>I ran SPICE simulations using field solved 2d models then measured
>>varying serpentine configurations. I examined impedance and propagation
>>delay variations as a function of varying spacing, and signal edge rate.
>>
>>When transmission lines are serpentined 'close' to themselves the
>>propagation delay decreases (The lines got faster). For example if I
>>compare a straight control line and a sepertined line of the same length
>>on the same layer, with all the fixturing nulled the propagation delay
>>went from 176ps/in (straight line) to 170 ps/inch (serpentined line).
>>You can think of the signal taking a shortcut across the distributed
>>self capacitance of the closely serpentined lines.
>>You might think a propagation delay reduction is good, but I also found
>>the variability of prop velocity increased. I believe the variability
>>increased because the capacitive coupling varies based on geometry,
>>while normally the dielectric constant variations are the only source of
>>prop delay variability (for a specific rise time and frequency). The
>>variability is a small effect but is important when doing source
>>syncronous designs.
>>
>>
>>Regards,
>>Bob
>
>
>
> ------------------------------------------------------------------
> 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 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
>
>

--
Robert J. Haller (rhaller@xxxxxxxxxx)
Principal Consultant
Signal Integrity Software Inc.
6 Clock Tower Place, Suite 250
Maynard, MA 01754
Phone: (978) 461-0449, ext 15


------------------------------------------------------------------
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 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 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
[SI-LIST] Re: Serpentine Traces

Other related posts:
