[SI-LIST] Re: AW: AW: Asymmetric differential stripline impedance
- From: "Lee " <leeritchey@xxxxxxxxxxxxx>
- To: <Gert.Havermann@xxxxxxxxxxx>, "SI-List" <si-list@xxxxxxxxxxxxx>
- Date: Fri, 4 Jan 2013 10:06:40 -0800
That's the way we have done this work for quite a while- let the fab shop
design the final stackup. Unfortunately, there is far more to designing a
stackup than just impedance, such as glass style, copper finish, etc. Most
of these, if not all are out of the scope of a fab shop's skill set. For
this reason, most of use have no choice but to take charge of the impedance
calculation as opposed to putting the burden on the fab shop. It was always
our job anyway! We just got away with forcing the fab shop to do it.
For these reasons, it is necessary to get impedance right before sending the
stackup off to a fab shop. That is why I argue for field solver based
calculators and good laminate data.
-----Original Message-----
From: Havermann, Gert
Sent: Friday, January 04, 2013 8:57 AM
To: Lee ; SI-List
Subject: [SI-LIST] AW: AW: Asymmetric differential stripline impedance
Lee,
I use it to find a starting point for 3D simulations. It can't be accurate
as one can not calculate with different prepreg styles or other real world
problems. But besides that its not a bad tool.
I think the biggest error in the end is the implementation of the design,
and there even 3D simulation doesn't help you if you don't know how PCBs are
made and which are the Materials used (not only electrical models, but also
processing related like flow behavior during pressing, copper fill of the
layer...). You know what I'm talking about.
If I have all the knowledge, then I take those parameters into my
calculation and do a 3D simulation of the right offset and the correct
GND-GND distance and correct material and surface roughness... And then I
know that the impedance will be at least close to where I wanted it to be.
For others without this detail of knowledge of PCB Fab and Materials, This
tool is a good starting point for their design. Then you hand this design to
a pcb vendor with knowledge in Impedance manufacturing and let him do the
fine tuning of the trace based on his experience to meet +/-10% impedance
match. If The vendor fails, he looses money, and you loose time, but with
the right partner it works great even at higher speeds.
The Processing has so much influence, that I usually just push my PCB maker
as far as I can to a point where he simply can't mess up my design, and then
I give him the freedom to implement his processing tolerances.
And quite frankly, if someone here asks for a tool that can do "offset
stripline", then I don't expect this person to know all the PCB processing
details yet, as I haven't seen any absolute symmetrical diff-trace in my
life. In reality they are all offset (sometimes a bit, sometimes a bit
more).
You are absolutely right, that no one should ever trust a free tool up to a
point where mistakes can cost money. But free tools can be supportive.
BR
Gert
PS: will you have a DC Booth again this year? If so, I'll stop by for a
talk.
----------------------------------------
Absender ist HARTING Electronics GmbH, Marienwerderstraße 3, D-32339
Espelkamp; Registergericht: Amtsgericht Bad Oeynhausen; Register-Nr.: HRB
8808; Vertretungsberechtige Geschäftsführer: Dipl.-Kfm. Edgar-Peter Düning,
Dipl.-Ing. Torsten Ratzmann, Dr.-Ing. Alexander Rost
-----Ursprüngliche Nachricht-----
Von: Lee [mailto:leeritchey@xxxxxxxxxxxxx]
Gesendet: Donnerstag, 3. Januar 2013 18:38
An: Havermann, Gert; SI-List
Betreff: Re: [SI-LIST] AW: Asymmetric differential stripline impedance
Polar's CITS25 is an equation based tool that is accurate only part of the
time. It does not use a field solver. I don't trust its results.
As with most free tools, they are often worth the price!
-----Original Message-----
From: Havermann, Gert
Sent: Wednesday, January 02, 2013 11:54 PM
To: SI-List
Subject: [SI-LIST] AW: Asymmetric differential stripline impedance
Polar's CITS25 software is quite accurate and easy to use. It comes with
several different impedance cells. Even though Polar is no longer supporting
this tool, you will still be able to find the free evaluation version
somewhere in the web. The only evaluation restriction is the total number of
calculations, and it can be reset with uninstalling and re-installing.
BR
Gert
----------------------------------------
Absender ist HARTING Electronics GmbH, Marienwerderstraße 3, D-32339
Espelkamp; Registergericht: Amtsgericht Bad Oeynhausen; Register-Nr.: HRB
8808; Vertretungsberechtige Geschäftsführer: Dipl.-Kfm. Edgar-Peter Düning,
Dipl.-Ing. Torsten Ratzmann, Dr.-Ing. Alexander Rost
-----Ursprüngliche Nachricht-----
Von: si-list-bounce@xxxxxxxxxxxxx [mailto:si-list-bounce@xxxxxxxxxxxxx] Im
Auftrag von Hithesh
Gesendet: Donnerstag, 3. Januar 2013 06:04
An: SI-List
Betreff: [SI-LIST] Asymmetric differential stripline impedance
Hi foks,
Is there any online tool to calculate the impedance of assymetric
differential stripline?
I searched, nothing available for asymmetric differential. It's either
asymmetric stripline or symmetric differential.
How to calculate differential impedance from single ended impedance?
This is with reference to USB signals.
Thanks
-Hithesh
------------------------------------------------------------------
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
-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2013.0.2805 / Virus Database: 2637/6003 - Release Date: 01/02/13
------------------------------------------------------------------
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
-----
No virus found in this message.
Checked by AVG - www.avg.com
Version: 2013.0.2805 / Virus Database: 2637/6003 - Release Date: 01/02/13
------------------------------------------------------------------
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:
