[SI-LIST] Re: Impedance confusion
- From: "Lakshmi N. Sundararajan - PTU" <lakshmi.s@xxxxxxxxxxx>
- To: "Doug Brooks" <dbrooks7@xxxxxxxxxx>, <si-list@xxxxxxxxxxxxx>
- Date: Fri, 21 Nov 2008 13:55:36 -0800
Actually my confusion arose from using Polar for impedance calculation
for edge coupled offset stripline.
There is an input H1, which is the height of the trace from the plane,
now this can be either 5 mils or 22 mils depending...
The impedance varies based on which value I choose?!
Is there a rule to pick only one of these two?
Thanks,
-LN
> -----Original Message-----
> From: Doug Brooks [mailto:dbrooks7@xxxxxxxxxx]
> Sent: Friday, November 21, 2008 1:18 PM
> To: Lakshmi N. Sundararajan - PTU; si-list@xxxxxxxxxxxxx
> Subject: Re: [SI-LIST] Impedance confusion
>
> Your confusion may be because:
> Offset stripline implies a single-ended impedance, while
> edge-coupled offset stripline implies a differential impedance.
> If the stackup is
> sig --- plane --- sig --- sig --- plane --- sig The inner
> layers are asymetric stripline from a single-ended
> standpoint, and if there is parallel coupling between the two
> inner signal layers that coupling is broadside differential
> coupling (unless, of course, it is simple crosstalk
> coupling.) Hope that helps.
>
>
>
>
>
>
> At 12:18 PM 11/21/2008, you wrote:
> >Hi Team,
> >
> >Between these two stackup,
> >a) SIGTOP-PP(5 mils)-SIGINNER1-PP(22 mils)-SIGBOT
> >b) SIGTOP-PP(22 mils)-SIGINNER2-PP(5 mils)-SIGBOT
> >
> >While computing the impedance of the SIGINNER* layer, it is offset
> >stripline or edge coupled offset stripline.
> >
> >Would the impedance be different between these two cases?
> >I ask this because, when board (a) is rotated it becomes
> board (b) and
> >hence I do not expect impedance to vary between these two stackups.
> >
> >Can anyone please confirm/clarify on this.
> >
> >Thanks,
> >-LN
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