[SI-LIST] Re: Via Impedance!
- From: "Lee Ritchey" <leeritchey@xxxxxxxxxxxxx>
- To: "G.Srinivasan" <srini@xxxxxxxxxxxx>, "Gopalakrishnan Sethuraj" <gopalak@xxxxxxxxxxx>
- Date: Wed, 14 Jul 2004 08:51:32 -0700
Srinivasan,
It is possible to design teh diameter of a via plated barrel and the
clearance openings in the power planes through which it passes such that
the structure is 50 ohms. When you do this, the openings in the planes
will so large that it will be difficult to maintain plane integrity.
When the via is used to change layers, if it is of a size consistent with
maintaining good plane integrity, it will appear as a tiny parasitic
capacitance on the transmission line resulting in a small negative
reflection. For most PCBs thinner than 100 mils, this is not a significant
disturbance and you don't have to worry about it.
This is true, even at 2.4 GB/S.
Lee W. Ritchey
Speeding Edge
P. O. Box 2194
Glen Ellen, CA 95442
Phone- 707-568-3983
FAX- 707-568-3504
I just used the energy it took to be angry to write some blues.
Count Basie
> [Original Message]
> From: G.Srinivasan <srini@xxxxxxxxxxxx>
> To: Gopalakrishnan Sethuraj <gopalak@xxxxxxxxxxx>
> Cc: <si-list@xxxxxxxxxxxxx>; <vijay@xxxxxxxxxxxx>
> Date: 7/14/2004 3:56:16 PM
> Subject: [SI-LIST] Via Impedance!
>
> Hi,
> I have a querry regarding how to ensure that the impedance of the via
is
> the same as that of the traces. For example, if I have a trace of 50 ohms
> running between two layers through a via, how can I calculate its
impedance?
> In Specctraquest, I saw that there is a field solver that generates a
model
> for the via based on its geometry and uses it for simulation. Does it
also
> gives the impedance of the via and provides help to achieve the required
via
> impedance?
>
> Regards,
> G.Srinivasan.
>
>
>
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