[SI-LIST] Re: Stripline Characteristic Impedance
- From: John Hans-Joerg <Hans-Joerg.John@xxxxxxxxxxxxxx>
- To: "'ched_chang@xxxxxxxxxxx'" <ched_chang@xxxxxxxxxxx>,si-list@xxxxxxxxxxxxx
- Date: Mon, 2 Dec 2002 09:03:06 +0100
Dear Chai,
the reason for the different results is the thickness of your trace! In
configuration (1) you get a distance to the nearest reference plane of =
(a -
35 my) =3D 165 my. In configuration (2) your distance to the reference =
plane
is equal a =3D 200 my. So you get for (1) a lower impedance than for =
(2). You
have to check your materials and than select configuration (1) or (2).
Regards
Hans-Joerg
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-----Original Message-----
From: Ched-Chang Chai [mailto:ched_chang@xxxxxxxxxxx]
Sent: Monday, December 02, 2002 6:30 AM
To: si-list@xxxxxxxxxxxxx
Subject: [SI-LIST] Stripline Characteristic Impedance
Dear all,
I have a question regarding the stripline characteristic impedance Zo.
I have the following stack-up:
Reference plane -------------
a
Trace ---
b
Reference plane -------------
where a<b.
When I used impedance calculator to get Zo, I have 2 ways to key in a =
and b=20
values:
(1) Use the stack-up shown above.
(2) Reverse it upside down, as shown below:
Reference plane -------------
b
Trace ---
a
Reference plane -------------
I got different values for Zo.
For example, a=3D0.2mm, b=3D0.4mm, trace width=3D0.15mm, trace =
thickness=3D0.035mm,=20
and dielectric constant=3D4.5, approach (1) gives 51ohm while approach =
(2)=20
gives 54ohm.
Can someone tell me which one is the correct value?
Thank you very much in advance.
--
Regards,
Chai
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