ARM DSTREAM-ST - MIPI 60 connector

4.2 PCB track impedance
You can calculate the PCB track impedance using the microstrip impedance formula.
87
Impedance
=
In
(E
r
+ 1.41 )
(0.81w + t)
5.98h
Ω
where:
h
Height above ground plane (inches)
w
Trace width (inches), and 0.1 < w/h < 2
t
Trace thickness (inches)
E
r
Relative permittivity of processor/prepreg, and 1 < E
r
< 15
This PCB track impedance formula applies only to microstrips (track on outer layer over a ground
plane).
The dimensions h, w, and t are shown in the following figure.
Ground plane
w
h
t
Figure 4-1 Track impedance
As an example, the following track (in microstrip form) has an impedance of 51.96Ω:
h
0.005 inch height above ground
w
0.007 inch width track
t
0.0014 inch thickness (1 oz. finished weight)
E
r
4.5 (FR4 laminate)
Note
As the track width increases, the impedance decreases.
4 Target board design for tracing with ARM
®
DSTREAM-ST
4.2 PCB track impedance
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