PMC-Sierra, Inc.
STANDARD PRODUCT
PM5945 -UTP5
PMC-940202 ISSUE 2. APRIL 7, 1995
APP_SAPI_UTP5
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87
5.98 × h
Zo
=
× ln
ε
r
+1.41
0.8 × w + t
and based on the following layer setup:
w
1 Oz Copper
t
ε
r
r
dielectric
dielectric
h1
h2
h3
Ground Plane
Power Plane
1 Oz Copper
t
ε
1 Oz Copper
dielectric ε
1 Oz Copper
r
t
where
εr = relative dielectric constant, nominally 5.0 for G -10 fibre - glass epoxy
t = thickness of the copper, fixed according to the weight of copper selected.
For 1 oz copper, the thickness is 1.4 mil. This thickness can be ignored
if w is great enough.
h1, h2, h3 = thickness of dielectric.
w = width of copper
The parameters h1, h2, and h3 can be specified. For example, if a 20 mil (including
the copper thickness on both sides of the board) two layer core is selected, dielectric
material that has the same relative dielectric constant can be added to the both
sides of the core to construct a 4 layer board.
Since all the controlled impedance traces are on the component side, only h1 is
relevant in calculating the trace width. The calculation for the reference design is
shown in the table below:
Note: The relative dielectric constant is specified to be between 4.8 and 5.4.
Parameter
Data
ε
r
4.8
62
5.4
62
4.8
62
5.4
62
h (mil)
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54
PMC [ PMC-SIERRA, INC ]
