AN2536 Freescale Semiconductor / Motorola, AN2536 Datasheet - Page 4

• Manufacturer Part Number: AN2536
• Description: MC9328MX1 and MC9328MXL High Speed Layout Design Guidelines
• Manufacturer: Freescale Semiconductor / Motorola

Design Consideration
Stripline Impedance
A circuit trace routed on an inside layer of the PCB with two low-voltage reference planes (i.e., power and
/ or GND) constitutes a stripline layout. You can use Equation 5 to calculate the impedance of a microstrip
trace layout.
Using the typical values of W = 9 mil, H = 24 mil, T = 1.4 mil,
solving for microstrip impedance (Z) yields the result of Figure 5. The measurement unit in mils.
4
Figure 5. Stripline Trace Impedance vs. Trace Width (W)
Freescale Semiconductor, Inc.
Figure 4. Impedance vs. Trace Thickness (T)
For More Information On This Product,
MC9328MX1/MXL Application Note
Z
o
Z
o
=
Go to: www.freescale.com
=
---------- -
60
4.1
------- -
60
ε
r
•
•
log
log




----------------------------------------------
0.67π1.4 )
------------------------------------------
0.67π T
4x 24
4 H
(
×
(
+
+
0.8W
)
0.8 9 ( )
ε
)


r


and (FR-4) = 4.1 with Equation 5 and
⋅
≈
Ω
From the previous figures, we found
the impedance is inversely
trace thickness (T) using the values
in Equation 3, keeping trace width
and dielectric height constant
proportional to trace width and
directly proportional to trace height
above the ground plane.
This figure shows impedance vs.
50Ω
This figure shows the
stripline trace impedance
vs. trace width (W) using
values in Equation 5,
keeping dielectric height
and trace thickness
constant.
MOTOROLA
Eqn. 5
Eqn. 6