EP2S180F1020C4 Datasheet, PDF (741/768 Pages) Altera Corporation – Stratix II Device Handbook, Volume 1

High-Speed Board Layout Guidelines
Figure 11–3. Microstrip Trace Impedance with Changing Trace Width
80
70
60
50
Z0 (Ω) 40
30
20
10
0
4
4.5
5
5.5
6
6.5
7
7.5
8
8.5
9
W (mil)
Z0
T = 1.4 mils
H = 5.0 mils
Figure 11–4 shows microstrip trace impedance with changing height,
using the values in the microstrip impedance equation, keeping trace
width and trace thickness constant.
Figure 11–4. Microstrip Trace Impedance with Changing Height
80
70
60
50
Z0 (Ω) 40
30
20
10
0
4
5
6
7
8
H (mil)
Z0
T = 1.4 mils
W = 8.0 mils
9
10
The impedance graphs show that the change in impedance is inversely
proportional to trace width and directly proportional to trace height
above the ground plane.
Altera Corporation
May 2007
11–5
Stratix II Device Handbook, Volume 2