Digital Signal Processing Reference
In-Depth Information
Aggressor Trace 1
Victim Trace
Aggressor Trace 2
Figure 9.2
Top view showing a victim trace fl anked by neighboring aggressor traces.
9.3.1 How Is the Capacitance Affected?
The capacitance for a tiny segment of the three traces illustrated in Figure 9.1 and
9.2 appears in Figure 9.3.
Figure 9.3 shows that when the victim and aggressors simultaneously switch in
phase with identical rise times, the voltage at each terminal simultaneously reaches
1V. This makes the voltage difference across either of the mutual capacitors (
C
12
or
C
23
) 0, which means no current flows and these capacitors can be removed without
altering the circuit behavior. The net result is that the total switched capacitance of
trace 2 is only
C
20
: its capacitance to ground.
0
→
1V
Aggressor 1
C
12
Δ
V = 0V
1V
Victim
Victim
0
→
1V
C
20
C
20
C
23
Δ
V = 0V
0
→
1V
Aggressor 2
Figure 9.3
When the victim and aggressor traces switch in phase, the victim capacitance is the
self-capacitance to ground (
C
20
).
