DALC208 Crosstalk behavior
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3 Crosstalk behavior
3.1 Crosstalk phenomena
Figure 13. Crosstalk phenomena
The crosstalk phenomenon is due to the coupling between 2 lines. The coupling factor (β12
or β21) increases when the gap across lines decreases, particularly in silicon dice. In the
example in Figure 13 the expected signal on load R
L2
is α
2
V
G2
, in fact the real voltage at this
point has got an extra value β
21
V
G1
. This part of the V
G1
signal represents the effect of the
crosstalk phenomenon of line 1 on line 2. This phenomenon has to be taken into account
when the drivers impose fast digital data or high frequency analog signals in the disturbing
line. The disturbed line will be more affected if it works with low voltage signal or high load
impedance (few kΩ). The following sections give the value of both digital and analog
crosstalk.
3.2 Digital crosstalk
Figure 14 shows the measurement circuit used to quantify the crosstalk effect in a classical
digital application. Figure 15 shows that in such a condition: signal from 0 V to 5 V and a rise
time of 5 ns, the impact on the disturbed line is less than 100mV peak to peak. No data
disturbance was noted on the concerned line. The same results were obtained with falling
edges.
Line 1
Line 2
V
G1
V
G2
R
G1
R
G2
DRIVERS
R
L1
R
L2
RECEIVERS
α
β
+
1
12
V
G1
V
G2
α
β
+
2
21
V
G2
V
G1
Figure 14. Digital crosstalk measurements Figure 15. Digital crosstalk results
DALC208SC6
100nF
+5V
Line 1
Line 2
V
G1
β
21
V
G1
+5V +5V
74HC04
+5V
Square
Pulse
Generator
5KHz
74HC04
