USBLC6-2

6/11

4. CROSSTALK BEHAVIOR

4.1. Crosstalk phenomena

Figure 11: Crosstalk phenomena

The crosstalk phenomena are due to the coupling between 2 lines. The coupling factor (

increases when the gap across lines decreases, particularly in silicon dice. In the example above the

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 perturbed line will be more affected if it works with low voltage

signal or high load impedance (few k

Ω).

Figure 12: Analog crosstalk measurements

Figure 12 gives the measurement circuit for the analog application. In usual frequency range of analog

signals (up to 240MHz) the effect on disturbed line is less than -55 dB (please see figure 13).

Line 1

Line 2

DRIVERS

RECEIVERS

α

β

+

1

12

α

β

+

2

21

SPECTRUM ANALYSER

Vout

50

Ω

TRACKING GENERATOR

Vg

Vin

50

Ω

TEST BOARD

C=100nF

Figure 13: Analog crosstalk results

As the USBLC6-2 is designed to protect high

speed data lines, it must ensure a good transmis-

sion of operating signals. The frequency response

(figure 5) gives attenuation information and shows

that the USBLC6-2 is well suitable for data line

transmission up to 480 Mbit/s while it works as a

filter for undesirable signals like GSM (900MHz)

frequencies, for instance.

100.0k

1.0M

10.0M

100.0M

1.0G

-120.00

-90.00

-60.00

-30.00

0.00

Analog Crosstalk

APLAC 7.91 User: ST Microelectronics Jan 12 2005

dB

f/Hz

Attenuation