AN589 Datasheet, PDF (1/8 Pages) STMicroelectronics – CROSSTALK BEHAVIOUR OF ITA25 IN RS232 TRANSMISSION

AN589
APPLICATION NOTE
CROSSTALK BEHAVIOUR OF
ITA25 IN RS232 TRANSMISSION
INTRODUCTION
Crosstalk is a digital interference phenomenon between data lines. The signal transmission by one data
line produces parasitic voltages on nearby channels. These disturbances are due mainly to capacitive
coupling or electro magnetic interference. This phenomenon occurs particulary when a great number of
lines are located in a small area, notably in the case of multiline protection circuits having a high density.
The decrease of available area and the increase in the number of lines managed by a board forces the
use of a single chip configuration to realize the protection function.
The goal of this paper is to quantify the parasitic effect of STMicroelectronics monolithic protection prod-
ucts.
TEST DIAGRAM
To analyse the crosstalk behavior we will take as an example the most commonly- used interface: RS232.
Figure 1. Test circuits
+/- 12V
Driver 1 R1
Receiver 1
R2
ITA25B3
R'2
Receiver 2
R'1 ^{Driver 2}
+/- 12V
Figure 1 shows the test circuits used to do the crosstalk measurements.
The equivalent circuits of the drivers and receivers have been determined from the RS232C standard. So
the following tests are done with:
R1 + R’1 = 500 Ohms and R2 + R’2 = 3 k Ohms.
May 2004
REV. 2A - 3601
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