AN588 datasheet(6/12 Pages) STMICROELECTRONICS

6 / 12 page

AN588 APPLICATION NOTE

6/12

Figure 6. The use of Transil Arrays as Emi Filter

Here is an example of a calculation of attentuation using the following hypothesis:

– L = 80nH (equal to an 8-cm track)

– C = 1100pF (ITA6U1M3 type)

This gives a cut-off frequency of FO = 17 MHz and an attenuation equal to 28dB at 80MHz.

The ITAxx assures a multi-channel protection without disturbing the signal transmissions.

The strong concentration of protection functions included in the ITAxx required the adoption of a new

monolithic technology. This concept, characterized by a high density of lines, generates parasitic capaci-

tances between adjacent channels. The trial testing done by our application laboratory showed that these

"crosstalk" disturbances were not sufficient enough to disrupt the most widely used numeric data trans-

mission lines.

An example of this would be the RS232 connection (VL = ±12V) where experimentation has allowed the

evaluation of the parasitic signals induced on the adjacent lines. This has showed them to be at ±2.5V

max (see Figure 8) for a duration of 0.4µs (see Figure 9).

Parasitic

Inductance

LC FILTER

SO 20

AN588 Datasheet(PDF) 6 Page - STMicroelectronics