02380242| Datasheet

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Chokes for Data and Signal Lines General
1 Data line choke applications

In the field of data and signal transmission, it is becoming more and more important to ensure the electromagnetic compatibility (EMC).
s The number of systems (EDP systems, industrial data capture systems etc.) being used for the

acquisition, processing, and distribution of data is continuously growing.
s Microelectronics are spreading into new fields of application (e.g. automotive electronics). s The introduction of the ISDN, ADSL and ATM, with the associated high transmission rates and

world-wide networks, has lead to new EMC problems. Up to recently, the use of shielded cables has been the main way of preventing data transmission from being disturbed by RF interference fields. A more economical solution is the use of symmetrical transmission line systems. In these, twisted pair lines are used in conjunction with data line chokes. The chokes used here have extremely good symmetry characteristics.

Z
....

~
CP

....

= Data line choke

Z = Characteristic impedance
CP

CP = Parasitic capacitances

SSB1407-X

Diagram showing the principle of a symmetrical transmission line with data line chokes 2 Technical advantages

The main advantages are the low space requirements even for high inductance values used to suppress the common-mode interferences. This is achieved by using bifilar windings, which are more favorable for producing chokes with excellent symmetry characteristic than other winding designs. This results in very low stray inductance, a characteristic that is highly desirable for achieving the lowest possible attenuation of the differential-mode data signal. Data line chokes suppress common-mode interferences coupled into the data lines from frequencies as low as 1 kHz up, whereby they have no effect on the data signals with bandwidths of up to several MHz.

Note:
To guarantee that the choke's function is fully achieved, care must be taken to ensure that the vector sum of all currents flowing through the choke is zero.

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