Interference-Free Operation: Effective EMC Protection Through Selective Use of Ferrites

The mandatory CE test of electronic devices in the EMC laboratory clearly shows if the circuit and housing design was planned with HF in mind. Even at low clock frequencies, for example with microcomputer-controlled devices, interference can suddenly occur that far exceeds the useful frequencies that must be maintained, depending on the limit values specified for the particular use.

EMC ferrites are recommended for later interference suppression to decouple mains-borne interference in the high-frequency range. These ferrites come in different designs and solve problems quickly and economically. The devices are available and don't need to be redesigned.

Wired and SMD ferrites in various versions are interesting for circuit interference suppression on the board. Effective decoupling measures can be initiated here directly at the source of the interference.

Help in Selecting EMC Ferrites

Ferrites used in EMC interference suppression are generally nickel-zinc ferrites. Their high surface resistance (>106 Ω) rules out leakage currents or contact short circuits. The special thing about these ferrites is that the actual percentage of the loss resistance dominates from approx. 100 MHz upwards. This results in many advantages:

  • The ferrite is an absorber for frequencies of approx. 10 MHz upwards, so it has only a minor impact on the useful signal
  • The low-pass filter effect is achieved with wired ferrites or SMD ferrites solely through the bushing, so a ground potential doesn't have to be available here as a third pin!
  • Broadband interference is suppressed using only a single component
  • No capacitive impact on data or measurement signal lines

EMC Ferrite Designs

Snap ferrites are excellent for attaching later to existing lines. The special patented fastener of the snap ferrite by Wurth Electronics offers security against unintended opening (key word "CE label"). The UL-94-V0-approved plastic housing also protects the ferrite from mechanical damage and its design offers increased contact pressure on the ferrite halves. This results in very high impedances, i.e. high interference suppression.

Typical applications are measurement transducers, monitor lines, printer cables, mouse cords, data transmission lines, appliances etc.

To learn more about how to select the right ferrite for effective EMC protection, check back with our blog or see our many ferrite products.

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