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Common mode choke: performance and basic parameters for its selection

The electronic systems installed in smart buildings to control elevators, access, or other applications in the field of home automation, are interconnected by a bus, forming a communications network.

This network is constantly exposed to radiation and external disturbances that contaminate it and fill it with electrical noise that can cause interference on the bus with consequent loss of information. Maybe turning a light “on” or “off” is not a problem, but when accessing a home or a floor, it could end up being one.

To prevent this from happening, a very important component is placed in the electronic system: the Common Mode Choke (CMCs). They serve to protect signal ports, enhancing them with immunity against conducted disturbances.
 

To evaluate the protection of a port, there are standards such as IEC 61000-4-6, which establishes how immune a device must be against electromagnetic disturbances that are induced in the bus and end up conducted into the interior of a device. Therefore, on many occasions, to obtain the CE marking, it is necessary to include these components in the device being designed. 

We can highlight 10 fundamental parameters when choosing the CMC:

1. Filter Type
2. Number of Lines
3. Inductance @ 100 kHz and Tolerance
4. Inductance @ Stray (typ.)
5. Current Rating
6. DC Resistance
7. V test
8. Operating temperature
9. Ratings
10. Mounting Type and Package

Coilmaster offers a wide variety of Common Mode Chokes (CMCs):

• High Frequency SMD Common Mode Choke - MM SERIES
• Signal / Data Line SMD Common Mode Choke (NiZn / MnZn Ring Core)
• High Current Power Line SMD Common Mode Choke

And depending on the final application, we must choose it bifilar or sectional:

Bifilar (without ‘S’)

• Less differential impedance
• High capacitive coupling
• Less leakage inductance
• Applications:
  • Líneas de datos, sensores…
  • USB, HDMI…

Sectional (con ‘S’)

• Low capacitive coupling
• High leakage inductance
• Applications
  • PSU input/output filter
  • SMPS decoupling

If you need support to choose the common mode Choke contact Eurotronix, our Field Application Engineers and Product Managers will guide you in choosing the PN that best suits your project.