Automotive common-mode filters with integrated ESD protection (ECMF)

Common mode filters (CMF) are filters that minimize common mode noise in differential transmission lines, power lines, and audio lines. They are used in non-automotive applications (USB, HDMI, Mipi, …) and automotive applications such as USB, CAN, CAN-FD, 100Base-T1, 1000Base-T1, LVDS, SerDes, ...

They're perfect for reducing common mode noise with frequencies ranging from a few megahertz to a few hundred megahertz while causing no signal degradation.

Common mode filter lets differential signals pass and attenuate common-mode noiseCommon mode filter lets differential signals pass and attenuate common-mode noise


Why common-mode filters are needed in automotive applications?

ST’s common-mode filters for Automotive applications are qualified as per AEC-Q101 and are compliant with standards IEC 61000-4-2 and ISO 10605.

They have been designed with electrostatic discharge protection for 2 differential line pairs that attenuate common mode signals while providing enhanced communications performances.

Designed to avoid RF antenna desense in applications where the high-speed differential links generate radiated noise at frequencies received by the RF antenna, they are specifically intended for non-shielded cables (UTP Unshielded Twisted Pair) often used in HDBaseT and IEEE 1000Base-T1 connectivity solutions for digital video and audio, Ethernet, and other control communications.

They are useful in SerDes (serializer/deserializer) applications including FPD-link, GMSL, and MIPI DSI or CSI to avoid radiation in vehicle-to-everything (V2X) (5.9 GHz) and Global Navigation Satellite System (GPS, Glonass, BeiDou, Galileo, and IRNSS) frequencies.

They help to ensure a successful certification for:

  • CISPR-25, international standard for radio disturbance characteristics
  • 2004/104/EC European standard for radiated emission and immunity
  • SAE J1113/41 for North America markets


ECMF types of products:

ST’s ECMF are available either in WLCSP package or DFN package to be compatible with industrial and automotive assembly requirements. Available in 2-lines or 4-lines, they offer an optimized flow-through footprint, with high common mode attenuation of unwanted frequencies.

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Benefits of automotive common-mode filters: 

  • High-Speed ESD protection & immunity
  • Improved ESD clamping thanks to dual clamping structure (ESD diode and serial resistor of inductance)
  • Improved receiver sensitivity by removing common mode noise in useful antenna bandwidth
  • Space and BOM savings by integrating both the ESD protection diodes and the common mode filter
  • Low serial resistance to reduce eye-diagram distortion
  • Help to ensure CISPR-25, international standard for radio disturbance characteristics, 2004/104/EC European standard for radiated emission and immunity and SAE J1113/41 for North America markets
  • High reduction of parasitic elements through integration.
  • Compatible with automotive assembly thanks to plastic package

FREE WEBINAR 10.7 GHz bandwidth common-mode filters for new USB4 and HDMI 2.1 standards

During this one hour webinar, you will learn how to optimize antenna RF sensitivity in noisy conditions in compliance with EMC standards for industrial and personal electronics applications. This webinar will help hardware engineers concerned with antenna de-sense or EMC standards compliance, as well as embedded systems engineers looking for ways to design more compact high-speed USB and HDMI connectors. There is a dedicated session with various RSSI, spectrum analyses, and transmission speed test results for Wi-Fi and 10 Gbps data transmission.


  • Why ECMF is required:
    • Noise suppression and common mode filtering
    • Antenna de-sense and immunity concerns for compliance with EMC standards
  • ST application lab session with:
    • SSI test results, spectrum analysis, and transmission speed test results of 10 Gbps USB transmission
    • Overview of latest USB4 and HDMI 2.1 standards
    • ST ECMF application and product overview