Common-mode filters with integrated ESD protection (ECMF)

Modern high-speed communication interfaces use a differential mode to speed up data transmission.

Reducing the signal amplitude in not sufficient because smaller signal amplitudes are more sensitive to noise in single-ended transmissions. To counter this, we transmit equal amplitude signals in reverse phase along two lines (D+, D-) and then take the differential at the receiver.

The differential transmission mode is preferable for high-speed data transmission applications because it’s less sensitive to noise or ground effects. This mode also reduces spurious radiation because the magnetic field around the two lines is canceled.

Single-ended transmission Differential transmission

Single-ended transmission differential mode transmission

Applications for common mode filters:

Ideal for high-speed data lines like MIPI DSI or CSI, HDMI, TMDS lines, or USB superspeed signals.

  • Notebook
  • Laptop
Streaming box
  • Streaming box
  • HDMI stick
Game console
  • Game console
  • Set top box
Docking station
  • Docking station
  • Tablet
  • Devices

Common mode filters for high-speed data lines

For high-speed data lines like MIPI DSI or CSI, HDMI, TMDS lines, or USB superspeed signals, ST has developed a range of common mode filters. They integrate ESD protection tailored to reject a wide range of frequency bands such as 700 MHz LTE, 2.4 GHz Bluetooth, and 2.4 and 5 GHz Wi-Fi, with a deep level of attenuation.

Common-mode filters avoid RF antenna desense in applications where the high-speed differential links generate radiated noise at the frequencies of the RF antenna. ST’s common-mode filters are highly useful in applications with RF receivers operating near high-speed differential data lines.

When subjected to common-mode noise, high-speed differential lines radiate unwanted noise. Common-mode filters prevent differential lines from radiating and interfering with other RF signals nearby.

ECMF types of products

ST’s ECMF are available in WLCSP and DFN packages that are compatible with industrial and automotive requirements. They’re available in 2-lines or 4-lines, and offer an optimized flow-through footprint with high common-mode attenuation of unwanted frequencies.

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Benefits of common-mode filters with integrated protection:

  • 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 ESD protection diodes and common-mode filter
  • Low serial resistance to reduce eye-diagram distortion
  • High reduction of parasitic elements through integration
  • Industrial optimization thanks to plastic package

Benefits of differential transmission with common-mode filter

Differential transmission schema

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