Common-Mode Filter + ESD (CMF+ESD)
Two-in-one parts: EMI filter for differential pairs plus integrated ESD protection.
What is it?
A CMF+ESD device combines a common-mode choke (which suppresses common-mode noise on a differential pair like USB or HDMI) with low-capacitance ESD diodes in a single small package. This saves board space and reduces parts count for high-speed differential interfaces. The common-mode choke rejects noise that appears on both lines equally (often radiated EMI), while the ESD diodes clamp static discharge events.
When do you need it?
- USB 2.0 / 3.2 / USB4 differential pairs in phones and notebooks that must pass radiated-emission tests.
- HDMI and DisplayPort lines near antennas (e.g., smartphones, laptops with mmWave radios).
- Automotive USB, HDMI and DisplayPort links that must keep noise away from nearby LTE, GPS, Wi-Fi and V2X receivers.
- Any design where board space for separate CMF + ESD diodes is tight.
How to pick the right one
- CMR (Common-Mode Rejection) at target frequency
- Check the impedance curve at the noise frequency you need to reject, typically 100 MHz to 6 GHz.
- DC resistance (RDC)
- Integrated CMF+ESD parts are a few ohms per line (Magnias: 3-7 Ω typical). Check the DC drop at your line current; it is negligible for data but matters if the line also carries power.
- Differential-mode capacitance
- Lowest for >5 Gbps signals, ESD diode portion should be <0.5 pF.
- ESD rating
- IEC 61000-4-2 contact discharge rating, ±8 kV minimum for system-level.
- Package
- Small QFN: QFN1.4x1.35-6L or QFN1.7x1.5-6L for one pair, QFN2.2x1.35-10L or QFN2.6x1.35-10L for two pairs.
What Magnias offers
Magnias CMF+ESD parts filter and protect one or two differential pairs for USB 2.0, USB 3.2 and USB4 (up to 20 Gbps, CMF410-N10L), HDMI 2.0 / 2.1, DisplayPort 2.0 / 2.1, 10G Ethernet, MIPI and SIM / SD lines, with IEC 61000-4-2 level 4 ESD ratings (±8 kV contact or better) and bandwidth up to 10.7 GHz. AEC-Q101 versions: CMF210-N6L-A, CMF409-N10-A and CMF4245-N10-A. CMF802-N16L is an 8-line EMI low-pass filter with ESD protection for slower lines such as MCU, LCD and camera-module signals.