How to select a common-mode choke for EPS communication cables?

When selecting a common-mode choke for EPS communication lines (such as RS485, CAN, USB), the following parameters should be considered:

1. Impedance characteristics: Sufficient common-mode impedance is required at the communication signal frequency and its harmonic bands (e.g., CAN 500kbps corresponds to approximately 2.5MHz 5th harmonic) to suppress noise. Refer to impedance-frequency curves for selection; for example, the CML series offers models with different impedance values.

2. Differential-mode insertion loss: The differential-mode insertion loss at the signal frequency should be sufficiently small to ensure signal integrity and not affect the communication eye diagram.

3. Rated current: It must be greater than the actual current on the communication line (usually very small, in the mA range).

4. DC resistance (DCR): The DCR should be as small as possible to reduce signal voltage drop.

5. Operating voltage: Meets the line-to-ground voltage requirements.

6. Package and mounting: Select surface mount (SMD) or through-hole package based on board space. It is best to obtain or measure the S-parameters (especially Sdd21 and Scc21) during selection to assess their actual impact on signal and noise.