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DS90UH947-Q1: Common Mode Choke Selection

Jared Becker
Genius 11855 points
Part Number: DS90UH947-Q1


Hi Team,

When selecting a common mode choke, what sort of impedance rating and DC resistance specification need to be taken into account?

I see that on the EVM, the common mode choke has the following specs:

Impendance = 90Ohm at 100Mhz, DC resistance = 410mOhm max

How did you come to select those specific criteria for the CMC?

Thank you!

Jared

  • 0
    TI__Expert 8165 points
    Jared,

    There is a training module on CMCs at training.ti.com/fpd-link-learning-center.

    Essentially, the CMC are there to filter out any noise created by the switching action of the gates within the device from propagating to the power sources supplying the VDD pins and causing EMI/EMC issues.

    The impedance of the CMC should be as high as it can be for the frequency band of interest (e.g. FPD-Link forward channel frequency components) and as low as possible at DC for minimal impact to the supply voltage levels.

    Regards,
    Davor