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LDC2114: Interference with coil of buck converter

test_user
Intellectual 625 points
Part Number: LDC2114


Hello,

do you know if the magnetic field of the coil neccesary for a buck converter will influence inductive touch sensing?

The coil of the buck converter (which operates at 500kHz) will only be separated a few mm benath the touch sensing coil.

Regards and thanks for your answer,

Clemens

  • 0
    TI__Genius 14270 points
    Hello Clemens,

    Yes, interference can happen if the converter coil is physically close enough, matches the frequency of the inductive sensor, and is an unshielded inductor. The inductive sensors are typically high Q and so will limit the interference from frequencies even a small amount off. You can also operate the LDC at higher frequencies than switch converters typically operate at.

    Regards,
    ChrisO
  • 0 in reply to Chris Oberhauser66
    Intellectual 625 points

    Hello Chris,

    thanks for your answer. So do you think with switch converter operating at 500kHz and LDC operating opertaing at 10MHz will lead to significant interference?

    Regards,

    Clemens

  • 0 in reply to test_user
    TI__Genius 14270 points
    Hello Clemens,

    The 500kHz switching frequency very unlikely to pose any issue, as that frequency is significantly different from the sensor frequency. If you actually do manage to have an interaction, use a shielded inductor for your switching converter will help significantly.

    The parameters to consider are:
    1) physical proximity - the interference is a near-field effect, and so you would typically need to closer than a few mm to even possibly have an interaction. For coils smaller than 10mm in diameter, you would probably need to be less than 1mm.
    2) interfering signal - the interfering frequency needs to be close to the sensor frequency and quite strong. With a 500kHz converter, you would need to have horrible harmonics before you have an issue, since the 20th harmonic is what will interfere with the sensor.
    3) sensor Q - if your sensor Q is low (<5), you will be more susceptible to interference. A higher Q will help.

    Regards,

    ChrisO
  • 0 in reply to Chris Oberhauser66
    Intellectual 625 points

    Hello Chris,

    thanks for your detailed explanation!

    Due to the fact that we're okay at all three points i think there won't be a problem.

    Maybe these three points could somehow be included in SNOA961,SNOA962 or SNOSD15B, because i think they are very interesting.

    Thanks for your help and kind regards,

    Clemens