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LDC2114: LDC2114 with CM-Chokes

test_user
Intellectual 625 points
Part Number: LDC2114
Other Parts Discussed in Thread: LDC1101EVM

Hello,

I just tried to use the LDC2114 with CM-Chokes (SRF3216-222).

I put them into the IN-lines as described in SNOA962, but signal isn't decreasing anymore when I push the button.

-Is LDC2114 suitable to use with CM-Chokes?

-Should I place the CM-Choke before or after the sensor capacitor?

Kind Regards,

Clemens

  • 0
    TI__Genius 13335 points
    Hello,
    When you add the common mode choke, did you adjust the LDC2114 settings (CNTSC, LC_DIVIDER, SENCYCx, FREQx, RPx, and GAIN)? If the LDC2114 is not configured properly for the sensor, or the sensor is outside of the design space, then it will not oscillate or give you a strong reading on the output. If possible, I would measure the sensor with the common-mode choke on an impedance analyzer to collect the sensor parameters, namely the Rp, Q factor, and the resonant frequency. If you're not able to get access to an impedance analyzer then you may consider using an LDC1101EVM to measure the sensor because it can be used to determine both the inductance value and resistance values. It will always help to see an oscilloscope capture of the sensor pins to make sure there is oscillation occurring as well as a screen capture/data log of the LDC2114 DATA values from the GUI and other register settings.
    Regards,
    Luke
  • 0 in reply to Luke LaPointe
    TI__Genius 13335 points
    Hello,
    I just wanted to check back in and see if you were still experiencing issues. If you have further updates or questions then feel free to post them here and we'd be happy to assist you, otherwise I will go ahead and close this thread.
    Thanks,
    Luke
  • 0 in reply to Luke LaPointe
    Intellectual 625 points

    Hello,

    I'm very sorry for my late response.

    You're right, we just put the chokes in the IN-lines without changing sensor parameters.

    Later we'll go in here deeper to determine the parameters.

    Meanwhile we were measuring our system in an EMC laboratory.

    We didn't have any problems with emission, but failed at radiated immunity.

    We tested two setups: The first one with 0.3mm SSL surface, and the second one with 0.5mm glass fascia and a very thin copper foil as target (less than 50 um)

    The setup with 0.3mm SSL surface had no problems with radiation, but the glass-version failed. (I've attached a diagram of the Output Datas)

    The output datas started to act up at 500MHz over a wide frequency range.

    Why do these two systems behave so different? Its the same hardware, only the mechanical setup is different.

    Kind regards,

    Clemens

    Luke LaPointe said:
    Hello,

    I just wanted to check back in and see if you were still experiencing issues. If you have further updates or questions then feel free to post them here and we'd be happy to assist you, otherwise I will go ahead and close this thread.
    Thanks,
    Luke