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LDC0851: Coil specs for ~2mm Target

Ting Ye
Genius 11800 points
Part Number: LDC0851
Other Parts Discussed in Thread: LDCCOILEVM, LDC1612, LDC1612EVM

Dear Team,

For measuring a 2-mm target with LDC0851, I use webench to get below coil specs.
May I confirm with you if below coil and compatible 10nF is optimized for the application?

The outer diameter is set by 2mm x 0.8 = 1.6mm = 62.999mil.

https://webench.ti.com/wb5/LDC/#/spirals?shape=Circular&lcTanKCapacitance=10000&turns=3&layers=4&spaceBetweenTrace=4&traceWidth=4&copperThickness=1.000&dout=62&temperature=25&partno=LDC0851&voltage=1.8&x12=8&x23=36.6&x34=8

Thank you.

Regards,
Ting

  • 0
    TI__Genius 17440 points

    Hello Ting,

    Unfortunately the Webench tool does not save your input when you link it. Could you take a screenshot of your inputs and share them?

    Best Regards,

  • 0 in reply to Kristin Jones93
    TI__Genius 11800 points

    Hello Kristin,

    It seems below design for the coil is at margin spec.

    May I know if you could suggest a coil and It seems below design for the coil is at margin spec.

    May I know if you could suggest a sensor design to meet measuring 2-mm target? Thank you. 

  • 0 in reply to Ting Ye
    TI__Genius 17440 points

    Hello Ting,

    This coil is not feasible for any of our inductive sensing devices. The LDC0851 requires a minimum sensor inductance of 1.8uH in order to drive the sensor, and our other LDC devices have minimum resonant impedance requirements (the very lowest is 350 ohms).

    In general, it would be very challenging to design a coil to detect such a small target. Before designing the coil, I recommend ordering the LDC1612EVM and the LDCCOILEVM. The LDC1612 is our highest resolution device and is most likely to be able to detect such a small target. The LDCCOILEVM has small coils that would be more suitable to the small target, but can still be driven by the LDC1612. If the LDC1612 cannot detect this target with any of the coils on the board, then I do not suggest pursuing inductive sensing for this application.

    Best Regards,