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LDC3114: Use case with both inductive and capacitive input sensing

Lars Wallden1
Prodigy 30 points
Part Number: LDC3114

Tool/software:

Hello, do you have any design examples where both inductive and capacitive inputs are used for the LDC3114?

In the application note snoa993a.pdf chapter 3 there is an example of this. Still, I cannot find any more information, for example, values for the LC net and recommended register settings for the use of a channel for capacitive input.

Is there any further documentation or can you recommend component values and register settings?

Best regards,

Lars Wallden

  • 0
    TI__Mastermind 23135 points

    Hello Lars,

    Thank you for considering to use Texas Instruments.  We are looking into your issue now and will provide an update later today.

  • 0 in reply to Patrick Simmons
    TI__Mastermind 23135 points

    Hello Lars,

    You can have a combination of inductive and capacitive sensors; however, each individual channel can only be one or the other.  For each channel you need to have a LC tank with a resonant frequency within the recommended operating range of 1 to 30 MHz.  For the capacitive sensing solution, your LC tank will be composed of a fixed value inductor and capacitor as well as a user’s finger which helps to form a variable capacitor with a plate attached at on of the LC tank nodes. The human body will act as a weak capacitor that should increase the capacitance.  Capacitive strength will depend on electrode surface area, distance the finger is from the electrode.  I think you might increase the sensitivity of the sensor or increase the value of the variable capacitor by having plates at both nodes of the LC tank that are separated from each other at the location you intend to detect a finger.

    I am not aware of a document that provides a detailed recipe on how to do a design, but these links might help with a general understanding of what to try.

    https://www.ti.com/lit/an/snoa970/snoa970.pdf

    https://www.allaboutcircuits.com/technical-articles/introduction-to-capacitive-touch-sensing/