8 Application and Implementation
Note
Information in the following applications sections is not part of the TI component specification,
and TI does not warrant its accuracy or completeness. TI’s customers are responsible for
determining suitability of components for their purposes, as well as validating and testing their design
implementation to confirm system functionality.
8.1 Application Information
The LDC3114 supports multiple buttons. Each button can be configured in various ways for optimal operation.
8.1.1 Theory of Operation
An AC current flowing through an inductor will generate an AC magnetic field. If a conductive material, such
as a metal object, is in close proximity to the inductor, the magnetic field will induce circulating eddy currents
on the surface of the conductor. The eddy currents are a function of the distance, size, and composition of the
conductor. If the conductor is deflected toward the inductor as shown in
, more eddy currents will be
generated.
Figure 8-1. Metal Deflection
The eddy currents create their own magnetic field, which opposes the original field generated by the inductor.
This effect reduces the effective inductance of the system, resulting in an increase in sensor frequency.
shows the inductance and frequency response of an example sensor with a diameter of 14 mm. As the
sensitivity of an inductive sensor increases with closer targets, the conductive plate should be placed quite close
to the sensor—typically 10% of the sensor diameter for circular coils. For rectangular or race-track-shaped coils,
the target to sensor distance should typically be less than 10% of the shorter side of the coil.
SNOSDD0 – DECEMBER 2021
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