SNOA961A February   2017  – February 2023 LDC2112 , LDC2114 , LDC3114 , LDC3114-Q1

 

  1.   Inductive Touch System Design Guide for HMI Button Applications
  2. 1Mechanical Design
    1. 1.1 Theory of Operation
    2. 1.2 Button Construction
    3. 1.3 Mechanical Deflection
    4. 1.4 Mechanical Factors that Affect Sensitivity
      1. 1.4.1 Target Material Selection
        1. 1.4.1.1 Material Stiffness
        2. 1.4.1.2 Material Conductivity
      2. 1.4.2 Button Geometry
      3. 1.4.3 Spacing Between Target and Sensor
    5. 1.5 Layer Stacks of Touch Buttons
      1. 1.5.1 Conductive Surface
      2. 1.5.2 Non-Conductive Surface
    6. 1.6 Sensor Mounting Reference
    7. 1.7 Sensor Mounting Techniques
      1. 1.7.1 Adhesive-Based
      2. 1.7.2 Spring-Based
      3. 1.7.3 Slot-Based
    8. 1.8 Mechanical Isolation
  3. 2Sensor Design
    1. 2.1 Overview
      1. 2.1.1 Sensor Electrical Parameters
      2. 2.1.2 Sensor Frequency
      3. 2.1.3 Sensor RP and RS
      4. 2.1.4 Sensor Inductance
      5. 2.1.5 Sensor Capacitance
      6. 2.1.6 Sensor Quality Factor
    2. 2.2 Inductive Touch
    3. 2.3 LDC211x/LDC3114 Design Boundary Conditions
    4. 2.4 Sensor Physical Construction
      1. 2.4.1 Sensor Physical Size
      2. 2.4.2 Sensor Capacitor Position
      3. 2.4.3 Shielding INn traces
      4. 2.4.4 Shielding Capacitance
      5. 2.4.5 CCOM Sizing
      6. 2.4.6 Multi-Layer Design
        1. 2.4.6.1 Sensor Parasitic Capacitance
      7. 2.4.7 Sensor Spacers
      8. 2.4.8 Sensor Stiffener
      9. 2.4.9 Racetrack Inductor Shape
    5. 2.5 Example Sensor
  4. 3Summary
  5. 4Revision History

2.4.4 Shielding Capacitance

The LC resonator sensor can respond to both inductive and capacitive changes. In order to prevent any capacitive effects from causing undesired signal responses, the metal target should have a fixed constant potential. Therefore in constructing the sensor-target system, the conductive target should be AC grounded to shield any external capacitances.

GUID-AB4457AC-A4FE-4840-928F-BF32C28006D1-low.pngFigure 2-7 AC Grounded Target for Shielding Capacitive Effects