TIDUC26A April   2022  – April 2024

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   6
  7. 1System Description
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
      1. 2.2.1 Inductive Touch Buttons
      2. 2.2.2 Sensor Coil Placement
      3. 2.2.3 Collecting Data from Multiple LDCs
      4. 2.2.4 Magnetic Dial Implementation
      5. 2.2.5 CORDIC Algorithm
    3. 2.3 Highlighted Products
      1. 2.3.1 LDC3114-Q1
      2. 2.3.2 TMAG5273
      3. 2.3.3 DRV2605
      4. 2.3.4 TLV75518
      5. 2.3.5 TCA9534
      6. 2.3.6 PCA9543
      7. 2.3.7 Sensor Control Board
  9. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Firmware and Programming
      1. 3.1.1 Operational Mode 1
      2. 3.1.2 Operational Mode 2
      3. 3.1.3 Operational Mode 3
    2. 3.2 Test Setup
    3. 3.3 Test Results
      1. 3.3.1 ABS Force Response
      2. 3.3.2 ABS Gain Corrected
      3. 3.3.3 Nylon Force Response
      4. 3.3.4 Nylon Gain Corrected
  10. 4Hardware Components
  11. 5Design and Documentation Support
    1. 5.1 Design Files
      1. 5.1.1 Schematics
      2. 5.1.2 BOM
    2. 5.2 Tools and Software
    3. 5.3 Documentation Support
    4. 5.4 Support Resources
    5. 5.5 Trademarks
  12. 6Revision History

3.3.4 Nylon Gain Corrected

The Nylon had a wider range in button forces required so the gain correction requires larger values than the ABS to obtain an even response.

GUID-20220331-SS0I-0BGS-JVFQ-314X6JQKXJZL-low.svgGUID-20220331-SS0I-2T4F-XTSG-KCTN6NMGD6ST-low.svg
(a) Left Side(b) Right Side

Figure 3-6 Nylon Gain Corrected

The downside to having the increased gain correction is the inverse response that can be seen on some button channels while other nearby buttons are pressed. This occurs due to the mechanical nature of the button design where the press on one button causes the other button surface to slightly flex away from the sensor coil. Since the data moves in the opposite direction from the button press, the impact can be ignored in the application and the baseline algorithm in the device has additional tools to handle this impact so that it does not become an issue. That being said, cases like this can be minimized by isolating the mechanical movement as best as possible.

Lastly, after gain correction on both materials, the difference between the two can be seen. From the graphs, the ABS has a larger response to each force applied than the Nylon. This is partially be due to the difference of materials but also due to the assembly of the housing. The adhesion between the PCB and button surface is done by hand on the test units and can lead to imperfections in the design. This shows the importance of having a tight assembly process to obtain consistent results between units.