SNOAAA5 April   2024 DRV8220 , FDC1004-Q1 , LDC3114-Q1 , TMAG5131-Q1 , TMAG5173-Q1 , TMAG6180-Q1

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1Introduction
  5. 2Automotive Door Handle Architectures
  6. 3Functional Demo Design
  7. 4Detailed Design Flow for Door Handle Functions
    1. 4.1 Door Open or Closed Detection With Magnetic Sensing
      1. 4.1.1 Demo Implementation of Open Close Detection Using TMAG5131-Q1
    2. 4.2 Deployable Door Handle Position Detection With Magnetic Sensing
      1. 4.2.1 Demo Implementation of Deployable Door Handle Position Sensing Using TMAG6180-Q1
    3. 4.3 Hand Proximity Detection With Capacitive Sensing
      1. 4.3.1 Overview of Capacitive Sensing Applications
      2. 4.3.2 Examples of Soft-Touch Detection Based on Capacitive Sensing in a Door Handle Demo
        1. 4.3.2.1 Touch Button
        2. 4.3.2.2 Door Handle
    4. 4.4 Push Button With Inductive Sensing
      1. 4.4.1 Inductive Push Buttons
      2. 4.4.2 Inductive Push Button Sensitivity
      3. 4.4.3 Target Material
      4. 4.4.4 Target Distance and Sensor Size
      5. 4.4.5 Design Example
  8. 5Summary
  9. 6References

4.4.4 Target Distance and Sensor Size

Inductive sensing relies on the interaction of EM fields generated by the inductive sensor and the eddy currents being induced on the conductive surface. The amount of eddy currents induced on the target surface decrease with an increase in DTARGET as the target conductive surface now captures a smaller portion of the electromagnetic field being generated by the inductive sensor. In turn, the size of electromagnetic field lines generated by an inductive sensing coil is directly proportional to the diameter of the sensor. Figure 4-27 shows how to set DTARGET as a percentage of the coil diameter for inductive touch. As Figure 4-27 shows, the best switch sensitivity happens when the DTARGET is within 20% of the diameter of the sensor coil. This can support push buttons with > 1um of target deflection.

GUID-B11663B5-FB37-42FC-A97E-7D954BD748B6-low.pngFigure 4-27 Button Sensitivity as a Function of Target to Sensor Distance (DTARGET) as a Percentage of the Sensor Coil Diameter