SNOA930C March   2015  – May 2021 LDC0851 , LDC1001 , LDC1001-Q1 , LDC1041 , LDC1051 , LDC1101 , LDC1312 , LDC1312-Q1 , LDC1314 , LDC1314-Q1 , LDC1612 , LDC1612-Q1 , LDC1614 , LDC1614-Q1 , LDC2112 , LDC2114 , LDC3114 , LDC3114-Q1

 

  1.   Trademarks
  2. 1The Sensor
    1. 1.1 Sensor Frequency
    2. 1.2 RS and RP
      1. 1.2.1 AC Resistance
      2. 1.2.2 Skin Effect
  3. 2Inductor Characteristics
    1. 2.1 Inductor Shape
      1. 2.1.1 Example Uses of Different Inductor Shapes
    2. 2.2 Number of Turns
    3. 2.3 Multiple Layers
      1. 2.3.1 Mutual Inductance of Coils in Series
      2. 2.3.2 Multi-Layer Parallel Inductor
      3. 2.3.3 Temperature Compensation
    4. 2.4 Inductor Size
    5. 2.5 Self-Resonance Frequency
      1. 2.5.1 Measurement of SRF
      2. 2.5.2 Techniques to Improve SRF for Wire-wound Inductors
  4. 3Capacitor Characteristics
    1. 3.1 Capacitor RS, Q, and SRF
    2. 3.2 Effect of Parasitic Capacitance
      1. 3.2.1 Recommended Capacitor Values
    3. 3.3 Capacitor Placement
  5. 4Physical Coil Design
    1. 4.1 Example Design Procedure Using WEBENCH
      1. 4.1.1 General Design Sequence
    2. 4.2 PCB Layout Recommendations
      1. 4.2.1 Minimize Conductors Near Sensor
      2. 4.2.2 Sensor Vias and Other Techniques for PCBs
  6. 5Summary
  7. 6References
  8. 7Revision History

4.1 Example Design Procedure Using WEBENCH

WEBENCH provides two methods for PCB coil design. The first method finds a coil design that fits a specific application, in which the desired measurement capabilities are used to recommend a sensor.

The second method is an interactive design tool in which the coil size, shape, number of turns, and other parameters can be adjusted to optimize the sensor design to fit a specific need. This tool can be accessed at WEBENCH Inductor Design Tool.

GUID-47D19CD7-CF79-4F9E-8CE7-15B14110CA81-low.pngFigure 4-1 WEBENCH Coil Designer Tool

The top-middle pull-down menu selects the desired coil shape – choices include:

  • Circular
  • Square
  • Hexagonal
  • Octagonal

As discussed earlier, for most applications a circular sensor is the optimum shape, although square coils may be useful for smaller geometry sensors.

The lower-left section of the screen is where various sensor parameters can be entered and adjusted. Parameters to enter include the size, number of turns, and PCB fabrication characteristics.

The middle section reports the sensor characteristics based on the current settings.

Finally, the sensor design can be exported to the following output formats:

  • Altium Designer

  • Cadence Allegro 16.0-16.6

  • CadSoft EAGLE PCB (v6.4 or newer)

  • DesignSpark PCB

  • Mentor Graphics PADS PCB

The output can then be imported into CAD tools to complete a system design.