TIDUF78 May   2024

 

  1.   1
  2.   Description
  3.   Resources
  4.   Features
  5.   Applications
  6.   Design Images
  7. 1System Description
    1. 1.1 Key System Specifications
  8. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Design Considerations
    3. 2.3 Highlighted Products
  9. 3System Design Theory
    1. 3.1 Hardware Design
    2. 3.2 Software Design
      1. 3.2.1 TMAG5170 SPI Frame
        1. 3.2.1.1 Serial Data In 32-Bit Frame
        2. 3.2.1.2 Serial Data Out 32-Bit Frame
      2. 3.2.2 TMAG5170 Register Configuration
      3. 3.2.3 SPI and Start-of-Conversion Timing
      4. 3.2.4 Linear Position Calculation
  10. 4Hardware, Software, Testing Requirements, and Test Results
    1. 4.1 Hardware
      1. 4.1.1 PCB Overview
      2. 4.1.2 MCU Interface Connector
    2. 4.2 Test Setup
    3. 4.3 Test Results
      1. 4.3.1 Magnetic Z and X Field Measurement
      2. 4.3.2 Linear Position Measurement
      3. 4.3.3 SPI Signal Measurement
  11. 5Design and Documentation Support
    1. 5.1 Design Files
      1. 5.1.1 Schematics
      2. 5.1.2 BOM
      3. 5.1.3 PCB Layout
        1. 5.1.3.1 Layout Prints
        2. 5.1.3.2 Layout Guidelines
    2. 5.2 Tools and Software
    3. 5.3 Documentation Support
    4. 5.4 Support Resources
    5. 5.5 Trademarks
  12. 6About the Author

1 System Description

Linear position sensing using Hall-effect sensors is used in many applications such linear servo drives, proximity switches in factory automation and linear motor transport systems. Depending on the application, either the sensor head with a Hall-effect sensor is moving over a static magnetic stripe with multiple poles, or a magnetic target is moving over a static Hall-effect sensor or an array of Hall-effect sensors.

Linear motor transport systems allow multiple magnetic movers traveling in one or even two dimensions with speeds up to 10m/s and a linear position accuracy and repeatability as low as 0.01mm. The magnetic field range present at the magnetic sensor depends on the mover’s sense magnet and the distance between the mover magnet to the static multi-position sensor printed-circuit board (PCB).

Figure 1-1 shows the sensing principle of the linear position sensing using equally spaced high-precision linear 3D Hall-effect sensors. The distance between each 3D Hall-effect sensor is system specific and depends on the magnetic strength of the mover, the magnet diameter, the airgap and the desired position accuracy. Typical distances between adjacent 3D Hall-effect sensors are system specific and can be in the range of 10mm to 50mm.

TIDA-060045 Cross PCB Section With Multiple 3D Hall-Effect Sensors Figure 1-1 Cross PCB Section With Multiple 3D Hall-Effect Sensors

This reference design demonstrates precision, low latency linear position sensing of a N45 magnet target using four 3D Hall-effect sensors TMAG5170 with a 25mm displacement. A common start-of-conversion signal enables simultaneous measurement of the four 3D Hall-effect sensors. The Z-axis, X-axis, and CRC data measured with the TMAG5170 are transmitted in a single 32-bit frame over 10MHz SPI for low latency and enhanced data integrity. The data can be read out through SPI either sequentially using the chip-select of the corresponding 3D Hall-effect sensors or all four sensors in parallel through an MCU. The digital interface with 3.3V I/O is compatible to the C2000™ MCU LaunchPad and enables evaluation of our 3D Hall-effect sensing technology with a C2000™, Sitara or other MCUs.