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

2.2 Design Considerations

Linear motor transport systems enable multiple magnetic movers travelling 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). Typically, the magnetic field ranges from 50mT to 300mT. Due to space requirements, small packages with highly integrated 3D Hall-effect sensor system-on-chip (SoC) are an advantage. An ambient operating temperature of the sensor beyond 85C, such as 125C, ambient enable higher power densities, while still capturing accurate sensor data under these extreme conditions. Since the position of multiple movers within one segment need to be detected at the same time, simultaneous sampling and low latency position measurement are important. 3D Hall-effect sensors with low latency digital interface offer an advantage over analog output SoC due to higher robustness against noise. A further advantage of an SoC with digital interface is the option to integrate diagnostics and monitoring of the SoC, for example die temperature, Hall-effect element or supply voltage diagnostics to increase system reliability.

Since the maximum field strength in Z-axis and X-axis can possibly not be identical, a 3D Hall-effect sensor which allows for individual range programming and optimization of each magnetic field axis helps support a higher position resolution and accuracy. Example system requirements of linear motor transport systems and the impact on the 3D Hall-effect sensor specifications are show in Table 2-1.

Table 2-1 Example Requirements for Magnetic Sensors for Linear Motor Transport Systems
PARAMETER EXAMPLE VALUE IMPACT TO POSITION SENSOR SoC
Mover speed up to 10m/s Impacts sensor sampling rate, closed loop position control frequency can be 4kHz or higher.
Mover position accuracy/repeatability as low as 0.01mm Impacts sensor resolution, accuracy and minimum displacement between adjacent sensors.
Sensor technology 3D/2D Hall-effect sensor 3D Hall-effect sensors enable two-dimensional position sensing.
Sensor magnetic field range 50mT … 300mT Full-scale magnetic field strength linear input range
Sensor resolution Typical 12-bit resolution SoC with programmable magnetic field range adjustment allow adjust input range for each axis and help increase resolution and accuracy.
Sensor interface Analog or serial digital Interface to MCU
Sensor latency as low as 100us Higher speed SPI, for example... 10MHz SPI help reduce system latency.
Simultaneous sampling of multiple movers position Sensor with low-jitter start-of-conversion capability. Sensor with hardware pin or SPI command-based start-of conversion signal input.
Sensor solution PCB area As small as possible. Integrated 3D Hall-effect SoC with digital interface enable smaller system footprint.
Operating temperature range

Small form-factor and high-power density lead to higher temperature inside a segment.

 3D Hall-effect SoC with greater 85C ambient temperature operating range.
EMC immunity SPI interface with CRC A digital interface with CRC offers higher robustness against impulse noise.
System reliability, predictive maintenance and fault detection 3D Hall-effect sensor, supply voltage, die temperature monitoring Enable through for example sensor with SPI and integrated diagnostics.