SBAS646A November   2018  – August 2020 DRV5057

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Pin Configuration and Functions
    1.     Pin Functions
  6. 6 Specifications
    1. 6.1 Absolute Maximum Ratings
    2. 6.2 ESD Ratings
    3. 6.3 Recommended Operating Conditions
    4. 6.4 Thermal Information
    5. 6.5 Electrical Characteristics
    6. 6.6 Magnetic Characteristics
    7. 6.7 Typical Characteristics
  7. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Magnetic Flux Direction
      2. 7.3.2 Sensitivity Linearity
      3. 7.3.3 Operating VCC Ranges
      4. 7.3.4 Sensitivity Temperature Compensation for Magnets
      5. 7.3.5 Power-On Time
      6. 7.3.6 Hall Element Location
    4. 7.4 Device Functional Modes
  8. 8 Application and Implementation
    1. 8.1 Application Information
      1. 8.1.1 Selecting the Sensitivity Option
      2. 8.1.2 Decoding a PWM
        1. 8.1.2.1 Decoding a PWM (Digital)
          1. 8.1.2.1.1 Capture and Compare Timer Interrupt
          2. 8.1.2.1.2 Oversampling and Counting With a Timer Interrupt
          3. 8.1.2.1.3 Accuracy and Resolution
        2. 8.1.2.2 Decoding a PWM (Analog)
    2. 8.2 Typical Applications
      1. 8.2.1 Full-Swing Orientation Example
        1. 8.2.1.1 Design Requirements
        2. 8.2.1.2 Detailed Design Procedure
        3. 8.2.1.3 Application Curve
      2. 8.2.2 Half-Swing Orientation Example
        1. 8.2.2.1 Design Requirements
        2. 8.2.2.2 Detailed Design Procedure
    3. 8.3 What to Do and What Not to Do
  9. 9 Power Supply Recommendations
  10. 10Layout
    1. 10.1 Layout Guidelines
    2. 10.2 Layout Examples
  11. 11Device and Documentation Support
    1. 11.1 Documentation Support
      1. 11.1.1 Related Documentation
    2. 11.2 Receiving Notification of Documentation Updates
    3. 11.3 Support Resources
    4. 11.4 Trademarks
    5. 11.5 Electrostatic Discharge Caution
    6. 11.6 Glossary
  12. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

8.2.1.2 Detailed Design Procedure

Linear Hall effect sensors provide flexibility in mechanical design because many possible magnet orientations and movements produce a usable response from the sensor. Figure 8-2 illustrates one of the most common orientations that uses the full north to south range of the sensor and causes a close-to-linear change in magnetic flux density as the magnet moves across the sensor. Figure 8-3 illustrates the close-to-linear change in magnetic field present at the sensor as the magnet moves a given distance across the sensor. The usable linear region is close to but less than the length (thickness) of the magnet.

When designing a linear magnetic sensing system, always consider these three variables: the magnet, sensing distance, and the range of the sensor. Select the DRV5057 with the highest sensitivity possible based on the system distance requirements without railing the sensor PWM output. To determine the magnetic flux density the sensor receives at the various positions of the magnet, use a magnetic field calculator or simulation software, referring to magnet specifications, and testing.

Determine if the desired accuracy is met by comparing the maximum allowed duty cycle least significant bit (%DLSBmax) with the noise level (PWM jitter) of the device. Equation 3 calculates the %DLSBmax by taking into account the used length of the linear region (travel distance), the desired resolution, and the output PWM swing (within the linear duty cycle range).

Equation 3. GUID-8D66CC14-4480-48ED-ADA9-F1F338E89760-low.gif

Thus, with this example (and a linear duty cycle range of 8%D to 92%D), using Equation 3 gives (92 – 8) / (10) × 0.1 = 0.84%DLSBmax. This value is larger than the 0.1%D jitter, and therefore the desired accuracy can be achieved by using Equation 2 to select a %DLSB that is equal to or less than 0.84. Then, simply calibrate the magnet position to align the sensor output along the movement path.