SLYS030 May   2021 TMAG5123

PRODUCTION DATA  

  1. 1 Features
  2. 2 Applications
  3. 3 Description
  4. 4 Revision History
  5. 5 Device Comparison Table
  6. 6 Pin Configuration and Functions
  7. 7 Specifications
    1. 7.1 Absolute Maximum Ratings
    2. 7.2 ESD Ratings
    3. 7.3 Recommended Operating Conditions
    4. 7.4 Thermal Information
    5. 7.5 Electrical Characteristics
    6. 7.6 Magnetic Characteristics
    7. 7.7 Typical Characteristics
  8. 8 Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Field Direction Definition
      2. 8.3.2 Device Output
      3. 8.3.3 Protection Circuits
        1. 8.3.3.1 Load Dump Protection
        2. 8.3.3.2 Reverse Supply Protection
      4. 8.3.4 Hall Element Location
      5. 8.3.5 Power-On Time
      6. 8.3.6 Propagation Delay
      7. 8.3.7 Chopper Stabilization
    4. 8.4 Device Functional Modes
  9. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 In-Plane Typical Application Diagrams
        1. 9.2.1.1 Design Requirements
        2. 9.2.1.2 Detailed Design Procedure
        3. 9.2.1.3 Application Curve
  10. 10Power Supply Recommendations
  11. 11Layout
    1. 11.1 Layout Guidelines
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Receiving Notification of Documentation Updates
    2. 12.2 Support Resources
    3. 12.3 Trademarks
    4. 12.4 Electrostatic Discharge Caution
    5. 12.5 Glossary
  13. 13Mechanical, Packaging, and Orderable Information

Package Options

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

9.2.1.2 Detailed Design Procedure

When designing a digital-switch magnetic sensing system, three variables should always be considered: the magnet, sensing distance, and threshold of the sensor.

The TMAG5123 device has a detection threshold specified by parameter BOP, which is the amount of magnetic flux required to pass through the Hall sensor mounted inside the TMAG5123. To reliably activate the sensor, the magnet must apply a flux greater than the maximum specified BOP. In such a system, the sensor typically detects the magnet before it has moved to the closest position, but designing to the maximum parameter ensures robust turn-on for all possible values of BOP. When the magnet moves away from the sensor, it must apply less than the minimum specified BRP to reliably release the sensor.

Magnets are made from various ferromagnetic materials that have tradeoffs in cost, drift with temperature, absolute maximum temperature ratings, remanence or residual induction (Br), and coercivity (Hc). The Br and the dimensions of a magnet determine the magnetic flux density (B) it produces in 3-dimensional space. For simple magnet shapes, such as rectangular blocks and cylinders, there are simple equations that solve B at a given distance centered with the magnet.

GUID-07534156-B781-4AA2-97E0-A348DFBACC7B-low.gifFigure 9-2 Rectangular Block and Cylinder Magnets

Use Equation 1 for the rectangular block shown in Figure 9-2:

Equation 1. GUID-A8CBF78D-6E87-4072-AE3E-73AEFEBB81DE-low.gif

Use Equation 2 for the cylinder shown in Figure 9-2:

Equation 2. GUID-17CE144B-4258-4F7F-8D4E-B5911BB5A7D6-low.gif

where

  • W is width.
  • L is length.
  • T is thickness (the direction of magnetization).
  • D is distance.
  • C is diameter.

An online tool, the Hall Effect Switch Magnetic Field Calculator, that uses these formulas is located at http://www.ti.com/product/tmag5123.

All magnetic materials generally have a lower Br at higher temperatures. Systems should have margin to account for this, as well as for mechanical tolerances.

For the TMAG5123B, the maximum BOP is 4.5 mT. Choosing a 1-cm cube NdFeB N45 magnet, Equation 1 shows that this point occurs at 3.05 cm. This means that, provided the design places the magnet within 3.05 cm from the sensor during a "turn-on" event, the magnet will activate the sensor. The removal of the magnet away from the device will ensure a crossing of the minimum BRP point and will return the device to its initial state.