TIDUC07 March   2022

 

  1.   Description
  2.   Resources
  3.   Features
  4.   Applications
  5.   5
  6. 1System Description
  7. 2System Overview
    1. 2.1 Block Diagram
    2. 2.2 Highlighted Products
      1. 2.2.1 TMAG5170
      2. 2.2.2 DRV5055A4
    3. 2.3 Design Considerations
      1. 2.3.1 Magnet Selection
      2. 2.3.2 Magnet Shape
      3. 2.3.3 Magnet Rotation Speed
      4. 2.3.4 Sensor Location
      5. 2.3.5 Expected Performance
      6. 2.3.6 Layout for Sensor Location
      7. 2.3.7 45° Alignment
  8. 3Hardware, Software, Testing Requirements, and Test Results
    1. 3.1 Hardware Requirements
    2. 3.2 Test Setup
      1. 3.2.1 Test Equipment
      2. 3.2.2 Test Hardware Configuration
      3. 3.2.3 Test Software Configuration and Initial Data Capture
    3. 3.3 Test Results
      1. 3.3.1 Calibration Methods
      2. 3.3.2 TMAG5170 On-Axis
      3. 3.3.3 TMAG5170 In-Plane
      4. 3.3.4 TMAG5170 Off-Axis
      5. 3.3.5 TMAG5170 45° Alignment
      6. 3.3.6 DRV5055 Off Axis Result
  9. 4Design and Documentation Support
    1. 4.1 Design Files
      1. 4.1.1 Schematics
      2. 4.1.2 BOM
    2. 4.2 Tools and Software
    3. 4.3 Documentation Support
    4. 4.4 Support Resources
    5. 4.5 Trademarks

3.3.6 DRV5055 Off Axis Result

For this device, the sensitivity matching of the sensors requires some normalization by the controller before performing calculations on the captured analog data. This alignment requires sensors spread about the magnet by 90° and occupies more space than a single TMAG5170, and presents additional opportunity for mechanical misalignment. Despite these drawbacks, it is still possible to follow the same method of harmonic adjustment to eliminate angle error.

GUID-20220208-SS0I-C1XM-41GM-SCMQ4JRWDZ4M-low.png Figure 3-21 DRV5055 Off-Axis Configuration

DRV5055 Off-Axis Mechanical Angle Error shows the resulting pre-calibrated error captured for this alignment. The challenge observed using this configuration is that the number of mechanical errors possible in the system are now doubled with a second sensor. This produces a more complex error profile. Despite this, the same procedure for calibration applies and yields excellent results.

Figure 3-22 DRV5055 Off-Axis Mechanical Angle Error
HARMONIC αi βi
1 –7.3 0.35
2 1.17 0.22
3 –2.23 0.28
4 –0.81 –0.14
5 –0.075 0.01
6 –0.035 0.02
7 –0.03 –0.005
8 –0.01 0

DRV5055 Off-Axis Calibrated Angle Error shows the resulting error after applying the harmonic data.

Figure 3-23 DRV5055 Off-Axis Calibrated Angle Error