SBOA518 January   2022 TMCS1100 , TMCS1100-Q1 , TMCS1101 , TMCS1101-Q1 , TMCS1107 , TMCS1107-Q1 , TMCS1108 , TMCS1108-Q1

 

  1.   Trademarks
  2. 1Introduction
  3. 2Device Operation
  4. 3Grounding
  5. 4Measurement Range
    1. 4.1 Swing Limitations
    2. 4.2 Noise Limitations
  6. 5External Fields
    1. 5.1 Earth's Magnetic Field
    2. 5.2 Conduction Paths
    3. 5.3 Additional Magnetic Components
  7. 6External Field Mitigation
    1. 6.1 Shielding
    2. 6.2 Calibration
  8. 7Summary

5 External Fields

When working with Hall sensors, external magnetic sources can influence the measurement for any device that does not have any additional circuitry for removing external fields, such as the TMCS1100 and TMCS1101. The Hall sensors present in such devices are unable to differentiate when it comes to a sensed magnetic field. Utilizing the magnetic coupling factor found in the data sheet, the sensors inside the package amplify the sensed field, and therefore the presence of any unwanted fields is manifested as an error on the output of the device.

With a quantifiable value of an external field, use Equation 6 to approximate the error produced internal to the TMCS110x from an external field. For a static field, this manifests as an offset in the measurement, while a dynamic or periodic field may look like a random signal coupled onto the output.

Equation 6. %ErrorexternalB-field=BexternalBideal, internal×100%

where

Equation 7. Bideal, internal =Load Current×Magnetic Coupling Factor

Recognizing that unaccounted external magnetic fields may lead to measurement error, it is imperative to identify what might produce such fields. These fields are not limited to sources external to a board under analysis, but can also be due to various components and structures on the board, as well as externally coupled sources, including and not limited to the Earth's magnetic field.