SBOS820A September 2019 – June 2020 TMCS1100
The TMCS1100 does not have stray field-rejection capabilities, so external magnetic fields from adjacent high-current traces or nearby magnets can impact the output measurement. The total sensitivity (S) of the device is comprised of the initial transformation of input current to magnetic field quantified as the magnetic coupling factor (G), as well as the sensitivity of the Hall element and the analog circuitry that is factory calibrated to provide a final sensitivity. The output voltage is proportional to the input current by the device sensitivity, as defined in Equation 11.
An external field, BEXT, is measured by the Hall sensor and signal chain, in addition to the field generated by the leadframe current, and is added as an extra input term in the total output voltage function:
Observable from Equation 12 is that the impact of an external field is an additional equivalent input current signal, IBEXT, shown in Equation 13. This effective additional input current has no dependence on Hall or analog circuitry sensitivity, so all gain variants have equivalent input-referred current error due to external magnetic fields.
This additional current error generates a percentage error defined by Equation 14.