Reference magnetic actuator for self-calibration of a very small Hall sensor array

The magnetic sensitivity drift is one of the main problems with Hall devices in silicon. Common compensation methods are not applicable for unpredictable changes and irreversible drifts of the sensor characteristics, such as aging effects or stress variations caused by thermal shocks. One way to cope with it is to use an integrated coil as a reference magnetic field for self calibration. However, the applicability of this idea is strongly limited by the poor current-magnetic field transfer ratio (efficiency) of an integrated coil. The actuator performances can be increased by scaling it down, because the magnetic efficiency is inversely proportional to the size. We measure the efficiency for one actuator to be 392 mT/A which can reach 2000 mT/A by adding 4 coils in series and a ferromagnetic layer at the surface of the chip.

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