Patent ID: 11971463
Assignee: ALLEGRO MICROSYSTEMS, LLC
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 5:
6. Method for compensating an output voltage of a MTJ sensing circuit comprising a plurality of MTJ sensor elements connected in a bridge configuration, the MTJ sensing circuit having an input for inputting a bias voltage and generating an output voltage proportional to the external magnetic field multiplied by the bias voltage and a gain sensitivity of the MTJ sensing circuit, wherein the gain sensitivity and the output voltage vary with temperature; the MTJ sensing circuit further comprising a temperature compensation circuit configured to provide a modulated bias voltage that varies as a function of temperature over a temperature range;
wherein the temperature compensation circuit further comprises a plurality of subrange resistors configured to pass a PTAT current, a plurality of comparators, and an array-based memory cell having a plurality of registers, each register representing a bias voltage corresponding to one of the temperature subranges;
the method comprising:
measuring temperature of the MTJ sensing circuit;
using the temperature compensation circuit to modulate the bias voltage with temperature such that the modulated bias voltage multiplied by the gain sensitivity is constant; comprising:
using the temperature compensation circuit to generate a plurality of reference voltages, each reference voltage corresponding to a temperature subrange of the temperature range;
generating a temperature dependent voltage for each subrange resistor, by forcing the PTAT current in the plurality of subrange resistors;
using the plurality of comparators to compare temperature dependent voltages to a plurality of fixed voltage references, and generating a hysteresis comparator output for each comparator; and
using the array-based memory cell to select one of the register depending on the hysteresis comparator output.