Sensor with common mode rejection and offset correction
AssigneeAllegro MicroSystems, LLC
InventorHernán D. Romero
Life of this patent
Estimating the term…
Abstract
A sensing bridge includes a first element type that is responsive to a magnetic field and a second element type that is not responsive to the magnetic field. The first element type can be a magnetoresistance element such as a TMR and the second element type can be a passive resistor. A switching matrix under control of a matrix controller is configured to change a total resistance of the sensing element by coupling or decoupling one or more dots of the TMR and/or passive resistor unit cells of the passive resistor to the sensing element. Test signal generation circuitry is configured to generate a common mode test magnetic field with which the common mode rejection ratio (CMRR) of a sensing bridge can be evaluated and corrected.
Claims19
A system, comprising:
- a sensing element including a first element of a first element type that is responsive to a magnetic field and a second element of a second element type that is not responsive to the magnetic field, wherein the second element is coupled to the first element and includes a plurality of passive resistor unit cells;
- a switching matrix that is configured to change a total resistance of the sensing element by coupling one or more of the plurality of passive resistor unit cells to the sensing element or by decoupling one or more of the plurality of passive resistor unit cells from the sensing element;
- and
- a matrix controller that is configured to cause the switching matrix to change the total resistance of the sensing element by coupling or decoupling one or more of the plurality of passive resistor unit cells.
A magnetic field sensor comprising:
- a sensing bridge including a sensing element configured to receive an applied magnetic field at a first frequency, wherein the sensing element includes one or both of a magnetoresistance element that is responsive to the applied magnetic field and that includes a plurality of dots and a passive resistor that is not responsive to the applied magnetic field and that includes a plurality of passive resistor unit cells;
- test signal generation circuitry configured to generate a common mode test magnetic field at a second frequency and combine the common mode test magnetic field with the applied magnetic field to generate a combined signal comprising a main signal portion;
- main processing circuitry configured to extract the main signal portion from the combined signal and produce a sensor output signal based on the main signal portion;
- and
- test signal processing circuitry configured to monitor a differential output of the sensing bridge at the second frequency to determine a sensitivity mismatch of the sensing bridge.
A magnetic field sensor comprising:
- a sensing bridge including a sensing element configured to receive an applied magnetic field at a first frequency, wherein the sensing element includes a magnetoresistance element that is responsive to the applied magnetic field and that includes a plurality of dots and a passive resistor that is not responsive to the applied magnetic field and that includes a plurality of passive resistor unit cells;
- test signal generation circuitry configured to generate a common mode test magnetic field at a second frequency and combine the common mode test magnetic field with the applied magnetic field to generate a combined signal comprising a main signal portion;
- main processing circuitry configured to extract the main signal portion from the combined signal and produce a sensor output signal based on the main signal portion;
- and
- test signal processing circuitry configured to monitor a differential output of the sensing bridge at the first frequency to determine an offset mismatch of the sensing bridge and to monitor the differential output of the sensing bridge at the second frequency to determine a CMRR of the sensing bridge.
Dependencies are inferred from the claim text.