Calibration of Hall Device Sensitivity Using an Auxiliary Hall Device

A method of operating a Hall effect sensor, the method comprising:

• providing a first bias current to a first Hall effect sensor element, and providing a second bias current to a second Hall effect sensor element, wherein the first Hall effect sensor element is adjacent the second Hall effect sensor element;
• exposing the first Hall effect sensor element and the second Hall effect sensor element to a target magnetic field to produce a respective first Hall voltage and a second Hall voltage;
• exposing the second Hall effect sensor element to a calibration magnetic field produced by an excitation coil within the Hall effect sensor device;
• producing an offset cancellation signal by comparing the second Hall voltage to the first Hall voltage;
• reducing offset in the first Hall voltage by combining the first Hall voltage and the offset cancellation signal;
• adjusting the second bias current to maintain a calibration signal produced by the calibration magnetic field at an approximate fixed value over a range of operation;
• and
• adjusting the first bias current to track the second bias current.

A Hall effect sensor comprising:

• a first Hall effect sensor positioned adjacent a second Hall effect sensor;
• a first bias current source coupled to the first Hall effect sensor;
• a second bias current source coupled to the second Hall effect sensor, wherein the first bias current generator is arranged to track the second bias current generator;
• an excitation coil positioned adjacent the second Hall effect sensor;
• and
• a feedback circuit coupled between an output of the second Hall effect sensor and a control input of the second bias current source.