Multi-turn magnetic sensing with rollover counting

1 . A method of multi-turn magnetic sensing with rollover counting, the method comprising:

resetting a multi-turn magnetic sensor to a reset state, wherein the multi-turn magnetic sensor comprises a magnetic spiral having N turns, and wherein N is a positive integer greater than 1;

updating an index value in association with the resetting; and

determining a turn count based on output signals from the multi-turn magnetic sensor, output signals from a second multi-turn magnetic sensor, and the index value, wherein the output signals from the multi-turn magnetic sensor are indicative of a state of the multi-turn magnetic sensor, wherein the turn count has a value having a magnitude that is greater than N, and wherein domain walls propagate in an opposite direction in the second multi-turn magnetic sensor compared to the multi-turn magnetic sensor.

2 . The method of claim 1 , wherein the resetting comprises applying a reset magnetic field to the multi-turn magnetic sensor using a coil.

3 . The method of claim 1 , wherein the resetting comprises causing a permanent magnet to move in proximity to the multi-turn magnetic sensor.

4 . The method of claim 1 , further comprising:

after additional rotation of a magnetic field following the determining, generating a turn count having a second value,

wherein the value represents clockwise rotations from an initialization state, and

wherein the second value represents counterclockwise rotations from the initialization state.

5 . The method of claim 1 , wherein the multi-turn magnetic sensor and the second multi-turn magnetic sensor are each filled with domain walls in the reset state.

6 . The method of claim 1 , wherein the turn count has a quarter turn resolution.

7 . The method of claim 1 , further comprising:

processing an output signal from an angle sensor to generate angle information; and

generating a position measurement based on the turn count and the angle information.

8 . A multi-turn magnetic sensing system with rollover counting, the multi-turn magnetic sensing system comprising:

a multi-turn magnetic sensor comprising a magnetic spiral with N turns, wherein N is a positive integer greater than 1;

a second multi-turn magnetic sensor comprising a second magnetic spiral, wherein domain walls propagate in opposite directions in the magnetic spiral and the second magnetic spiral; and

processing circuitry comprising:

memory configured to store an index value; and

a decoder configured to determine a turn count with a value having a magnitude that is greater than N based on output signals from the multi-turn magnetic sensor, output signals from the second multi-turn magnetic sensor and the index value, wherein the output signals from the multi-turn magnetic sensor are indicative of a state of the multi-turn magnetic sensor, wherein the turn count represents a number of rotations of a magnetic field.

9 . The multi-turn magnetic sensing system of claim 8 , further comprising a magnetic reset configured to magnetically reset the magnetic spiral.

10 . The multi-turn magnetic sensing system of claim 9 , wherein the magnetic reset comprises a coil configured to apply a reset magnetic field to magnetically reset the magnetic spiral in response to a control signal from the processing circuitry.

11 . The multi-turn magnetic sensing system of claim 9 , wherein the processing circuitry is configured to update the index value in association with magnetically resetting the magnetic spiral.

12 . The multi-turn magnetic sensing system of claim 9 , wherein the processing circuitry is configured to update the index value in response to detecting rotation of the magnetic field after magnetically resetting the magnetic spiral.

13 . The multi-turn magnetic sensing system of claim 8 , wherein the second magnetic spiral has N turns.

14 . The multi-turn magnetic sensing system of claim 8 , wherein the processing circuitry is configured to detect a change in rotation direction of the magnetic field.

15 . The multi-turn magnetic sensing system of claim 8 , wherein the decoder is configured to determine the turn count with a second value having a magnitude that is greater than N, wherein the value represents clockwise rotations from an initialization state, and the second value represents counterclockwise rotations from the initialization state.

16 . The multi-turn magnetic sensing system of claim 8 , further comprising an angle sensor, wherein the processing circuitry is configured to output a position measurement based on the turn count and angle information from the angle sensor.

17 . A multi-turn magnetic sensing system with rollover counting, the multi-turn magnetic sensing system comprising:

a first multi-turn magnetic sensor comprising a first magnetic spiral with N turns, wherein N is a positive integer greater than 1;

a second multi-turn magnetic sensor, wherein domain walls propagate in opposite directions in the second multi-turn magnetic sensor and the first multi-turn magnetic sensor in response to a magnetic field; and

a decoder configured to output a turn count based on an index value and states of the first multi-turn magnetic sensor and the second multi-turn magnetic sensor, wherein the decoder is configured to determine the turn count for more than N full clockwise rotations of the magnetic field from an initialization state and to determine the turn count for more than N full counterclockwise rotations of the magnetic field from the initialization state.

18 . The multi-turn magnetic sensing system of claim 17 , further comprising a magnetic reset configured to magnetically reset the first multi-turn magnetic sensor to a reset state, and processing circuitry configured to update the index value in association with magnetically resetting the first multi-turn magnetic sensor.