Device and current sensor for providing information indicating a safe operation of the device of the current sensor
An example of a device comprises a signal generator to generate a signal causing a magnetic self test field for a magneto-resistive sensing element. A signal input is configures to receive a first sensor signal at a first time instant before the magnetic self test field is applied and a second sensor signal at a second time instant after the magnetic self test field is applied. An evaluation circuit is configured to determine information indicating a safe operation based on an evaluation of the first sensor signal and the second sensor signal.
1. A device, comprising:
a signal generator to generate a signal causing a magnetic self test field for a magneto-resistive sensing element;
a signal input to receive a first sensor signal of the magneto-resistive sensing element at a first time instant before the magnetic self test field is applied and a second sensor signal of the magneto-resistive sensing element at a second time instant after the magnetic self test field is applied; and
an evaluation circuit to determine information indicating a safe operation based on an evaluation of the first sensor signal and the second sensor signal,
wherein the evaluation is configured to determine that the magneto-resistive sensing element is in a safe operation state if a difference between the first sensor signal and the second sensor signal corresponds to an expected response of the magneto-resistive sensing element to the magnetic self test field.
2. The device of claim 1 , wherein the signal is configured to cause a current through a compensation coil of the magneto-resistive sensing element.
3. The device of claim 1 , wherein the signal is configured to cause a current through a flipping coil of an anisotropic magneto-resistive sensing element.
4. The device of claim 3 , wherein the signal is configured to cause a current through the flipping coil which is smaller than a further current used to flip a direction of a magnetization of the anisotropic magneto-resistive sensing element.
5. The device of claim 3 , wherein the signal is configured to cause a flipping current through the flipping coil which generates a magnetic flipping field causing a flipping of a direction of a magnetization of the anisotropic magneto-resistive sensing element.
6. The device of claim 1 , wherein the signal generator is further configured to cause a further magnetic self test field after the second time instant.
7. A current sensor comprising:
at least one magneto-resistive sensing element to provide a sensor signal in response to a magnetic field;
a signal generator to cause a magnetic self test field at the magneto-resistive sensing element;
a readout circuit to receive a first sensor signal of the magneto-resistive sensing element at a first time instant before the magnetic self test field is applied and a second sensor signal of the magneto-resistive sensing element at a second time instant after the magnetic self test field is applied; and
an evaluation circuit to determine information indicating a safe operation of the current sensor based on an evaluation of the first sensor signal and the second sensor signal;
wherein the evaluation circuit is configured to determine that the magneto-resistive sensing element is in a safe operation state if a difference between the first sensor signal and the second sensor signal corresponds to an expected response of the magneto-resistive sensing element to the magnetic self test field.
8. The current sensor of claim 7 , further comprising:
at least one compensation coil to compensate an external magnetic field at the magneto-resistive sensing element at least partly if a current flows through the compensation coil, wherein the signal generator is configured to cause a current through the compensation coil.
9. The current sensor of claim 7 , comprising four magneto-resistive sensing elements, the magneto-resistive sensing elements being coupled as a Wheatstone bridge.
10. The current sensor of claim 7 , wherein the magneto-resistive sensing element is an anisotropic magneto-resistive sensing element.
11. The current sensor of claim 10 , further comprising:
at least one flipping coil to flip a direction of a magnetization of the anisotropic magneto-resistive sensing element.
12. The current sensor of claim 11 , wherein the signal generator is configured to cause a flipping current through the flipping coil, the flipping current generating a magnetic flipping field used to flip the magnetization of the anisotropic magneto-resistive sensing element.
13. The current sensor of claim 12 wherein the signal generator generates a current through the flipping coil which is smaller than the flipping current.
14. The current sensor of claim 12 , wherein the evaluation circuit is configured to determine that the magneto-resistive sensing element is in a safe operation state if a difference between the first sensor signal and the second sensor signal corresponds to an expected offset of the magneto-resistive sensing element.