Magneto-Resistive Sensor With Test Mode Activation

• US 20080258716A1
• Filed: 03/04/2005
• Published: 10/23/2008
• Est. Priority Date: 03/16/2004
• Status: Active Grant

• Current Assignee: NXP B.V. (NXP Semiconductors NV)
• Original Assignee: NXP B.V. (NXP Semiconductors NV)
• Inventors: Hinz, Michael
• Granted Patent: US 7,626,384 B2
• Time in Patent Office: Days
• US Class Current: 324/207.21
• CPC Class Codes: G01D 18/00 Testing or calibrating apparatus or arrangements provided for in groups G01D1/00 - G01D15/00
• CPC Class Codes: G01D 5/145 influenced by the relative movement between the Hall device and magnetic fields see G01R33/06

Abstract

In particular in automotive applications, sensor systems comprising geometrical leak shift sensor elements must fulfill properties and requirements with respect to quality, accuracy and safety. For this, sensors have to be tested and trimmed. According to an exemplary embodiment of the present invention, a magneto-resistive sensor is provided, allowing for a testing and trimming of the sensor elements by applying a homogenous magnetic field to the sensor Advantageously, this allows for the provision of a magneto-resistive sensor, having a simple arrangement.

Claims

1. Magneto-resistive sensor, comprising:

a first plurality of first magneto-resistive elements;

a second plurality of second magneto-resistive elements;

a first signal processing unit which is connected to the first plurality of first magneto-resistive elements for generating a first output signal;

wherein the first output signal has a first phase;

a second signal processing unit which is connected to the second plurality of second magneto-resistive elements for generating a second output signal;

wherein the second output signal has a second phase;

wherein the sensor has an operation mode and a test mode;

a third signal processing unit for processing the first and second output signals;

wherein the third signal processing unit is adapted to activate one of the operation mode and the test mode on the basis of the first and second output signals; and

wherein, when the first and second plurality of first and second magneto-resistive elements are exposed to an homogeneous magnetic field, the third signal processing unit is adapted to activate the test mode.

2. The sensor of claim 1, wherein the third signal processing unit is adapted to activate the test mode when a phase difference between the first phase and the second phase is essentially one of 0 and π

.

3. The sensor of claim 1,

wherein the first plurality of first magneto-resistive elements form a first bridge generating a first bridge signal

wherein the second plurality of second magneto-resistive elements form a second bridge generating a second bridge signal;

wherein the first processing unit includes an adder for adding the first and second bridge signals;

wherein the second processing unit includes a subtractor for subtracting the first bridge signal from the second bridge signal; and

wherein the third signal processing unit is adapted to activate the test mode when a signal level of one of the first and second output signals is below a preset level.

4. The sensor of claim 1,

wherein the first and second pluralities of first and second magneto-resistive elements are geometrically displaced with respect to each other;

wherein the sensor is one of a position sensor, revolution speed sensor and angle sensor, in particular for automotive applications; and

wherein, in the test mode, the first and second pluralities of first and second magneto-resistive elements are adjustable.

5. The sensor of claim 1,

wherein the third signal processing unit is adapted to activate the operation mode when the first and second plurality of first and second magneto-resistive elements are at least one of no longer exposed to the homogenous magnetic field and exposed to the inhomogenous field;

and

wherein the first and second plurality of first and second magneto-resistive elements are arranged such that in the operation mode, an exposure of the first and second plurality of first and second magneto-resistive elements to an inhomogeneous magnetic field causes a phase difference of essentially π

/2 between the first and second phase.

6. Method of operating a magneto-resistive sensor, the magneto-resistive sensor comprising:

a first plurality of first magneto-resistive elements;

a second plurality of second magneto-resistive elements;

a first signal processing unit which is connected to the first plurality of first magneto-resistive elements for generating a first output signal;

wherein the first output signal has a first phase;

a second signal processing unit which is connected to the second plurality of second magneto-resistive elements for generating a second output signal;

wherein the second output signal has a second phase;

wherein the sensor has an operation mode and a test mode;

a third signal processing unit for processing the first and second output signals; and

wherein the third signal processing unit is adapted to activate one of the operation mode and the test mode on the basis of the first and second output signals;

the method comprising the step of;

activating the test mode when an homogeneous magnetic field is applied to the first and second plurality of first and second magneto-resistive elements.

7. Method of at least one of testing and trimming a magneto-resistive sensor, the method comprising:

applying a homogenous magnetic field to the magneto-resistive sensor; and

performing one of a testing and

trimming of the magneto-resistive sensor when the homogenous magnetic field is applied to the magneto-resistive sensor.

9. The device of claim 7,

wherein the coil arrangement comprises a Helmholtz coil arrangement.

8. Device for at least one of testing and trimming of a magneto-resistive sensor, the device comprising:

a coil arrangement adapted to generate a homogenous magnetic field.