MAGNETIC-FIELD-ANGLE MEASUREMENT DEVICE AND ROTATIONAL-ANGLE MEASUREMENT APPARATUS USING SAME

• US 20130063135A1
• Filed: 05/14/2010
• Published: 03/14/2013
• Est. Priority Date: 05/14/2010
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Suzuki, Mutsumi, Iwasawa, Hiroshi, Iwamura, Masahiro
• Granted Patent: US 9,506,997 B2
• Time in Patent Office: Days
• US Class Current: 324/207.14
• CPC Class Codes: G01R 33/098 comprising tunnel junctions, e.g. tunnel magnetoresistance sensors
• CPC Class Codes: G11C 7/06 Sense amplifiers; Associated circuits , e.g. timing or triggering circuits
• CPC Class Codes: H10N 50/10 Magnetoresistive devices

Abstract

In a magnetic-field angle detection device and a rotation angle detection device in which the accuracy of the measured angle is not degraded even if the MR ratio of the tunneling magnetoresistance element is increased. In a magnetic-field-angle measurement apparatus including a magnetic-field-angle detection circuit and a magnetic sensor having a tunneling magnetoresistance element with a pinned magnetic layer, the magnetic-field-angle detection circuit has a power-supply unit that outputs a constant voltage as a bias voltage to the tunneling magnetoresistance element of the magnetic sensor and a current-detection unit that detects an output current of the tunneling magnetoresistance element. The accuracy of the measured angle of the magnetic-field angle detection device and the rotation angle detection device is improved by measuring the tunneling magnetoresistance element current while maintaining the terminal voltage of the tunneling magnetoresistance element constant with input impedance of the current-detection unit as zero.

Claims

1-16. -16. (canceled)

17. A magnetic-field-angle measurement apparatus comprising:

a magnetic sensor; and

a magnetic-field-angle detection circuit,

wherein the magnetic sensor has a tunneling magnetoresistance element with a pinned magnetic layer,

the tunneling magnetoresistance element of the magnetic sensor has first and second feeding terminals and a first sensing terminal,

the magnetic-field-angle detection circuit has a power-supply unit that outputs a constant voltage as a bias voltage to the tunneling magnetoresistance element of the magnetic sensor and a current-detection unit that detects a flowing current through the tunneling magnetoresistance element,

a terminal voltage of the tunneling magnetoresistance element is detected through the first sensing terminal, and

the power-supply unit performs feedback control such that the terminal voltage matches a predetermined voltage value.

18. The magnetic-field-angle measurement apparatus according to claim 17,

wherein the tunneling magnetoresistance element has a second sensing terminal in addition to the first sensing terminal, and

the terminal voltage of the tunneling magnetoresistance element is detected through the first and second sensing terminals.

19. The magnetic-field-angle measurement apparatus according to claim 17,

wherein the power-supply unit has a differential amplifier with differential inputs of an output voltage of the first sensing terminal and an output of a reference-voltage generation unit.

20. The magnetic-field-angle measurement apparatus according to claim 17,

wherein the power-supply unit generates a pulsed voltage.

21. The magnetic-field-angle measurement apparatus according to claim 17,

wherein the magnetic sensor has two tunneling magnetoresistance elements in which angles of magnetization of the pinned magnetic layers are different from each other by 90°

.

22. A rotation-angle measurement apparatus comprising:

the magnetic-field-angle measurement apparatus according to claim 17; and

a magnet fixed to a rotation unit.

23. A magnetic-field-angle measurement apparatus comprising:

a magnetic sensor; and

a magnetic-field-angle detection circuit,

wherein the magnetic sensor has a tunneling magnetoresistance element with a pinned magnetic layer, a free magnetic layer, and a tunnel-insulator layer,

the magnetic-field-angle detection circuit has a power-supply unit that outputs a constant voltage as a bias voltage to the tunneling magnetoresistance element of the magnetic sensor and a current-detection unit that detects a flowing current between the pinned magnetic layer and the free magnetic layer of the tunneling magnetoresistance element, and

input impedance of the current-detection unit is set to zero.

24. The magnetic-field-angle measurement apparatus according to claim 23,

wherein the current-detection unit has an operational amplifier that detects a flowing current through the tunneling magnetoresistance element, and

the input impedance of the current-detection unit is set to zero by connecting the input terminal of the operational amplifier to virtual ground.

25. The magnetic-field-angle measurement apparatus according to claim 23,

wherein the power-supply unit outputs a constant voltage of a pulsed voltage as a bias voltage to the tunneling magnetoresistance element of the magnetic sensor.

26. The magnetic-field-angle measurement apparatus according to claim 23,

wherein the magnetic sensor has two tunneling magnetoresistance elements in which angles of magnetization of the pinned magnetic layers are different from each other by 90°

.

27. A rotation-angle measurement apparatus comprising:

the magnetic-field-angle measurement apparatus according to claim 23; and

a magnet fixed to a rotation unit.

28. A magnetic-field-angle measurement apparatus comprising:

a magnetic sensor; and

a magnetic-field-angle detection circuit,

wherein the magnetic sensor has a tunneling magnetoresistance element with a pinned magnetic layer, a free magnetic layer, and a tunnel-insulator layer,

the magnetic-field-angle detection circuit has a current-supply unit and a current-detection unit that detects a flowing current between the pinned magnetic layer and the free magnetic layer of the tunneling magnetoresistance element,

the current-supply unit has a voltage-input terminal connected to a voltage-generation unit, a current-input terminal to which a current from the current-detection unit is input, and a current-output terminal through which a current is output to the magnetic sensor,

a flowing current of the current-input terminal and a flowing current of the current-output terminal are equal,

a voltage of the current-output terminal is set on the basis of a voltage of the voltage-generation unit, and

the current-detection unit is connected to the current-input terminal of the current-supply unit, and the magnetic sensor is connected to the current-output terminal.

29. The magnetic-field-angle measurement apparatus according to claim 28,

wherein the current-supply unit has a field-effect transistor and a current-supply unit operational amplifier, and

one terminal of the field-effect transistor and the voltage-generation unit are connected to input terminals of the current-supply unit operational amplifier.

30. The magnetic-field-angle measurement apparatus according to claim 28,

wherein the current-supply unit has a transistor with a base to which an output voltage of the voltage-generation unit is input.

31. The magnetic-field-angle measurement apparatus according to claim 28,

wherein the voltage-generation unit generates a pulsed voltage.

32. The magnetic-field-angle measurement apparatus according to claim 28,

wherein the magnetic sensor has two tunneling magnetoresistance elements in which angles of magnetization of the pinned magnetic layers are different from each other by 90°

.

33. The magnetic-field-angle measurement apparatus according to claim 32,

wherein the magnetic-field-angle detection circuit has the two current-supply units, and

the current-supply units are electrically connected to the two tunneling magnetoresistance elements, respectively.

34. A rotation-angle measurement apparatus comprising:

the magnetic-field-angle measurement apparatus according to claim 28; and

a magnet fixed to a rotation unit.