JP2005274447A - Ic chip, mi sensor, electronic equipment with mi sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an IC chip, an MI sensor, an electronic equipment with the MI sensor capable of reducing a size, capable of connecting the plurality of MI elements, and having excellent S/N ratio. <P>SOLUTION: The IC chip 13 is constituted of a pulse generation circuit 20 for generating a short pulse width of pulse signal, an XYZ-axis switching circuit 21 for distributing the pulse signal, based on an XYZ-axis switching signal, a switching circuit 24 for supplying the current-amplified pulse signal into a control input part to supply an excitation current to the MI elements 12, a sampling circuit 31 for detecting a peak value of a detection signal induced in the MI elements 12 by the excitation current, and the like. The peak value of the detection signal is easily detected by a control signal for the pulse signal in the sampling circuit 31, since the pulse signal after distributed from the XYZ-axis switching circuit 21 serves as the control signal for the switching circuit 24 and the control signal for the sampling circuit 31. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an IC chip used for an MI (magneto-impedance effect) sensor capable of detecting a weak magnetic field, an MI sensor, and an electronic device including the MI sensor.

  Conventionally, Hall sensors, fluxgate sensors, magnetoresistive (MR) sensors, etc. have been put to practical use as magnetic sensors. Among these, the fluxgate sensor has a feature of high detection sensitivity of 1 μOe, and the MR sensor has a magnetosensitive element having a size of several tens of μm, and has features of low power consumption and high-speed response.

  On the other hand, as a magnetic sensor, a magnetic impedance effect type (MI) sensor using a magnetic impedance effect (MI effect) has been proposed. The MI sensor has a structure in which a detection coil is wound around an amorphous wire made of a soft magnetic material. The MI sensor generates a skin effect by supplying a high-frequency or pulsed excitation current to the amorphous wire, and the impedance changes due to the change in the magnetic permeability of the amorphous wire by the action of the external magnetic field applied in the longitudinal direction of the amorphous wire. Changes, and the external magnetic field is detected using a phenomenon in which a detection signal corresponding to the magnitude of the external magnetic field is induced in the detection coil.

The MI sensor has features such as (1) a magnetic field detection limit of 1 μOe and high sensitivity, and (2) low power consumption because a short pulse current is used. Taking advantage of these features, MI sensors have begun to be mounted on portable electronic devices such as an electronic compass (see, for example, Patent Documents 1 and 2).
JP-A-6-176930 JP 2001-296127 A

  By the way, the detection signal induced in the detection coil of the MI element is an analog signal, and its peak value is proportional to the magnitude of the longitudinal component of the amorphous wire of the external magnetic field. Therefore, the signal-to-noise ratio (S / N ratio) of the MI sensor can be improved by accurately detecting the peak value of the detection signal.

  However, the detection signal induced with the rise of the pulsed excitation current has a short time width of several nsec to several tens of nsec, and the detection signal has a steep waveform. A voltage value deviated from the peak value of the signal is detected, and the S / N ratio is likely to be deteriorated. Although it is conceivable to improve the S / N ratio by shortening the rise time of the excitation current and increasing the peak value of the detection signal, the change in the voltage value of the detection signal becomes large and the detection timing becomes more difficult. There is a problem of becoming.

  Further, it is necessary to provide a circuit for supplying an excitation current to each of the plurality of MI elements and a circuit for detecting a detection signal, and there is a problem that detection of the detection signal becomes more difficult due to variations in the circuit for each MI element.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide an IC chip, an MI sensor, and an S / N ratio that can be reduced in size and that can connect a plurality of MI elements, It is to provide an electronic device provided with an MI sensor.

  According to one aspect of the present invention, an excitation current is supplied to a plurality of MI elements that detect an external magnetic field, and a detection signal corresponding to the magnitude of the external magnetic field is supplied from the plurality of MI elements based on the excitation current. An IC chip comprising: pulse generation means; current supply switching means for supplying an excitation current to the MI element; and sampling means for detecting a substantially peak value of a detection signal supplied from the MI element, The current supply switching means and the sampling means are provided for each MI element, and the pulse generation means generates the control input section of the current supply switching means and the control input section of the sampling means corresponding to one MI element. There is provided an IC chip comprising switching means for simultaneously distributing pulse signals.

  According to the present invention, when detecting the peak value of the detection signal corresponding to the magnitude of the external magnetic field from the plurality of MI elements, the pulse signal for controlling the timing of the excitation current for inducing the detection signal and the detection timing are set. For the pulse signal to be controlled, a pulse signal distributed simultaneously for each MI element by the switching means is used. Therefore, even if the waveform of the pulse signal is deformed or delayed by the switching means, it is based on the same pulse signal, so that it is possible to prevent the detection synchronization from shifting, and as a result, the peak value of the detection signal can be reliably ensured. Therefore, an IC chip having a good S / N ratio can be realized.

  The switching unit may distribute the pulse signal based on a switching signal supplied from the outside of the IC chip. By supplying a switching signal from an MPU or the like connected to the IC chip, the IC chip detects the magnitude of the external magnetic field decomposed for each MI element, and outputs the output signal to the MPU or the like as an output signal. The size and direction can be detected.

  A delay unit is provided between the switching unit and the control input unit of the current supply switching unit, and the sampling unit detects a detection signal based on a pulse signal supplied to the control input unit of the sampling unit. The pulse signal supplied to the control input unit of the current supply switching unit may be delayed so that the detection signal and the peak of the detection signal are synchronized. By delaying the detection signal, the peak of the detection signal can be easily synchronized when the sampling means is shut off.

  The peak of the detection signal may be formed corresponding to the rise of the excitation current. By using the peak of the detection signal induced when the exciting current rises, it can be easily synchronized with the pulse signal supplied to the control input unit of the sampling means.

  Further, another delay unit is provided between the switching unit and the control input unit of the sampling unit, and the other delay unit is detected by the sampling unit based on a pulse signal supplied to the control input unit of the sampling unit. The pulse signal supplied to the control input unit of the sampling means may be delayed so that the signal is detected and the peak of the detection signal is synchronized. By delaying the pulse signal supplied as a control signal to the sampling means instead of delaying the detection signal described above, the peak of the detection signal can be easily synchronized when the sampling means is shut off.

  The peak of the detection signal may be formed corresponding to the fall of the excitation current. By using the peak of the detection signal induced when the excitation current falls, it can be easily synchronized with the pulse signal supplied to the control input unit of the sampling means.

  The switching signal may be composed of a 2-bit parallel signal connected to the three MI elements. By making the switching signal a 2-bit parallel signal, the pulse signal can be serially distributed to the three MI elements.

  According to another aspect of the present invention, there is provided an MI sensor comprising any one of the above IC chips and a plurality of MI elements connected to the IC chip, and further an electronic device comprising the above MI sensor is provided. Is done.

  According to the present invention, since the above-described IC chip has a good S / N ratio, it is possible to realize an MI sensor and an electronic apparatus that are accurate and reliable in detecting the magnitude and direction of the external magnetic field.

  According to the present invention, the pulse signal supplied from the pulse generating means is distributed to each MI element by the switching means, the pulse signal for controlling the timing of the excitation current for inducing the detection signal, and the detection by the sampling means. Since the pulse signal for controlling the timing is used, the peak value of the detection signal corresponding to the magnitude of the external magnetic field can be reliably detected. As a result, an IC chip having a good S / N ratio can be realized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a perspective view of an MI sensor according to an embodiment of the present invention. Referring to FIG. 1, the MI sensor 10 of the present embodiment includes three magneto-impedance effect elements (hereinafter abbreviated as “MI elements”) 12 _X , 12 _Y , 12 z disposed in a case 11. (Hereinafter, unless otherwise specified, the symbols “12 _X , 12 _Y , 12 z” for the X axis, Y axis, and Z axis are abbreviated as “12”, and the same applies to the other symbols). It is composed of an IC chip 13 or the like that is connected and disposed in the case 11. The MI element 12 includes two MI elements 12 _X and 12 _Y arranged in the case 11 so as to be substantially perpendicular to each other in the same plane (X axis and Y axis), and these MI elements 12 _X , 12 _Y and Z-axis MI element 12 z arranged perpendicular to _Y.

  In the MI sensor 10, the IC chip 13 supplies an excitation current to each MI element 12, and detection signals corresponding to the magnitudes of the X-axis, Y-axis, and Z-axis components of the external magnetic field are generated for each axis by the magnetic impedance effect. An MPU or the like connected to the MI sensor 10 is guided to a detection coil (described later) of the MI element 12 and the IC chip 13 processes the detection signal and outputs an output signal corresponding to the magnitude of each axial component of the external magnetic field. (Not shown), the magnetic field components in the three-axis directions are synthesized by the MPU or the like, and the direction and magnitude of the external magnetic field can be detected.

The case 11 is made of ceramic, glass, plastic, silicon, or the like, and has a rectangular recess in which the IC chip 13 is accommodated at substantially the center. The case 11 is formed with a recess having a length of about 4 mm and a width of several millimeters in which the X-axis and Y-axis MI elements 12 _X and 12 _Y are accommodated, and a recess or a through hole in which the Z-axis MI element is disposed. Is formed. As shown in FIG. 1, a part of the Z-axis MI element may protrude from the upper surface of the case 11 or may protrude from the bottom surface of the case. A case electrode 14 is provided on the periphery of the upper surface of the case 11, and the case electrode 14 is connected to terminals of an IC chip 13 and an electronic substrate that transmits and receives signals such as an XYZ switching signal described later by a wire 15 or the like. The

  The IC chip 13 is configured by a CMOS or bipolar IC having a circuit to be described later. On the surface of the IC chip 13, an excitation current electrode 16 for connecting to the MI element 12, an excitation current ground electrode 16 G, and a detection signal electrode 17 are provided. An output electrode 19 for supplying an output signal to an external MPU or the like, and an external connection electrode 19 such as a ground electrode for a ground potential are provided. The IC chip 13 supplies a pulsed excitation current flowing through the amorphous wire (shown in FIG. 3) of the MI element 12 via the excitation current electrode 16 and the excitation current wire 16a, and the magnitude of the external magnetic field. The detection signal corresponding to is supplied via the detection signal electrode 17, and an output signal corresponding to the magnitude of the external magnetic field is output to an MPU or the like connected to the IC chip 13 by a circuit described later.

  As described above, the MI element 12 has three longitudinal directions arranged in the case 11 in parallel with the X axis, the Y axis, and the Z axis, respectively, and decomposes the external magnetic field into the three axis directions of the X axis, the Y axis, and the Z axis. And detecting the size of each component.

  FIG. 2 is a perspective view showing an example of the MI element. Referring to FIG. 2, the MI element 12 is supplied with an exciting current from the IC chip 13 connected to the amorphous wire 41, a detection coil 42 formed so as to wind the amorphous wire 41, and the amorphous wire 41. Terminal 43 and the like. The MI element 12 has, for example, a shape with a length of several mm, a width of 1 mm, and a height of 0.3 mm. The MI element 12 can detect the magnitude of the longitudinal component of the amorphous wire 41 with respect to the external magnetic field applied to the MI element 12 by the magnetic impedance effect. In addition, in order to detect the direction of the external magnetic field, the longitudinal directions of the amorphous wires 41 of the three MI elements 12 do not necessarily have to be substantially vertical, and may not be parallel to each other. However, from the viewpoint of efficiency, it is preferable that the longitudinal directions of the amorphous wires of the three MI elements 12 are vertical.

  The amorphous wire 41 is made of a soft magnetic amorphous magnetic material having a length of about 2 mm and a diameter of several tens of μm. For example, FeB, CoB, FeNiSiB, FeCoSiB, CoSiB, or the like can be used as the amorphous magnetic material. From the viewpoint of the linearity of the detection signal induced in the detection coil 42, the external magnetic field exhibits magnetostriction when the external magnetic field is several Oe or less. No material or a material that has been heat-treated after drawing is preferred. Although a soft magnetic thin film or a soft magnetic thin body can be used in place of the amorphous wire 41, an amorphous wire is more preferable because the demagnetizing field in the width direction of the soft magnetic thin film or the soft magnetic thin body is larger than that of the amorphous wire. . Also, a non-magnetic conductor wire is used as the core material in place of the amorphous wire 41, and the surface is coated with a soft magnetic material with a thickness of 10 nm to 5 μm by electrodeposition, vapor deposition, sputtering, CVD, etc. May be used. As the soft magnetic material in this case, soft magnetic materials such as NiFe (permalloy) and FeAlSi can be used in addition to the above-described FeB, CoB, FeNiSiB, FeCoSiB, and CoSiB. For example, Al, Cu or the like can be used as the core agent, which is preferable in that the selection range is expanded compared to the amorphous wire, and more preferable in that a core material that can be easily connected to the terminal 43 can be selected.

  The length of the amorphous wire 41 may be 2 mm or less, and further 1 mm or less. Due to the principle of the magneto-impedance effect, even if the amorphous wire 41 is shortened, the detection sensitivity of the external magnetic field is not deteriorated, which is preferable in that the size can be reduced. The problem when the length is shortened is that the bonding of the amorphous wire and the terminal 43 made of Al or the like becomes more difficult, but this is possible by the ultrasonic thermocompression bonding method. The detection coil 42 wound in the circumferential direction of the amorphous wire 41 is, for example, 10 t to 100 t, and preferably 10 t to 30 t from the viewpoint of miniaturization.

  FIG. 3 is a circuit diagram of the IC chip according to the first embodiment, and FIG. 4 is a waveform diagram of the circuit shown in FIG.

  This will be described with reference to FIG. 3 and FIG. 4 as appropriate. The IC chip 13 includes an excitation current generation unit 13A for supplying an excitation current to the MI element 12, and a signal processing unit 13B that processes a detection signal from the MI element 12 and transmits an output signal to an external MPU or the like. Is done.

  The exciting current generator 13A uses a pulse generator circuit 20 that generates a pulse signal with a short pulse width, and uses the pulse signal as a control signal for the switching circuit 24 and a control signal for the sampling circuit 31, for X-axis, Y-axis, and Z-axis. Switching circuit 24 and sampling circuit 31 XYZ axis switching circuit 21 that distributes to them, delay circuit 22 that delays the pulse signal, buffer circuit 23 that amplifies the pulse signal, and a pulse signal that has been amplified in current The switching circuit 24 is configured to supply the exciting current to the MI element 12 by being supplied to the unit.

  The signal processing unit 13B includes a sampling circuit 31 and a hold circuit 32 that respectively detect peak values of detection signals from the X-axis, Y-axis, and Z-axis MI elements 12, and an amplification circuit 33 that amplifies the detected signal. And an output circuit 34 and the like. Each circuit will be specifically described below.

In the pulse generation circuit 20, a pulsed clock signal of several hundred kHz to several tens of MHz is generated by an oscillation circuit using a multivibrator or a crystal oscillator, and the clock signal is divided and delayed by an integration circuit or the like. For example, “AND” of the inverted signal of the delayed signal and the original signal is taken to generate a pulse with a short time width of about 1 to 50 nsec, for example, as shown in FIG. 4A. In this embodiment, as an example, the pulse period is 500 kHz and the pulse width is 45 nsec. The pulse signal generated by the pulse generation circuit 20 is transmitted to the XYZ axis switching circuit 21.
The XYZ axis switching circuit 21 is provided between the pulse generation circuit 20, the delay circuit 22 and the buffer circuit 30 provided for each axis, and the pulse signal supplied from the pulse generation circuit 20 is shown in FIG. Based on the XYZ axis switching signals shown in FIGS. 4B-1 and B-2 supplied from the outside such as an MPU connected to the MI sensor shown, the delay circuit 22 and buffer for the X axis, Y axis, and Z axis Distributed to the circuit 30.

  Here, the XYZ axis switching signal is supplied to the switching signal electrodes 46-1 and 46-2, and is composed of a 2-bit parallel signal of the XYZ axis switching signal B-1 and the XYZ axis switching signal B-2. As shown in FIGS. 4B-1, B-2, and Cx to Cz, the pulse signal is for the X axis when both the XYZ axis switching signal B-1 and the XYZ axis switching signal B-2 are “High”. When the XYZ axis switching signal B-1 is “High” and the XYZ axis switching signal B-2 is “Low”, the signal is distributed to the Y axis connecting line Cy, and the XYZ axis switching signal B− is distributed. When 1 is “Low” and the XYZ-axis switching signal B-2 is “High”, the signal is distributed to the Z-axis connection line Cz. The correspondence relationship between the XYZ axis switching signal and the distribution destination is not limited to the above-described correspondence relationship, and the XYZ axis switching signal is not limited to 2 bits. Moreover, although the example in which the XYZ axis switching circuit 21 is switched every two pulse signals has been shown, it may be every one pulse signal, or three or more. The XYZ axis switching signal may be generated inside the IC chip.

The delay circuit 22 is provided with three circuits 22 _X , 22 _Y , and 22 _Z for the X axis, the Y axis, and the Z axis between the XYZ axis switching circuit 21 and the buffer circuit 23. For example, the integration circuit and the buffer The pulse signal is delayed by a predetermined time, and the timing of the detection signal and the control signal in the sampling circuit 31 to be described later is matched.

The buffer circuit 23 is provided with three circuits 23 _X , 23 _Y , and 23 _Z for the X-axis, Y-axis, and Z-axis, and is configured from several to ten or more buffers connected in series. For example, the product of the gate width and the gate length of the CMOS-FET may be set to be gradually increased so that a larger drive current can flow toward the downstream buffer. A larger current can be supplied to the control input section of the switching circuit 24, and the turn-on of the switching circuit 24 can be speeded up.

The switching circuit 24 is provided with three circuits 24 _X , 24 _Y , 24 _Z for the X axis, the Y axis, and the Z axis, and is configured by, for example, a MOS-FET. In the switching circuit 24, the pulse signal is input from the buffer circuit 23 to the gate 24-1 that is a control input unit of the switching circuit 24. When this MOS-FET is turned on by a pulse signal, an exciting current is supplied from the source to the MI element 12 of each axis through the exciting current electrode 16. The waveform of the excitation current is as shown in FIGS. That is, the exciting current is supplied sequentially, that is, in time series, to the X-axis MI element 12 _X , the Y-axis MI element 12 _Y , and the Z-axis MI element 12 _Z. This prevents the excitation current flowing through the MI element 12 of each axis from affecting the detection signals of the other axes.

  Here, the excitation current is preferably in the range of 100 mA to 500 mA. If it is less than 100 mA, a sufficient output voltage is not induced in the detection coil 42 of the MI element 12, and the signal-to-noise ratio is lowered, that is, the magnetic field detection sensitivity is lowered. On the other hand, when the current is larger than 500 mA, noise generated at the time of switching is superimposed on the detection signal and the signal-to-noise ratio is lowered.

  The exciting current is taken out from the switching circuit 24 to the exciting current electrode 16. The exciting current electrode 16 is provided near the switching circuit 24 and near one end in the longitudinal direction of the amorphous wire 41 of the MI element 12. The exciting current electrode 16 is preferably provided as close to the amorphous wire 41 as possible. Since the exciting current is a relatively large current, if the wiring from the switching circuit 24 to the amorphous wire 41 is too long, the wiring acts as an antenna to radiate electromagnetic waves, and the electromagnetic waves are superimposed on the detection signal, for example, and the signal-to-noise ratio. Will be reduced.

  A pulsed excitation current flows through the amorphous wire 41 connected to the excitation current electrode 16 and is dropped to the excitation current ground electrode 16G connected to the other end.

  As shown in FIGS. 4Ex to Ez, detection signals are respectively induced at both ends of the X-axis, Y-axis, and Z-axis detection coils 42 in accordance with the magnitude of the longitudinal component of the amorphous wire 41 of the external magnetic field. This detection signal is supplied from the detection coil 42 to the sampling circuit 31 via the detection signal electrode 17.

In the sampling circuit 31, the pulse signal distributed in the XYZ axis switching circuit 21 is supplied to the control input unit SW-1, and the peak value of the main peak of the detection signal is sampled. Specifically, the sampling circuit 31 includes analog switches SW _X , SW _Y , and SW _Z. That is, as shown in FIGS. 4Ex to Ez, the pulse signals shown in FIGS. 4SW _X −1 to SW _Z −1 correspond to the detection signals, and the control inputs SW _X −1 of the analog switches SW _X , SW _Y , and SW _Z. , SW _Y −1, SW _Z −1, for example, when the pulse signal is “High”, the detection signal is transmitted through the analog switches SW _X , SW _Y , SW _Z , and the peak value is held by the hold circuit 32. (It will be described in detail later).

  Since the pulse signal is increased to an amount of current for driving the control input SW-1 of the analog switch, a buffer 30 is provided between the XYZ axis switching circuit 21 and the control input SW-1 of the analog switch. . The buffer circuit 30 is configured in substantially the same manner as the buffer circuit 23 described above.

  The hold circuit 32 includes a capacitor Cap and the like, and holds the peak value of the main peak of the detection signal detected by the sampling circuit 31. As a result, the detection signal shown in FIG. 4G in which the peak values of the X-axis, Y-axis, and Z-axis detection signals connected in time series shown in FIGS. 4Ex to Ez are held is obtained. Note that one end of the capacitor Cap is set to a predetermined reference voltage by the reference voltage generation circuit 26.

  In the amplifier circuit 33 and the output circuit 34, the held detection signal is amplified, and an output signal in which the voltage value and the like are amplified in the same shape as the waveform shown in FIG. 4G is output as an analog detection signal.

  The analog output signal may be output as a digital signal by providing an AD conversion circuit on the output side of the amplifier circuit 33. The digital signal may be either a serial signal or a parallel signal. In addition, when the detection signal is supplied to the AD conversion circuit, the amplifier circuit 33 and the output circuit 34 may be omitted.

  Next, the sampling timing of the detection signal will be described in detail with reference to an X-axis circuit signal as an example. It goes without saying that the signals of the Y-axis and Z-axis circuits are the same.

  FIG. 5 is a diagram illustrating the sampling timing of the detection signal. Referring to FIG. 5 and FIG. 3 described above, the pulse signal Cx on the output side of the XYZ axis switching circuit 21 is delayed by a predetermined time (about 26 nsec in this case) by the delay circuit 22 to become the pulse signal shown in FIG. 5Dx. In response to this pulse signal, an exciting current flows through the MI element 12, and a detection signal shown in FIG. 5Ex is induced and input to the analog switch SWx.

On the other hand, the pulse signal Cx is delayed by about 1 nsec due to the parasitic capacitance or the like as shown in FIG. 5SW _X −1 through the buffer to the control input section SW _X −1 of the analog switch, and the control input section 24 _X − of the switching circuit 24 _x. 1 is input. The analog switch is opened and closed in response to the control signal shown in FIG. 5 SW _X- 1, and the analog switch is cut off at the peak position of the detection signal (tenth nsec from the rise of Dx) or slightly past the peak. Is done. As a result, as shown in FIG. 5G, the peak value or the peak value near the peak can be sampled.

  As described above, since sampling is performed in synchronization with the pulse signal falling from “High” to “Low”, it is necessary to strictly match the timing. Furthermore, in addition to the X axis, time alignment of the Y axis and the Z axis is necessary.

  In the present embodiment, a pulse signal distributed by one XYZ axis switching circuit 21 is used as a control signal for each switching circuit 24 and sampling circuit 31. Therefore, the timing of the detection signal and the control signal in the sampling circuit 31 can be easily matched. Even between the axes, the buffer circuit 23 and the switching circuit 24 are configured in substantially the same manner, so that the timing can be easily adjusted between the axes.

  FIG. 6 is a diagram illustrating an example of an XYZ axis switching circuit. Referring to FIG. 6, the XYZ axis switching circuit 21 includes a NAND element 48a, an AND element 48b, a buffer element 48c, and the like. The XYZ axis switching signals 1 and 2 are calculated and the pulse signal from the pulse generating circuit 20 is calculated. Are distributed to the X-axis, Y-axis, and Z-axis circuits using the NAND element 48d. Since the NAND element 48d through which the pulse signal circulates is more complex in configuration than the buffer element, variations between the NAND elements 48d are likely to increase due to transient characteristics such as rise time and fall time. In the present embodiment, since only one such XYZ axis switching circuit 21 is used, a shift in the rise time of the pulse signal that has circulated through the NAND element 48d is suppressed by suppressing the number of NAND elements 48d used. And the amount of delay can be suppressed, and deformation of the waveform of the detection signal of each axis can be suppressed. Therefore, it is possible to facilitate the sensitivity matching between the axes of the MI element 12 with respect to the external magnetic field.

  FIG. 7 is a circuit example of an XYZ axis switching circuit of a comparative example not according to the present invention. Referring to FIG. 7, the XYZ axis switching circuit 101 of the comparative example not according to the present invention is composed of two XYZ axis switching units 101-1 and 101-2. The pulse signal from the pulse generation circuit 20 is distributed to the X-axis, Y-axis, and Z-axis delay circuits and buffer circuits by the XYZ-axis switching circuits 101-1 and 101-2. When the circuit example shown in FIG. 6 is applied to the XYZ axis switching circuits 101-1 and 101-2, for example, the signal supplied to the X-axis circuit is different from the control signal for the switching circuit and the control signal for the sampling circuit. By passing through the NAND element 48d, a pulse signal timing shift or waveform deformation due to variations in transient characteristics occurs, resulting in different pulse signals. As a result, it becomes difficult to match the timing of the detection signal and the pulse signal as the control signal of the sampling circuit. Also, the sensitivity deviation between the axes increases. From these facts, the superiority of an IC chip constituted by one XYZ axis switching circuit is apparent from the ease of timing adjustment and the substantially uniform sensitivity between the axes.

  FIG. 8 is a diagram illustrating another example of the sampling timing of the detection signal. In FIG. 5 described above, an example is shown in which the main peak of the detection signal generated at the rise of the excitation current is sampled. However, in FIG. 8, the main peak of the detection signal generated at the fall of the excitation current is sampled. This is an example. The X-axis signal will be described in detail as an example.

  Referring to FIG. 8 and FIG. 3 described above, for example, a pulse signal Cx having a pulse width of 20 nsec on the output side of the XYZ axis switching circuit 21 becomes a pulse signal shown in FIG. 8Dx with a delay of about 1 nsec due to parasitic capacitance or the like (this book In the example, the delay circuit of FIG. 3 is not provided.) In response to this pulse signal, an exciting current flows through the amorphous wire 41x of the MI element 12, and the detection signal shown in FIG. 8Ex is induced and input to the analog switch SWx.

On the other hand, a delay circuit is newly provided between the XYZ axis switching circuit 21 and the buffer circuit 30 in FIG. 3, and the pulse signal Cx is delayed by a predetermined time (about 4 nsec in this case) by the delay circuit. supplied by the waveform and the delay amount shown in FIG 8SW _X -1 to the control input unit SW _X -1 of the switch. The analog switch SWx is opened and closed in response to the control signal shown in FIG. 8 SW _X- 1, and the analog switch SWx is located at the peak position of the detection signal (several nsec after the fall of Dx) or slightly past the peak. It is interrupted by. As a result, as shown in FIG. 8G, a substantially peak value can be sampled and held.

  Thus, in the case shown in FIG. 8 as well, in the same way as in the case of FIG. 5 described above, the sampling is performed synchronously when the pulse signal falls from “High” to “Low”. Furthermore, in addition to the X axis, time alignment of the Y axis and the Z axis is required. As described above, in this embodiment, the pulse signal distributed by one XYZ axis switching circuit 21 is used as the control signal for the switching circuit 24 and the sampling circuit 31 for each axis. Therefore, the timing of the detection signal and the control signal in the sampling circuit 31 can be easily matched. Also in the circuits between the axes, the buffer circuit 23 and the switching circuit 24 are configured in substantially the same manner, so that the timing between the axes can be easily adjusted.

(Second Embodiment)
FIG. 9 is an exploded view showing a mobile phone as an example of an electronic apparatus according to the second embodiment of the present invention. Referring to FIG. 9, a mobile phone 50 includes a display unit 51, an operation unit 52, an antenna 53, a speaker 54, a microphone 55, an electronic substrate 56, an MI sensor 58 mounted on the electronic substrate 56, and the like. It is configured.

  The MI sensor 58 has the configuration of the first embodiment described above, and the X-axis and Y-axis MI elements are arranged in parallel to the electronic substrate 56 and the Z-axis is perpendicular to the electronic substrate. The MI sensor 58 can detect the azimuth and angle of the mobile phone 50 based on the direction of geomagnetism. For example, the map near the current location received by the mobile phone 50 and displayed on the display unit 51 is rotated on the display unit in accordance with the azimuth and angle of the mobile phone 50 detected by the MI sensor. In particular, when the cellular phone 50 is directed to the true north, the direction of the true north is perpendicular to the electronic substrate. Even in such a case, since the geomagnetism can be detected by the MI element for the Z axis, the azimuth and angle can be stably displayed.

  As described above, the mobile phone 50 is characterized in that the MI sensor 58 is the MI sensor according to the first embodiment. Since the MI sensor 58 has a good S / N ratio, the detection of the azimuth and angle is accurate and reliable. Note that the basic configuration of the mobile phone 50 having a communication function is well known, and detailed description thereof is omitted in this specification.

  Note that although the electronic device of this embodiment has been described using a mobile phone as an example, it is not limited to a mobile phone. For example, the present invention can be applied to portable terminals, car navigation devices, and the like.

  The preferred embodiment of the present invention has been described in detail above, but the present invention is not limited to the specific embodiment, and various modifications and changes can be made within the scope of the present invention described in the claims. Is possible.

1 is a perspective view of an MI sensor according to a first embodiment of the present invention. It is a perspective view which shows an example of MI element. 1 is a circuit diagram of an MI sensor according to a first embodiment. FIG. 4 is a waveform diagram of the circuit shown in FIG. 3. It is a figure which shows the timing of sampling of a detection signal. It is a figure which shows an example of a switching circuit. It is a circuit example of the switching circuit of the comparative example which is not based on this invention. It is a figure which shows the other example of the timing of sampling of a detection signal. It is an exploded view which shows the mobile telephone as an example of the electronic device which concerns on the 2nd Embodiment of this invention. 10 ... MI sensor 11 ... casing _{12,12 X, 12 Y, 12 Z} ... MI element 13 ... IC chip 13A ... exciting current generator 13B ... signal processor 14 ... case electrode 15 ... wire 16 ... exciting current electrodes 16a ... excitation current wire 16G ... exciting current ground electrode 17 ... detection signal electrodes 19 ... connecting electrodes 20 pulse generating circuit 21 ... XYZ axis switching circuit 22 ... delay circuit _{23,23 X, 23 Y, 23 Z} , 30 ... Buffer circuits 24, 24 _X , 24 _Y , 24 _Z ... switching circuit 26 ... reference voltage generation circuit 31 ... sampling circuit 32 ... hold circuit 33 ... amplification circuit 34 ... output circuit 41, 41 _X , 41 _Y ... amorphous wire 42, 42 _X , 42 _Y ... detection coil 43 ... terminal 46-1, 46-2 ... switching signal electrode 50 ... mobile phone Cap ... capacitor

Claims (9)

An IC chip that supplies an excitation current to a plurality of MI elements that detect an external magnetic field, and that receives detection signals corresponding to the magnitude of the external magnetic field from the plurality of MI elements based on the excitation current,
Pulse generating means;
Current supply switching means for supplying an exciting current to the MI element;
Sampling means for detecting a substantially peak value of a detection signal supplied from the MI element;
The current supply switching means and sampling means are provided for each MI element,
An IC chip comprising switching means for simultaneously distributing the pulse signals generated by the pulse generating means to the control input part of the current supply switching means corresponding to one MI element and the control input part of the sampling means.   2. The IC chip according to claim 1, wherein the switching unit distributes a pulse signal based on a switching signal supplied from the outside of the IC chip. A delay means is provided between the switching means and the control input part of the current supply switching means,
The delay means controls the control input of the current supply switching means so that the time when the sampling means detects the detection signal based on the pulse signal supplied to the control input section of the sampling means is synchronized with the peak of the detection signal. 3. The IC chip according to claim 1, wherein a pulse signal supplied to the unit is delayed.   4. The IC chip according to claim 3, wherein the peak of the detection signal is formed corresponding to the rise of the excitation current. Other delay means are provided between the switching means and the control input part of the sampling means,
The other delay means includes a control input section of the sampling means so that the time when the sampling means detects the detection signal based on a pulse signal supplied to the control input section of the sampling means is synchronized with the peak of the detection signal. 5. The IC chip according to claim 1, wherein a pulse signal supplied to the circuit is delayed.   6. The IC chip according to claim 5, wherein the peak of the detection signal is formed corresponding to the fall of the excitation current.   The IC chip according to claim 2, wherein the IC chip is connected to three MI elements, and the switching signal is a 2-bit parallel signal. An IC chip according to any one of claims 1 to 7;
A MI sensor comprising a plurality of MI elements connected to the IC chip. An electronic device comprising the MI sensor according to claim 8.

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