JP4523838B2 - Magnetic sensor circuit and semiconductor device - Google Patents

Description

  The present invention relates to a magnetic sensor circuit and a semiconductor device used for an MI (Magneto-Impedance Effect) sensor capable of detecting a weak magnetic field.

  As a small and high-performance magnetic sensor, a magnetic impedance effect type sensor (MI sensor) using a magnetic impedance (MI) effect has been proposed. The MI sensor uses an MI element as a magnetosensitive element, and detects the strength of a magnetic field applied to the soft magnetic amorphous wire of the MI element. The MI effect is a phenomenon in which the impedance changes greatly in proportion to the magnetic field strength applied to the soft magnetic amorphous wire when a pulse current having a width for a short time is passed through the soft magnetic amorphous wire.

  The MI sensor includes an impedance detection method for detecting the impedance of the soft magnetic amorphous wire and an inductance detection method for detecting only the inductance component of the soft magnetic amorphous wire.

  The impedance detection method is advantageous in that the structure of the MI element is simple because the MI element is composed only of an amorphous wire. However, since the output characteristics are symmetric with respect to the zero magnetic field, it is necessary to detect the direction of the magnetic field separately, and the circuit configuration becomes complicated when measuring both positive and negative magnetic fields.

  On the other hand, the inductance detection method has a complicated structure because the MI element has a structure in which a detection coil is wound around an amorphous wire. However, since a linear output is obtained with respect to a negative to positive magnetic field with a zero magnetic field interposed therebetween, the circuit configuration is relatively simple. 1 and 2, see Non-Patent Document 1.)

  FIG. 1 is a circuit diagram of a conventional MI sensor. Referring to FIG. 1, MI elements 101 and 102 each measure and output a magnetic field along two axes, the X axis and the Y axis. The MI sensor 100 alternately supplies the pulse signal generated by the pulse generation circuit 103 to the X-axis MI element 101 and the Y-axis MI element 102 by the timing signal generation circuit 104. Then, the detection signal induced in the detection coil of each of the MI elements 101 and 102 is held and detected by the sample and hold circuit 105, amplified by the differential amplifier circuit 106, and output.

  By the way, the MI sensor is mounted on a mobile terminal such as a mobile phone, an automobile, etc. and used outdoors. Therefore, it is expected that the temperature range of the environment in which the MI sensor is used is used in an environment of about 40 ° C. from below freezing point.

For this reason, there has been proposed an MI sensor equipped with a temperature compensation circuit and having a small magnetic field intensity detection error even in an environment where the temperature changes (see Patent Document 2).
JP 2004-119517 A JP 2000-19235 A Journal of Japan Society of Applied Magnetics, Vol. 27, no. 11 (2003) p1063-p1068

  In the MI sensor of Patent Document 2, as shown in FIG. 2, feedback is applied using an operational amplifier 112 to compensate for the temperature characteristics of the Schottky barrier diode 111 used in the peak hold circuit 110. However, in this temperature compensation method, as described in Patent Document 2, when the unity gain bandwidth of the operational amplifier 112 used for feedback is 100 MHz or less, the output decreases rapidly. Therefore, there is a problem that a high-speed operational amplifier is required. In addition, the magnetic field strength detection stability may be insufficient in an environment where the temperature changes rapidly.

  Further, since the MI sensor is miniaturized, circuits other than the MI element are almost formed on the IC chip. The temperature characteristics of the MI sensor are affected by the circuit arrangement within the IC chip and the design of individual elements. In order to compensate for such temperature characteristics by changing the element constants or changing the circuit, the development period becomes longer and the manufacturing cost is affected.

  Accordingly, the present invention has been made in view of the above problems, and an object of the present invention is to provide a magnetic sensor circuit and a semiconductor device capable of measuring magnetic field strength with high accuracy in an environment where temperature changes occur. .

  The magnetic sensor circuit according to claim 1, wherein an excitation current is supplied to the MI element, and a detection signal corresponding to a magnetic field intensity is supplied from the MI element based on the excitation current. A pulse current supply circuit for supplying current; a sample hold circuit for holding a substantially peak value of the detection signal and outputting a hold signal; and detecting a temperature of the magnetic sensor circuit and based on a temperature signal corresponding to the temperature Temperature compensation means for compensating the temperature characteristic of the magnetic sensor circuit with respect to the hold signal, and the temperature compensation means switches the relationship between the temperature change direction and the temperature signal change direction. A magnetic sensor circuit having a switching unit is provided.

  According to the first aspect of the present invention, the temperature detection circuit and the temperature compensation circuit for compensating the voltage fluctuation of the hold signal caused by the temperature change are connected to the output side of the sample hold circuit. The temperature detection circuit is provided with a temperature signal polarity switching circuit that switches the change direction of the temperature signal with respect to the temperature change. By providing the temperature signal polarity switching circuit, the direction of increase / decrease of the voltage value of the temperature signal can be set according to the direction of change of the voltage value of the hold signal with respect to the direction of temperature change. Temperature compensation is possible.

  In addition, since the magnetic sensor circuit according to the present invention has a substantially direct current hold signal, temperature compensation is easy and temperature compensation can be performed with high accuracy.

  As described in claim 2, in the magnetic sensor circuit according to claim 1, the temperature compensation means detects a temperature of the magnetic sensor circuit, and outputs a temperature signal corresponding to the temperature; and The temperature compensation circuit comprises a temperature compensation circuit for correcting the voltage value of the hold signal based on the temperature signal, and the temperature signal polarity switching unit is provided in the temperature detection circuit.

  According to the second aspect of the present invention, the temperature detection circuit for detecting the temperature of the magnetic sensor circuit is provided, and the temperature detection circuit is provided with the temperature signal polarity switching unit, whereby the magnetic sensor circuit with respect to the voltage value of the hold signal. The correction corresponding to the temperature can be surely performed.

  According to a third aspect of the present invention, in the magnetic sensor circuit according to the first or second aspect, the MI element is composed of an amorphous wire and a detection coil, and the sample and hold circuit is configured so that the pulse current is passed through the amorphous wire. Is supplied with a detection signal induced in the detection coil.

  According to the third aspect of the present invention, since the detection signal of the inductance-type MI element has a linear output with respect to the negative to positive magnetic field with the zero magnetic field interposed therebetween, the magnetic sensor circuit is more effective than the impedance detection type. Can be simplified.

  The magnetic sensor circuit according to any one of claims 1 to 3, wherein the sample and hold circuit includes a switch circuit and a hold capacitor, and the switch circuit includes the pulse current. An open / close control signal is supplied on the basis of the timing.

  According to the fourth aspect of the present invention, the temperature characteristics of the switch circuit of the sample and hold circuit can be compensated by the temperature compensation means.

  The magnetic sensor circuit according to any one of claims 1 to 4, further comprising an amplifier circuit between the sample and hold circuit and a temperature compensation circuit, wherein the amplifier circuit includes: The amplification factor is higher than that of the temperature compensation circuit.

  According to the fifth aspect of the present invention, the weak hold signal is first amplified to a relatively large voltage by the amplifier circuit, so that a decrease in the S / N ratio due to mixing of noise or the like in the temperature compensation circuit can be suppressed. Further, since the temperature compensation amount can be set finely by setting the amplification factor of the temperature compensation circuit low, fine adjustment can be easily performed, and as a result, the variation amount due to the temperature change of the hold signal can be corrected with high accuracy.

  According to a sixth aspect of the present invention, in the magnetic sensor circuit according to any one of the first to fifth aspects, the temperature compensation circuit corrects the hold signal using the temperature signal as a reference voltage value.

  According to the sixth aspect of the invention, by correcting the hold signal using the temperature signal corresponding to the temperature, it is possible to compensate for the fluctuation amount due to the temperature change of the hold signal.

  As described in claim 7, in the magnetic sensor circuit according to any one of claims 1 to 6, the temperature signal has a voltage value corresponding to the temperature.

  According to the seventh aspect of the present invention, by correcting the hold signal using the temperature signal corresponding to the temperature, it is possible to correct the fluctuation amount due to the temperature change of the hold signal with high accuracy.

  As described in claim 8, in the magnetic sensor circuit according to any one of claims 1 to 7, in the temperature detection circuit, cathode sides are set to the same potential, and the first PN junction element, A second PN junction element to which a current having a current density smaller than that of the first PN junction element is supplied, and each of the anode sides of the first and second PN junction elements, A subtracting circuit for outputting a temperature signal having a voltage value corresponding to the potential difference, and the temperature signal polarity switching unit includes each of the anode side of the first or second PN junction element and each of the two inputs of the subtracting circuit. Are connected to each other by polarity switch circuits.

  According to the eighth aspect of the invention, the temperature of the magnetic sensor circuit is detected using the potential difference on the anode side of the first and second PN junction elements, so that the temperature can be reliably detected. Further, since the voltage value corresponding to the potential difference is used as the temperature signal, temperature compensation corresponding to the temperature of the magnetic sensor circuit can be performed.

  According to a ninth aspect of the present invention, in the magnetic sensor circuit according to the eighth aspect of the present invention, the polarity switch circuit is supplied with a switching signal that controls the relationship between the temperature change direction and the temperature signal change direction.

  According to the ninth aspect of the present invention, the relationship between the temperature change direction and the temperature signal change direction can be easily controlled by the switching signal. Furthermore, it is possible to reliably correct the voltage fluctuation of the hold signal of the magnetic sensor circuit without changing the design of the magnetic sensor circuit or the circuit element.

  According to a tenth aspect of the present invention, in the magnetic sensor circuit according to the ninth aspect, the temperature detection circuit further includes a proportional coefficient control circuit that controls a proportional coefficient of a voltage value of a temperature signal with respect to the temperature.

  According to the tenth aspect of the present invention, even when MI elements having different voltage values of the detection signal with respect to the magnetic field strength are connected, temperature compensation can be achieved by controlling the proportionality coefficient. Further, when the amount of fluctuation of the voltage value of the hold signal with respect to a predetermined temperature change changes, it can be reliably corrected by controlling the proportionality coefficient.

  According to the eleventh aspect, in the magnetic sensor circuit according to the tenth aspect, the proportionality coefficient is controlled in a state where the magnetic field strength of the magnetic field applied to the MI element is substantially zero.

  According to the eleventh aspect of the invention, the proportionality coefficient can be easily set by setting the proportionality coefficient in a state where the magnetic field intensity is zero.

  As described in claim 12, in the magnetic sensor circuit according to any one of claims 8 to 11, the first and second PN junction elements are first and second elements having different element areas. Each of the first and second transistors has a collector and a base connected to each other, and a current of substantially the same magnitude is supplied to its emitter, and each of the emitters is connected to a polarity switch circuit. It becomes.

  13. A semiconductor device according to claim 13, wherein an excitation current is supplied to the MI element, and a detection signal corresponding to the magnetic field intensity is supplied from the MI element based on the excitation current. A semiconductor device comprising the magnetic sensor circuit according to any one of the above is provided.

  According to the thirteenth aspect of the present invention, any one of the above magnetic sensor circuits can reliably compensate for the temperature according to the temperature characteristics thereof, so that even in an outdoor environment where the temperature changes drastically, it is highly accurate. A semiconductor device capable of detecting the magnetic field strength can be realized. Furthermore, since the semiconductor device can be reduced in size, it is possible to reduce the size of a portable terminal equipped with a magnetic sensor circuit.

  According to the present invention, the temperature detection circuit and the temperature compensation circuit for compensating for the voltage fluctuation of the hold signal caused by the temperature change are connected to the output side of the sample hold circuit. A temperature signal polarity switching circuit for switching the direction of signal change is provided. By providing the temperature signal polarity switching circuit, the increase / decrease direction of the voltage value of the temperature signal can be easily set according to the change direction of the voltage value of the hold signal with respect to the temperature change direction. Temperature compensation can be ensured, and highly accurate temperature compensation is possible.

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

(First embodiment)
FIG. 3 is a block diagram of the magnetic sensor circuit according to the first embodiment of the present invention. The magnetic sensor circuit of FIG. 3 is preferably mounted on a semiconductor device, for example, one IC chip. FIG. 3 also shows MI elements connected to the semiconductor device.

  Referring to FIG. 3, a magnetic sensor circuit 10 according to the present embodiment includes a pulse generation circuit 11, a pulse current supply circuit 12, a delay circuit 13, a sample hold circuit 14, an amplification circuit 15, a temperature detection circuit 16, and a temperature. The compensation circuit 18 is configured. An MI element 26 is connected to the magnetic sensor circuit 10. The MI element 26 has its input side connected to the output side of the pulse current supply circuit 12 and its output side connected to the sample hold circuit 14.

  The pulse generation circuit 11 periodically outputs a pulse signal to the pulse current supply circuit 12. The pulse generation circuit 11 is composed of, for example, an oscillation circuit using a multivibrator or a crystal oscillator. The pulse signal has a pulse width of about several tens of nsec, and the pulse interval is appropriately set according to a desired response speed.

  The pulse current supply circuit 12 amplifies the pulse signal and supplies an excitation current to the amorphous wire 27 of the MI element 26 connected to the semiconductor device. The exciting current is a pulsed current having the same time width as the pulse signal. The pulse current supply circuit 12 outputs a timing signal to the delay circuit 13 simultaneously with the excitation current.

  The MI element 26 includes an amorphous wire 27 and a detection coil 28 wound around the amorphous wire 27. The MI element 26 detects the strength of the magnetic field applied to the amorphous wire 27 by a so-called inductance method. The amorphous wire 27 is made of a soft magnetic amorphous magnetic material having a length of about several mm and a diameter of several tens of μm. For example, FeB, CoB, FeNiSiB, or the like can be used as the amorphous magnetic material. Instead of the amorphous wire 27, a soft magnetic thin film or a soft magnetic thin body may be used. The detection coil 28 is wound around the amorphous wire 27, for example, 10 to 100 turns.

  When an exciting current flows through the amorphous wire 27, a detection signal is induced in the detection coil 28 by the MI effect. The peak value of the detection signal is proportional to the intensity of the component along the longitudinal direction of the amorphous wire 27 in the magnetic field applied to the amorphous wire 27. As will be described later, the detection signal has a peak corresponding to each of the rise and fall of the excitation current. Any peak may be used, but a peak having a large peak value may be used because the S / N ratio is good. In the present embodiment, the peak of the detection signal corresponding to the rise of the excitation current is used.

  On the other hand, the delay circuit 13 delays the timing signal by a predetermined delay time and outputs it to the control input unit 20 a of the switch circuit 20. For example, the delay time is set to several nsec to several tens of nsec.

  The sample hold circuit 14 includes a switch circuit 20, a reference voltage source 21, and a hold capacitor 22. The switch circuit 20 performs an on / off operation according to a timing signal input to the control input unit 20 a and outputs a detection signal to the capacitor 22.

  One end of the capacitor 22 is connected to the reference voltage source 21 and one end of the detection coil, and the other end is connected to the switch circuit 20. The capacitor 22 has a function of holding a detection signal.

  4A to 4D are diagrams showing operation timings and waveforms. 4A shows the excitation current, FIG. 4B shows the timing signal delayed by the delay circuit, FIG. 4C shows the detection signal induced in the detection coil, and FIG. 4D shows the hold signal.

  4A to 4D, with respect to the excitation current shown in FIG. 4A, the timing signal shown in FIG. 4B is delayed by a predetermined time Δt from the rise of the excitation current. From “High” to “Low”. The switch circuit 20 is controlled to be turned on / off according to the state of the timing signal. That is, when the timing signal is “High”, the switch circuit 20 is turned on (conducted), and while the timing signal is “High”, the detection signal shown in FIG. The supplied potential of the capacitor 22 rises.

When the timing signal becomes “Low”, the switch circuit is turned off, and the voltage of the detection coil 28 at that time is held in the capacitor 22 as shown in FIG. Since the other electrode of the capacitor 22 is set to the reference voltage (V _DD / 2), the voltage of the capacitor 22 becomes (the _peak value where the detection signal is held) + V _DD / 2 (hereinafter, the capacitor 22). Is called “hold signal”).

  By the way, when the ON resistance and the ON / OFF threshold value of the switch circuit 20 change due to the temperature characteristics, the voltage of the hold signal may fluctuate and the output signal of the magnetic sensor circuit may fluctuate. In such a case, the detection accuracy of the magnetic field strength and direction of the magnetic sensor circuit decreases. In addition, the magnitude of the excitation current and the rise time may fluctuate due to temperature changes, and in order to detect magnetic field strength with high accuracy, it is necessary to comprehensively compensate for the temperature characteristics of the elements that make up the magnetic sensor circuit. There is. When the magnetic sensor circuit 10 is formed on an IC, for example, a CMOS type IC or a mixed type IC of a CMOS transistor and a bipolar transistor, such temperature characteristics may cause a problem.

  In the magnetic sensor circuit 10 according to the present embodiment, the temperature detection circuit 16 and the temperature compensation circuit 18 are provided on the output side of the sample and hold circuit 14, and the voltage fluctuation of the hold signal is compensated to solve the above problems. Is. The temperature detection circuit 16 and the temperature compensation circuit 18 of the magnetic sensor circuit 10 are particularly effective when the switch circuit 20 is mounted on an IC as an analog switch.

  The hold signal is supplied to the amplifier circuit 15 and amplified at a predetermined amplification factor. The amplifier circuit 15 may have a configuration in which a voltage follower with an amplification factor of 1 is connected to the output side of the capacitor 22. The amplifier circuit 15 may or may not be provided.

The temperature detection circuit 16 detects the temperature of the magnetic sensor circuit 10 and supplies a temperature signal having a voltage value corresponding to the temperature to the temperature compensation circuit 18. The temperature signal is set such that the voltage value of the temperature signal increases or decreases with increasing temperature. The voltage value V (T) of the temperature signal is expressed by the product of the temperature T and a positive or negative proportional coefficient α, that is, V (T) = α × (T−T ₀ ) + β. Here, T ₀ is a reference temperature, and β is a reference voltage at the reference temperature T ₀ . When the proportionality coefficient α is a positive value, the voltage value V (T) of the temperature signal increases as the temperature increases, and V (T) decreases as the temperature decreases. On the other hand, when the proportionality coefficient α is a negative value, the voltage value V (T) of the temperature signal decreases as the temperature increases, and V (T) increases as the temperature decreases.

  The temperature detection circuit 16 further includes a temperature signal polarity switching circuit 17 that switches the sign of the proportionality coefficient α, that is, switches between a positive value and a negative value of α. The temperature signal polarity switching circuit 17 switches between a case where the voltage value V (T) of the temperature signal is increased and a case where the voltage value V (T) of the temperature signal is increased as the temperature rises by switching between a positive value and a negative value of α. This switching is performed by supplying a switching signal to the temperature signal polarity switching circuit 17. The switching signal may be supplied by providing a switching signal setting circuit in the magnetic sensor circuit, or may be supplied from the outside.

  The temperature compensation circuit 18 corrects the hold signal amplified by the amplifier circuit 15 with the temperature signal and outputs it as an output signal. Specifically, the temperature compensation circuit 18 adds the voltage value of the temperature signal to the hold signal as a temperature compensation amount. An amplifier circuit may be further provided on the output side of the temperature compensation circuit 18.

  The temperature compensation amount is determined by the relationship between the temperature and the voltage value of the temperature signal, that is, the setting of the proportional coefficient α and the temperature of the magnetic sensor circuit 10 described above. For example, the proportional coefficient α is set by changing the temperature of the magnetic sensor circuit 10 by setting the magnetic field strength applied to the MI element 26 to zero. At this time, the proportionality coefficient α is selected so that the voltage value of the output signal is substantially equal to and constant with the desired reference voltage value. For selection of the proportional coefficient α, the absolute value of α is set by the amplification factor of the operational amplifier in the temperature detection circuit, for example, and the sign of α is performed by the temperature signal polarity switching circuit 17.

  In the magnetic sensor circuit 10, the voltage variation of the hold signal may occur due to its temperature characteristics, for example, the temperature characteristics of the ON resistance of the switch circuit 20 of the magnetic sensor circuit, the temperature characteristics of the ON / OFF threshold value of the switch circuit 20, and the like. Even in such a case, the magnetic sensor circuit 10 according to the present exemplary embodiment includes the temperature detection circuit 16 and the temperature compensation that connect the voltage variation of the hold signal caused by the temperature change to the output side of the sample hold circuit 14. The circuit 18 compensates the temperature. The temperature detection circuit 16 is provided with a temperature signal polarity switching circuit 17 that switches the changing direction of the temperature signal to be output with respect to the temperature change. By providing the temperature signal polarity switching circuit 17, the increase / decrease direction of the voltage value of the temperature signal can be set according to the change direction of the voltage value of the hold signal with respect to the temperature change direction. Temperature compensation is possible.

  In addition, the magnetic sensor circuit 10 according to the present embodiment is easy to compensate for temperature because the hold signal is a substantially DC signal, and enables highly accurate temperature compensation. Next, examples according to the present embodiment will be described.

[Example]
FIG. 5 is a circuit diagram of a magnetic sensor circuit of an example according to the first embodiment of the present invention. The magnetic sensor circuit of FIG. 5 is preferably mounted on a semiconductor device, for example, one IC chip. FIG. 5 shows a circuit downstream from the sample hold circuit in the magnetic sensor circuit, and also shows the MI element connected to the magnetic sensor circuit. The magnetic sensor circuit shown in FIG. 5 is set so that the voltage of the hold signal increases as the temperature rises.

  Referring to FIG. 5, in the two MI elements MIx and MIy, amorphous wires are arranged along the x-axis and y-axis of the two-dimensional orthogonal coordinate system. That is, the two MI elements MIx and MIy are arranged perpendicular to each other, and the x-axis and y-axis components of the magnetic field are detected.

  One end of each detection coil of the x-axis and y-axis MI elements MIx and MIy is connected to each of the two analog switches SWx and SWy, and the other end is connected to a reference voltage source. Timing signals are supplied in time series to the control input units of the analog switches SWx and SWy. As described with reference to FIGS. 3 and 4, the timing signal is delayed from the exciting current by a predetermined time. The analog switches SWx and SWy are opened and closed by a timing signal. The output sides of the analog switches SWx and SWy are commonly connected and connected to the capacitor C14. The capacitor C14 holds the detection signals of the x-axis and y-axis MI elements MIx and MIy in time series (hold signal).

The reference voltage source 45 includes resistors R24 and R25 connected in series with one end connected to a power source and the other end grounded. The resistance values of the resistors R24 and R25 are set equal to each other, and a voltage ½ of the power supply voltage V _DD is taken out from the intersection of the resistors R24 and R25 and connected to a common connection point of each detection coil. Note that trimming means is provided in one or both of the resistors R24 and R25 in order to accurately match the resistance values of the resistors R24 and R25.

  The voltage (hold signal) of the capacitor C14 is output to the non-inverting input terminal of the operational amplifier A12 via the resistor R26.

The amplifier circuit 42 includes operational amplifiers A11 and A12 and resistors R11 to R14. The operational amplifier A12 has an inverting input terminal connected to the output terminal of the operational amplifier A11 via the resistor R13. The non-inverting input terminal of the operational amplifier A11 is connected to the connection point between the series resistors R11 and R12. The resistors R11 and R12 connected in series have one end connected to the power source and the other end grounded. Since the resistors R11 and R12 have the same resistance value, a voltage that is ½ of the power supply voltage V _DD is applied to the non-inverting input terminal of the operational amplifier A11. Since the inverting input terminal and the output terminal of the operational amplifier A11 are short-circuited, a voltage that is ½ of the power supply voltage V _DD is output to the output terminal of the operational amplifier A11. The output terminal of the operational amplifier A11 is connected to the inverting input terminal of the operational amplifier A12 via the resistor R13.

A resistor R14 is connected between the inverting input terminal and the output terminal of the operational amplifier A12. Therefore, the operational amplifier A12 differentially amplifies the hold voltage with an amplification factor determined by R14 / R13, using a voltage half that of the power supply voltage V _DD as a reference voltage. The output terminal of the operational amplifier A12 is connected to the non-inverting input terminal of the operational amplifier A13.

  Note that trimming means is provided in one or both of the resistors R11 and R12 in order to accurately match the resistance values of the resistors R11 and R12.

  The temperature detection circuit 43 includes two PMOS transistors M1 and M2 constituting a current mirror circuit, two diode-connected PNP transistors Q1 and Q2, operational amplifiers A15 to A18, resistors 18 to 23, and a temperature signal polarity switching circuit. 47.

  The PNP transistors Q1 and Q2 are selected so that their element areas are different. For example, the element area of the PNP transistor Q2 is set to about 10 times Q1. The values of currents flowing through the emitters of the PNP transistors Q1 and Q2 are substantially equal because they are the drain currents of the PMOS transistors M1 and M2 constituting the current mirror circuit. Therefore, the current densities at the PN junctions of PNP transistors Q1 and Q2 are different from each other, and the emitter voltage of PNP transistor Q1 is higher than the emitter voltage of Q2. Since the potential difference between two PN junctions biased at different current densities is proportional to the absolute temperature, the difference voltage between the emitter voltages of the PNP transistors Q1 and Q2 is a voltage proportional to the temperature. The emitter electrodes of the PNP transistors Q1 and Q2 are connected to the non-inverting input terminals of the operational amplifier A15 and the operational amplifier A16.

  Each of the operational amplifier A15 and the operational amplifier A16 constitutes a voltage follower. The output terminals of the operational amplifier A15 and the operational amplifier A16 are connected to the temperature signal polarity switching circuit 47, respectively.

  The temperature signal polarity switching circuit 47 includes four switch circuits SW1 to SW4 and an inverter INV. The switch circuits SW1 and SW2 and the switch circuits SW3 and SW4 are in the same open / close state in conjunction with each other. Further, the polarity switching signal is supplied as a control signal to the switch circuit, and the switching operation of the switch circuit is performed according to the state of the polarity switching signal. For example, when the polarity switching signal is “High”, the switch circuits SW1 and SW2 are closed and the switch circuits SW3 and SW4 are opened. On the other hand, when the polarity switching signal is “Low”, the switch circuits SW1 and SW2 are opened, and the switch circuits SW3 and SW4 are closed.

The output side of the temperature signal polarity switching circuit 47 is connected to the input terminal of the operational amplifier A17 via the variable resistor R18 or R20. When the polarity switching signal is “High”, the switch circuits SW1 and SW2 are closed. In this state, the output terminal of A15 and the inverting input terminal of A17 are connected, and the output terminal of A16 and the non-inverting input terminal of A17 are connected. In this connected state, the rise in temperature, since the emitter voltage of the transistor Q2 is larger voltage decrease than the emitter voltage of the transistor Q1, the voltage of the non-voltage at the inverting input terminal V ₊ and the inverting input terminal of A17 V _- (= V ₊ −V ₋ ) increases. As a result, the output voltage of A17 increases. That is, this connection state is a state in which the sign of the proportional coefficient α described above is set to a positive value.

On the other hand, when the polarity switching signal is “Low” and the switch circuits SW3 and SW4 are closed, the output terminal of A15 and the non-inverting input terminal of A17 are connected, and the output terminal of A16 and the inverting input terminal of A17 are connected. Connected. In this connected state, the rise in temperature, since the emitter voltage of the transistor Q2 is larger voltage decrease than the emitter voltage of the transistor Q1, the voltage at the inverting input terminal of A17 V _- and the non-inverting input terminal voltage V ₊ (= V ₋ −V ₊ ) increases. As a result, the output voltage of A17 decreases. That is, this connection state is a state in which the sign of the proportionality coefficient α is set to a negative value.

The operational amplifier A18 outputs a voltage that is ½ of the power supply voltage V _{DD in} the same manner as the operational amplifier A11 described above. That is, the non-inverting input terminal of the operational amplifier A18 is connected to the connection point between the series resistors R22 and R23. The resistors R22 and R23 connected in series have one end connected to the power source and the other end grounded. Trimming means is provided in one or both of the resistors R22 and R23. This is because the offset adjustment for adjusting the sample hold voltage in the zero magnetic field to ½ of the power supply voltage V _DD is performed by trimming the resistor R22 or R23 at the reference temperature. For this reason, the output voltage of the operational amplifier A18 is a voltage obtained by adding an offset voltage to a half voltage of the power supply voltage V _DD . The output terminal of the operational amplifier A18 is connected to the inverting input terminal of the operational amplifier A17 via the resistor R21.

  A15 and A16 are connected to the input terminal of the operational amplifier A17 in accordance with the connection state of the temperature signal polarity switching circuit 47 described above. The operational amplifier A17 amplifies at an amplification factor determined by the ratio between the resistors R18 and R19 and the ratio between the resistors R20 and R21, and outputs the result to the inverting input terminal of the operational amplifier A13.

  The resistors R18 and R20 are provided with trimming adjusting means so that the gain of the operational amplifier A17 can be controlled. Note that the means for adjusting the resistance value by trimming may be provided in the resistors R19 and R21 or in both. By controlling the amplification factor, a proportional coefficient with the temperature signal with respect to the temperature is controlled. Accordingly, even if MI elements having different detection signal voltage values with respect to the magnetic field intensity are connected, temperature compensation can be achieved by controlling the proportionality coefficient. Further, when the amount of change in the voltage value of the hold signal with respect to a predetermined temperature change fluctuates, the voltage value of the hold signal can be corrected by controlling the proportional coefficient.

  Further, the output of the operational amplifier A17, that is, the temperature signal may be output to the outside of the magnetic sensor circuit 40. The temperature information can be supplied to an operation check of the temperature detection circuit 43 and an electronic device on which the magnetic sensor circuit 40 is mounted.

  The temperature compensation circuit 44 includes an operational amplifier A13 and resistors R15 and R16. The operational amplifier A13 is supplied with a hold signal at a non-inverting input terminal and operates as a non-inverting amplifier circuit for the hold signal. The operational amplifier A13 is supplied with a temperature signal at its inverting input terminal and operates as an inverting amplifier circuit for the temperature signal. The amplification factor of the inverting amplifier circuit is represented by -R16 / R15. When the resistors R15 and R16 have the same resistance value, the amplification factor is -1. In this case, the amplification factor is 2 for the hold signal.

  In this way, the operational amplifier A13 functions as a differential amplifier between the hold signal and the temperature signal, and an output signal is output as a difference signal between the hold signal and the temperature signal. In this manner, the voltage variation of the hold signal due to the temperature characteristic of the magnetic sensor circuit is corrected in the operational amplifier A13. As a result, a temperature compensated output signal is output from the magnetic sensor circuit.

  Here, the operational amplifier A17 constitutes a proportional coefficient control circuit that controls the absolute value of the proportional coefficient α determined by the ratio between the resistors R18 and R19 and the ratio between the resistors R20 and R21. The proportional coefficient control circuit compensates for the amount of fluctuation of the voltage value of the hold signal in the zero magnetic field due to temperature change by controlling the amplification factor of the operational amplifier A17. The resistors R18 to R21 are set as follows.

  Assume that the amplification factor for the voltage value of the temperature signal in the operational amplifier A13 is set to −1 as described above. Next, in a state where the magnetic field applied to the MI element is zero (zero magnetic field), the absolute value of the voltage change of the hold signal with respect to a predetermined temperature change and the output voltage change of the temperature compensation circuit 43 are the same. Is set to the amplification factor of the operational amplifier A17. The amplification factor of the operational amplifier A17 is set by resistors R18 to R21. By setting in this way, it is possible to correct the fluctuation amount of the voltage value of the hold signal in the zero magnetic field due to the temperature change. As a result, the magnetic sensor circuit 40 suppresses the voltage fluctuation of the output signal due to the temperature change in the state where the normal magnetic field strength is detected.

  Moreover, it is preferable to set the amplification factor of the operational amplifier A12 higher than the amplification factor of the operational amplifier A13. For example, the amplification factor in the operational amplifier A12 is 8 times, and the amplification factor in the operational amplifier A13 is doubled. By setting in this way, a weak hold signal is first amplified to a relatively large voltage by the operational amplifier A12, so that a decrease in the S / N ratio due to mixing of noise or the like in the operational amplifier A13 can be suppressed. Further, since the temperature compensation amount can be set finely by setting the gain of the operational amplifier A13 low, fine adjustment can be easily performed and compensation can be made with high accuracy.

  The temperature compensation operation of the magnetic sensor circuit 40 is performed as follows. In the temperature signal polarity switching circuit 47, the switch circuits SW1 and SW2 are closed and the switch circuits SW3 and SW4 are opened.

  It is assumed that the temperature value of the magnetic sensor circuit 40 is increased and the voltage value of the hold signal in the zero magnetic field is increased. Then, when the temperature compensation operation is not performed, the output voltage value of the operational amplifier A13 increases.

  However, when the temperature rises, the emitter voltage of the PNP transistor Q2 of the temperature detection circuit 43 decreases from the emitter voltage of Q1, and the difference increases. The emitter voltage of the PNP transistor Q1 is supplied to the non-inverting input terminal of the operational amplifier A17 via the switch circuit SW2, and the emitter voltage of the PNP transistor Q2 is supplied to the inverting input terminal of the operational amplifier A17 via the switch circuit SW1. Therefore, the output voltage value of the operational amplifier A17 increases and the output of the operational amplifier A13 decreases. As described above, the decrease in the voltage value of the hold signal due to the temperature rise can be corrected by the temperature compensation operation. In addition, when temperature falls, the reverse compensation operation | movement when temperature rises is performed.

  When the temperature of the magnetic sensor circuit 40 rises and the voltage value of the hold signal in the zero magnetic field decreases, the temperature signal polarity switching circuit 47 opens the switch circuits SW1 and SW2 and closes the switch circuits SW3 and SW4. Set to state.

  According to the present embodiment, the amplification circuit 42 and the temperature detection circuit 43 and the temperature compensation circuit 44 that compensate for the voltage fluctuation of the hold signal caused by the temperature change are provided on the output side of the sample hold circuit 41. The temperature detection circuit 43 detects the temperature and outputs a temperature signal corresponding to the temperature. The voltage variation of the hold signal is compensated by the temperature signal. The temperature detection circuit 43 is provided with a temperature signal polarity switching circuit 47 that switches the change direction of the output temperature signal with respect to the temperature change. By providing the temperature signal polarity switching circuit 47, the temperature signal increase / decrease direction can be set according to the change direction of the hold voltage with respect to the temperature change direction, so that temperature compensation can be reliably performed according to the characteristics of the magnetic sensor circuit. Become. Furthermore, since the hold signal is substantially a direct current signal, temperature compensation can be easily performed using the temperature signal. In addition, the operational amplifier used in the temperature compensation circuit 44 does not need a particularly excellent high frequency characteristic, and therefore, highly accurate temperature compensation is possible.

(Second Embodiment)
FIG. 6A is a diagram showing a mobile phone as an example of an electronic apparatus according to the second embodiment of the present invention, and FIG. 6B is an enlarged view of a magnetic sensor.

  6A and 6B, the mobile phone 50 includes a display unit 51, an operation unit 52, an antenna 53, a speaker 54, a microphone 55, an electronic board 56, and an electronic board 56. It is composed of a mounted MI sensor 58 and the like.

  The MI sensor 58 includes a semiconductor device 59 in which the magnetic sensor circuit (not shown) of the first embodiment described above is formed, and two MI elements connected to the semiconductor device 59. The two MI elements MIx and MIy are arranged so as to be orthogonal to each other along the surface of the electronic substrate. Each of the MI elements MIx and MIy is connected to a magnetic sensor circuit of the semiconductor device 59 through a wiring such as a wire.

  The MI sensor 58 detects the azimuth / angle that the mobile phone 50 is facing based on the direction of geomagnetism, for example, the azimuth / angle that the longitudinal direction of the operation unit 52 points to. On the display unit 51 of the mobile phone 50, the map near the current location is displayed so that the azimuth / angle pointed to by the longitudinal direction of the operation unit 52 is on the top.

  As described above, in the mobile phone 50, the MI sensor 58 has the magnetic sensor circuit according to the first embodiment mounted on the semiconductor device. Since the magnetic sensor circuit can detect the magnetic field intensity with high accuracy even if the temperature changes, the direction and angle can be detected accurately and reliably. Further, since the semiconductor device 59 is composed of one semiconductor chip, the magnetic sensor circuit can be reduced in size. As a result, the mobile phone 50 can be downsized by using the semiconductor device 59.

  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. Although the electronic device of the present 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.

  Although preferred embodiments and examples of the present invention have been described in detail above, the present invention is not limited to such specific embodiments or examples, and is within the scope of the present invention described in the claims. Various modifications and changes are possible.

It is a circuit diagram of the conventional MI sensor. It is a circuit diagram of another conventional MI sensor. 1 is a block diagram of a magnetic sensor circuit according to a first embodiment of the present invention. (A)-(D) are figures which show an operation timing and a waveform. It is a circuit diagram of the magnetic sensor circuit of the Example which concerns on 1st Embodiment. (A) is a figure which shows the mobile telephone as an example of the electronic device which concerns on the 2nd Embodiment of this invention, (B) is an enlarged view of a magnetic sensor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 40 Magnetic sensor circuit 11 Pulse generation circuit 12 Pulse current supply circuit 13 Delay circuit 14 Sample hold circuit 15 Amplifier circuit 16 Temperature detection circuit 17, 47 Temperature signal polarity switching circuit 18 Temperature compensation circuit 20 Switch circuit 20a Control input part 21 Reference | standard Voltage source 22 Capacitor 26 MI element 27 Amorphous wire 28 Detection coil 50 Mobile phone 58 Magnetic sensor 59 Semiconductor device MI1, MI2, MIx, MIy MI element

Claims (13)

A magnetic sensor circuit that supplies an excitation current to an MI element, and a detection signal corresponding to the magnetic field intensity is supplied from the MI element based on the excitation current,
A pulse current supply circuit for supplying a pulse current to the MI element;
A sample and hold circuit for holding a substantially peak value of the detection signal and outputting a hold signal;
Temperature compensation means for detecting the temperature of the magnetic sensor circuit and compensating the temperature characteristic of the magnetic sensor circuit with respect to the hold signal based on a temperature signal corresponding to the temperature;
The magnetic sensor circuit according to claim 1, wherein the temperature compensation means includes a temperature signal polarity switching unit that switches a relationship between the temperature change direction and the temperature signal change direction. The temperature compensation means includes
A temperature detection circuit that detects the temperature of the magnetic sensor circuit and outputs a temperature signal corresponding to the temperature;
Based on the temperature signal, a temperature compensation circuit for correcting the voltage value of the hold signal,
The magnetic sensor circuit according to claim 1, wherein the temperature signal polarity switching unit is provided in a temperature detection circuit. The MI element comprises an amorphous wire and a detection coil,
3. The magnetic sensor circuit according to claim 1, wherein the sample-and-hold circuit is supplied with a detection signal that is induced in a detection coil when the pulse current is passed through the amorphous wire. The sample hold circuit comprises a switch circuit and a hold capacitor,
The magnetic sensor circuit according to claim 1, wherein the switch circuit is supplied with an open / close control signal based on the timing of the pulse current. An amplifier circuit is further provided between the sample hold circuit and the temperature compensation circuit,
The magnetic sensor circuit according to claim 1, wherein the amplification circuit has an amplification factor higher than that of the temperature compensation circuit.   The magnetic sensor circuit according to claim 1, wherein the temperature compensation circuit corrects a hold signal using the temperature signal as a reference voltage value.   The magnetic sensor circuit according to claim 1, wherein the temperature signal has a voltage value corresponding to the temperature. The temperature detection circuit includes:
A first PN junction element whose cathode sides are set to the same potential, and a second PN junction element to which a current having a current density smaller than that of the first PN junction element is supplied;
A subtracting circuit connected to each of the anode sides of the first and second PN junction elements and outputting a temperature signal having a voltage value corresponding to a potential difference between the anode sides;
2. The temperature signal polarity switching unit includes a polarity switch circuit that connects each of the anode side of the first or second PN junction element and each of two inputs of the subtracting circuit. 7. The magnetic sensor circuit according to claim 1.   9. The magnetic sensor circuit according to claim 8, wherein the polarity switch circuit is supplied with a switching signal for controlling a relationship between the change direction of the temperature and the change direction of the temperature signal.   The magnetic sensor circuit according to claim 1, wherein the temperature detection circuit further includes a proportional coefficient control circuit that controls a proportional coefficient of a voltage value of a temperature signal with respect to the temperature.   11. The magnetic sensor circuit according to claim 10, wherein the proportionality coefficient is controlled in a state where the magnetic field strength applied to the MI element is substantially zero. The first and second PN junction elements include first and second transistors having different element areas,
The collector and base of each of the first and second transistors are connected to each other, a current of substantially the same magnitude is supplied to the emitter, and each of the emitters is connected to a polarity switch circuit. The magnetic sensor circuit according to claim 8, wherein the magnetic sensor circuit is any one of claims 8 to 11. A semiconductor device that supplies an excitation current to an MI element and is supplied with a detection signal corresponding to the magnetic field intensity from the MI element based on the excitation current,
A semiconductor device comprising the magnetic sensor circuit according to claim 1.

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