JP2882485B2 - Magnetic detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention converts a magnetic state into an electric signal using a magnetoresistive element whose electric resistance is determined by a magnetic state, and detects a magnetic change speed. The present invention relates to a magnetic detection device.

[Conventional technology]

For position sensors or rotational speed sensors, there are strong demands for high detection accuracy, a wide range of operating temperature, a simple structure, and the like, and magnetic detection sensors have come to be used. This is because the magnetoresistive element has high sensitivity, is relatively stable to temperature changes, and is easy to manufacture.
Further, in an electronic circuit that converts a magnetic state into an electric signal,
It is also important that the design of the detection circuit is easy because the magnetic state directly determines the resistance value. The above features are effective for building a magneto-resistive element and a detection circuit in one chip.

FIG. 18 shows a conventional sensor circuit including a resistance bridge circuit 101 widely used as a resistance value detection circuit and a voltage amplification circuit 102 for detecting and amplifying the output voltage _VBO . The resistance bridge circuit output voltage V _BO is stable against temperature changes.

[Problems to be solved by the invention]

However, the voltage amplification circuit 102 which is an analog circuit
The offset voltage is generated due to a change in the characteristics of a transistor, which is a component of an amplifier circuit, a shift in the resistance value of a resistance element, etc. due to a change in temperature. Although a certain degree of improvement is possible with a temperature compensation circuit, the circuit becomes complicated and the production efficiency decreases. If the temperature becomes higher, the compensation circuit itself cannot operate normally. Therefore, the configuration shown in FIG. 18 is not suitable as a detection circuit for a device having a wide operating ambient temperature range such as a rotation speed sensor for an automobile, and particularly, a wheel speed for an ABS (Antilock Brake System). Since the sensor is mounted near the brake of a vehicle that tends to be hot, a wide range of operation guarantee temperature is required. In the future, the sensor needs to be integrated into one chip, and the operating ambient temperature range of the detection circuit becomes wider and stricter. Therefore, a detection circuit that operates stably over a wide operating temperature range is required.

The present invention has been made in view of the above-described problems, and has as its object to provide a magnetic detection device that operates stably in a wide operating temperature range and is suitable for use in an integrated circuit.

It is another object to increase the detection sensitivity of such a magnetic detection device.

[Means for solving the problem]

In order to achieve the above object, a magnetic detection device according to claim 1 of the present application has a magnetoresistive element whose resistance value changes with a change in magnetism, and generates a pulse whose frequency changes with a change in magnetism to be detected. An oscillation circuit to be output and a comparison pulse having a frequency different from that of the oscillation circuit are input, and a phase state or a phase difference between the comparison pulse and a pulse output from the oscillation circuit is compared to change the magnetic state. And a detection circuit for detecting.

In the magnetic detection device according to the second aspect, the frequency of the comparison pulse according to the first aspect changes in the opposite direction to the change in the frequency of the pulse output from the oscillation circuit due to a change in the magnetism to be detected. It is characterized by being output from a comparison oscillation circuit.

Further, in the magnetic detection device according to the third aspect, the comparison oscillator according to the second aspect includes a comparative magnetoresistive element whose resistance value changes in a direction opposite to that of the magnetoresistive element due to a change in magnetism to be detected. Features.

In the magnetic detection device according to the fourth aspect, the first aspect is as follows.
In the oscillation circuit and the comparison oscillation circuit described above, an odd number of inverters are connected in series, an input of a first inverter and an output of an inverter at the last stage are connected via a first resistor, A capacitor and a second resistor are connected in series from the input of the inverter to the output of the inverter of a predetermined odd-numbered stage, and from the connection point between the capacitor and the second resistor, A circuit connected to an output of a predetermined even-numbered inverter via a third resistor having a small resistance value, wherein the oscillation circuit having the magnetoresistive element includes the first resistor, the second resistor, A magnetoresistive element is used for at least two of the third resistors, and when receiving a magnetism, a potential at a connection point between the second resistor and the third resistor changes.

[Action]

According to the magnetic detection device of the present invention, when no magnetism acts on the magnetoresistive element in the oscillation circuit, the frequency of the pulse of the oscillation circuit and the frequency of the comparison pulse substantially match. When the temperature as a whole is uniform, the absolute value of the frequency of both pulses changes, but it is always the same. Therefore, the influence of temperature is removed by comparing the phase state or the phase difference between the comparison pulse and the pulse output from the oscillation circuit by the detection circuit. When magnetism acts on the magnetoresistive element of the oscillation circuit, the resistance value changes in accordance with the state of the magnetism. Change. Since this change depends only on the magnetic state without depending on the temperature change, the magnetic state can be detected. As with the temperature change, the fluctuation of the power supply voltage can be compensated for by comparing the relationship between the phase states of the two pulses or the phase difference. In this way, the magnetic state can be detected stably under a wide temperature range.

According to the magnetic detecting device of the present invention, the comparison pulse is output from the comparison oscillation circuit whose frequency changes in the opposite direction to the frequency change of the pulse output from the oscillation circuit due to the change in the magnetism to be detected. Therefore, the amount of change due to magnetism can be expanded and detected. Thereby, the magnetic state can be detected with high accuracy.

Further, according to the magnetic detecting device of the present invention, the potential at the connection point between the second resistor and the third resistor changes when the magnetism is received by the magnetoresistive element. The oscillation frequency can be controlled not only by charging and discharging by the
The change in the frequency with respect to the change in the resistance value can be increased, and the detection sensitivity can be increased.

〔Example〕

 Hereinafter, the present invention will be described using embodiments shown in the drawings.

FIG. 1 shows the configuration of a magnetic detection device according to a first embodiment of the present invention. This embodiment is a so-called gear detection type magnetic detection device in which a magnetic sensor is disposed between a gear made of a magnetic material and a bias magnet, and is suitably used for a wheel speed sensor for ABS and the like. Basically, a molded chip 1 in which a magnetoresistive element is molded with resin, a metallic inner case 2, an outer case 3, a bias magnet 4, an output pin 5,
It consists of a connector 6. The bias magnet 4 is inserted into the groove 7 of the connector 6, and the inner case 2 is fixed to the connector with an adhesive (not shown) or the like. The mold chip 1 is fixed directly above the bias magnet 4 with an adhesive or the like (not shown), and is bonded to the output pin 5 previously formed integrally with the connector 6 by means such as solder. Finally, the outer case 3 is pressed into the connector 6 and the end 8 is swaged. Reference numeral 9 denotes an example of a detection target, which is a rotating gear made of a magnetic material. When configured as a wheel speed sensor, a wheel shaft passes through the center of the rotating gear 9.

Next, the configuration of the mold chip 1 is shown in FIG. A ferromagnetic magnetoresistive element 1b made of Ni-Co or Ni-Fe is formed in a U-shape by means such as photoetching on a glass plate, an insulating substrate 1a made of high-resistance Si or Si having an oxide film formed thereon. One end of the conductive layer 1c is connected and arranged.
The insulating substrate 1a on which the magnetoresistive element 1b and the conductive layer 1c are formed is fixed on a lead frame 1d with a die bonding paste 1e, and the other end of the conductive layer 1c and the lead frame 1d are connected by a bonding wire 1f. Then mold resin
1g is injection molded. When, for example, Si is used, the insulating substrate 1a is etched in a tapered shape except for a portion 1h where the magnetoresistive element 1b is arranged, thereby forming a thin portion 1i. The above-mentioned bonding wire 1f is formed on the thin portion 1i. When using an insulating substrate 1a in which an oxide film is formed on Si, another circuit element such as an oscillation circuit to be described later may be formed in or on this Si.

3 (a) to 3 (d) show a method of forming the thin portion 1i when Si is used for the insulating substrate 1a. The plane orientation of the surface of the Si substrate uses the (100) plane. In FIG. 3A, an oxide film 1j (hatched portion) is formed on the Si substrate 1a. FIG. 3B is a sectional view. Thereafter, when an alkaline anisotropic etching is performed, a thin portion 1i is formed without changing the thick portion 1h as shown in FIG. 3 (c), and a tapered portion is formed between the thick portion 1h and the thin portion 1i. 1k is formed at an angle of about 54 degrees.
The cross-sectional shape is as shown in FIG. Further, if an oxide film (not shown in the thin portion) is formed on the surface, the insulating substrate 1a is formed.

Next, FIG. 4 shows a block diagram of a detection circuit which is a main part of the present embodiment. This circuit outputs a change in the magnetic field acting on the magnetoresistive element in two values, high and low, of the pulse output, and is used as, for example, a detection circuit of a rotational speed sensor.

FIGS. 5 and 6 are timing charts showing the timing states of the block output signals in the block diagram of FIG. 4, and show the operating principle of this embodiment.

The magnetoresistive elements 10 and 20 in FIG. 4 (corresponding to the magnetic detecting element and the comparative magnetic detecting element, respectively) are formed on the insulating substrate 1a as shown in FIG. Change the longitudinal direction of the pattern by 90 degrees with the same size,
By forming them on one chip, they are arranged so that their resistance values change in opposite directions to the action of the same magnetic field.
Oscillation circuit 30 and 40 (respectively corresponding to Comparative oscillation circuit and the oscillation circuit) Sadamari oscillation frequency by the resistance value of the magnetoresistive elements 10 and 20, and outputs a clock A _C, B _C having a frequency equal to the frequency. The counters 50 and 60 receive the clocks A _C and B _C from the oscillation circuits 30 and 40, and divide the frequency by, for example, ８.
Ripple carry pulse outputs A _O and B _O (corresponding to a pulse and a comparison pulse, respectively) are output. Timing comparator 70
A (corresponding to a detection circuit) receives A _O and B _O of the counters 50 and 60 as inputs and detects the relative relationship between the rising timings of the A _O and B _O signals. High (H) when A _O rises earlier than B _O
Slow time and outputs an output signal C _O which is a low (L). Therefore, one pulse output is obtained for one cycle of the magnetic (field) change, and the frequency of the pulse output matches the frequency at which the magnetism changes. When the rotation frequency and the magnetic varying frequency is a fixed relationship, the frequency of the pulse output C _O will be representing the rotational frequency.

Figure 5 is a clock B _C when the frequency of the clock A _C with respect to the frequency of the clock B _C higher, A _C, ripple carry pulse output B _O of the counter 50, 60, A _O, pulse output of the timing comparator 70 Indicates the timing relationship of _CO . The clocks B _C and A _C are frequency-divided by the counters 50 and 60, for example, by ８, so that the phase difference T _C between the clocks B _C and A _C due to the frequency difference is the output of the counters 50 and 60. As the phase difference T _D between the ripple carry pulse outputs B _O and A _O , that is, as a phase difference eight times as large as T _C
T _D can be obtained, and the pulse phase difference can be detected stably. Outputs a value high ripple carry pulse output A _O of the rising time of the ripple carry pulse output B _O as an output C _C of the timing comparator. Therefore, C _O goes high at the time of rising of B _O.

Figure 6 is a clock B _C during lower frequency of the clock A _C with respect to the frequency of the clock B _C, A _C, ripple carry pulse output B _C of the counter 50, 60, A _O, pulse timing comparator 11 Indicates the timing relationship of the output _CO . Similar to the description of FIG. 5, and outputs a value low ripple carry pulse output A _O of the rising time of the ripple carry pulse output B _O as the output of the timing comparator. Therefore, C _O goes low when B _O rises.

FIG. 7A is a circuit configuration showing an example of the oscillation circuits 30 and 40, in which a generally known oscillation circuit is applied to the present embodiment. FIG. 7B shows operation waveforms at points K, H, I, and J in FIG. 7A. 31,3 in the figure
Inverters 2 and 33 are connected in series.
Is connected to the output of the inverter 33 via the magnetoresistive elements 10 and 20 (the resistance value is R _O ), and the input of the inverter 31 is connected to the output of the inverter 32 via the capacitor 34. The oscillation frequency f ₀ is Becomes Also, the threshold value V _{TH of the} inverters 31, 32, 33 is This is a value determined by the charging / discharging time of the resistance value R _O of the magnetoresistive elements 10 and 20 and the capacitance value C _O of the capacitor 34.

FIG. 8 shows an example of the timing comparator 70, and a rising edge trigger type D-type flip-flop 71 is shown.
Connected to the data input terminal 72 a ripple carry pulse output A _O of the counter 60 is connected to the clock input terminal 73 of the pulse output B _OH of the hysteresis control circuit 74.

Ripple carry pulse output A _O connected to input terminal 72 at the time of rising of output B _OH of hysteresis control circuit 74
Is output to the output terminal 75. Therefore, the output _CO of the timing comparator shown in FIGS. 5 and 6 becomes a pulse output signal of the output terminal 75 of the D flip-flop 71 shown in FIG.

FIG. 9 shows an example of the hysteresis control circuit 74. This hysteresis control circuit, NAND gate 74 which receives the pulse output B _OD and the D-type flip-flop output C _O of the pulse delay circuit 74a which receives the ripple carry pulse output B _O
b and C _O are input, and the output of inverter 74c that inverts C _O and B
NAND gate 74d to the _O to the input, and a NAND gate 74e for outputting NADN gate 74b, receives the output of 74d output B _OH of the clock input of the D-type flip-flop 71.

Figure 10 is a timing chart showing the operation of the hysteresis control circuit 74, obtaining a pulse output B _OD delayed by a delay time T _HD against ripple carry pulse output B _O as the output B _OD of the pulse delay circuit 74a. When the timing comparator output C _O is low, B _O is selected and becomes the hysteresis control circuit output B _OH , and when C _O is high, B _OD is selected and becomes the hysteresis control circuit output B _OH .

Therefore, in the configuration of the present embodiment, what determines the oscillation frequency of the oscillation circuits 30 and 40 is the resistance value R _O of the magnetoresistive elements 10 and 20, the capacitance value C _{O of the} capacitor, and the characteristic values of the transistors of the inverters 31 to 33. However, a pair of oscillating circuits having almost the same values as described above can be formed because they are built on one chip. Therefore, the magnetoresistive element 1 in the oscillation circuits 30 and 40
When magnetism does not affect 0,20, a pair of oscillation circuits 30,40
Have almost the same oscillation frequency. If the temperature of the entire chip is uniform with respect to temperature change, the values of the above three factors that determine the oscillation frequency change equally, so that the absolute value of the oscillation frequency changes. , 40 are always equal. Therefore, a pair of oscillation circuits
Detecting the ratio of the oscillating frequencies of 30,40 will eliminate the effect of temperature.

When magnetism acts on the pair of oscillation frequencies 30 and 40, the resistance values of the magnetoresistive elements 10 and 20 change according to the state of the magnetism. I do. This change in frequency ratio depends only on the magnetic state. The fluctuation of the power supply voltage can be corrected by taking the ratio of the oscillation frequency as in the case of the temperature change. Thus, a pair of oscillation circuits whose oscillation frequency is determined by the magnetic state
By detecting the change in the oscillation frequency ratio of 30, 40 by the timing comparator 70, the magnetic state can be stably detected under a wide operating temperature range. Since the detection circuit of the present invention can be constituted by a basic digital circuit, a characteristic change of a transistor which is a problem in an analog circuit,
Since the fluctuation of the resistance value of the resistance element and the fluctuation of the capacitance value of the capacitor do not cause any problem, normal operation can be performed even at a high temperature which cannot be operated by an analog circuit, and the IC can be easily formed.

In general, in order to connect the conductive layer 1c and the lead frame 1d with the bonding wire 1f, the bonding must be performed at a predetermined curvature in order to secure the tensile strength of the bonding wire 1f. Since the bonding wire 1f is connected to the thin portion 1i of 1a,
The gap from the magnetoresistive element 1b (10, 20) to the mold resin 1g can be reduced, and by extension the magnetoresistive element
The gap from 1b (10, 20) to the rotary gear 9 can be made as small as possible, and the sensitivity can be improved.

Next, as an example that can further improve the sensitivity,
A second embodiment of the present invention will be described. FIG. 11 shows a block diagram of a detection circuit of the magnetic detection device of the second embodiment. The first
In the embodiment, the magnetoresistive element is used for both circuit configurations of the oscillation circuits 30 and 40, but in the present embodiment, the magnetoresistive element 80 is provided only on the oscillation circuit 30 side, and the resistance of the oscillation circuit 40 side is resistance by magnetism. Use a reference resistor 90 whose value does not change.

FIG. 12 (a) shows the oscillation circuits 30, 40, which are the main parts of this embodiment.
12 (b) shows operation waveforms at points B, D, E, F and A in FIG. 12 (a). In FIG. 12 (a), 31 (41), 32 (42), 33 (43) are inverters connected in series similarly to the circuit of FIG. 7 (a). _Is connected to the output of the inverter 33 (43) via the resistor R _1X (R ₁ ), and the inverter 31 (4
Connect the input of 1) to the output of the inverter 31 (41) via the capacitor 35 (45) and the resistor R _2X (R ₂ ) in series, and connect the capacitor 35 (45) and the resistor R _2X (R ₂ ) from the resistor R _3X (R ₃₎
The circuit is connected to the output of the inverter 32 through a resistor R _1X , R
_At least one of _2X and R _3X has a magnetoresistive element 80
Use

The oscillation frequency f ₁ of the oscillation circuit 30 and 40, Becomes Also, the threshold value V _{TH of} the inverters 31 (41), 32 (42) and 33 (43) is When, Becomes The voltage at point A is determined by the resistance division (R2 _(X) , R3 _(X) ) of the voltages at points E and F. The higher voltage is V _AH , the lower voltage is V _AL , and the difference is V _AS . When the voltage at the point D (the input voltage of the inverter 31 (41)) reaches the threshold value of the inverter 31 (41), the potentials of E, F, and B are sequentially inverted, and the voltage at the point D becomes V _TH center to positive or to V _AS shift in the negative direction. Then, it approaches the threshold value again by charging and discharging C ₁ R _{1 (X)} ,
The same operation is repeated. Frequency f ₁ is lower by increasing the V _AS, f ₁ is increased by reducing the V _AS.

In the first embodiment, the oscillation frequency f ₀ is determined only by the charging and discharging time of R ₀ and C _0. However, according to the present embodiment, the voltage at the point A is changed to R _{2 (X)} , It can be controlled by R3 _(X) , and the degree of freedom of frequency control can be increased.

This will be described in more detail below with reference to FIG. In the oscillation circuit shown in FIG. 7A, a resistance change of the resistor _R0 is used as a means for modulating the frequency. That is,
When the resistance R ₀ changes to R ₀ + ΔR ₀ , the slope of the charge / discharge that determines the frequency is indicated by the characteristic L as shown in FIG. 19 (a), and conversely, when the resistance R ₀ changes to R ₀ −ΔR ₀ , Is represented by a characteristic M. Due to the change in resistance from R ₀ -ΔR ₀ to R ₀ + ΔR ₀ , a period modulation ΔT ₀ occurs. here,
The voltage at point H at t = 0 is V _TH + V _DD and is constant.

On the other hand, in the oscillation circuit shown in FIG. 12 (a), R ₂ and R ₃ are used in addition to the resistor R ₁ as means for modulating the frequency.
Here, R ₁ , R ₂ , and R ₃ are all formed by magnetoresistive elements, and the direction of resistance change is R ₁ + ΔR ₁ , R ₂ + ΔR ₂ , R ₃ under a predetermined magnetic field.
It is arranged to be −ΔR ₃ . That is, if R ₁ and R ₂ are arranged so as to change in phase and R ₃ and R ₁ change in opposite phases, (1) R ₁ → R ₁ + ΔR ₁ , R ₂ → R ₂ + ΔR ₂ , R ₃ → R ₃ At −ΔR ₃ The charge / discharge slope is the same as that of the oscillation circuit of FIG. 7 (a), but the voltage at t = 0 as shown in FIG. 19 (b) is Becomes

That is, when R ₁ is R ₁ + [Delta] R _1, when the time constant of the charge and discharge becomes long, so increasing the t = 0 the voltage (starting voltage of charge and discharge).

(2) When R ₁ → R ₁ −ΔR ₁ , R ₂ → R ₂ −ΔR ₂ , R ₃ → R ₃ + ΔR ₃ The slope of charging and discharging is the same as that of the oscillation circuit of FIG. 7 (a). However, the charge / discharge start at t = 0 is Becomes That is, when the R ₁ is the time constant of the charge and discharge by the R ₁ - [Delta] R ₁ is shortened, the lower the discharge starting voltage of the t = 0.

In this way, the means for modulating the frequency by adding the resistances R ₂ and R _{3 to} the oscillation circuit by using the magneto-resistive elements and setting the phase of the resistance change as described above in FIG. By modulating the charge / discharge start voltage in addition to the charge / discharge time constant, the period modulation ΔT ₁ can be increased, and the frequency can be further greatly changed.

Next, the oscillation circuit shown in FIG. 7 (a) and FIG. 12 (a)
The difference in sensitivity of the oscillation circuit shown in Fig. 12 will be described, and how the respective resistance values of the oscillation circuit in Fig. 12 (a) can be improved in a good state will be described. First, when the sensitivity is calculated in the oscillation circuit shown in FIG. That is, if the resistance change is 1%, the frequency change is also 1% (absolute value).

On the other hand, a numerical calculation of the sensitivity in the oscillation circuit of FIG. Here, it is assumed that the resistance change changes as follows.

R ₁ increases by 1%.

R ₂ increases by 1%.

R ₃ → Decrease by 1%.

Also, R ₂ / R ₃ was used as a parameter, and C _{1 was set to} 220 PF.

FIG. 20 is a graph of Table 1.

As is clear from the graph, (1) If the resistance ratio R ₂ / R ₃ is increased, the sensitivity decreases and approaches the sensitivity of the oscillation circuit shown in FIG. 7A.

(2) When the resistance ratio approaches 1, the sensitivity becomes infinite. However, the oscillation frequency becomes infinite and the oscillation itself becomes unstable.

Therefore, the optimum values of the resistance values R ₁ , R ₂ and R ₃ are determined based on the following concept.

(1) The resistances R ₁ , R ₂ , and R ₃ should be sufficiently larger than the internal resistance of the inverter.

(2) If the resistances R ₁ , R ₂ , R ₃ are small, the current consumption increases.

(3) If the resistances R ₁ , R ₂ , and R ₃ are increased, the impedance of the sensing unit increases, and the resistance to noise is reduced.

For the above reasons, it is appropriate that R ₁ , R ₂ , and R ₃ be about ₁ kΩ to ₁ kΩ.

(1) When the ratio R ₂ / R ₃ between R ₂ and R ₃ approaches 1, sensitivity increases, but oscillation becomes unstable.

(3) the ratio R ₂ / R ₃ of R ₂ and R ₃ are not much different sensitivity of the oscillator circuit of Figure second. 7 (a) 10 or more.

For the above reasons, it is appropriate that R ₂ / R ₃ is about 1.5 to 4.

Next, experimental values of the sensitivity characteristics of the oscillation circuit shown in FIG. 7A and the oscillation circuit shown in FIG. 12A will be specifically described.

(1) Oscillation circuit in Fig. 7 Toshiba Corporation's TC40H004 is used as the inverter, and _R0 = 10k
When Ω, C ₀ = 220pF, V _DD = 5V, sensitivity is 0.8 at room temperature
2 (1% change in resistance, frequency change 0.82%).

(2) using a Toshiba Corporation 40H004 as Figure 12 oscillating circuit inverter, R _1x = 10k
Ω, R _3X = 2 kΩ or 1 kΩ, C ₁ = 220 pF, V _DD = 5 V,
The value of R _2X was changed at room temperature, and the sensitivity in the following four cases was examined using R _2X / R _3X as a parameter.

Change R _1X by 0-2%.

Change R _2X by 0-2%.

R _2X is simultaneously changed at the same rate by 0 to 2%.

R _2X , R _3X are simultaneously reversed for positive and negative, and the absolute value is 0-
Change by 2%.

The results are shown in FIGS. 13 (a) and (b). From the results, it can be seen that the combination of the change of resistance
The oscillation circuit shown can increase the sensitivity by a factor of 2.5 or more.

As described above, the present invention has been described using the first and second embodiments. However, the present invention is not limited thereto, and various modifications can be made as shown below, for example, without departing from the gist of the present invention.

FIG. 1 shows an example in which the rotating gear 9 is not magnetized. However, as shown in FIG. 14, when the rotating gear 9a is magnetized alternately on the N pole and the S pole, as shown in FIG. The bias magnet 4 can be omitted.

In the second embodiment, the circuit configuration of the oscillation circuit is the fifteenth embodiment.
The positions where the resistors R _2X and R _3X are connected may be changed to the output sides of the inverters 32 and 33, respectively (FIG. 15 (a)). Also, the number of inverters may be an odd number of three or more (FIG. 15 (b)). Further, the number of inverters connected between the resistors R _2X and R _3X may be one or more and an odd number (FIG. 15 (c)).
In short, the resistance R _2X to the circuit configuration of FIG. 7 (a), when composing the oscillation circuit of high sensitivity by adding R _3X, the resistance R _2X
The resistance can be set voltage at the connection point A between the R _3X, when the oscillator circuit is subjected to magnetic, the use of the magneto-resistive element to the resistance R _1X to R _3X as the potential at point A changes It is good.

In this case, the ratio of the resistor R _2X to the resistor R _3X (R _2X /
If R _3X ) is 1 or less, oscillation deviates from the circuit stabilization condition, and the ratio must be greater than 1. If at least one of the resistors R _1X , R _2X and R _3X is formed by a magnetoresistive element, frequency modulation is performed. It must be formed by a resistance element.

Further, in the second embodiment, when magnetoresistive elements are used for R _1X and R _2X , and R _2X and R _3X and they are simultaneously changed, if they are changed at the same rate, the circuit design becomes easy, but it is not necessarily limited to the same rate It will not be done.

In each of the above embodiments, two oscillation circuits are used.
It is also possible to use more than one oscillation circuit and compare the outputs from them.

In the first embodiment, the sensitivity is improved by connecting the bonding wire 1f to the thin portion 1i of the insulating substrate 1a as shown in FIG. 2, but this is achieved by the manufacturing method shown in FIG. May be formed.

First, in FIG. 16 (a), an oxide film is formed on a Si substrate 1l.
1m (shaded area) is formed. The shapes of the cross section taken along the line AA and the cross section taken along the line BB are as shown in FIGS. Thereafter, when an alkali-based anisotropic etching is performed, the thinned portion 1n and the tapered portions 1o and 1p are formed as shown in FIG. In FIG. 4D, the shapes of the AA section and the BB section are
FIGS. 7E and 7F respectively. FIG. 17 shows an example in which the magnetoresistive element 1q and the conductive layer 1 are formed using this insulating substrate. A magneto-resistive element 1q is formed in a U-shape on the thick portion 1s. The conductive layer 1r is formed over the thick portion 1s, the tapered portion 1p, and the thin portion 1n of the insulating substrate, and the thin portion 1n is provided with a bonding pad 1t. In FIG. 7A, the shape of the AA cross section is shown in FIG. 7B, and the shape of the BB cross section is shown in FIG. In the embodiment shown in FIG. 17, since three surfaces around the bonding pad 1t on the thin portion 1n are surrounded by the thick portion, the strength of the thin portion at the time of bonding is shown in FIG. Increase compared to the example.

Further, the bonding pad 1t on the insulating substrate may be provided without performing the taper etching of the insulating substrate.

〔The invention's effect〕

As described above, according to the first aspect of the present invention, it is possible to provide a magnetic detection device that operates stably over a wide range of operating ambient temperature and is suitable for use in an integrated circuit.

Further, according to the second aspect, there is an effect that the magnetic detection sensitivity can be increased.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a magnetic detection device according to a first embodiment of the present invention,
FIG. 2 is a cross-sectional view showing the structure of the mold chip 1, FIGS. 3 (a) to 3 (d) are cross-sectional views for explaining a method of forming a thin portion, and FIG. 4 is a circuit diagram of the detection circuit of the first embodiment. Block diagram, fifth
FIGS. 6 and 7 are timing charts showing timing states of block output signals in the circuit of FIG. 4, FIG. 7 (a) is a circuit diagram showing an example of an oscillation circuit, and FIG. 7 (b) is a circuit diagram of FIG. FIG. 8 is a circuit diagram showing an example of a timing comparator, FIG. 9 is a circuit diagram showing an example of a hysteresis control circuit, FIG. 10 is a timing chart showing an operation of the hysteresis control circuit, FIG. 11 is a block diagram of a detection circuit of a magnetic detection device according to a second embodiment of the present invention.
12 (a) is a circuit diagram of the oscillation circuit of the second embodiment, FIG. 12 (b) is an operation waveform diagram in FIG. 12 (a), and FIGS. 13 (a) and 13 (b) are sensitivity of the oscillation circuit. FIG. 14 is a diagram showing experimental results of characteristics, FIG. 14 is another configuration diagram of the magnetic detection device of the present invention, and FIG.
16 (a), 16 (b) and 16 (c) are other circuit diagrams of the oscillation circuit of the second embodiment, and FIGS. 16 (a) to 16 (f) are for explaining another method of manufacturing the thin portion of the insulating substrate. FIGS. 17 (a) to 17 (c)
16 shows an example in which a magnetoresistive element and a conductive layer are formed on the insulating substrate of FIG. 16, FIG. 18 is a circuit diagram of a conventional sensor, and FIG. 19 (a) is a point H in the circuit of FIG. 7 (b). 19 (b) is a diagram showing the charging and discharging at point D in the circuit of FIG. 12 (a), and FIG. 20 is a diagram showing the resistance ratio R ₂ / R _3.
FIG. 4 is a diagram illustrating a relationship between the sensitivity and the sensitivity. 1. Mold chip, 1a ... Insulating substrate, 1b ... Magnetoresistance element, 1c ... Conductive layer, 1f ... Bonding wire, 1i ...
Thin section, 10, 20 …… Magnetic resistance element, 30, 40 …… Oscillation circuit, 50,
60… Counter, 70… Timing comparator, 31,32,33,41,
42,43 …… Inverter, R _1X , R _2X , R _3X , R ₁ , R ₂ , R ₃ …… Resistance,
35,45 …… Capacitors.

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tadashi Hattori 14 Iwatani, Shimowasumi-cho, Nishio-shi, Aichi Pref. Japan Automobile Parts Research Institute Co., Ltd. Surveyed field (Int.Cl. ⁶ , DB name) G01P 3/488 G01R 33/06

Claims (4)

(57) [Claims] An oscillation circuit having a magnetoresistive element having a resistance value changed by a change in magnetism, outputting a pulse whose frequency changes by a change in magnetism to be detected, and a comparison pulse having a frequency different from that of the oscillation circuit. And enter
A detection circuit for detecting the state of the magnetism by comparing a phase state or a phase difference between the comparison pulse and a pulse output from the oscillation circuit. 2. The method according to claim 1, wherein the comparison pulse is output from a comparison oscillation circuit whose frequency changes in a direction opposite to a change in the frequency of the pulse output from the oscillation circuit due to a change in the magnetism to be detected. The magnetic detection device according to claim 1, wherein: 3. The magnetic detecting device according to claim 2, wherein the comparative oscillator has a comparative magnetoresistive element whose resistance value changes in a direction opposite to that of the magnetoresistive element according to a change in magnetism to be detected. . 4. The oscillation circuit and the comparison oscillation circuit,
An odd number of inverters are connected in series, an input of the first inverter and an output of the last stage inverter are connected via a first resistor, and a capacitor and a second resistor are connected from the input of the first stage inverter. Are connected in series to the output of a predetermined odd-numbered inverter, and a connection point between the capacitor and the second resistor is connected via a third resistor having a smaller resistance value than the second resistor. An oscillation circuit having a magneto-resistive element connected to an output of a predetermined even-numbered inverter, wherein at least two of the first, second, and third resistors have a magneto-resistance. 2. The magnetism detecting device according to claim 1, wherein an element is used to change a potential at a connection point between the second resistor and the third resistor by receiving magnetism.