JP2005265751A - Magnetic detection circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a circuit constitution technique capable of compensating effectively temperature dependency of a magnetic-electric conversion characteristic of a Hall element, irrespective of dispersion in manufacturing, in a magnetic sensor formed into a monolithic IC having the Hall element and a peripheral circuit thereof on one semiconductor chip. <P>SOLUTION: The Hall element is driven by a voltage, a circuit is provided to generate a voltage having the temperature dependency expressed by the expression Y=aT<SP>2</SP>+b or Y=aT<SP>2</SP>+bT (a, b are constants, T is absolute temperature), and the voltage generated in the circuit is impressed to the Hall element as the driving voltage, so as to compensate the temperature dependency of the magnetic-electric conversion characteristic of the Hall element. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a technology effective when applied to temperature compensation and manufacturing variation compensation of a magnetic sensor driving circuit and a signal detection circuit using a Hall element. For example, the Hall element and its peripheral circuit are formed on one silicon chip. The present invention relates to a technology that is effective when used in a monolithic IC magnetic sensor.

  Conventionally, Hall elements having magnetic-electrical conversion characteristics have been used as sensors in various measuring instruments and control systems. It is known that the magnetic-electrical conversion characteristics of Hall elements are temperature-dependent, and magnetic sensors using Hall elements are sometimes used in environments with relatively large temperature changes. In order to obtain a stable and stable output, various temperature compensation circuits have been conventionally proposed. For example, there are inventions described in Patent Document 1 and Patent Document 2.

  The invention of Patent Document 1 uses a resistor having the same type of structure as a Hall element for a load of a transconductance amplifier that drives a Hall element at a constant voltage in an integrated circuit and amplifies a magnetic-electrically converted electric signal. Temperature compensation is performed. The invention of Patent Document 2 performs temperature compensation of the magneto-electric conversion characteristics by driving the Hall element with a current having a negative temperature coefficient of about −1000 ppm / ° C.

Also, paying attention to the fact that the temperature dependence of the Hall element magnetic-electrical conversion characteristics substantially coincides with the temperature dependence of the drive current, the monitoring means for detecting the drive current of the Hall element, and the voltage proportional to the detected current And a circuit for generating temperature, and a temperature compensation is performed by applying a stable threshold voltage to a comparator for discriminating the output of the Hall element. In addition, there is a device in which the temperature dependence of the magneto-electric conversion characteristics is compensated by driving the Hall element with a constant voltage source having an appropriate temperature dependence.
US Pat. No. 4,760,285 Japanese Patent Laid-Open No. 10-253728

  Although there is not much problem in terms of temperature compensation in the above prior art, in the invention of Patent Document 1 and the method of monitoring the drive current of the Hall element, the variation in parameters in the manufacturing process (hereinafter simply referred to as manufacturing variation). In other words, the resistance value varies, and the gain of the amplifier and the threshold voltage of the comparator vary, thereby varying the magnetic-electrical conversion characteristics of the entire system.

  At present, most of the drive circuits for magnetic sensors using Hall elements are monolithic ICs, but the Hall elements on a semiconductor chip are generally formed using an epitaxial layer, in which case the epitaxial layer Because of the relatively large variation in carrier concentration and thickness, the input impedance of the element itself varies. Since the magnetic-electrical conversion characteristics of the Hall element are proportional to the product of the Hall mobility and the applied voltage, in the method in which the Hall element is driven by current as in Patent Document 2, the input impedance varies depending on the manufacturing variation of the element. When variations occur, the applied voltage changes and the magnetic-electric conversion characteristics vary. In addition, there is a problem that the yield of the IC decreases when the resistance value or the characteristic variation of the Hall element is large.

  By the way, with regard to the constant voltage circuit, a circuit that can generate a relatively stable constant voltage regardless of temperature fluctuations and device manufacturing variations, or a circuit that can generate a constant voltage proportional to temperature and independent of device manufacturing variations. Various circuit types have been proposed. Therefore, in order to reduce the variation in the magnetic-electrical conversion characteristics of the Hall element due to the manufacturing variation, the method of driving the Hall element by voltage is more advantageous than the method of driving the Hall element by current, but it is made of an epitaxial layer. Although the Hall element is relatively small in manufacturing variation in carrier concentration and hole mobility, the hole mobility is likely to fluctuate due to a temperature change. Therefore, the magneto-electric conversion characteristics of the element fluctuate due to the temperature change.

  In the case of silicon or GaAs ICs, the magneto-electric conversion characteristics of the Hall element have a negative temperature dependency. To compensate for this negative temperature dependency, the applied voltage must have a positive temperature dependency. Although it is relatively difficult to realize a drive circuit and an amplifier circuit having a positive temperature dependency, even if it can be realized, the characteristics of the elements constituting the Hall element and the circuit are manufacturing variations. If it varies, the magnetic-electrical conversion characteristics of the Hall elements will vary, and as a result, the variation in the magnetic-electrical conversion characteristics of the entire system will increase. Furthermore, the conventional technique for compensating for this temperature dependence largely depends on the manufacturing process of the Hall element and the manufacturing process of the peripheral circuit such as the drive circuit / amplifier circuit. Variations in conversion characteristics cannot be reduced sufficiently, and improving the process may increase costs.

  Even in the conventional method in which temperature compensation is performed by driving the Hall element with a constant voltage source having an appropriate temperature dependency, the characteristics vary due to variations in the elements constituting the temperature compensation circuit, and the constants are constant. In order to make a voltage source have a desired temperature dependency, a resistance having a low temperature dependency and a small manufacturing variation is required, but it is difficult to form such a resistor on a silicon chip. However, there is a problem that an external resistance element is required to improve accuracy, or trimming of the resistance value is required.

SUMMARY OF THE INVENTION An object of the present invention is to provide a monolithic IC magnetic sensor having a Hall element and its peripheral circuit on a single semiconductor chip, and the temperature dependence of the magneto-electric conversion characteristics of the Hall element regardless of manufacturing variations of the peripheral circuit. It is an object of the present invention to provide a circuit configuration technique capable of effectively compensating.
Another object of the present invention is to provide a circuit configuration technique suitable for making a Hall element and a peripheral circuit having a function of performing temperature compensation thereof into a monolithic IC on one semiconductor chip.
The above and other objects and novel features of the present invention will become apparent from the description of the present specification and the accompanying drawings.

Outlines of representative ones of the inventions disclosed in the present application will be described as follows.
In other words, the Hall element is driven with a voltage, and a circuit is provided that generates a voltage having a temperature dependency represented by Y = aT ² + b or Y = aT ² + bT (a and b are constants, T is an absolute temperature), The voltage generated in the circuit is applied as a driving voltage to the Hall element to compensate for the temperature dependence of the magneto-electric conversion characteristics of the Hall element.

  Here, instead of applying a voltage having a temperature dependency represented by the above formula as a drive voltage to the Hall element, an amplifier circuit that amplifies the output of the Hall element has a gain that has a temperature dependency represented by the above formula. You may control to. In addition, in a sensor that provides a comparator that discriminates the output of the Hall element and outputs a signal that is binarized with respect to the magnetic input, the threshold level of the comparator is set to 1 / based on the temperature dependence expressed by the above equation. By controlling to be Y, accurate detection output that is not affected by temperature may be compensated even if the magneto-electric conversion characteristics of the Hall element change depending on temperature.

  When a Hall element is formed on a silicon chip, an n-type semiconductor layer consisting of an epitaxial layer or a diffusion layer is used. In this case, the magneto-electric conversion characteristics of the Hall element depend on the carrier concentration, resulting in manufacturing variations. If a voltage having a temperature dependency represented by the above formula is applied as a drive voltage to the Hall element or the gain of the amplifier circuit is controlled to have the temperature dependency represented by the above formula, Even if the magnetic element-electric conversion characteristics of the Hall element vary due to variations, a detection output with little temperature dependence can be obtained. Further, in a sensor that outputs a binarized signal with respect to a magnetic input, the Hall element is controlled by controlling the threshold level of the comparator to be 1 / Y based on the temperature dependency represented by the above formula. Even if the magnetic-electrical conversion characteristics of this change depending on the temperature, an accurate binarized output that is not affected by the temperature can be obtained.

  The above-described means of the present invention is most effective when applied to a case where a magnetic sensor having a Hall element is formed as a monolithic IC. However, when the Hall element and the peripheral circuit are formed on different semiconductor chips. Is also effective. The semiconductor chip on which the Hall element is formed is not limited to silicon or GaAs, but is effective when applied to silicon or GaAs.

The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.
That is, in a monolithic IC magnetic sensor having a Hall element and its peripheral circuit on one silicon chip, the temperature dependence of the Hall element's magnetic-electrical conversion characteristics is effectively compensated regardless of manufacturing variations, and the temperature is reduced. Even if it changes, a stable detection output can be obtained. In addition, it becomes easy to make a Hall element and a peripheral circuit having a function of performing temperature compensation on a single silicon chip as a monolithic IC, thereby improving the yield.

Preferred embodiments of the present invention will be described below with reference to the drawings.
The first embodiment of the present invention includes a circuit that drives a Hall element with a voltage and generates a voltage having a temperature dependency represented by Y = aT ² + b (a and b are constants, T is an absolute temperature). The voltage generated by the circuit is applied as a drive voltage to the Hall element to compensate for the temperature dependence of the magneto-electric conversion characteristics of the Hall element.

  In general, in a monolithic integrated circuit, it is easy to obtain a voltage proportional to the absolute temperature T and almost independent of manufacturing variations. It is also relatively easy to obtain a constant voltage source that is substantially independent of temperature and manufacturing variations. A band gap reference voltage circuit is well known as one of such constant voltage generation circuits. The adjustment of the constants a and b can be realized by appropriately setting the size ratio of two elements such as the same type of resistor. A resistance element formed by a monolithic IC process has a large variation in resistance value of each element and a small temperature coefficient, but the resistance ratio has a small variation and temperature dependency is very small. Therefore, when the Hall element is driven by generating a constant voltage using the resistance ratio, a temperature-compensated magneto-electric conversion characteristic almost independent of the manufacturing process can be obtained.

In addition, although the input resistance and output resistance of the Hall element vary greatly due to manufacturing variations of the Hall element, the Hall mobility does not change much. For example, in the case of n-type silicon having a carrier concentration of 1 × 10 ¹⁵ cm ⁻³ , the change in hole mobility is about 10% at most even if the carrier concentration is shifted by one digit. In a normal silicon IC process, it is relatively easy to suppress the carrier concentration variation to about 10%. Therefore, a monolithic structure in which a Hall element composed of an epitaxial layer or an n-type diffusion layer and its peripheral circuit are formed on one semiconductor chip. In the IC, it can be considered that there is no variation in the Hall mobility of the Hall element.

By the way, normally, the magnetic-electrical conversion characteristics of the Hall element can be described as follows.
VH = k ・ μH ・ Vi ・ B (1)

Here, VH is the Hall voltage (the output voltage of the Hall element), k is a constant depending on the shape of the Hall element, μH is the Hall mobility, Vi is the applied voltage (input voltage) to the Hall element, and B is the applied magnetic flux density. is there. From equation (1), the magnetic-electrical conversion rate is
VH / B = k · μH · Vi (2)
And is proportional to the product of μH and Vi. For silicon μH is larger than p-type towards the n-type, for better low concentration is greater than in the case of high concentration, exclusively low concentration ^{(1 × 10 14 cm -3 ~1} × 10 16 cm -3 approximately ) N-type semiconductor is used. In this case, the temperature dependency of μH is about −4000 to −8000 ppm / ° C., but in this concentration region, the variation in μH due to variation in concentration is small and can be ignored. Therefore, if the applied voltage Vi can be made a value independent of the manufacturing process, VH / B can be made a value independent of the manufacturing process. Hereinafter, n-type silicon will be described, but the principle is the same except that the numerical values are different.

However, to compensate for the temperature dependence of μH at the same time, the following equation obtained by differentiating equation (2) with temperature:
{(VH / B) / dT} (VH / B) = (dμH / dT) / μH + (dVi / dT) / Vi (3)
Needs to be ≈0. On the other hand, μH can be expressed as follows.
μH = μH0 · exp (αT) (4)
Here, μHO is μH at the reference temperature T0, and α is −0.004 to −0.0008 / ° C., that is, −4000 to −8000 ppm / ° C.

Therefore, from Equation (3) and Equation (4),
(dVi / dT) / Vi =-(dμH / dT) / μH0 · exp (αT)
Is obtained. Here, since dμH / dT = αμH0 · exp (αT),
(dVi / dT) / Vi = -α (5)
Is the temperature compensation condition.

Next, a voltage source that is stable against process variations in the monolithic IC process will be considered.
Although details will be described in a specific example described later, the temperature dependent voltage source is widely known as a VT voltage source, and the generated voltage Vthermal is as follows.
Vthermal = (lnN) · (kB · T / q) = (lnN) · VT (6)

Here, ln is a logarithmic function, N is an emitter area ratio, kB is a Boltzmann constant, q is an elementary charge, and VT = kB · T / q. Therefore, Vthermal is a voltage proportional to the temperature T, and its coefficients are all constants and are completely independent of process variations. On the other hand, a voltage source such as a band gap reference voltage circuit is well known as a voltage source that is stable with respect to process variations and independent of temperature, and this voltage is VBG.

  Based on the above Vthermal and VBG, the object can be achieved if the applied voltage Vi is generated by means possible in the monolithic IC process and the equation (5) is satisfied. In the monolithic IC process, there are constant multiplication, addition (or subtraction), and multiplication / division circuits as stable and simple arithmetic circuits against process variations, and the following voltages can be generated using these circuits. The block is shown in FIG.

In FIG. 1, 10 is a VT voltage generating circuit for generating a voltage having a temperature dependency, 20 is a VBG voltage generating circuit for generating a voltage having no temperature dependency, and 30 is a component corresponding to aT ² in Y = aT ² + b. , 40 is a constant multiplier for obtaining a component corresponding to b in Y = aT ² + b, and 50 is an adder (or a subtractor may be used) for calculating aT ² + b. The voltage Vi generated by the circuit of FIG. 1 is expressed as follows: Vi = a1 · (Vthermal) ² / VBG + b1 · VBG (7)
It can be expressed as Here, a1 and b1 are constants. When equation (7) is transformed using equation (6),
Vi = {a1 · (lnN) ² / VBG) · VT ² + b1 · VBG (8)
It becomes. This equation is further obtained from VT = kB · T / q.
Vi = {a1 · (lnN) ² · kB ² / q ² · VBG)} T ² + b1 · VBG (9)
And transformed. Here, {a1 · (lnN) ² · kB ² / q ² · VBG)} is a constant, so it is set as “a”, and when b1 · VBG is set as “b”, a and b do not depend on the process. It can be regarded as an independent constant.

When the above formula (8) or (9) is differentiated by the temperature T, the following formula is obtained.
(dVi / dT) / Vi = (2 · T) / {T 2 + (b / a)} ...... (10)
When the formula (5) is satisfied at the reference temperature T0, from the formulas (5) and (10),
(b / a) = − (2 / α) · T0−T0 ² (11)
Under this condition, substituting equation (11) into equation (10),
(dVi / dT) / Vi = −α [1 + {(T−T0) / T0}] / [1−αTo {(T−T0) / To}
+ (ΑT0 / 2) {(T-T0) / T0} ² ] (12)
Is obtained. From equation (12), (dVi / dT) / Vi = −α is established approximately in the vicinity of T = T0.

Here, assuming a use temperature range from −25 ° C. to 100 ° C., the reference temperature is T 0 = 310 K (about 37 ° C.), and the temperature coefficient α of the hole mobility μH 0 is −0.0053 / ° C., ie −5500 ppm. / B, (b / a) = 1.66 × 10 ⁴ , and when the magnetic-electric conversion rate represented by the equation (2) at this time is actually calculated, it is as shown in FIG. It can be seen that the temperature is compensated.

FIG. 3 shows a specific example of a circuit that generates a voltage having a temperature dependency represented by Vi = a1 · (Vthermal) ² / VBG + b1 · VBG, that is, Y = aT ² + b. In FIG. 3, the numbers “1”, “2”, “4”, and “9” added in the vicinity of the symbol indicating the bipolar transistor represent the size of the transistor, particularly the emitter, as a ratio.

  In FIG. 3, a circuit composed of transistors Q6, Q8, and Q9 and resistors R3, R4, and R5 is a bandgap reference voltage circuit that generates a voltage having no temperature dependency. The collectors of the transistors Q8 and Q9 A potential corresponding to the bandgap voltage VBG (approximately 1.26 V) is generated at the node A coupled through the via. The transistor Q5 is connected in series to the node A via the resistor R8, so that a potential VB that is twice the band gap voltage VBG is generated at the node B to which the emitter of Q5 is connected. Yes. A circuit 60 including transistors Q1 to Q4 and resistors R1 and R2 is a bias circuit that applies a bias to the band gap reference voltage circuit.

In the bandgap reference voltage circuit of this embodiment, when the emitter area ratio of the transistors Q8 and Q9 is N (N = 9 in this embodiment), the voltage VR3 generated in the resistor R3 is VR3 = VT (lnN). . This corresponds to the voltage generation circuit 10 depending on the temperature T in FIG. Therefore, the collector current IcQ8 of the transistor Q8 is
IcQ8 = VT (lnN) / R3 (18)
The temperature-dependent current represented by In the circuit of FIG. 3, R4 = R5 is set, so that IcQ8 = IcQ9. Furthermore, transistors Q5 and Q7 have an emitter area ratio of 2: 1.
IcQ8 = IcQ9 = IcQ5 / 2 = IcQ7 = IcQlO = IcQ12 = VT (lnN) / R3 (19)
And IcQ7 is a temperature-dependent current. R3≈R4 / 10.

In the circuit of FIG. 3, the transistors Q10 and Q12 in series form a square circuit, and the collector current of the transistor Q7 is passed through this, so that the current IVT ² squared by the temperature-dependent voltage VT. Is generated and transferred to the transistor Q11 by the current mirror circuit.

Transistors Q20 to Q23 and resistors R9 and R10 connected between a node F to which a voltage VB having no temperature dependency is drawn from the node B and applied and a ground point are circuits for generating the voltage VBG in FIG. A circuit corresponding to 20 is configured. The resistors R9 and R10 in this circuit have a resistance ratio of 2: 1, that is, R9 = 2 · R10, and the base-emitter voltages VBE of Q20, Q21, and Q22 are almost equal, that is, VBEQ20 = VBEQ22. . Therefore, the current IcQ23 flowing through the transistor Q23 is expressed by the following equation: IcQ23 = IcQ21 + IcQ22 = IcQ20 + IcQ22
= (2.VBG-VBEQ20-VBEQ22) / R9 + VBEQ20 / R10
= 2 ・ VBG / R9−2 ・ VBEQ20 / R9 + 2 ・ VBEQ20 / R9
= 2 VBG / R9 (20)
It is represented by

The current IcQ23 (hereinafter referred to as IVBG) generated by this circuit is transferred to the transistor Q24 that forms a current mirror with the transistor Q23, and the collector current of Q24 is drawn from the transistor Q11, so that the transistor Q15 The current IVT ² / IVBG corresponding to the value obtained by dividing the square current IVT ² by the current IVBG flows. That is, Q10, Q11, Q12, and Q15 constitute a multiplier / divider, and since IcQ23 = IcQ24 = IcQ11, IcQ15 = IcQ10 · IcQ12 / IcQ11 = {VT ² · (lnN) ² · R9} (2 · VBG ・ R3 ² ) (21)
It becomes. This current is transferred to Q14 by a current mirror composed of transistors Q13 and Q14.

Transistors Q18, Q19 and resistors R11, R12 constitute a circuit corresponding to the constant multiplier circuit 40 in FIG. 1, and the collector current IcQ17 of Q17 is a constant multiplier according to the resistance ratio of the resistors R11, R12 by the constant multiplier circuit. And output as IcQ19. This current IcQ19 is expressed by the following equation: IcQ19 = R11 / R12 · IcQ17 = R11 / R12 · IcQ23
= 2 ・ (R11 / R12) (VBG / R9) (22)
It is represented by

Since the transistors Q14 and Q19 through which the currents IcQ14 and IcQ19 flow are coupled to each other to form a current adding circuit, the currents IcQ14 and IcQ19 are added together by the common collector, and further, the resistance R7 generates a voltage from the current. Therefore, the potential VD of the node D is expressed by the following equation: VD = R7 · (IcQ14 + IcQ19)
＝ R7 ・ [{VT ²・ (lnN) ²・ R9} / (2 ・ VBG ・ R3 ² )
+2 ・ (R11 / R12) (VBG / R9)}]
= {(R7 / R3) (R9 / R3) (lnN) ² / (2 · VBG)} · VT ²
+2 ・ (R11 / R12) (R7 / R9) ・ VBG
= (R7 / R3) (R9 / R3) (lnN) ² / (2 · VBG) · (kB / q) ² · T ²
＋2 ・ (R11 / R12) (R7 / R9) ・ VBG ...... (23)

Factor of the first term of T ² of the term of the equation (23) is only constant and the resistance ratio that is independent of the process, the same applies to the second term. For this reason, if the resistors R2 to R10 are formed as the same type of resistor in the monolithic IC, the potential VD of the node D becomes a voltage that is extremely stable against process variations and has a desired temperature dependency. The circuit 70 comprising the transistors Q29 to Q34 and the resistors R13 and R14 receiving the potential VD of the node D has a voltage obtained by dividing the output voltage by the resistors R13 and R14 fed back to the inverting input terminal (the input voltage ( This is an impedance conversion amplifier that outputs a voltage proportional to VD).

  In this embodiment, the power source terminal of the Hall element is connected between the node E on the emitter side of the transistor 25 and the ground so that sufficient power can be supplied to the Hall element. Also in this case, if the resistors R13 and R14 are of the same type, the voltage between the node E and the ground has exactly the same temperature dependency as the potential of the node D. FIG. 4 shows the potential of the node E with respect to temperature, that is, the applied voltage of the Hall element, and FIG. 5 shows the magneto-electric conversion characteristics of the Hall element when the driving circuit of this embodiment is used. It can be seen from FIG. 5 that a sufficient temperature compensation effect is obtained.

The case where the Hall element drive voltage is Y = aT ² + b has been described above. However, the Hall element drive voltage may be Y = aT ^2, that is, b = 0, or b may be negative. When Y = aT ² or when b is negative, a higher temperature coefficient can be obtained than when Y = aT ² + b and b is positive. Therefore, not only can the temperature dependence of the Hall element itself be large (in the case of low concentration), but also the temperature dependence of the magnetic field generated by the magnet used in the application is usually negative in many cases. Considering this, such a method is also effective because Y = aT ² or b may be negative because the temperature dependence of the system may be stabilized.

  In addition, since the present embodiment has been made in consideration of making the circuit configuration simple and easy to understand, the circuit is as shown in FIG. 3, but in the circuit of FIG. 3, the base current of each transistor may cause an error. is there. Therefore, if a multiplier / divider using an operational amplifier circuit, an adder (subtractor), or the like is used as a multiplier / divider / adder (subtractor), a circuit with higher accuracy can be realized. Furthermore, in this embodiment, an analog multiplier / divider is used, but an analog multiplier may be used, or a digital multiplier / divider circuit, a digital multiplier circuit, a DSP (digital signal processor), or the like may be used. .

Next, a second embodiment of the present invention will be described. In the second embodiment, a Hall element is driven with a voltage, and a circuit for generating a voltage having a temperature dependency represented by Y = aT ² + bT (a and b are constants, T is an absolute temperature) is provided. The voltage generated in the circuit is applied as a drive voltage to the Hall element to compensate for the temperature dependence of the magneto-electric conversion characteristics of the Hall element.

Specifically, by using a temperature-dependent VT voltage source, the following expression Vi = a1 · (Vthermal) ² / VBG + b1 · Vthermal (13)
Is generated and applied to the Hall element as a drive voltage.

Here, a1 and b1 are constants. Equation (13) is modified and Vi = {a1 · (lnN) ² / VBG} · VT ² + b1 · (lnN) VT (14)
further,
Vi = {a1 · (lnN) ² · kB ² / (q ² · VBG)} · T ² + b1 (kB / q) T (15)
It becomes. Here, {a1 · (lnN) ² · kB ² / q ² · VBG)} is a constant, so it is set to a. Similarly, if b1 (kB / q) is set to b, a and b depend on the process. Can be regarded as independent constants.

Here, when the equation (14) or (15) is differentiated by the temperature T, the following equation is obtained.
(DVi / dT) / Vi = {2 · T + (b / a)} / {T 2 + (b / a) T} ...... (16)

When the equation (5) is satisfied at the reference temperature T0, from the equations (5) and (16),
(B / a) =-(2T0 + αT0 ² ) / (1 + αT0) (17)
Is obtained. Although the calculation of the differential equation based on the temperature at this time is omitted, assuming the operating temperature range from -25 ° C to 100 ° C, the reference temperature is T0 = 310K (about 37 ° C), and the temperature coefficient of the hole mobility μH0 When α is −0.0053 / ° C., that is, −5500 ppm / ° C., (b / a) = 130. At this time, when the magnetic-electric conversion rate represented by the equation (2) is obtained by calculation, it is as shown in FIG. 6 and it can be seen that sufficient temperature compensation is performed. In the case of the second embodiment, (b / a) is considerably smaller than the calculated value of the expression (11) in the first embodiment. This means that the range of selection of the Hall element material and circuit system is expanded.

The circuit for generating a voltage having a temperature dependency represented by Y = aT ² + bT according to the second embodiment is an adder (subtracter) 50 from the VT generation circuit 10 as indicated by a broken line A in the block diagram of FIG. This is possible by supplying a current represented by a linear function of temperature T to the circuit, and a specific circuit thereof is not shown, but can be realized by slightly modifying the circuit of FIG.

  The method for controlling the applied voltage of the Hall element has been described above. However, the gain of an amplifier that drives the Hall element with a constant voltage that does not depend on temperature and amplifies the output voltage of the Hall element is the same as the voltage at the node D. You may have sex. In this case, the output voltage of the Hall element remains temperature dependent (= α), but temperature compensation can be performed at the output of the amplifier. As a specific example of the method for controlling the gain in this way, there is a method using an amplifier that has two controllable current sources and the gain is determined by the current ratio.

FIG. 7 shows a specific example of such a gain-adjustable amplifier.
In the variable gain amplifier of FIG. 7, the input voltage Vin is expressed by the following equation: Vout = Vc + Vo = Vc + A. (I2 / I1) .Ro.Vin (24)
Is converted into a voltage represented by Here, Vc is the voltage from the constant voltage source applied to the non-inverting input terminal of the voltage follower VF, A is the gain of the amplifier, I2 / I1 is the current ratio of the constant current sources I1 and I2, and Ro is the voltage follower VF. This is the resistance value of the resistor connected between the output terminal and the output node of the amplifier. From equation (24), it can be seen that the gain of the amplifier can be changed by changing the current value I2 of the constant current source I2 while keeping the current value I1 of the constant current source I1 constant.

Therefore, as the currents of the constant current sources I1 and I2, the voltage V-current converted current VB at the node B of the circuit of the embodiment of FIG. 3 (in other words, the current similar to IcQ17) and the voltage VD at the node D are set as voltage. -By using a current converted current (in other words, a current similar to IcQ14 + IcQ19), even if the input of the amplifier of FIG. 7 does not have temperature dependence, the output of the amplifier is similar to that of the first embodiment. It is possible to give a temperature dependence of ² + b.

  Furthermore, in the case of a magnetic sensor using a binarized output with respect to a magnetic input, the temperature dependency of the magnetic threshold value may be compensated. FIG. 8 shows a schematic configuration of a magnetic sensor using such a binarized output.

  In FIG. 8, 100 is a semiconductor chip such as single crystal silicon, 110 is a Hall element formed as an n-type epitaxial layer on the semiconductor chip, and 120 generates a driving voltage to be applied to one terminal of the Hall element 110. The constant voltage power supply circuit 130 is an amplifier that amplifies the output of the Hall element by connecting a pair of output terminals of the Hall element 2 to the differential input terminal, and 140 is an output voltage of the amplifier 130 and a predetermined threshold value VTH. The comparator 150 compares the threshold values VTH, and the threshold value VTH supplied to the comparator 140 is generated.

The voltage input to the comparator 140 is compared with the threshold value VTH, and the output is used to drive the open-collector output bipolar transistor Q0 on and off, and output from the output terminal OUT in the form of an output current. An external resistor and capacitor connected to the output terminal OUT are elements for reducing noise. In this embodiment, the threshold value VTH supplied to the comparator 140 is such as 1 / Y based on the voltage Y as shown by Y = aT ² + b generated by the circuit as shown in FIG. It is controlled to have temperature dependence. According to such a system, as in the above-described embodiment, an accurate detection output that is not affected by temperature can be obtained even if the magnetic-electric conversion characteristics of the Hall element change depending on the temperature.

  The invention made by the present inventor has been specifically described based on the embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Nor. For example, in the above embodiment, the case where the Hall element is applied to a monolithic IC magnetic sensor formed on one semiconductor chip together with the elements constituting the peripheral circuit has been described. However, the present invention is not limited thereto, It can be applied to a hybrid IC magnetic sensor composed of an IC and an electronic component.

  The present invention is most effective when applied to a magnetic sensor used in an environment with a large temperature change, such as a vehicle speed sensor, a wheel speed sensor, a crank angle sensor, etc., but for applications other than automobiles such as washing machines and air conditioners. It can also be used for magnetic sensors in household electrical products such as detecting the position of the rotor of a brushless motor, as well as position sensors represented by non-contact micro switches, flow meters, vehicle height adjustments, shift levers, and the like.

1 is a block diagram illustrating a configuration example of a first embodiment of a constant voltage generation circuit that generates a temperature-compensated constant voltage (Hall element drive voltage). FIG. It is a characteristic view which shows the magnetic-electrical conversion characteristic of the Hall element to which the voltage produced | generated by the constant voltage generation circuit of FIG. 1 was applied. FIG. 2 is a circuit diagram illustrating a specific circuit example of the constant voltage generation circuit of FIG. 1. It is a graph which shows the relationship with respect to the temperature of the voltage applied to a Hall element by the constant voltage generation circuit of FIG. FIG. 4 is a characteristic diagram showing magnetic-electric conversion characteristics of a Hall element to which a voltage generated by the constant voltage generation circuit of FIG. 3 is applied. It is a characteristic view which shows the magnetic-electrical conversion characteristic of the Hall element to which the voltage produced | generated by the constant voltage generation circuit of 2nd Embodiment was applied. It is a circuit diagram which shows the circuit example of the variable gain amplifier which amplifies the output of the Hall element used for the magnetic sensor of 3rd Embodiment. It is a block diagram which shows the structural example of the magnetic sensor of 4th Embodiment.

Explanation of symbols

10 VT voltage generation circuit 20 VBG voltage generation circuit 30 multiplier / divider 40 constant multiplication circuit 50 adder (subtractor)
DESCRIPTION OF SYMBOLS 100 Semiconductor chip 110 Hall element 120 Constant voltage power supply circuit 130 Constant current source 140 Comparator

Claims (5)

A magnetic detection circuit comprising a Hall element and a constant voltage driving circuit for generating a driving voltage applied to the Hall element, formed on one semiconductor chip, wherein the constant voltage circuit is Y = aT ² + b Alternatively, a drive voltage having a temperature dependency represented by Y = aT ² + bT (a and b are constants and T is an absolute temperature) is generated, and the magneto-electric conversion characteristics of the Hall element are determined by the temperature dependency of the drive voltage. A magnetic detection circuit characterized by compensation. A magnetic detection circuit formed on a single semiconductor chip, comprising: a Hall element; a constant voltage drive circuit that generates a drive voltage applied to the Hall element; and a variable gain amplifier circuit that amplifies the output of the Hall element. The constant voltage driving circuit is configured to generate a voltage having no temperature dependence, and the gain of the amplifier circuit is Y = aT ² + b or Y = aT ² + bT (a and b are constants, T is A magnetic detection circuit controlled to have a temperature dependency represented by (absolute temperature). A Hall element, a constant voltage driving circuit that generates a driving voltage applied to the Hall element, a comparator that discriminates an output of the Hall element, and a constant voltage circuit that generates a threshold value supplied to the comparator. The constant voltage power supply circuit is configured to generate a voltage having no temperature dependence, and the constant voltage circuit is configured such that Y = aT ² + b or Y = The threshold value is controlled to be 1 / Y based on the temperature dependence represented by aT ² + bT (a and b are constants and T is an absolute temperature). Magnetic detection circuit.   The constant voltage driving circuit includes a first current generation circuit that generates a current having temperature dependency, a second current generation circuit that generates a current having no temperature dependency, the first current generation circuit, and a second current generation Output from the multiplier / divider circuit that receives the current generated by the circuit, the constant multiplier circuit that outputs a current proportional to the current generated by the second current generator circuit, and the multiplier / divider circuit and the constant multiplier circuit. The magnetic detection circuit according to claim 1, comprising: a current synthesis circuit for adding or subtracting a current to be generated; and a current-voltage conversion means for converting the synthesized current into a voltage.   The magnetic detection circuit according to claim 1, wherein the Hall element is formed of an epitaxial layer or an n-type semiconductor layer formed on the semiconductor chip.

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