JP4244895B2 - Physical quantity sensor and manufacturing method thereof - Google Patents

Description

  The present invention relates to a physical quantity sensor that corrects a temperature-dependent component of a sensor output in a physical quantity sensor, and a manufacturing method thereof.

  Conventionally, a physical quantity sensor such as a pressure sensor that detects a physical quantity, for example, a pressure of a pressure medium, is known. In such a physical quantity sensor, a sensing unit is formed on a semiconductor substrate, and a desired physical quantity is detected by the sensing unit.

  However, depending on the temperature to which the physical quantity sensor is exposed, an offset component depending on the temperature is included in the sensor output of the physical quantity sensor. This is based on the fact that the physical quantity sensor is made of a semiconductor. Such an offset component of the sensor output depending on the temperature includes a primary component and a secondary component that change with respect to the temperature. The primary component is a component in which the sensor output changes linearly depending on the temperature, and the secondary component is a component in which the sensor output changes depending on the square of the temperature. Therefore, it is considered that a physical quantity sensor capable of obtaining a highly accurate sensor output can be realized by correcting the temperature characteristics of each component.

  By the way, some physical quantity sensors have large secondary component characteristics in the temperature characteristics of sensor output, and such physical quantity sensors cannot obtain accurate sensor outputs. Therefore, a method of correcting the secondary component in the temperature characteristic of the sensor output of the physical quantity sensor, particularly the pressure sensor has been proposed (see, for example, Patent Document 1). Hereinafter, a method for correcting the secondary component of the temperature characteristic of the sensor output will be described with reference to FIGS.

  FIG. 7 is a diagram illustrating a correction process for correcting the secondary component of the temperature characteristic of the conventional sensor output. FIG. 8 is a diagram showing how the offset temperature characteristic of the pressure sensor is adjusted. FIG. 8A is a diagram showing the state of sensitivity adjustment (room temperature) in FIG. FIG. 8B is a diagram showing the state of the offset temperature characteristic adjustment (room temperature-high temperature) and the offset characteristic adjustment (room temperature) of FIGS. 7B and 7C.

  First, a semiconductor substrate in which a pressure sensor is formed is prepared, and sensor output sensitivity adjustment is performed at room temperature (FIG. 7A). By this sensitivity adjustment, as shown in FIG. 8A, the sensor output is adjusted to an optimum value. Thereafter, the temperature characteristic of the sensor output of this pressure sensor is examined.

  Subsequently, offset temperature characteristic adjustment (room temperature-high temperature) is performed (FIG. 7B). That is, in the state where the pressure shown in FIG. 8A is zero (P = 0), the sensor output is corrected in the room temperature-high temperature range.

  As shown in FIG. 8B, the inclination of the sensor output with respect to the room temperature-high temperature region is adjusted to be flat. Specifically, a reverse inversion characteristic shown in FIG. 8A is created, and this inversion characteristic is added to the sensor output. Thereby, the secondary component of the sensor output which changes depending on the temperature is canceled out.

Thereafter, offset characteristic adjustment (room temperature) is performed (FIG. 7C). That is, the sensor output is offset-corrected so that the sensor output becomes a target value at room temperature. In this way, the secondary component of the temperature characteristic of the sensor output is corrected.
JP 2002-286573 A

  However, in the above conventional technique, many circuits are required to correct the secondary component of the temperature characteristics of the sensor output, and many circuit components (such as an operational amplifier and a resistor) are prepared to form the circuit. There must be. In addition, since many circuit components and a circuit composed of circuit components are required, the circuit configuration of the entire physical quantity sensor becomes complicated as well as a circuit that corrects the secondary component.

  Further, since the circuit configuration becomes complicated, the correction process becomes complicated in the sensor output correction method. That is, as shown in FIG. 8B, in the secondary component of the sensor output, the temperature dependence of the sensor output near room temperature is eliminated, but in the low temperature and high temperature regions, the temperature dependent component of the sensor output. Remains.

  In view of the above points, an object of the present invention is to provide a physical quantity sensor capable of correcting a secondary component of temperature characteristics with high accuracy and a method for manufacturing the same.

  In order to achieve the above object, according to the first aspect of the present invention, there is provided a physical quantity sensor having a secondary component correction circuit (40) for correcting a secondary component of the temperature characteristic of the sensor output, wherein the secondary component correction circuit is A resistor (R11, R13) having a temperature characteristic and a secondary component that changes secondarily with respect to the temperature, and a resistor that is connected in series to the resistor having the temperature characteristic and does not have a temperature characteristic ( R12, R14), a plurality of diodes (DI1 to DI4), and an operational amplifier (41), which are configured as a half-wave rectifier circuit that is an inverting amplifier circuit, and input to the operational amplifier by the rectification characteristics of the diode. A temperature characteristic adjusting circuit (CI) that outputs the output voltage Vo as a constant value when the value of the input voltage Vi exceeds a predetermined voltage value, and has a temperature characteristic resistor and temperature The potential between the resistor and the non-resistive resistor is VR, and this potential VR is connected to the input terminal of the operational amplifier of the temperature characteristic adjusting circuit, and has a temperature characteristic by increasing the temperature received by the resistor having the temperature characteristic. When the resistance value of the resistor changes and the potential VR becomes larger than the output voltage Vo, the temperature characteristic adjusting circuit outputs a constant voltage corresponding to the rectifying characteristic of the diode as the output voltage Vo, and the resistor having the temperature characteristic When the resistance value of the resistor having the temperature characteristic changes due to the lowering of the received temperature and the potential VR becomes smaller than the output voltage Vo, the temperature characteristic adjusting circuit generates a voltage corresponding to the temperature characteristic of the resistor having the temperature characteristic. The output voltage Vo is output, and at the output voltage Vo, the connection point between the linear waveform that shows a constant value with respect to temperature and the linear waveform that changes with temperature is broken. Assuming that the point is a point, the temperature characteristic adjusting circuit moves the bending point to a lower temperature side with respect to the temperature by changing and inputting the value of the input voltage Vi when the potential VR is smaller than the output voltage Vo. The second component of the temperature characteristic of the sensor output is corrected by making the output voltage Vo constant with respect to the temperature.

  As described above, the potential VR that changes depending on the temperature characteristics can be output as a constant value by the temperature characteristics adjustment circuit that is a semi-rectifier circuit using a diode. Thereby, it is not necessary to use a complicated circuit, and the secondary component of the temperature characteristic can be easily corrected at a low cost. Therefore, the secondary component of the temperature characteristic can be reliably corrected by adjusting the rectification characteristic of the diode on the high temperature side of the temperature characteristic and adjusting the input voltage Vi on the low temperature side.

  According to a second aspect of the present invention, the temperature characteristic adjusting circuit includes a polarity switch (SW1, SW2) that is switched according to the polarity of the temperature coefficient of the resistor having the temperature characteristic.

  Thus, the polarity switch is switched according to the polarity (positive or negative) of the temperature coefficient of the resistor. Thereby, the secondary component of the temperature characteristic can be corrected by the temperature characteristic adjusting circuit regardless of which polarity the resistor has.

  The invention according to claim 3 is characterized in that the output voltage Vo is added to the sensor output of the physical quantity sensor.

  In this manner, the corrected output voltage Vo is added to the sensor output of the physical quantity sensor. Thereby, the secondary component of the temperature characteristic which a physical quantity sensor has can be canceled.

  In the invention described in claim 4, the resistor (R11, R13) having a temperature characteristic and having a secondary component that changes secondarily with respect to the temperature and the resistor having the temperature characteristic are connected in series. And a resistor (R12, R14) having no temperature characteristics, a plurality of diodes (DI1 to DI4), and an operational amplifier (41), which are configured as a half-wave rectifier circuit that is an inverting amplifier circuit, A temperature characteristic adjusting circuit (CI) that outputs the output voltage Vo as a constant value when the value of the input voltage Vi input to the operational amplifier exceeds a predetermined voltage value due to the rectifying characteristics of the diode, and has temperature characteristics There is provided a secondary component correction circuit (40) in which the potential between the resistor and the resistor having no temperature coefficient is VR, and this potential VR is connected to the input terminal of the operational amplifier of the temperature characteristic adjusting circuit. A method of manufacturing a physical quantity sensor, in which when a temperature received by a resistor having a temperature characteristic increases and the potential VR becomes larger than the output voltage Vo, a constant voltage corresponding to the rectification characteristic of the diode is output in the temperature characteristic adjustment circuit. When the potential VR is lower than the output voltage Vo due to the temperature received by the resistor having temperature characteristics, the voltage corresponding to the temperature characteristics of the resistor having temperature characteristics is output as the output voltage Vo in the temperature characteristic adjusting circuit. The connection point between the correction process to be performed and the linear waveform that shows a constant value with respect to the temperature at the output voltage Vo and the linear waveform that changes with respect to the temperature is used as a bending point, and the value of the input voltage Vi is changed in the temperature characteristic adjustment circuit. And a correction step of outputting an output voltage Vo independent of temperature by moving the bending point to a low temperature side with respect to the temperature. It is characterized.

  In this way, the temperature characteristic is corrected using a circuit formed of a diode. As a result, the secondary component correction circuit can be made inexpensive and simple, and the number of correction steps can be reduced. Further, since the rectification characteristic of the diode is used, the output voltage Vo can be set to a constant value. This can be easily realized by changing the value of the input voltage Vi of the temperature characteristic adjusting circuit on the high temperature side and the temperature characteristic adjusting circuit on the low temperature side. In this way, the secondary component of the temperature characteristic can be corrected.

  The invention according to claim 5 is characterized in that the correction step of outputting the output voltage Vo independent of temperature includes a correction step of adding the output voltage Vo to the sensor output of the physical quantity sensor.

  In this way, the output voltage Vo is added to the sensor output of the physical quantity sensor. Thereby, the secondary component of the temperature characteristic which the sensor output of a physical quantity sensor has can be canceled.

In the invention described in claim 6, the signal the signal is included in accordance with the polarity of the resistor having a temperature characteristic in the input voltage Vi is characterized in that it is input to the operational amplifier.

  In this way, the input voltage Vi includes a signal corresponding to the polarity (positive or negative) of the temperature coefficient of the resistor having temperature characteristics. Thus, regardless of which polarity the resistor having the temperature characteristic has, the temperature characteristic adjustment circuit can correct the secondary component of the temperature characteristic.

  In addition, the code | symbol in the bracket | parenthesis of each said means shows the correspondence with the specific means as described in embodiment mentioned later.

(First embodiment)
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the present embodiment, a pressure sensor will be described as a physical quantity sensor. FIG. 1 is an overall circuit diagram of a pressure sensor according to an embodiment of the present invention. As illustrated in FIG. 1, the pressure sensor includes a memory circuit 10, a pressure detection unit 20, a primary component correction circuit 30, a secondary component correction circuit 40, an adder 50, and an amplifier 60. Composed.

The memory circuit 10 outputs a desired control signal based on a signal input from the TRIM terminal. Specifically, the memory circuit 10 includes a command signal for detecting pressure in the pressure detector 20, an input voltage V _{T in} the primary component correction circuit 30, an input voltage Vi and polarity signal in the secondary component correction circuit 40, and an adder 50. The signal for correcting the offset component (offset correction voltage) is D / A converted and output.

  The pressure detection unit 20 detects pressure and generates an electric signal having a level corresponding to the detected value. The pressure detection unit 20 has a known configuration using, for example, a piezoresistance effect, and includes a bridge circuit 21 formed on its upper surface by a diaphragm distorted by pressure and a diffusion resistor. In addition, a sensor drive current circuit 22 that outputs a drive current to the bridge circuit 21 and an amplifier 23 that amplifies the output signal of the bridge circuit 21 are provided.

The primary component correction circuit 30 corrects the primary component of the sensor output signal output from the pressure detector 20 described above. FIG. 2 is a circuit diagram of the primary component correction circuit 30. As shown in FIG. 2, the primary component correction circuit 30 includes two resistors R1 and R2 having different temperature characteristics and an operational amplifier 31, and is configured as an inverting amplifier circuit. Therefore, in the primary component correction circuit 30, when the input voltage V _T is input from the memory circuit 10, the output voltage V _T0 = (− R2 / R1) V _T is output. Then, a value V _T + V _T0 = (1− (R2 / R1)) V _{T obtained} by adding the input voltage V _T to the output voltage V _T0 is calculated, and the calculated value is added to the sensor output. Thus, the primary component of the temperature characteristic of the sensor output is canceled.

  The secondary component correction circuit 40 corrects the secondary component of the sensor output signal output from the pressure detector 20 described above. FIG. 3 is a circuit diagram of the secondary component correction circuit 40 of the pressure sensor shown in FIG. As shown in FIG. 3, the secondary component correction circuit 40 includes first to fourth resistors R11 to R14, first and second adjustment resistors R21 and R22, a temperature characteristic adjustment circuit CI, and an output resistor. R40.

  The first and second resistors R11 and R12 create a potential V1 that changes according to temperature. Of these first and second resistors R11 and R12, the first resistor R11 has temperature dependency, and the second resistor R12 has no temperature dependency. Further, one end of the first resistor R11 is grounded, and the other end is connected to one end of the second resistor R12. A potential V1 is set between the other end side of the first resistor R11 and one end side of the second resistor R12. Note that the potential V1 corresponds to the potential VR of the present invention together with the potential V2 described later.

  With such a connection configuration, when the temperature received by the first and second resistors R11 and R12 changes, the resistance value of the first resistor R11 changes according to the temperature. Along with this, the value of the potential V1 also changes. For example, if the first resistor R11 has a positive temperature coefficient, the resistance value of the first resistor R11 increases and the value of the potential V1 also increases as the temperature received by the first and second resistors R11, R12 increases. To do. In the present embodiment, when the temperature coefficient of the first resistor R11 (and a third resistor R13 described later) is positive, the polarity is positive.

  The first adjustment resistor R21 plays a role of connecting the potential V1 and the temperature characteristic adjustment circuit CI.

  The temperature characteristic adjustment circuit CI has a function of eliminating the temperature characteristic of the first resistor R11, that is, correcting a secondary component of the temperature characteristic, and includes a first polarity switch SW1, an operational amplifier 41, resistors R31 to R33, and , First and second diodes DI1 and DI2.

  The first polarity switch SW1 connects (conducts) or opens (disconnects) one end side and the other end side of the first polarity switch SW1 according to an input signal. The first polarity switch SW1 is formed as a MOS transistor on a semiconductor substrate, for example. The operational amplifier 41 amplifies an input voltage with a predetermined amplification factor and outputs the amplified voltage. The first polarity switch SW1 employs two switches, one that is arranged on the output side of the operational amplifier 41, which will be described later, and one that connects the potential V1 and the temperature characteristic adjustment circuit CI.

  The resistors R31 and R33 control the amplification factor (= R33 / R31) when the operational amplifier 41 functions as an inverting amplifier circuit. The resistor R32 protects the first diode DI1. These resistors R31 to R33 do not have temperature characteristics.

  When a voltage is applied in the forward direction, the first and second diodes DI1 and DI2 output a constant voltage value when the current flowing through the diodes DI1 and DI2 exceeds a predetermined value. Conversely, when a voltage is applied in the reverse direction, no current flows through these diodes DI1 and DI2.

  In the temperature characteristic adjusting circuit CI, an operational amplifier 41, resistors R31 to R33, and first and second diodes DI1 and DI2 constitute an inverting amplifier circuit. That is, the output voltage Vc of the temperature characteristic adjustment circuit CI is output as a value obtained by amplifying the input voltage Vi input to the temperature characteristic adjustment circuit CI by the values of the resistors R31 and R33 (specifically, R33 / R31).

  Furthermore, the temperature characteristic adjusting circuit CI also has a function as a rectifier circuit due to the presence of the first and second diodes DI1 and DI2. Specifically, when the temperature received by the first resistor R11 increases, the resistance value increases and the value of the potential V1 also increases. Accordingly, V1> Vo and the first and second diodes DI1 and DI2 are turned on, so that the potential Vc shown in FIG. 3 becomes a constant value. That is, when the temperature received by the first resistor R11 is in the room temperature-high temperature region, the potential Vc is a constant value in the temperature characteristic adjustment circuit CI.

  Conversely, when the temperature received by the first resistor R11 decreases, the resistance value decreases and the value of the potential V1 also decreases. Accordingly, V1 <Vo, the first and second diodes DI1 and DI2 are turned off, and the output obtained by inverting the temperature characteristics of the first and second resistors R11 and R12 becomes the potential Vc. That is, the potential Vc has a voltage value depending on the temperature in the room temperature-low temperature region.

  FIG. 4 is a diagram showing the relationship between the temperature received by the first resistor R11 and the potential Vc in the temperature characteristic adjustment circuit CI. FIG. 4A is a diagram illustrating the potential Vc with respect to the temperature change of the first resistor R11 when the first polarity switch SW1 is turned on. As shown in FIG. 4A, when the temperature of the first resistor R11 is in the room temperature-high temperature region, the value of the potential Vc does not depend on the temperature and is a constant value due to the rectification characteristics of the first and second diodes DI1 and DI2. It has become. On the other hand, when the temperature of the first resistor R11 is in a low temperature-room temperature region, the value of the potential Vc changes depending on the temperature according to the temperature characteristics of the first resistor R11.

  In FIG. 4A, the value of the input voltage Vi of the temperature characteristic adjusting circuit CI changes at a connection point between a line having a constant potential Vc value and a line depending on temperature (hereinafter referred to as a bending point). And move. For example, when the input voltage Vi increases, the potential difference between the input voltage Vi and the potential V1 decreases, and the current flowing through the first and second diodes DI1 and DI2 also decreases. Thereby, the rectification characteristics of the diodes DI1 and DI2 cannot be obtained, and the potential Vc changes according to the temperature. On the contrary, when the input voltage Vi decreases, the potential difference between the input voltage Vi and the potential V1 increases, and the current flowing through the first and second diodes DI1 and DI2 increases. Thereby, the potential Vc is kept constant by the rectification characteristics of the diodes DI1 and I2.

  From the above, when the value of the input voltage Vi increases, the bending point moves to the high temperature side due to the rectification characteristics of the first and second diodes DI1 and DI2, and when the value of the input voltage Vi decreases, the bending point moves to the low temperature side. Moving. Therefore, by reducing the value of the input voltage Vi, the bending point can be moved to the low temperature side, and the temperature characteristic of the potential Vc can be eliminated. This potential Vc is output to the adder 50 described later via the resistor R40 as the output voltage Vo of the secondary component correction circuit.

  In the present embodiment, the input voltage Vi is input from the memory circuit 10 to the temperature characteristic adjustment circuit CI as a value including a signal for connecting the first polarity switch SW1. That is, the input voltage Vi is a signal obtained by combining a DAC value (for example, 7 bits) for moving the bending point and a polarity signal (for example, 1 bit) for connecting the first polarity switch SW1 (or a second polarity switch SW2 described later). (Total 8 bits) and input to the operational amplifier 41 of the temperature characteristic adjustment circuit CI.

  The resistor R40 serves to output the output voltage Vo of the temperature characteristic adjusting circuit CI to the adder 50.

  The above is the configuration of the secondary component correction circuit 40 when the polarity is positive (the state where the first polarity switch SW1 is connected). In the present embodiment, the temperature coefficient of the first resistor R11 and the third resistor R13 described below may be negative. In order to cope with such a negative polarity, the secondary component correction circuit 40 shown in FIG. 3 is provided with a circuit corresponding to the case where the polarities of the first and third resistors R11 and R13 are reversed. Yes.

  Therefore, when the polarity is negative, the secondary component correction circuit 40 includes the third resistor R13 having the temperature characteristic, the fourth resistor R14 having no temperature characteristic, and the second adjustment resistor R22. . The temperature characteristic adjustment circuit CI of the secondary component correction circuit includes a second polarity switch SW2, and third and fourth diodes DI3 and DI4.

  Similar to the first and second resistors R11 and R12, the third and fourth resistors R13 and R14 create a potential V2 that changes according to the temperature. In the present embodiment, one end side of the fourth resistor R14 is grounded, and the other end side is connected to one end side of the third resistor R13. The potential V2 is set between the other end side of the fourth resistor R14 and one end side of the third resistor R13.

  The second adjustment resistor R22 serves to connect the potential V2 and the second polarity switch SW2 of the temperature characteristic adjustment circuit CI. The third and fourth diodes DI3 and DI4 have the same functions as the first and second diodes DI1 and DI2. Note that the resistors R31 to R33, the operational amplifier 41, and the resistor R40 included in the secondary component correction circuit 40 are common components regardless of polarity.

  In this way, when forming a circuit in which the second polarity switch SW2 is connected, the potential Vc of the temperature characteristic adjustment circuit CI has a waveform shown in FIG. 4B with respect to the temperature. FIG. 4B is a diagram illustrating the potential Vc with respect to the temperature change of the third resistor R13 when the second polarity switch SW2 is turned on. As shown in FIG. 4B, the bending point can be moved to the low temperature side by reducing the value of the input voltage Vi, and the secondary component of the temperature characteristic of the third resistor R13 can be corrected. It is like that.

  Thus, according to the polarities of the first and third resistors R11 and R13, one of the first polarity switch SW1 and the second polarity switch SW2 is connected, and the first and third resistors R11 and R13 are connected. The secondary component of the temperature characteristic is corrected.

  The adder 50 adds and outputs the sensor output signal of the pressure detector 20, the temperature characteristic correction signals of the primary and secondary component correction circuits 30 and 40, and the offset correction voltage. The amplifier 60 amplifies the signal input from the adder 50 with a desired amplification factor and outputs it as a sensor output of the pressure sensor. The above is the configuration of the pressure sensor.

  Next, a method for correcting the temperature characteristics of the pressure sensor in the pressure sensor manufacturing method will be described with reference to FIGS. In the following, correction of temperature characteristics of a pressure sensor that detects relative pressure will be described.

FIG. 5 is a diagram showing a temperature characteristic correction process of the pressure sensor. FIG. 6 is a diagram showing sensor output in each step shown in FIG. FIG. 6A is a diagram showing how sensitivity is adjusted in FIG. FIG. 6B is a diagram showing the offset temperature characteristic adjustment and the offset characteristic adjustment in FIG. FIG. 6C is a diagram showing the state of offset characteristic adjustment (low temperature) in FIG. Further, the sensor output shown in FIG. 6 indicates a signal (voltage value) output from the output terminal _{VOUT of the} pressure sensor shown in FIG.

  First, a pressure sensor shown in FIG. 1 is prepared on a semiconductor substrate. In the step shown in FIG. 5A, sensitivity adjustment of the pressure sensor at room temperature is performed. That is, when the pressure sensor is formed, there is a sensitivity variation in the sensor output of the pressure sensor. That is, in this step, sensitivity adjustment is performed so as to minimize this sensitivity variation. Specifically, a signal is output from the memory circuit 10 to the sensor drive current circuit 22, and the output of the bridge circuit 21 is adjusted to an optimum value. As a result, as shown in FIG. 6A, the initial value (broken line) of the sensor output of the pressure sensor is as adjusted (straight line).

  In the step shown in FIG. 5B, offset temperature characteristic adjustment (room temperature-high temperature) is performed. In this step, first, the temperature characteristic of the sensor output in a state where no pressure is applied to the pressure sensor (P = 0) is examined. The temperature characteristic thus obtained is obtained as an initial value (broken line) shown in FIG. 6B, for example.

Subsequently, the primary component of the temperature characteristic of the sensor output of the pressure sensor is corrected. That is, the signal output from the primary component correction circuit 30 is added to the sensor output of the pressure sensor. Specifically, a desired value of both the input voltage V _T changes the value of the resistance values R1, R2 from the memory circuit 10 primary component correction circuit 30 are determined, the input voltage V _T and the output voltage as described above the primary component of the temperature property of the sensor output by the sensor output of the pressure sensor is added to the sum _(V T ₊ V _T0) with V _T0 is canceled. Here, the value of the resistors R1, R2 and the input voltage _{V T} is fixed. At this time, the sensor output has an adjusted (straight line) waveform in FIG.

  Thereafter, in the step shown in FIG. 5C, offset characteristic adjustment (room temperature) is performed. This is done by adding the offset correction voltage output from the memory circuit 10 at room temperature to the adjusted (straight line) waveform in FIG. That is, when a desired offset correction voltage is added to the sensor output by the adder 50, the waveform after adjustment (straight line) in FIG. 6B is shifted to the target value. Then, the value of the offset correction voltage is fixed.

  Next, in the step shown in FIG. 5D, offset characteristic adjustment (low temperature) is performed. That is, the secondary component of the temperature characteristic of the sensor output of the pressure sensor is corrected. This is done as follows. First, the input voltage Vi (DAC value) is input from the memory circuit 10 to the temperature characteristic adjustment circuit CI of the secondary component correction circuit 40. This input voltage Vi includes a polarity signal for connecting one of the first and second polarity switches SW1 and SW2 of the temperature characteristic adjusting circuit CI. In the present embodiment, the second polarity switch SW2 is connected from the low temperature side slope of the offset correction waveform shown in FIG. Therefore, the input voltage Vi and the polarity signal for connecting the second polarity switch SW2 are input to the secondary component correction circuit 40.

  In the secondary component correction circuit 40, when the input voltage Vi is input to the temperature characteristic adjustment circuit CI, the second polarity switch SW2 is connected. As a result, the room temperature-high temperature side output voltage Vo of the temperature characteristic becomes flat with respect to the temperature due to the rectification characteristics of the third and fourth diodes DI3 and DI4 of the temperature characteristic adjustment circuit CI. On the other hand, on the low temperature side of the temperature characteristic, the value of the input voltage Vi, that is, the DAC value is lowered, and the bending point is shifted to the low temperature side. The output voltage Vo with the bending point shifted to the low temperature side is output from the secondary component correction circuit 40 and added to the sensor output after the process of FIG. Therefore, as shown in FIG. 6C, the waveform before the adjustment of the sensor output becomes flat with respect to the temperature as after the adjustment. Here, the input voltage Vi when the bending point is shifted to the low temperature side is fixed. As described above, the temperature characteristics of the sensor output are corrected.

  As described above, in the present embodiment, the secondary component correction circuit 40 corrects the secondary component of the temperature characteristic of the pressure sensor output using the rectification characteristics of the diodes DI1 to DI4. In this manner, the voltage V1 (or voltage V2) that varies depending on the temperature characteristics can be output as a constant value by using the diodes DI1 to DI4 and the temperature characteristic adjusting circuit CI that is a half rectifier circuit. Thereby, it is not necessary to use a complicated circuit, and the secondary component of the temperature characteristic can be easily corrected at a low cost. Therefore, by adjusting the rectifying characteristics of the diodes DI1 to DI4 on the high temperature side of the temperature characteristic and adjusting the input voltage Vi input to the temperature characteristic adjustment circuit on the low temperature side, the secondary component of the temperature characteristic of the sensor output of the pressure sensor is surely obtained. It can be corrected.

  Also, the polarity switches SW1 and SW2 are switched according to the polarity (positive or negative) of the temperature coefficient of the resistors R11 and R13. As a result, regardless of the polarity of the resistors R11 and R13, the temperature characteristic adjusting circuit CI can correct the secondary component of the temperature characteristic. And the secondary component of the temperature characteristic which a pressure sensor has can be canceled by adding the obtained output voltage Vo to the sensor output of the pressure detection part 20. FIG.

  As described above, the temperature characteristic is corrected using a circuit formed of a diode. As a result, the secondary component correction circuit 40 can be made inexpensive and simple, and the number of correction steps can be reduced.

(Other embodiments)
In the first embodiment, the pressure sensor is described as an example of the physical quantity sensor. However, the secondary component correction circuit 40 shown in FIG. 3 is used for all physical quantity sensors having a secondary component in the temperature characteristics of the sensor output. Can do.

  In the temperature characteristic correction method shown in the first embodiment, the offset correction (step of FIG. 5C) may be performed after the offset characteristic adjustment (step of FIG. 5D).

1 is an overall circuit diagram of a physical quantity sensor according to an embodiment of the present invention. FIG. 2 is a circuit diagram of a primary component correction circuit shown in FIG. 1. FIG. 2 is a circuit diagram of a secondary component correction circuit shown in FIG. 1. FIG. 4 is a diagram showing the relationship between the temperature of the first resistor and the potential Vc in the temperature characteristic adjusting circuit of FIG. 3, where (a) shows a case where a first polarity switch is connected, and (b) shows a case where a second polarity switch is connected. It is the figure which showed the relationship between the temperature of the 1st resistance in case, and the electric potential Vc. It is the figure which showed the correction | amendment process of the secondary component of the temperature characteristic of a pressure sensor. 6A and 6B are diagrams showing sensor outputs in each step shown in FIG. 5, in which FIG. 5A is a diagram showing how sensitivity adjustment is performed in FIG. 5, and FIG. The figure which showed the mode of offset characteristic adjustment (room temperature), (c) is the figure which showed the mode of offset characteristic adjustment (low temperature) of FIG. It is the figure which showed the correction process which correct | amends the secondary component of the temperature characteristic of the conventional sensor output. FIGS. 8A and 8B are diagrams illustrating how the offset temperature characteristics of the pressure sensor are adjusted, in which FIG. 7A illustrates the sensitivity adjustment (room temperature) in FIG. 7 and FIG. 7B illustrates the offset temperature characteristics adjustment in FIG. It is the figure which showed the mode of offset characteristic adjustment (room temperature).

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Memory circuit, 20 ... Pressure detection part, 30 ... Primary component correction circuit,
31, 41, operational amplifier, 40, secondary component correction circuit, 50, adder, 60, amplifier,
R11 to R14: first to fourth resistors, R21, R22: first and second adjustment resistors,
CI: temperature characteristic adjustment circuit, SW1, SW2: first and second polarity switches,
R31 to R33, R40... Resistors, DI1 to DI4... First to fourth diodes.

Claims (6)

A physical quantity sensor having a secondary component correction circuit (40) for correcting a secondary component of temperature characteristics of the sensor output,
The secondary component correction circuit includes:
Resistors (R11, R13) having a temperature characteristic and having a secondary component that changes secondarily with respect to the temperature, and resistors that are connected in series to the resistor having the temperature characteristic and have no temperature characteristic ( R12, R14),
A plurality of diodes (DI1 to DI4) and an operational amplifier (41) are provided, which are configured as a half-wave rectifier circuit that is an inverting amplifier circuit, and an input voltage input to the operational amplifier by the rectification characteristics of the diode A temperature characteristic adjusting circuit (CI) that outputs the output voltage Vo as a constant value when the value of Vi exceeds a predetermined voltage value;
The potential between the resistor having the temperature characteristic and the resistor not having the temperature characteristic is VR, and this potential VR is connected to the input terminal of the operational amplifier of the temperature characteristic adjusting circuit,
When the resistance value of the resistor having the temperature characteristic changes due to an increase in temperature received by the resistor having the temperature characteristic, and the potential VR becomes larger than the output voltage Vo, the temperature characteristic adjusting circuit includes the diode A constant voltage corresponding to the rectifying characteristic is output as the output voltage Vo, and the resistance value of the resistor having the temperature characteristic is changed by lowering the temperature received by the resistor having the temperature characteristic, so that the potential VR becomes the output voltage. When smaller than Vo, the temperature characteristic adjusting circuit outputs a voltage corresponding to the temperature characteristic of the resistor having the temperature characteristic as the output voltage Vo,
When a connecting point between a linear waveform that shows a constant value with respect to temperature and a linear waveform that changes with temperature in the output voltage Vo is a bending point,
When the potential VR is smaller than the output voltage Vo, the temperature characteristic adjusting circuit moves the bending point to a lower temperature side with respect to the temperature by changing and inputting the value of the input voltage Vi. The physical quantity sensor is characterized in that the secondary component of the temperature characteristic of the sensor output is corrected by making the output voltage Vo constant with respect to the temperature. The physical quantity sensor according to claim 1, wherein the temperature characteristic adjusting circuit includes polarity switches (SW1, SW2) that are switched in accordance with a polarity of a temperature coefficient of a resistor having the temperature characteristic. The physical quantity sensor according to claim 1, wherein the output voltage Vo is added to a sensor output of the physical quantity sensor. Resistors (R11, R13) having a temperature characteristic and having a secondary component that changes secondarily with respect to the temperature, and resistors that are connected in series to the resistor having the temperature characteristic and have no temperature characteristic ( R12, R14),
A plurality of diodes (DI1 to DI4) and an operational amplifier (41) are provided, which are configured as a half-wave rectifier circuit that is an inverting amplifier circuit, and are input to the operational amplifier according to the rectification characteristics of the diode. A temperature characteristic adjusting circuit (CI) that outputs the output voltage Vo as a constant value when the value of the voltage Vi exceeds a predetermined voltage value;
A potential between a resistor having a temperature characteristic and a resistor not having the temperature coefficient is VR, and this potential VR is connected to the input terminal of the operational amplifier of the temperature characteristic adjusting circuit. A physical quantity sensor manufacturing method comprising:
When the potential VR is higher than the output voltage Vo due to the temperature received by the resistor having the temperature characteristic, the temperature characteristic adjustment circuit outputs a constant voltage according to the rectification characteristic of the diode, and the temperature characteristic When the potential VR is lower than the output voltage Vo due to the temperature received by the resistor having the resistance, the voltage corresponding to the temperature characteristic of the resistor having the temperature characteristic is output as the output voltage Vo in the temperature characteristic adjusting circuit. A correction process to
In the output voltage Vo, a connecting point between a linear waveform that shows a constant value with respect to temperature and a linear waveform that changes with temperature is used as a bending point, and the value of the input voltage Vi is changed in the temperature characteristic adjusting circuit. And a correction step of outputting an output voltage Vo independent of the temperature by moving the bending point to the low temperature side with respect to the temperature. 5. The method of manufacturing a physical quantity sensor according to claim 4, wherein the correction step of outputting the output voltage Vo independent of the temperature includes a correction step of adding the output voltage Vo to a sensor output of the physical quantity sensor. . Method of manufacturing a physical quantity sensor according to claim 4 or 5, characterized in that signal including the signal according to the polarity of the resistor having a front Stories temperature characteristic to the input voltage Vi is input to the operational amplifier.

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