JP2006060531A - Temperature characteristic compensation circuit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce variation in an oscillation frequency caused by temperature fluctuation, while suppressing increase in a packaging area. <P>SOLUTION: Surface acoustic wave devices W1 and W2 are configured to have mutually different frequency characteristics for temperature. Frequency/voltage conversion circuits F1 and F2 are provided for converting oscillation frequencies f1 and f2 of the surface acoustic wave devices W1 and W2 into voltages V1 and V2, respectively. Also, an operational amplifier P1 is provided for computing difference between V1 and V2 outputted from the frequency/voltage conversion circuits F1 and F2. An output of the operational amplifier P1 is connected to a control voltage terminal of varicaps Cg1, Cg1, while the output is connected to a control voltage terminal of varicaps Cg2, Cg2 via an inverter N7. Inverters N1-N7, the frequency/voltage conversion circuits F1 and F2, the operational amplifier P1, resistors R1 and R2, the varicaps Cg1, Cg1, and varicaps Cg2, Cg2 are formed at a semiconductor chip. The surface acoustic wave devices W1 and W2 are laminated on the semiconductor chip at which these elements were formed. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a temperature characteristic compensation circuit, and is particularly suitable for application to a method for compensating temperature characteristics using a plurality of surface acoustic wave devices having different temperature characteristics.

In a conventional temperature characteristic compensation circuit, in order to suppress fluctuations in the frequency of the oscillator due to temperature changes, the control voltage of the oscillator is controlled while referring to the characteristics of a device having excellent temperature characteristics.
Further, for example, in Patent Document 1, a plurality of crystal oscillators having different temperature characteristics are provided, and by selectively driving any one of the crystal oscillators according to the temperature according to the output of the temperature sensor, the temperature characteristics of the crystal oscillator are adjusted. A method of compensation is disclosed.
Japanese Utility Model Publication No. 60-158310

However, in the conventional temperature characteristic compensation method, in order to refer to the characteristics of a device having excellent temperature characteristics, it is necessary to externally attach individual components such as a thermistor, which causes an increase in mounting area. Further, in order to make the temperature characteristic compensation circuit into an IC, a temperature sensor, an A / D converter, and the like are required, and there is a problem in that the circuit scale and power consumption are increased.
Therefore, an object of the present invention is to provide a temperature characteristic compensation circuit capable of reducing fluctuations in oscillation frequency due to temperature changes while suppressing an increase in mounting area.

  In order to solve the above-described problem, according to a temperature characteristic compensation circuit according to an aspect of the present invention, first and second voltage-controlled SAW oscillators having different frequency characteristics with respect to temperature, and the first voltage-controlled SAW A first frequency / voltage conversion circuit for converting the oscillation frequency of the oscillator into a first voltage; a second frequency / voltage conversion circuit for converting the oscillation frequency of the second voltage-controlled SAW oscillator into a second voltage; A difference calculation circuit that inputs a difference between the first voltage and the second voltage as a control voltage of the first voltage-controlled SAW oscillator; and an inverted voltage of the difference calculated by the difference calculation circuit. And an inverting circuit that inputs the control voltage of the second voltage-controlled SAW oscillator.

  Thus, the oscillation frequencies of the first and second voltage-controlled SAW oscillators can be matched only at a specific temperature, and the oscillation frequencies of the first and second voltage-controlled SAW oscillators can be adjusted to each other according to a temperature change. The control voltage can be applied to the first and second voltage controlled SAW oscillators so that the difference between the oscillation frequencies of the first and second voltage controlled SAW oscillators becomes zero. it can. For this reason, even when a temperature change occurs, the oscillation frequency of the first and second voltage controlled SAW oscillators can always be converged to one point determined by a specific temperature, and the first and second voltage changes due to the temperature change. The frequency fluctuation of the voltage controlled SAW oscillator can be suppressed.

  According to the temperature characteristic compensation circuit of one aspect of the present invention, the first and second voltage-controlled SAW oscillators having different frequency characteristics with respect to temperature and the oscillation frequency of the first voltage-controlled SAW oscillator are set to voltages. A first frequency / voltage conversion circuit that converts and inputs the control voltage of the second voltage-controlled SAW oscillator; and an oscillation frequency of the second voltage-controlled SAW oscillator is converted into a voltage, and the first voltage control And a second frequency / voltage conversion circuit that inputs the control voltage of the SAW oscillator.

  Thus, the oscillation frequencies of the first and second voltage-controlled SAW oscillators can be matched only at a specific temperature, and the oscillation frequencies of the first and second voltage-controlled SAW oscillators can be adjusted to each other according to a temperature change. The control voltage is applied to the first and second voltage controlled SAW oscillators so that they can be made different and the oscillation frequency fluctuations of the first and second voltage controlled SAW oscillators cancel each other. Can do. For this reason, even when a temperature change occurs, the oscillation frequency of the first and second voltage controlled SAW oscillators can always be converged to one point determined by a specific temperature, and the first and second voltage changes due to the temperature change. The frequency fluctuation of the voltage controlled SAW oscillator can be suppressed.

According to the temperature characteristic compensation circuit of one aspect of the present invention, a plurality of surface acoustic wave devices stacked on a semiconductor chip and having different frequency characteristics with respect to temperature are formed on the semiconductor chip. And an oscillation frequency correction unit that corrects an oscillation frequency of an oscillator in which the surface acoustic wave device is incorporated, based on an output from the device.
Accordingly, the oscillation frequency can be corrected based on the temperature characteristics of the surface acoustic wave device, and the surface acoustic wave device can be integrated on the semiconductor chip. Therefore, temperature characteristic compensation can be performed without externally attaching individual components such as a thermistor, and fluctuations in oscillation frequency due to temperature changes can be reduced while suppressing an increase in mounting area.

According to the temperature characteristic compensation circuit of one aspect of the present invention, the surface acoustic wave device includes the thin film piezoelectric body stacked on the semiconductor chip, and an IDT electrode formed on the thin film piezoelectric body. It is characterized by providing.
As a result, the surface acoustic wave device can be stacked on the semiconductor chip by depositing the thin film piezoelectric body on the semiconductor chip, and the oscillation frequency fluctuation due to temperature change is reduced while suppressing an increase in mounting area. Can be made.

  Further, according to the temperature characteristic compensation circuit according to one aspect of the present invention, the oscillation frequency correction unit includes a first feedback circuit constituting a first oscillator in which the first surface acoustic wave device is incorporated, A second feedback circuit constituting a second oscillator incorporating the surface acoustic wave device, a first variable capacitor for controlling an oscillation frequency of the first oscillator, and an oscillation of the second oscillator A second variable capacitor for controlling the frequency, a first frequency / voltage conversion circuit for converting the oscillation frequency of the first oscillator into a first voltage, and the oscillation frequency of the second oscillator as a second frequency. A second frequency / voltage conversion circuit for converting to a voltage; a difference calculating circuit for calculating a difference between the first voltage and the second voltage; and inputting the difference to the first variable capacitor; and the difference calculation Invert the difference calculated in the circuit , Characterized in that it comprises an inverting circuit for input to the second variable capacitor.

  As a result, it becomes possible to stack the surface acoustic wave device on the semiconductor chip while allowing the portions other than the surface acoustic wave device to be formed on the semiconductor chip among the components of the temperature characteristic compensation circuit, and to The oscillation frequency can be corrected based on the temperature characteristics of the surface wave device. For this reason, the oscillation frequency fluctuation | variation by a temperature change can be reduced, suppressing the increase in a mounting area.

  Further, according to the temperature characteristic compensation circuit according to one aspect of the present invention, the oscillation frequency correction unit includes a first feedback circuit constituting a first oscillator in which the first surface acoustic wave device is incorporated, A second feedback circuit constituting a second oscillator incorporating the surface acoustic wave device, a first variable capacitor for controlling an oscillation frequency of the first oscillator, and an oscillation of the second oscillator A second variable capacitor for controlling the frequency, a first frequency / voltage conversion circuit for converting the oscillation frequency of the first oscillator into a voltage and inputting the voltage to the second variable capacitor, and the second And a second frequency / voltage conversion circuit that converts an oscillation frequency of the oscillator into a voltage and inputs the voltage to the first variable capacitor.

  As a result, it is possible to stack the surface acoustic wave device on the semiconductor chip while allowing the portions other than the surface acoustic wave device to be formed on the semiconductor chip among the components of the temperature characteristic compensation circuit. It is possible to correct the oscillation frequency based on the temperature characteristics of the surface acoustic wave device while simplifying the configuration. For this reason, while suppressing an increase in mounting area, it is possible to reduce fluctuations in oscillation frequency due to temperature changes, and it is possible to suppress an increase in the circuit scale and power consumption of the semiconductor chip.

In the temperature characteristic compensation circuit according to one aspect of the present invention, the first surface acoustic wave device and the second surface acoustic wave device have frequency changes in opposite directions with respect to temperature. And
As a result, the oscillation frequencies of the oscillators in which the first and second surface acoustic wave devices are incorporated can be made different from each other in accordance with the temperature change. For this reason, it becomes possible to detect the difference between the oscillation frequencies of the oscillators due to temperature changes, and to suppress frequency fluctuations of the first and second voltage-controlled SAW oscillators due to temperature changes.

According to the temperature characteristic compensation circuit of one aspect of the present invention, the first surface acoustic wave device uses a two-layer structure of ZnO / SiO ₂ or a two-layer structure of SiO ₂ / ZnO as the thin film piezoelectric body. In the second surface acoustic wave device, ZnO is used as the thin film piezoelectric body.
Accordingly, the first surface acoustic wave device can have a positive temperature characteristic, and the second surface acoustic wave device can have a negative temperature characteristic. For this reason, the first surface acoustic wave device and the second surface acoustic wave device can each have characteristics in which frequency changes due to temperature are opposite to each other, and the difference between the oscillation frequencies of the oscillation frequencies due to temperature changes. Can be detected.

Hereinafter, a temperature characteristic compensation circuit according to an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a temperature characteristic compensation circuit according to the first embodiment of the present invention.
In FIG. 1, the surface acoustic wave devices W1 and W2 are provided with IDT (interdigital transducer) electrodes for exciting the surface acoustic waves and reflector electrodes for reflecting the surface acoustic waves. The IDT electrode can be composed of a pair of comb electrodes arranged so as to engage with each other.

Here, between the comb-shaped electrodes of the surface acoustic wave device W1, three-stage inverters N1 to N3 are connected, and the surface acoustic wave device W1 and the inverters N1 to N3 constitute a SAW oscillator. A resistor R1 is connected between the comb electrodes of the surface acoustic wave device W1, and varicaps Cg1 and Cg1 are connected to a pair of comb electrodes, respectively.
Further, three-stage inverters N4 to N6 are connected between the comb electrodes of the surface acoustic wave device W2, and the SAW oscillator is configured by the surface acoustic wave device W2 and the inverters N4 to N6. A resistor R2 is connected between the comb electrodes of the surface acoustic wave device W2, and varicaps Cg2 and Cg2 are connected to a pair of comb electrodes, respectively.

  In addition, frequency / voltage conversion circuits F1 and F2 for converting the oscillation frequencies f1 and f2 of the surface acoustic wave devices W1 and W2 into voltages V1 and V2, respectively, are provided, and output from the frequency / voltage conversion circuits F1 and F2. An operational amplifier P1 for calculating the difference between the voltages V1 and V2 is provided. The output of the operational amplifier P1 is connected to the control voltage terminals of the varicaps Cg1 and Cg1, and is connected to the control voltage terminals of the varicaps Cg2 and Cg2 via the inverter N7.

Here, the surface acoustic wave devices W1 and W2 can be configured to have different frequency characteristics with respect to temperature. When the frequency characteristics with respect to the temperature of the surface acoustic wave devices W1 and W2 are made different from each other, the materials of the piezoelectric bodies to which the surface acoustic waves are excited can be made different. For example, by using ZnO as a piezoelectric body on which the IDT electrode of the surface acoustic wave device W1 is disposed, the surface acoustic wave device W1 can have negative temperature characteristics. Further, by using SiO ₂ as a piezoelectric body on which the IDT electrode of the surface acoustic wave device W2 is disposed, the surface acoustic wave device W2 can have positive temperature characteristics.

FIG. 2 is a diagram showing the relationship between the temperature and the oscillation frequency of the surface acoustic wave device of FIG.
In FIG. 2, when the piezoelectric body of the surface acoustic wave device W1 is made of ZnO, the frequency of the surface acoustic wave device W1 can be lowered as the temperature rises, and the surface acoustic wave device W1 has a negative temperature. It can have characteristics. On the other hand, when the piezoelectric body of the surface acoustic wave device W2 is composed of SiO ₂ , the frequency of the surface acoustic wave device W2 can be increased as the temperature rises, and the surface acoustic wave device W2 has a positive temperature characteristic. Can be given.

In FIG. 1, the output from the surface acoustic wave device W1 is fed back via inverters N1 to N3, and a signal having an oscillation frequency f1 is input to the frequency / voltage conversion circuit F1. When the signal having the oscillation frequency f1 is input to the frequency / voltage conversion circuit F1, the oscillation frequency f1 is converted to the voltage V1 and input to the inverting input terminal of the operational amplifier P1.
On the other hand, the output from the surface acoustic wave device W2 is fed back via the inverters N4 to N6, and the signal of the oscillation frequency f2 is input to the frequency / voltage conversion circuit F2. When the signal having the oscillation frequency f2 is input to the frequency / voltage conversion circuit F2, the oscillation frequency f2 is converted to the voltage V2 and input to the normal input terminal of the operational amplifier P1.

  When the voltages V1 and V2 from the frequency / voltage conversion circuits F1 and F2 are input to the operational amplifier P1, the operational amplifier P1 calculates a difference between these voltages V1 and V2, and uses the varicaps Cg1 and Cg1 as control voltages. input. The operational amplifier P1 inputs the difference between the voltages V1 and V2 to the varicaps Cg2 and Cg2 as a control voltage via the inverter N7.

  Here, when the temperature of the surface acoustic wave devices W1 and W2 increases, the oscillation frequency f1 of the surface acoustic wave device W1 decreases and the oscillation frequency f2 of the surface acoustic wave device W2 increases. For this reason, the oscillation frequency f1 of the surface acoustic wave device W1 is smaller than the oscillation frequency f2 of the surface acoustic wave device W2, and the voltage V1 output from the frequency / voltage conversion circuit F1 is the voltage output from the frequency / voltage conversion circuit F2. It becomes lower than V2. As a result, the voltage output from the operational amplifier P1 becomes high level, and this high level voltage is input to the varicaps Cg1 and Cg1, and the low level voltage obtained by inverting the high level voltage by the inverter N7 is changed to the varicap. Input to the caps Cg2 and Cg2.

  Here, the capacities of the varicaps Cg1, Cg1, Cg2, and Cg2 decrease as the control voltage increases. Therefore, when a high level voltage is input to the varicaps Cg1 and Cg1, the oscillation frequency f1 of the surface acoustic wave device W1 increases as shown in FIG. On the other hand, when a low level voltage is input to the varicaps Cg2 and Cg2, the oscillation frequency f2 of the surface acoustic wave device W2 decreases. When the oscillation frequency f1 of the surface acoustic wave device W1 increases and the oscillation frequency f2 of the surface acoustic wave device W2 decreases, the oscillation frequency f1 of the surface acoustic wave device W1 and the oscillation frequency f2 of the surface acoustic wave device W2 The difference becomes small, and it becomes stable when the oscillation frequency f1 of the surface acoustic wave device W1 and the oscillation frequency f2 of the surface acoustic wave device W2 coincide.

  On the other hand, when the temperatures of the surface acoustic wave devices W1 and W2 decrease, the oscillation frequency f1 of the surface acoustic wave device W1 increases and the oscillation frequency f2 of the surface acoustic wave device W2 decreases. Therefore, the oscillation frequency f1 of the surface acoustic wave device W1 is larger than the oscillation frequency f2 of the surface acoustic wave device W2, and the voltage V1 output from the frequency / voltage conversion circuit F1 is a voltage output from the frequency / voltage conversion circuit F2. It becomes higher than V2. As a result, the voltage output from the operational amplifier P1 becomes low level, and this low level voltage is input to the varicaps Cg1 and Cg1, and the high level voltage obtained by inverting the low level voltage by the inverter N7 is the varicap Cg2. , Cg2.

  Accordingly, as shown in FIG. 2B, the oscillation frequency f1 of the surface acoustic wave device W1 decreases and the oscillation frequency f2 of the surface acoustic wave device W2 increases. When the oscillation frequency f1 of the surface acoustic wave device W1 decreases and the oscillation frequency f2 of the surface acoustic wave device W2 increases, the oscillation frequency f1 of the surface acoustic wave device W1 and the oscillation frequency f2 of the surface acoustic wave device W2 The difference becomes small, and it becomes stable when the oscillation frequency f1 of the surface acoustic wave device W1 and the oscillation frequency f2 of the surface acoustic wave device W2 coincide.

As a result, it is possible to mutually cancel the frequency fluctuations caused by the temperature changes of the surface acoustic wave devices W1 and W2, and the frequency fluctuations of the SAW oscillator due to the temperature changes can be suppressed.
The inverters N1 to N7, the frequency / voltage conversion circuits F1 and F2, the operational amplifier P1, the resistors R1 and R2, and the varicaps Cg1, Cg1, Cg2, and Cg2 are formed on the semiconductor chip, and the semiconductor chip on which these elements are formed. The surface acoustic wave devices W1 and W2 may be stacked on top.

FIG. 3 is a cross-sectional view showing a configuration example of the temperature characteristic compensation circuit of FIG.
In FIG. 3, an element formation region 2 is provided in the semiconductor substrate 1, and elements such as transistors, resistors, and capacitors are formed in the element formation region 2. An interlayer insulating film 3 is formed on the semiconductor substrate 1 provided with the element forming region 2, and a wiring layer 4 connected to the element forming region 2 is formed on the interlayer insulating film 3. Also, pad electrodes 5 a and 5 b connected to the wiring layer 4 are formed on the interlayer insulating film 3. In the elements formed in the element formation region 2 and the wiring layer 4, the inverters N1 to N7, the frequency / voltage conversion circuits F1 and F2, the operational amplifier P1, the resistors R1 and R2, and the varicaps Cg1, Cg1, and Cg2 in FIG. , Cg2 and the like can be configured. In addition, as a material of the semiconductor substrate 1, Si, Ge, SiGe, SiC, SiSn, PbS, GaAs, InP, GaP, GaN, ZnSe etc. can be used, for example.

An SiO ₂ layer 6 is formed on the interlayer insulating film 3 so as to avoid the pad electrodes 5a and 5b. On the SiO ₂ layer 6, a two-layer structure of ZnO layer / SiO ₂ layer or SiO 2 is formed. A two-layer structure of ₂ layers / ZnO layer 7a and a ZnO layer 7b are laminated. An IDT electrode 8a and a connection electrode 9a connected to the IDT electrode 8a are formed on the 7a having a two-layer structure of ZnO layer / SiO ₂ layer or a two-layer structure of SiO ₂ layer / ZnO layer. Has been. The connection electrode 9a is connected to the pad electrode 5a via the Au wire 10a. On the other hand, an IDT electrode 8b is formed on the ZnO layer 7b, and a connection electrode 9b connected to the IDT electrode 8b is formed. The connection electrode 9b is connected to the pad electrode 5b through the Au wire 10b.

The surface acoustic wave device W1 shown in FIG. 1 is composed of the two-layer structure of ZnO layer / SiO ₂ layer or the two-layer structure of SiO ₂ layer / ZnO layer 7a and the IDT electrode 8a, and the ZnO layer 7b and the IDT electrode 8b. The surface acoustic wave device W2 of FIG. 1 can be configured.
As a result, the oscillation frequency can be corrected based on the temperature characteristics of the surface acoustic wave devices W1 and W2, and the surface acoustic wave devices W1 and W2 are integrated on the semiconductor substrate 1 provided with the element formation region 2. Can be Therefore, temperature characteristic compensation can be performed without externally attaching individual components such as a thermistor, and fluctuations in oscillation frequency due to temperature changes can be reduced while suppressing an increase in mounting area.

FIG. 4 is a diagram showing a configuration of a temperature characteristic compensation circuit according to the second embodiment of the present invention.
In FIG. 4, three-stage inverters N11 to N13 are connected between the comb electrodes of the surface acoustic wave device W11, and the surface acoustic wave device W11 and the inverters N11 to N13 constitute a SAW oscillator. A resistor R11 is connected between the comb electrodes of the surface acoustic wave device W11, and varicaps Cg11 and Cg11 are connected to the pair of comb electrodes, respectively.

  Three-stage inverters N14 to N16 are connected between the comb electrodes of the surface acoustic wave device W12, and the surface acoustic wave device W12 and the inverters N14 to N16 constitute a SAW oscillator. A resistor R12 is connected between the comb electrodes of the surface acoustic wave device W12, and varicaps Cg12 and Cg12 are connected to the pair of comb electrodes, respectively.

  Further, frequency / voltage conversion circuits F11 and F12 for converting the output frequencies f1 and f2 of the surface acoustic wave devices W11 and W12 to voltages V1 and V2, respectively, are provided, and the output from the frequency / voltage conversion circuit F12 is a varicap Cg1, The output from the frequency / voltage conversion circuit F11 is connected to the control voltage terminals of the varicaps Cg12 and Cg12 while being connected to the control voltage terminal of Cg1.

  Here, the surface acoustic wave devices W11 and W12 can be configured to have different frequency characteristics with respect to temperature. In addition, inverters N11 to N16, frequency / voltage conversion circuits F11 and F12, resistors R11 and R12, and varicaps Cg11, Cg11, Cg12, and Cg12 are formed on a semiconductor chip, and elastically formed on the semiconductor chip on which these elements are formed. Surface wave devices W11 and W12 may be stacked.

The output from the surface acoustic wave device W11 is fed back through the inverters N11 to N13, and a signal having the oscillation frequency f1 is input to the frequency / voltage conversion circuit F11. When the signal having the oscillation frequency f1 is input to the frequency / voltage conversion circuit F11, the oscillation frequency f1 is converted to the voltage V1 and input to the varicaps Cg12 and Cg12 as a control voltage.
On the other hand, the output from the surface acoustic wave device W12 is fed back through the inverters N14 to N16, and the signal having the oscillation frequency f2 is input to the frequency / voltage conversion circuit F12. When the signal of the oscillation frequency f2 is input to the frequency / voltage conversion circuit F12, the oscillation frequency f2 is converted to the voltage V2, and is input to the varicaps Cg11 and Cg11 as a control voltage.

  Here, when the temperature of the surface acoustic wave devices W11 and W12 increases, the oscillation frequency f1 of the surface acoustic wave device W11 decreases and the oscillation frequency f2 of the surface acoustic wave device W12 increases. For this reason, the voltage V1 output from the frequency / voltage conversion circuit F11 decreases, and the voltage V2 output from the frequency / voltage conversion circuit F12 increases. As a result, the control voltage input to the varicaps Cg11 and Cg11 increases, and the control voltage input to the varicaps Cg12 and Cg12 decreases.

Accordingly, the oscillation frequency f1 of the surface acoustic wave device W11 increases, the oscillation frequency f2 of the surface acoustic wave device W12 decreases, and the oscillation frequency f1 of the surface acoustic wave device W11 and the oscillation frequency f2 of the surface acoustic wave device W12 are reduced. Stable at the point of coincidence.
On the other hand, when the temperatures of the surface acoustic wave devices W11 and W12 decrease, the oscillation frequency f1 of the surface acoustic wave device W11 increases and the oscillation frequency f2 of the surface acoustic wave device W12 decreases. For this reason, the voltage V1 output from the frequency / voltage conversion circuit F11 increases, and the voltage V2 output from the frequency / voltage conversion circuit F12 decreases. As a result, the control voltage input to the varicaps Cg11 and Cg11 is lowered, and the control voltage input to the varicaps Cg12 and Cg12 is increased.

Accordingly, the oscillation frequency f1 of the surface acoustic wave device W11 decreases, the oscillation frequency f2 of the surface acoustic wave device W12 increases, and the oscillation frequency f1 of the surface acoustic wave device W11 and the oscillation frequency f2 of the surface acoustic wave device W12 Stable at the point of coincidence.
As a result, the surface acoustic wave devices W11 and W12 can be stacked on the semiconductor chip while enabling the portions other than the surface acoustic wave devices W11 and W12 of the components of the temperature characteristic compensation circuit to be formed on the semiconductor chip. In addition, the oscillation frequency can be corrected based on the temperature characteristics of the surface acoustic wave devices W11 and W12 while simplifying the circuit configuration. For this reason, while suppressing an increase in mounting area, it is possible to reduce fluctuations in oscillation frequency due to temperature changes, and it is possible to suppress an increase in the circuit scale and power consumption of the semiconductor chip.

1 is a circuit diagram showing a configuration of a temperature characteristic compensation circuit according to a first embodiment of the present invention. The figure which shows the relationship between the temperature and oscillation frequency of the surface acoustic wave apparatus of FIG. FIG. 2 is a cross-sectional view illustrating a configuration example of a temperature characteristic compensation circuit in FIG. 1. The circuit diagram which shows the structure of the temperature characteristic compensation circuit which concerns on 2nd Embodiment of this invention.

Explanation of symbols

W1, W2, W11, W12 surface acoustic wave device, F1, F2, F11, F12 frequency / voltage conversion circuit, P1 operational amplifier, N1-N7, N11-N16 inverter, R1, R2, R11, R12 resistance, Cg1, Cd1, Cg2, Cd2, C11, Cd11, Cg12, Cd12 Varicap, 1 semiconductor substrate, 2 element formation region, 3 interlayer insulation film, 4 wiring layer, 5a, 5b pad electrode, 6, 7b SiO ₂ layer, 7a ZnO layer, 8a 8b IDT electrode, 9a, 9b Connection electrode, 10a, 10b Au wire

Claims (8)

First and second voltage controlled SAW oscillators having different frequency characteristics with respect to temperature;
A first frequency / voltage conversion circuit for converting an oscillation frequency of the first voltage-controlled SAW oscillator into a first voltage;
A second frequency / voltage conversion circuit for converting the oscillation frequency of the second voltage-controlled SAW oscillator into a second voltage;
A difference calculating circuit for inputting a difference between the first voltage and the second voltage as a control voltage of the first voltage-controlled SAW oscillator;
A temperature characteristic compensating circuit comprising: an inverting circuit that inputs an inverted voltage of the difference calculated by the difference calculating circuit as a control voltage of the second voltage-controlled SAW oscillator. First and second voltage controlled SAW oscillators having different frequency characteristics with respect to temperature;
A first frequency / voltage conversion circuit that converts an oscillation frequency of the first voltage-controlled SAW oscillator into a voltage and inputs the voltage as a control voltage of the second voltage-controlled SAW oscillator;
Temperature characteristic compensation comprising: a second frequency / voltage conversion circuit that converts an oscillation frequency of the second voltage-controlled SAW oscillator into a voltage and inputs the voltage as a control voltage of the first voltage-controlled SAW oscillator circuit. A plurality of surface acoustic wave devices stacked on a semiconductor chip and having different frequency characteristics with respect to temperature,
A temperature characteristic compensation comprising: an oscillation frequency correction unit formed on the semiconductor chip and configured to correct an oscillation frequency of an oscillator in which the surface acoustic wave device is incorporated based on an output from the surface acoustic wave device. circuit. The surface acoustic wave device includes:
The thin film piezoelectric body laminated on the semiconductor chip;
The temperature characteristic compensation circuit according to claim 3, further comprising an IDT electrode formed on the thin film piezoelectric body. The oscillation frequency correction unit is
A first feedback circuit constituting a first oscillator incorporating the first surface acoustic wave device;
A second feedback circuit constituting a second oscillator incorporating the second surface acoustic wave device;
A first variable capacitor for controlling the oscillation frequency of the first oscillator;
A second variable capacitor for controlling the oscillation frequency of the second oscillator;
A first frequency / voltage conversion circuit for converting the oscillation frequency of the first oscillator into a first voltage;
A second frequency / voltage conversion circuit for converting the oscillation frequency of the second oscillator into a second voltage;
A difference calculation circuit that calculates a difference between the first voltage and the second voltage and inputs the difference to the first variable capacitor;
The temperature characteristic compensation circuit according to claim 4, further comprising: an inverting circuit that inverts the difference calculated by the difference calculating circuit and then inputs the inverted value to the second variable capacitor. The oscillation frequency correction unit is
A first feedback circuit constituting a first oscillator incorporating the first surface acoustic wave device;
A second feedback circuit constituting a second oscillator incorporating the second surface acoustic wave device;
A first variable capacitor for controlling the oscillation frequency of the first oscillator;
A second variable capacitor for controlling the oscillation frequency of the second oscillator;
A first frequency / voltage conversion circuit that converts an oscillation frequency of the first oscillator into a voltage and inputs the voltage to the second variable capacitor;
5. The temperature characteristic compensation circuit according to claim 4, further comprising: a second frequency / voltage conversion circuit that converts the oscillation frequency of the second oscillator into a voltage and inputs the voltage to the first variable capacitor.   7. The temperature characteristic compensation circuit according to claim 5, wherein the first surface acoustic wave device and the second surface acoustic wave device have frequency changes in opposite directions with respect to temperature. In the first surface acoustic wave device, a two-layer structure of ZnO / SiO ₂ or a two-layer structure of SiO ₂ / ZnO is used as the thin film piezoelectric body. In the second surface acoustic wave device, ZnO as the thin film piezoelectric body is used. 8. The temperature characteristic compensating circuit according to claim 7, wherein:

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