JP2020005298A - Oscillator, electronic apparatus, and mobile body - Google Patents

Abstract

To provide an oscillator excellent in frequency control compared with the conventional art.SOLUTION: An oscillator 1 includes: a vibration element 3; an oscillation circuit 10; and a temperature compensation circuit 40, for example, as a frequency control circuit. An equivalent series capacitance C1(fF) when a resonance frequency of the vibration element 3 is defined as Fr(MHz) satisfies C1≥0.00279×Fr-0.05684×Fr+2.69481.SELECTED DRAWING: Figure 10

Description

  The present invention relates to an oscillator, an electronic device, and a moving object.

  A temperature-compensated crystal oscillator (TCXO: Temperature Compensated Crystal Oscillator) includes a crystal oscillator and an integrated circuit (IC) for oscillating the crystal oscillator, and the IC operates in a predetermined temperature range. By compensating (temperature compensating) for a deviation (frequency deviation) of the oscillation frequency from a desired frequency (nominal frequency), high frequency accuracy can be obtained. An AT-cut resonator is used as a resonator of a temperature compensated crystal oscillator (TCXO). Since the AT-cut vibrator exhibits a cubic curve in frequency temperature characteristics, there is an advantage that a stable frequency can be obtained in a wide temperature range as compared with vibrators of other cuts. In recent years, the size reduction of AT-cut vibrators has been promoted by applying photolithography technology to crystal processing. An AT-cut vibrator is described in Patent Document 1, for example. A temperature-compensated crystal oscillator (TCXO) is described in, for example, Patent Document 2.

JP 2005-094410 A JP 2013-243481 A

  However, as the size of the AT-cut resonator decreases, the frequency-variable sensitivity (element sensitivity) of the AT-cut resonator decreases, and therefore, for example, is larger than the width of the frequency deviation of the AT-cut resonator in a desired temperature range. In order to realize the frequency variable width, it is necessary to widen the variable range of the voltage (temperature compensation voltage) applied to the variable capacitance element by the IC. Then, the temperature compensation voltage exceeding the voltage range in which the capacitance value changes almost linearly is applied to the variable capacitance element, the temperature compensation accuracy is deteriorated, and the output frequency of the temperature compensated oscillator is changed according to the temperature. Due to the fluctuation, there is a problem that the frequency deviation increases.

  The present invention has been made in view of the above-described problems, and according to some aspects of the present invention, it is possible to provide an oscillator that is more excellent in frequency control than a conventional oscillator. Further, according to some embodiments of the present invention, an electronic device and a moving object using the oscillator can be provided.

  SUMMARY An advantage of some aspects of the invention is to solve at least a part of the problems described above, and the invention can be implemented as the following aspects or application examples.

[Application Example 1]
The oscillator according to this application example includes a vibrating element, an oscillation circuit, and a frequency control circuit. When the resonance frequency of the vibrating element is Fr (MHz), the equivalent series capacitance C1 (fF) is C1 ≧ 0. .00279 × Fr ² −0.05684 × Fr + 2.669481.

  Various oscillating circuits such as a Pierce oscillating circuit, an inverter-type oscillating circuit, a Colpitts oscillating circuit, and a Hartley oscillating circuit may be configured by the oscillating element and the oscillating circuit.

According to this application example, by using the vibrating element having a high frequency variable sensitivity defined by the condition of C1 ≧ 0.00279 × Fr ² −0.05684 × Fr + 2.669481, the oscillator having more excellent frequency control than the conventional oscillator is used. For example, it is possible to realize a temperature-compensated oscillator having a smaller frequency deviation than the conventional one.

[Application Example 2]
In the oscillator according to the application example, the equivalent series capacitance C1 may be larger than 1.5 fF.

  The oscillator according to this application example realizes an oscillator that is more excellent in frequency control than the conventional one by using a vibrating element having a high frequency variable sensitivity defined on the condition that the equivalent series capacitance C1 is larger than 1.5 fF. For example, it is possible to realize a temperature-compensated oscillator having a smaller frequency deviation than the conventional one.

[Application Example 3]
In the oscillator according to the application example, the frequency control circuit may change an oscillation frequency with respect to an input voltage, and a rate of change of the frequency with respect to the input voltage may be equal to or greater than 42 ppm / V. .

  According to this application example, by using the vibrating element having a high frequency variable sensitivity defined by the condition that the rate of change of the frequency is 42 ppm / V or more, it is possible to realize an oscillator that is more excellent in frequency control than before, For example, it is possible to realize a temperature-compensated oscillator having a smaller frequency deviation than the conventional one.

[Application Example 4]
The oscillator according to the above application example satisfies γ ≧ 0.022 × Fr ² −4.969 × Fr + 417.929, where γ is the capacitance ratio C0 / C1 between the equivalent parallel capacitance C0 and the equivalent series capacitance C1. Good.

According to this application example, by using a vibrating element having a high frequency variable sensitivity defined by the condition of γ ≧ 0.022 × Fr ² −4.969 × Fr + 417.929, an oscillator that is more excellent in frequency control than before is used. For example, it is possible to realize a temperature-compensated oscillator having a smaller frequency deviation than the conventional one.

[Application Example 5]
The oscillator according to the above application example may have a frequency deviation of not less than -150 ppb and not more than +150 ppb in a temperature range of not less than -40 ° C and not more than + 85 ° C.

  The oscillator according to this application example is a unique oscillator that approaches the frequency temperature characteristic of OCXO having a frequency deviation of −150 ppb or more and +150 ppb or less in a temperature range of −40 ° C. or more and + 85 ° C. or less. Therefore, for example, the oscillator according to this application example can be used in an electronic device that requires high frequency accuracy such as an OCXO.

[Application Example 6]
In the oscillator according to the application example, a frequency deviation of the vibrating element with respect to a third-order or more approximate expression of a frequency-temperature characteristic of the vibrating element may be equal to or more than -150 ppb and equal to or less than +150 ppb.

  According to this application example, an oscillator having a frequency-temperature characteristic of −150 ppb or more and +150 ppb or less can be easily realized even when the variation in the temperature characteristics of the oscillation circuit and the frequency control circuit is taken into consideration, so that the yield of the oscillator can be improved. it can.

[Application Example 7]
An electronic device according to this application example includes any one of the oscillators described above.

[Application Example 8]
The moving body according to this application example includes any of the oscillators described above.

  According to these application examples, since an oscillator having better frequency control than that of the related art is used, it is possible to realize, for example, an electronic device and a mobile body with high reliability.

FIG. 2 is a perspective view of the oscillator according to the embodiment. 2A is a cross-sectional view of the oscillator according to the present embodiment, FIG. 2B is a top view of the oscillator of the present embodiment, and FIG. 2C is a bottom view of the oscillator. FIG. 2 is a functional block diagram of the oscillator according to the embodiment. FIG. 6 is a flowchart illustrating an example of a procedure of a method of manufacturing the oscillator. The figure which shows an example of the relationship between a temperature compensation voltage and compensation voltage sensitivity. The figure which plotted the actual measurement value of the frequency deviation of an oscillator. FIG. 4 is a diagram showing actually measured values of frequency temperature characteristics of an oscillator. FIG. 3 is an equivalent circuit diagram of the vibration element. The figure which plotted the compensation voltage sensitivity of the oscillator. FIG. 4 is a diagram illustrating a relationship between an oscillator frequency and an equivalent series capacitance. The figure which shows the relationship between the frequency of an oscillator, and the capacitance ratio of equivalent parallel capacitance and equivalent series capacitance. FIG. 4 is an explanatory diagram of a frequency deviation of a vibration element. FIG. 2 is a functional block diagram illustrating an example of a configuration of the electronic apparatus according to the embodiment. FIG. 2 is a diagram illustrating an example of an external appearance of the electronic apparatus according to the embodiment. The figure which shows an example of the moving body of this embodiment.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the invention described in the claims. In addition, all of the configurations described below are not necessarily essential components of the invention.

1. Oscillator [Configuration of oscillator]
1 and 2 are diagrams illustrating an example of the structure of the oscillator according to the present embodiment. FIG. 1 is a perspective view of the oscillator, and FIG. 2A is a sectional view taken along the line AA ′ of FIG. FIG. 2B is a top view of the oscillator, and FIG. 2C is a bottom view of the oscillator. However, FIG. 2 (B) is shown without the lid 5 of FIG. 2 (A).

  As shown in FIGS. 1 and 2A, an oscillator 1 according to the present embodiment includes an integrated circuit (IC) 2, a vibrating element (vibrating piece) 3, a package 4, a lid (lid), which are semiconductor devices. 5, and external terminals (external electrodes) 6.

  As the vibration element 3, for example, a crystal vibration element, a surface acoustic wave (SAW) resonance element, another piezoelectric vibration element, a MEMS (Micro Electro Mechanical Systems) vibration element, or the like can be used. As the substrate material of the vibration element 3, a piezoelectric single crystal such as quartz, lithium tantalate, lithium niobate, a piezoelectric ceramic such as lead zirconate titanate, or a silicon semiconductor material can be used. As the excitation means of the vibration element 3, a device using a piezoelectric effect or an electrostatic drive using Coulomb force may be used.

  The package 4 houses the integrated circuit (IC) 2 and the vibration element 3 in the same space. Specifically, the package 4 is provided with a concave portion, and the integrated circuit (IC) 2 and the vibration element 3 are accommodated by covering the concave portion with the lid 5. Two terminals of the integrated circuit (IC) 2 (XO terminal and XI terminal in FIG. 3 described later) and two terminals of the vibration element 3 (excitation electrodes 3a and 3b) are provided inside the package 4 or on the surface of the concave portion. Wiring (not shown) for electrical connection is provided. In addition, wiring (not shown) electrically connected to each external terminal 6 is provided inside the package 4 or on the surface of the concave portion, and each wiring and each terminal of the integrated circuit (IC) 2 are made of gold or the like. Bonding wire 7.

  As shown in FIG. 2C, the oscillator 1 has an external terminal VDD serving as a power supply terminal, an external terminal VSS1 serving as a ground terminal, and a terminal to which a signal for frequency control is input on the bottom surface (the back surface of the package 4). Four external terminals 6, an external terminal VC1 and an external terminal OUT1 which is an output terminal, are provided. A power supply voltage is supplied to the external terminal VDD1, and the external terminal VSS1 is grounded.

  The vibrating element 3 has metal excitation electrodes 3a and 3b on its front and back surfaces, respectively, and has a desired frequency (frequency required for the oscillator 1) according to the mass of the vibration element 3 including the excitation electrodes 3a and 3b. ).

  In the present embodiment, the vibration element 3 is housed in a package (container) 8 (the vibration element 3 is fixed to an electrode pad 11 disposed on a base 8a with a connection member 12 such as a conductive adhesive). Has been). The package 8 includes a base 8a and a lid (lid) 8b sealing the base 8a, and the base 8a is joined to the package 4 by an adhesive member 9 such as lysine. Further, the integrated circuit (IC) 2 is joined to the lid 8b by the adhesive member 9.

  That is, as shown in FIG. 2B, when the oscillator 1 is viewed in a plan view from above, the integrated circuit (IC) 2 and the package 8 (the vibrating element 3) overlap, and the package accommodating the vibrating element 3 is provided. The integrated circuit (IC) 2 is directly attached to the lid 8b of the eighth. As a result, the heat generated by the integrated circuit (IC) 2 is conducted to the vibration element 3 in a short time, so that the temperature difference between the integrated circuit (IC) 2 and the vibration element 3 is reduced, and a frequency control circuit, such as a temperature compensation circuit described later, is used. The error of the temperature compensation by 40 is small. Therefore, the structure of the oscillator 1 shown in FIGS. 2A to 2C is more effective for improving the frequency accuracy. The material of the lid 8b is desirably a metal having high thermal conductivity.

  FIG. 3 is a functional block diagram of the oscillator 1. As shown in FIG. 3, the oscillator 1 is an oscillator including a vibrating element 3 and an integrated circuit (IC) 2 for oscillating the vibrating element 3, and the integrated circuit (IC) 2 and the vibrating element 3 are mounted on a package 4. Is contained.

  The integrated circuit (IC) 2 is connected to a VDD terminal serving as a power supply terminal, a VSS terminal serving as a ground terminal, an OUT terminal serving as an output terminal, a VC terminal serving as a terminal to which a signal for controlling frequency is input, and a connection with the vibration element 3. An XI terminal and an XO terminal, which are terminals, are provided. The VDD terminal, the VSS terminal, the OUT terminal, and the VC terminal are exposed on the surface of the integrated circuit (IC) 2 and are connected to the external terminals VDD1, VSS1, OUT1, and VC1 provided in the package 4, respectively. The XI terminal is connected to one end (one terminal) of the vibration element 3, and the XO terminal is connected to the other end (the other terminal) of the vibration element 3.

  In the present embodiment, the integrated circuit (IC) 2 includes an oscillation circuit 10, an output circuit 20, a frequency adjustment circuit 30, an AFC (Automatic Frequency Control) circuit 32, a temperature compensation circuit 40, a temperature sensor 50, a regulator circuit 60, and a storage unit. 70, and a serial interface (I / F) circuit 80. Note that the integrated circuit (IC) 2 may have a configuration in which some of these elements are omitted or changed, or other elements are added.

  The regulator circuit 60 supplies power to a part or all of the oscillation circuit 10, the frequency adjustment circuit 30, the AFC circuit 32, the temperature compensation circuit 40, and the output circuit 20 based on the power supply voltage VDD (positive voltage) supplied from the VDD terminal. Generate a constant voltage to be a voltage or a reference voltage.

  The storage unit 70 has a nonvolatile memory 72 and a register 74, and is configured to be able to read / write the nonvolatile memory 72 or the register 74 from an external terminal via a serial interface circuit 80. In the present embodiment, since there are only four terminals of the integrated circuit (IC) 2 connected to the external terminal of the oscillator 1, VDD, VSS, OUT, and VC, the serial interface circuit 80 outputs, for example, a voltage of the VDD terminal. When the voltage is higher than the threshold value, a clock signal input from the VC terminal and a data signal input from the OUT terminal are received, and data is read / written from / to the nonvolatile memory 72 or the register 74.

  The nonvolatile memory 72 is a storage unit for storing various control data, and may be, for example, various rewritable nonvolatile memories such as an EEPROM (Electrically Erasable Programmable Read-Only Memory) and a flash memory. However, various non-rewritable nonvolatile memories such as a one-time programmable read only memory (PROM) may be used.

  The nonvolatile memory 72 stores frequency adjustment data for controlling the frequency adjustment circuit 30 and temperature compensation data for controlling, for example, the temperature compensation circuit 40 as the frequency control circuit (primary compensation data,..., N). Next compensation data) is stored. Further, the nonvolatile memory 72 also stores data (not shown) for controlling the output circuit 20 and the AFC circuit 32, respectively.

  The frequency adjustment data is data for adjusting the frequency of the oscillator 1. When the frequency of the oscillator 1 deviates from a desired frequency, the frequency adjustment data is rewritten so that the frequency of the oscillator 1 becomes the desired frequency. It can be fine-tuned to get closer.

  The temperature compensation data (first-order compensation data,..., N-order compensation data) is data for correcting the frequency-temperature characteristic of the oscillator 1, which is calculated in the temperature compensation adjustment step of the oscillator 1. The first to n-th coefficient values corresponding to the respective order components of the frequency temperature characteristic of No. 3 may be used. Here, as the maximum order n of the temperature compensation data, a value that cancels the frequency-temperature characteristics of the vibrating element 3 and can also correct the influence of the temperature characteristics of the integrated circuit (IC) 2 is selected. For example, n may be an integer value larger than the main order of the frequency temperature characteristics of the vibration element 3. For example, if the vibrating element 3 is an AT-cut quartz vibrating element, the frequency-temperature characteristic exhibits a cubic curve, and its main order is 3, so that n is an integer value larger than 3 (for example, 5 or 6). May be selected. Note that the temperature compensation data may include compensation data of all the first to nth orders, or may include only compensation data of a part of the first to nth orders.

  Each data stored in the nonvolatile memory 72 is transferred from the nonvolatile memory 72 to the register 74 when the power of the integrated circuit (IC) 2 is turned on (when the voltage of the VDD terminal rises from 0 V to a desired voltage), It is held in the register 74. Then, the frequency adjustment data held in the register 74 is input to the frequency adjustment circuit 30, and the temperature compensation data (first-order compensation data,..., N-order compensation data) held in the register 74 is input to the temperature compensation circuit 40. ) Is input, and each control data held in the register 74 is also input to the output circuit 20 and the AFC circuit 32.

  When the nonvolatile memory 72 cannot be rewritten, when the oscillator 1 is inspected, each data of the register 74 in which each data transferred from the external memory via the serial interface circuit 80 via the serial interface circuit 80 is held is stored. Each data is directly written to the bit, and the oscillator 1 is adjusted and selected so as to satisfy a desired characteristic, and the adjusted and selected data is finally written to the nonvolatile memory 72. When the nonvolatile memory 72 is rewritable, each data may be written to the nonvolatile memory 72 from an external terminal via the serial interface circuit 80 when the oscillator 1 is inspected. However, since writing to the non-volatile memory 72 generally takes a long time, when the oscillator 1 is inspected, each data is directly written to each bit of the register 74 from an external terminal via the serial interface circuit 80 in order to shorten the inspection time. Each data that has been written and adjusted / selected may be finally written to the nonvolatile memory 72.

  The oscillation circuit 10 oscillates the oscillation element 3 by amplifying the output signal of the oscillation element 3 and feeds it back to the oscillation element 3, and outputs an oscillation signal based on the oscillation of the oscillation element 3. For example, the oscillation stage current of the oscillation circuit 10 may be controlled by the control data held in the register 74.

  The frequency adjustment circuit 30 generates a voltage corresponding to the frequency adjustment data held in the register 74 and applies the generated voltage to one end of a variable capacitance element (not shown) functioning as a load capacitance of the oscillation circuit 10. As a result, the oscillation frequency (reference frequency) of the oscillation circuit 10 at a predetermined temperature (for example, 25 ° C.) and the voltage of the VC terminal becomes a predetermined voltage (for example, VDD / 2) becomes substantially the desired frequency. Is controlled (fine-tuned).

  The AFC circuit 32 generates a voltage corresponding to the voltage of the VC terminal and applies the generated voltage to one end of a variable capacitance element (not shown) functioning as a load capacitance of the oscillation circuit 10. Thereby, the oscillation frequency of the oscillation circuit 10 (the oscillation frequency of the vibration element 3) is controlled based on the voltage value of the VC terminal. For example, the gain of the AFC circuit 32 may be controlled by the control data held in the register 74.

  The temperature sensor 50 is a temperature-sensitive element that outputs a signal (for example, a voltage corresponding to the temperature) according to a temperature around the temperature sensor 50. The temperature sensor 50 may be of a positive polarity having a higher output voltage as the temperature is higher, or may be of a negative polarity having a lower output voltage as the temperature is higher. It is desirable that the temperature sensor 50 be such that the output voltage changes as linearly as possible with a temperature change in a desired temperature range in which the operation of the oscillator 1 is guaranteed.

  The temperature compensation circuit 40 receives the output signal from the temperature sensor 50, generates a voltage (temperature compensation voltage) for compensating the frequency-temperature characteristics of the vibrating element 3, and functions as a load capacitance of the oscillation circuit 10. It is applied to one end of a capacitive element (not shown). Thus, the oscillation frequency of the oscillation circuit 10 is controlled so as to be substantially constant regardless of the temperature. In the present embodiment, the temperature compensating circuit 40 includes primary voltage generating circuits 41-1 to n-th voltage generating circuits 41-n and an adding circuit 42.

  Primary voltage generation circuits 41-1 to n-th voltage generation circuits 41-n receive an output signal from the temperature sensor 50 and respond to the primary compensation data to the n-th compensation data held in the register 74, respectively. And a primary compensation voltage to an n-th compensation voltage for compensating the n-th component from the first-order component of the frequency temperature characteristic.

  The adding circuit 42 adds and outputs the primary compensation voltage to the n-th compensation voltage generated by the primary voltage generation circuits 41-1 to 41-n, respectively. The output voltage of the adder circuit 42 becomes the output voltage (temperature compensation voltage) of the temperature compensation circuit 40.

  The output circuit 20 receives an oscillation signal output from the oscillation circuit 10, generates an oscillation signal for external output, and outputs the oscillation signal to the outside via the OUT terminal. For example, the frequency division ratio and output level of the oscillation signal in the output circuit 20 may be controlled by the control data held in the register 74.

  The oscillator 1 configured in this manner is a voltage-controlled temperature-compensated oscillator (oscillating element 3) that outputs an oscillation signal of a constant frequency according to the voltage of the external terminal VC1 regardless of the temperature within a desired temperature range. If it is a crystal vibrating element, it functions as a VC-TCXO (Voltage Controlled Temperature Compensated Crystal Oscillator).

[Oscillator manufacturing method]
FIG. 4 is a flowchart illustrating an example of a procedure of a method of manufacturing the oscillator 1 according to the present embodiment. A part of steps S10 to S70 in FIG. 4 may be omitted or changed, or another step may be added. In addition, the order of each step may be appropriately changed to the extent possible.

  In the example of FIG. 4, first, the integrated circuit (IC) 2 and the vibration element 3 (the package 8 containing the vibration element 3) are mounted on the package 4 (S10). In step S10, the integrated circuit (IC) 2 and the vibrating element 3 are connected by wiring provided inside the package 4 or on the surface of the concave portion, and when power is supplied to the integrated circuit (IC) 2, the integrated circuit (IC) 2 And the vibration element 3 are electrically connected.

  Next, the package 4 is sealed with the lid 5, and heat treatment is performed to adhere the lid 5 to the package 4 (S20). By this step S20, the assembly of the oscillator 1 is completed.

  Next, the reference frequency (frequency at the reference temperature T0 (for example, 25 ° C.)) of the oscillator 1 is adjusted (S30). In this step S30, the frequency is measured by oscillating the oscillator 1 at the reference temperature T0, and the frequency adjustment data is determined so that the frequency deviation approaches zero.

  Next, the VC sensitivity of the oscillator 1 is adjusted (S40). In this step S40, at the reference temperature T0, the oscillator 1 is oscillated in a state where a predetermined voltage (for example, 0 V or VDD) is applied to the external terminal VC1, the frequency is measured, and a desired VC sensitivity is obtained. The adjustment data of the AFC circuit 32 is determined.

  Next, the temperature compensation of the oscillator 1 is adjusted (S50). In the temperature compensation adjustment step S50, the frequency of the oscillator 1 is measured at a plurality of temperatures in a desired temperature range (for example, −40 ° C. or more and 85 ° C. or less), and the frequency temperature characteristic of the oscillator 1 is determined based on the measurement result. Generate temperature compensation data (primary compensation data,..., N-order compensation data) for correction. More specifically, the temperature compensation data calculation program uses the frequency measurement results at a plurality of temperatures to calculate the frequency temperature characteristics of the oscillator 1 (the frequency temperature characteristics of the vibrating element 3 and the temperature characteristics of the integrated circuit (IC) 2). ) Is approximated by an n-th order equation with temperature (output voltage of the temperature sensor 50) as a variable, and temperature compensation data (first order compensation data,..., N-th order compensation data) corresponding to the approximation equation is obtained. Generate. For example, the temperature compensation data calculation program sets temperature compensation data (primary compensation data,..., Etc.) such that the frequency deviation at the reference temperature T0 is 0 and the width of the frequency deviation in a desired temperature range is reduced. n-order compensation data).

  Next, the data obtained in steps S30, S40, and S50 are stored in the non-volatile memory 72 of the storage unit 70 (S60).

  Finally, the frequency temperature characteristics of the oscillator 1 are measured, and the quality is determined (S70). In this step S70, the frequency of the oscillator 1 is measured while gradually changing the temperature, and it is evaluated whether or not the frequency deviation is within a predetermined range in a desired temperature range (for example, −40 ° C. or more and 85 ° C. or less). If the frequency deviation is within the predetermined range, it is determined to be good, and if not, the product is determined to be defective.

[Oscillator frequency temperature characteristics]
The frequency temperature characteristic of the oscillator 1 has a correlation with the frequency variable sensitivity (element sensitivity) of the vibration element 3. FIG. 5 is a diagram illustrating an example of a relationship between the temperature compensation voltage and the compensation voltage sensitivity (the degree of frequency change with respect to a change in the temperature compensation voltage). In FIG. 5, the horizontal axis represents the temperature compensation voltage (unit: V), and the vertical axis represents the compensation voltage sensitivity (unit: ppm / V). The solid line is a graph when the vibration element 3 having high frequency variable sensitivity is used, and the broken line is a graph when the vibration element 3 having low frequency variable sensitivity is used.

  As shown in FIG. 5, when the vibrating element 3 having low frequency variable sensitivity is used, the frequency variable width of the oscillator 1 is set to be equal to the frequency deviation of the vibrating element 3 in a desired temperature range (for example, −40 ° C. to + 85 ° C.). In this case, it is necessary for the integrated circuit (IC) 2 to widen the variable range of the temperature compensation voltage (ΔV2 in FIG. 5). Then, a temperature compensation voltage exceeding a voltage range in which the compensation voltage sensitivity becomes substantially constant is applied to the variable capacitance element (for example, a varactor), and the temperature compensation accuracy is deteriorated. Deteriorates. On the other hand, when the vibrating element 3 having high frequency variable sensitivity is used, the integrated circuit (IC) 2 can narrow the variable range of the temperature compensation voltage (ΔV1 in FIG. 5). Then, the temperature compensation voltage applied to the variable capacitance element falls within a voltage range where the compensation voltage sensitivity is substantially constant, and the frequency temperature characteristics of the oscillator 1 are improved.

  That is, the higher the frequency variable sensitivity of the vibrating element 3, the smaller the frequency deviation of the oscillator 1 in a desired temperature range. Since the compensation voltage sensitivity increases as the frequency variable sensitivity of the vibrating element 3 increases, it can be said that the frequency deviation of the oscillator 1 in a desired temperature range can be reduced as the compensation voltage sensitivity increases.

FIG. 6 shows measured values of the frequency deviation of the oscillator 1 having a nominal frequency of 19.2 MHz (oscillator 1 at −40 ° C. to + 85 ° C.) using each of three vibrating elements having different frequency variable sensitivities as the vibrating element 3. FIG. 4 is a diagram in which the worst value of the frequency deviation (absolute value) of the data is plotted. In FIG. 6, the horizontal axis represents the compensation voltage sensitivity (unit: ppm / V) at the center voltage of the variable range of the temperature compensation voltage, and the vertical axis represents the frequency deviation (worst value) of the oscillator 1 (unit: ppm). . The solid line is a curve obtained by approximating the plotted three points (points A, B, and C) by a quadratic polynomial. Assuming that the horizontal axis is x and the vertical axis is y, y = 0.036x ² The curve satisfies −0.3242x + 7.4074. As shown in FIG. 6, the frequency deviation (worst value) (point A) of the oscillator 1 having the compensation voltage sensitivity of about 32 ppm / V exceeds 0.7 ppm, while the compensation voltage sensitivity is about 41 ppm / V. The frequency deviation (worst value) (point B) of the oscillator 1 is smaller than 0.2 ppm. Further, the frequency deviation (worst value) (point C) of the oscillator 1 having the compensation voltage sensitivity of about 47 ppm / V is smaller than 0.15 ppm.

  7 (A) and 7 (B) show measured values of the frequency temperature characteristic of the oscillator 1 corresponding to the point A and measured values of the frequency temperature characteristic of the oscillator 1 corresponding to the point C, respectively. 7A and 7B, the horizontal axis represents temperature (unit: ° C.), and the vertical axis represents frequency deviation (unit: ppm). As shown in FIG. 7A, the oscillator 1 having a compensation voltage sensitivity of about 32 ppm / V corresponding to the point A has the largest frequency deviation (absolute value) around −40 ° C. and exceeds 0.7 ppm. . On the other hand, as shown in FIG. 7B, the oscillator 1 having a compensation voltage sensitivity of about 47 ppm / V corresponding to the point C has a frequency deviation of ± 0.15 ppm in a temperature range of −40 ° C. to + 85 ° C. (± 150 ppb: -150 ppb or more and +150 ppb or less).

  The temperature ranges of 0 ° C. to + 70 ° C., −5 ° C. to + 85 ° C., and −40 ° C. to + 85 ° C. are typical temperature ranges that define the frequency temperature characteristics of the oscillators on the market. There has not been a temperature-compensated oscillator having a frequency deviation of -150 ppb or more and +150 ppb or less in a temperature range of not less than + 85 ° C or not less than -40 ° C and not more than + 85 ° C. That is, the oscillator 1 from which the actual measurement value at the point C in FIG. 6 (the actual measurement value in FIG. 7B) is obtained is a unique temperature-compensated oscillator unlike any other, and for example, OCXO is used. It can also be used for electronic devices that require such high frequency accuracy.

  According to the approximate curve in FIG. 6, the 19.2 MHz oscillator 1 whose compensation voltage sensitivity (compensation voltage sensitivity at the center voltage of the variable range of the temperature compensation voltage) is 42 ppm / V or more is −40 ° C. or more and + 85 ° C. or less. It can be said that the frequency deviation is -150 ppb or more and +150 ppb or less in the temperature range of. However, if the frequency variable sensitivity of the vibrating element 3 is too high, the variable range of the temperature compensation voltage becomes too narrow, the temperature compensation accuracy deteriorates, and the frequency deviation of the oscillator 1 may increase. Therefore, according to the approximation curve of FIG. 6, in order to make the frequency deviation of the oscillator 1 of 19.2 MHz in the temperature range of −40 ° C. to + 85 ° C. to −150 ppb to +150 ppb, the compensation voltage sensitivity (variable temperature compensation voltage) The compensation voltage sensitivity at the center voltage of the range) is preferably 47 ppm / V or less.

  By using a vibrating element having high frequency variable sensitivity, which has not been used in the conventional temperature-compensated oscillator, as the vibrating element 3, the oscillator 1 having a compensation voltage sensitivity of not less than 42 ppm / V and not more than 47 ppm / V can be realized. .

  Since the frequency variable sensitivity of the vibration element 3 increases in proportion to the size of the excitation electrodes 3a and 3b of the vibration element 3, it is possible to realize the vibration element 3 with high frequency variable sensitivity by increasing the excitation electrodes 3a and 3b. Can be. However, if the excitation electrodes 3a and 3b are too large, the vibrating element 3 becomes too large and hinders downsizing of the oscillator 1, and the frequency variable sensitivity of the vibrating element 3 becomes too high and the frequency temperature characteristic of the oscillator 1 becomes too high. In some cases, the size of the excitation electrodes 3a and 3b (the vibrating element 3) is preferably set to an appropriate size.

  Here, in the equivalent circuit of the vibrating element 3 shown in FIG. 8, the equivalent parallel capacitance C0 is determined by the area of the excitation electrodes 3a and 3b and the interval between the excitation electrodes 3a and 3b. As the equivalent parallel capacitance C0 increases, the equivalent series capacitance C1 increases. Therefore, there is a correlation between the equivalent series capacitance C1 and the compensation voltage sensitivity.

  FIG. 9 is a diagram plotting the compensation voltage sensitivity of the oscillator 1 using each of the four vibrating elements having a different equivalent series capacitance C1 as the vibrating element 3. In FIG. 9, the horizontal axis is the equivalent series capacitance C1 (unit: fF), and the vertical axis is the compensation voltage sensitivity (unit: ppm / V) at the center voltage of the variable range of the temperature compensation voltage. The solid line is a straight line that is linearly approximated to the plotted four points (D point, E point, F point, and G point). Assuming that the horizontal axis is x and the vertical axis is y, y = 6.793x + 31.662. Is a straight line that satisfies According to the approximation straight line in FIG. 9, the oscillator 1 using the vibrating element having the equivalent series capacitance C1 larger than 1.5 fF as the vibrating element 3 has the compensation voltage sensitivity (compensation voltage sensitivity at the center voltage of the variable range of the temperature compensation voltage). Is 42 ppm / V or more. The oscillator 1 using the vibrating element having an equivalent series capacitance C1 smaller than 2.5 fF as the vibrating element 3 has a compensation voltage sensitivity (compensation voltage sensitivity at the center voltage of the variable range of the temperature compensation voltage) of 47 ppm / V or less. It is.

  That is, by using a vibrating element whose equivalent series capacitance C1 is larger than 1.5 fF and smaller than 2.5 fF as the vibrating element 3, the compensation voltage sensitivity (compensation voltage sensitivity at the center voltage of the variable range of the temperature compensation voltage) is improved. The oscillator 1 of 42 ppm / V or more and 47 ppm / V or less and having a frequency deviation of -150 ppb or more and +150 ppb or less in a temperature range of -40 ° C or more and + 85 ° C or less can be realized.

  By the way, as the frequency of the oscillator 1 increases, a vibration element having a higher resonance frequency is used as the vibration element 3. The resonance frequency Fr is expressed by Expression (1) using the equivalent series capacitance C1 and the equivalent series inductance L1 in the equivalent circuit of FIG.

  As the vibrating element 3 has a higher resonance frequency, the vibrating reed becomes thinner and the mass becomes smaller, so that the equivalent series inductance L1 becomes smaller, and the interval between the excitation electrodes 3a, 3b becomes smaller, so that the equivalent series capacitance C1 becomes larger. Since the equivalent series capacitance C1 increases, the compensation voltage sensitivity of the oscillator 1 increases.

FIG. 10 is a diagram showing the relationship between the frequency of the oscillator 1 and the equivalent series capacitance C1, where the horizontal axis is the nominal frequency of the oscillator 1 (the resonance frequency of the vibrating element 3) (unit: MHz), and the vertical axis is the equivalent. This is the series capacitance C1 (unit: fF). In FIG. 10, points H, I, J, K, and L are equivalent in the oscillator 1 using each of the five vibration elements having the same excitation electrode size and different resonance frequency as the vibration element 3. It is a plot of the measured value of the series capacitance C1. The points M, N, and O plot actual measured values of the equivalent series capacitance C1 in the oscillator 1 using each of the three vibrating elements having the same excitation electrode size and different resonance frequency as the vibrating element 3. It was done. The vibrating elements corresponding to the H point, the I point, the J point, the K point, and the L point are larger in size and higher in frequency variable sensitivity than the vibrating elements corresponding to the M point, the N point, and the O point. The solid line is a curve obtained by approximating the plotted five points (H point, I point, J point, K point, and L point) with a quadratic polynomial. Assuming that the horizontal axis is x and the vertical axis is y, is a curve that satisfies the y = 0.00279x ² -0.05684x + 2.69481. The broken line is a straight line that is linearly approximated to the three plotted points (M point, N point, and O point). If the horizontal axis is x and the vertical axis is y, y = 0.06x + 0.55. It is a straight line that satisfies.

As described above, in the oscillator 1, if the equivalent series capacitance C1 is larger than 1.5 fF, it can be said that the compensation voltage sensitivity is 42 ppm / V or more, so that the points H, I, J, K, L, M The oscillator 1 corresponding to the points N, O has a compensation voltage sensitivity of 42 ppm / V or more. Further, based on the approximate straight line indicated by the broken line, the oscillator 1 whose equivalent series capacitance C1 satisfies C1 ≧ 0.06 × Fr + 0.55 (fF) when the resonance frequency of the vibrating element 3 is Fr has a compensation voltage sensitivity. Since it can be said that it is 42 ppm / V or more, it is possible to satisfy the frequency temperature characteristic in which the frequency deviation is −150 ppb or more and +150 ppb or less at −40 ° C. or more and + 85 ° C. or less. Further, from the approximate curve shown by the solid line, the equivalent series capacitance C1 (fF) when the resonance frequency of the vibrating element 3 is Fr (MHz) is C1 ≧ 0.00279 × Fr ² −0.05684 × Fr + 2.669481. Since it can be said that the oscillator 1 that satisfies the above condition has a compensation voltage sensitivity considerably higher than 42 ppm / V, it is easier to satisfy the frequency temperature characteristic of the frequency deviation of −150 ppb to +150 ppb at −40 ° C. or more and + 85 ° C. or less.

  As described above, in the 19.2 MHz oscillator 1, the compensation voltage sensitivity may be 47 ppm / or less (the equivalent series capacitance C1 is 2.5 fF or less) in order to satisfy the frequency deviation of −150 ppb or more and +150 ppb or less. Preferably, the upper limit of the compensation voltage sensitivity (equivalent series capacitance C1) differs according to the frequency of the oscillator 1. Therefore, it is desirable that the excitation electrodes 3a and 3b (the vibrating element 3) of the vibrating element 3 have an appropriate size according to the frequency of the oscillator 1.

In FIG. 10, the conditions of the oscillator 1 having excellent frequency temperature characteristics are defined by the relationship between the frequency of the oscillator 1 and the equivalent series capacitance C1, but the frequency of the oscillator 1 and the capacitance of the equivalent parallel capacitance C0 and the equivalent series capacitance C1 are defined. It can also be defined in relation to the ratio γ (= C0 / C1). FIG. 11 is a diagram showing the relationship between the frequency of the oscillator 1 and the capacitance ratio γ, where the horizontal axis represents the nominal frequency of the oscillator 1 (the resonance frequency of the vibrating element 3) (unit: MHz), and the vertical axis represents the capacitance ratio. γ. In FIG. 11, points P, Q, R, S, and T correspond to five vibrating elements corresponding to points H, I, J, K, and L in FIG. Is a plot of the actually measured value of the capacitance ratio γ in the oscillator 1 using the equation (1). The solid line is a curve obtained by approximating the plotted five points (P point, Q point, R point, S point, and T point) by a quadratic polynomial. Assuming that the horizontal axis is x and the vertical axis is y, is a curve that satisfies the y = 0.022x ² -4.969x + 417.929. From this approximate curve, the capacitance ratio γ (= C0 / C1) between the equivalent parallel capacitance C0 and the equivalent series capacitance C1 when the resonance frequency of the vibrating element 3 is Fr (MHz) is γ ≧ 0.022 × Fr ² It can be said that the oscillator 1 that satisfies −4.969 × Fr + 417.929 easily satisfies the frequency temperature characteristic of −150 ppb to +150 ppb at −40 ° C. to + 85 ° C.

[effect]
As described above, according to the present embodiment, by using the vibrating element 3 whose equivalent series capacitance C1 is larger than 1.5 fF or the vibrating element 3 whose compensation voltage sensitivity is 42 ppm / V or more, -40 ° C. or more It has the characteristic that the frequency deviation is -150 ppb or more and +150 ppb or less in the temperature range of + 85 ° C. or less, and it can be used for electronic devices that require high frequency accuracy such as OCXO. A new temperature-compensated oscillator 1 can be realized.

In particular, when the resonance frequency of the vibrating element is Fr (MHz), the equivalent series capacitance C1 (fF) satisfies C1 ≧ 0.00279 × Fr ² −0.05684 × Fr + 2.669481, or the equivalent parallel capacitance C0. By using the vibrating element 3 whose capacitance ratio γ (= C0 / C1) to the equivalent series capacitance C1 satisfies γ ≧ 0.022 × Fr ² −4.969 × Fr + 417.929, the compensation voltage sensitivity becomes higher than 42 ppm / V. Therefore, an oscillator having higher frequency accuracy can be realized.

  In the temperature compensation adjustment step S50 in FIG. 4, the frequency temperature characteristics of the oscillator 1 (including the frequency temperature characteristics of the vibrating element 3 and the temperature characteristics of the integrated circuit (IC) 2) are changed to the temperature (output voltage of the temperature sensor 50). Is approximated by an n-th order equation having the following equation, and temperature compensation data (first order compensation data,..., N-th order compensation data) corresponding to the approximation equation is generated. It is required to more accurately approximate the frequency temperature characteristics of the oscillator 1. Here, since the frequency temperature characteristic of the vibrating element 3 is dominant in the frequency temperature characteristic of the oscillator 1, the frequency temperature characteristic of the vibrating element 3 is more accurately approximated, in other words, the frequency temperature characteristic of the vibrating element 3 is reduced. It is desirable that the frequency deviation with respect to the approximate expression be small.

  For example, if the vibrating element 3 is an AT-cut vibrating element, its frequency temperature characteristic (solid line in FIG. 12) exhibits a cubic curve (the main order is 3) as shown in FIG. The frequency deviation dF / F of the vibrating element 3 with respect to the third-order or higher approximation formula (broken line in FIG. 12) of the frequency temperature characteristic of No. 3 is 0 ° C. or more and + 70 ° C. or less, -5 ° C. or more and + 85 ° C. It is desirable that the temperature be -150 ppb or higher and +150 ppb or lower at + 85 ° C or lower. In this way, in the temperature compensation adjustment step S50, even if the variation in the temperature characteristics of the integrated circuit (IC) 2 is taken into consideration, the temperature is 0 ° C or more and + 70 ° C or less, -5 ° C or more and + 85 ° C or less, or -40 ° C or more. Temperature compensation data for realizing the oscillator 1 having a frequency deviation of −150 ppb or more and +150 ppb or less at + 85 ° C. or less is easily generated. As a result, in step S70 of FIG. 4, if the frequency deviation is evaluated to be within the range of −150 ppb or more and +150 ppb or less, the probability of a non-defective product increases, and the yield can be improved.

  Since the frequency temperature characteristics of the vibrating element 3 change depending on parameters such as the positions and shapes of the excitation electrodes 3a and 3b and the shape and dimensions of the vibrating element 3, in the design stage of the vibrating element 3, for example, variations in characteristics during mass production may occur. By determining the parameter value so that no dip occurs in the frequency temperature characteristic even at the upper limit and the lower limit, it is possible to realize the vibrating element 3 in which the frequency deviation dF / F is −150 ppb or more and +150 ppb or less at −40 ° C. or more and + 85 ° C. or less. is there.

  Further, in the temperature compensation adjustment step S50, in order to further reflect the temperature characteristics of the integrated circuit (IC) 2 in the temperature compensation data generated, the number of temperatures for measuring the frequency may be increased, or the frequency of the oscillator 1 may be increased. It is also effective to approximate the temperature characteristics by a higher-order equation. For example, if the vibrating element 3 is an AT-cut vibrating element, it is desirable that the frequency be measured at a temperature of 10 points or more at −40 ° C. or more and + 85 ° C., and the frequency temperature characteristic of the oscillator 1 be approximated by a fifth-order or more equation . With this configuration, in the temperature compensation adjustment step, the oscillator 1 having a frequency temperature characteristic of −150 ppb or more and +150 ppb or less at −40 ° C. or more and + 85 ° C. or less taking into account the temperature characteristic of the integrated circuit (IC) 2 It becomes easier to generate temperature compensation data. As a result, the yield can be further improved.

  The oscillator 1 of the present embodiment described above is an oscillator (such as a VC-TCXO) having a temperature compensation function and a voltage control function (frequency control function), but has a temperature that does not have a voltage control function (frequency control function). It may be a compensated oscillator (TCXO or the like). Further, the above-described oscillator 1 of the present embodiment may be a voltage-controlled oscillator (such as a VCXO) having no temperature compensation function and having an AFC circuit 32 as a frequency control circuit.

2. Electronic Device FIG. 13 is a functional block diagram illustrating an example of a configuration of the electronic device according to the present embodiment. FIG. 14 is a diagram illustrating an example of the external appearance of a smartphone that is an example of the electronic apparatus according to the embodiment.

  The electronic device 300 of the present embodiment includes an oscillator 310, a CPU (Central Processing Unit) 320, an operation unit 330, a ROM (Read Only Memory) 340, a RAM (Random Access Memory) 350, a communication unit 360, and a display unit 370. It is configured. Note that the electronic device of the present embodiment may have a configuration in which some of the components (each unit) in FIG. 13 are omitted or changed, or other components are added.

  The oscillator 310 includes an integrated circuit (IC) 312 and a vibration element 313. The integrated circuit (IC) 312 oscillates the vibration element 313 to generate an oscillation signal. This oscillation signal is output from the external terminal of the oscillator 310 to the CPU 320.

  The CPU 320 performs various calculation processes and control processes using an oscillation signal input from the oscillator 310 as a clock signal according to a program stored in the ROM 340 or the like. More specifically, the CPU 320 performs various processes in accordance with an operation signal from the operation unit 330, a process for controlling the communication unit 360 to perform data communication with an external device, and a process for displaying various information on the display unit 370. And the like for transmitting the display signal.

  The operation unit 330 is an input device including an operation key, a button switch, and the like, and outputs an operation signal according to a user operation to the CPU 320.

  The ROM 340 stores programs, data, and the like for the CPU 320 to perform various calculation processes and control processes.

  The RAM 350 is used as a work area of the CPU 320, and temporarily stores programs and data read from the ROM 340, data input from the operation unit 330, calculation results executed by the CPU 320 according to various programs, and the like.

  The communication unit 360 performs various controls for establishing data communication between the CPU 320 and the external device.

  The display unit 370 is a display device including an LCD (Liquid Crystal Display) and displays various information based on a display signal input from the CPU 320. The display unit 370 may be provided with a touch panel functioning as the operation unit 330.

  By applying the above-described oscillator 1 of the present embodiment as the oscillator 310, for example, a highly reliable electronic device can be realized.

  Various electronic devices can be considered as the electronic device 300, for example, personal computers (for example, mobile personal computers, laptop personal computers, tablet personal computers), mobile terminals such as smartphones and mobile phones, and the like. Digital cameras, inkjet type ejection devices (eg, inkjet printers), storage area network devices such as routers and switches, local area network devices, mobile terminal base station devices, televisions, video cameras, video recorders, car navigation devices, real-time Clock device, pager, electronic organizer (including with communication function), electronic dictionary, calculator, electronic game machine, game controller, word processor, word processor Stations, video phones, TV monitors for security, electronic binoculars, POS terminals, medical equipment (for example, electronic thermometers, sphygmomanometers, blood glucose meters, electrocardiogram measuring devices, ultrasonic diagnostic devices, electronic endoscopes), fish finder, various measurements Examples include devices, instruments (for example, instruments for vehicles, aircraft, and ships), flight simulators, head mounted displays, motion traces, motion tracking, motion controllers, and PDRs (pedestrian position and orientation measurement).

  As an example of the electronic device 300 of the present embodiment, a terminal base station device or the like that performs wired or wireless communication with a terminal by using the oscillator 310 described above as a reference signal source or a variable voltage oscillator (VCO) or the like A transmission device that functions as a communication device. By applying, for example, the above-described oscillator 1 of the present embodiment as the oscillator 310, an electronic device 300 that is desired to have high frequency accuracy, high performance, and high reliability, which can be used for a communication base station, for example, can be provided. Can also be realized at low cost.

3. Moving Object FIG. 15 is a diagram (top view) illustrating an example of the moving object of the present embodiment. A moving object 400 shown in FIG. 15 includes an oscillator 410, controllers 420, 430, and 440 that perform various controls such as an engine system, a brake system, and a keyless entry system, a battery 450, and a backup battery 460. Note that the moving object of the present embodiment may have a configuration in which some of the components (each unit) in FIG. 15 are omitted, or other components are added.

  The oscillator 410 includes an unillustrated integrated circuit (IC) and a vibration element, and the integrated circuit (IC) oscillates the vibration element to generate an oscillation signal. This oscillation signal is output from an external terminal of the oscillator 410 to the controllers 420, 430, and 440, and is used, for example, as a clock signal.

  Battery 450 supplies power to oscillator 410 and controllers 420, 430, and 440. The backup battery 460 supplies power to the oscillator 410 and the controllers 420, 430, and 440 when the output voltage of the battery 450 drops below a threshold.

  By applying, for example, the oscillator 1 of the present embodiment described above as the oscillator 410, a highly reliable moving object can be realized.

  As the moving body 400, various moving bodies can be considered, and examples thereof include an automobile (including an electric vehicle), an aircraft such as a jet aircraft and a helicopter, a ship, a rocket, an artificial satellite, and the like.

  The present invention is not limited to this embodiment, and various modifications can be made within the scope of the present invention.

  The above-described embodiments and modifications are merely examples, and the present invention is not limited to these. For example, each embodiment and each modified example can be appropriately combined.

  The invention includes substantially the same configuration as the configuration described in the embodiment (for example, a configuration having the same function, method, and result, or a configuration having the same object and effect). Further, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. Further, the invention includes a configuration having the same operation and effect as the configuration described in the embodiment, or a configuration capable of achieving the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

1 oscillator, 2 integrated circuit (IC), 3 vibrating element, 3a, 3b excitation electrode, 4 package, 5 lid, 6 external terminal (external electrode), 7 bonding wire, 8 package, 8a base, 8b lid, 9 adhesive member Reference Signs List 10 oscillation circuit 11 electrode pad 12 connection member 20 output circuit 30 frequency adjustment circuit 32 AFC circuit 40 temperature compensation circuit 41-1 primary voltage generation circuit 41-n nth voltage generation circuit 42 Adder circuit, 50 temperature sensor, 60 regulator circuit, 70 storage unit, 72 non-volatile memory, 74 register, 80 serial interface (I / F) circuit, 300 electronic equipment, 310 oscillator, 312 integrated circuit (IC), 313 vibrating element , 320 CPU, 330 operation unit, 340 ROM, 350 R M, 360 communication unit, 370 display unit, 400 mobile, 410 oscillator, 420, 430 and 440 controllers, 450 battery, 460 backup battery

[Application Example 4]
The oscillator according to the above application example satisfies γ ≦ 0.022 × Fr ² −4.969 × Fr + 417.929, where γ is the capacitance ratio C0 / C1 between the equivalent parallel capacitance C0 and the equivalent series capacitance C1. Good.

According to this application example, by using a vibrating element having a high frequency variable sensitivity defined by the condition of γ ≦ 0.022 × Fr ² −4.969 × Fr + 417.929, an oscillator that is more excellent in frequency control than before is used. For example, it is possible to realize a temperature-compensated oscillator having a smaller frequency deviation than the conventional one.

In FIG. 10, the conditions of the oscillator 1 having excellent frequency temperature characteristics are defined by the relationship between the frequency of the oscillator 1 and the equivalent series capacitance C1, but the frequency of the oscillator 1 and the capacitance of the equivalent parallel capacitance C0 and the equivalent series capacitance C1 are defined. It can also be defined in relation to the ratio γ (= C0 / C1). FIG. 11 is a diagram showing the relationship between the frequency of the oscillator 1 and the capacitance ratio γ, where the horizontal axis represents the nominal frequency of the oscillator 1 (the resonance frequency of the vibrating element 3) (unit: MHz), and the vertical axis represents the capacitance ratio. γ. In FIG. 11, points P, Q, R, S, and T correspond to five vibrating elements corresponding to points H, I, J, K, and L in FIG. Is a plot of the actually measured value of the capacitance ratio γ in the oscillator 1 using the equation (1). The solid line is a curve obtained by approximating the plotted five points (P point, Q point, R point, S point, and T point) with a quadratic polynomial. Assuming that the horizontal axis is x and the vertical axis is y, is a curve that satisfies the y = 0.022x ² -4.969x + 417.929. From this approximate curve, the capacitance ratio γ (= C0 / C1) between the equivalent parallel capacitance C0 and the equivalent series capacitance C1 when the resonance frequency of the vibrating element 3 is Fr (MHz) is γ ≦ 0.022 × Fr ² It can be said that the oscillator 1 that satisfies −4.969 × Fr + 417.929 easily satisfies the frequency temperature characteristic of −150 ppb to +150 ppb at −40 ° C. to + 85 ° C.

In particular, when the resonance frequency of the vibrating element is Fr (MHz), the equivalent series capacitance C1 (fF) satisfies C1 ≧ 0.00279 × Fr ² −0.05684 × Fr + 2.669481, or the equivalent parallel capacitance C0. By using the vibrating element 3 whose capacitance ratio γ (= C0 / C1) to the equivalent series capacitance C1 satisfies γ ≦ 0.022 × Fr ² −4.969 × Fr + 417.929, the compensation voltage sensitivity becomes higher than 42 ppm / V. Therefore, an oscillator having higher frequency accuracy can be realized.

Claims (8)

Including a vibration element, an oscillation circuit and a frequency control circuit,
When the resonance frequency of the vibration element is Fr (MHz), the equivalent series capacitance C1 (fF) is
C1 ≧ 0.00279 × Fr ² −0.05684 × Fr + 2.669481
Meet the oscillator.   The oscillator according to claim 1, wherein the equivalent series capacitance C1 is larger than 1.5 fF. The frequency control circuit changes the oscillation frequency with respect to the input voltage,
3. The oscillator according to claim 1, wherein a change rate of a frequency with respect to the input voltage is 42 ppm / V or more. 4. When the capacitance ratio C0 / C1 between the equivalent parallel capacitance C0 and the equivalent series capacitance C1 is γ,
γ ≧ 0.022 × Fr ² −4.969 × Fr + 417.929
The oscillator according to any one of claims 1 to 3, which satisfies the following.   5. The oscillator according to claim 1, wherein a frequency deviation is in a range from −150 ppb to +150 ppb in a temperature range from −40 ° C. to + 85 ° C.   The oscillator according to any one of claims 1 to 5, wherein a frequency deviation of the vibrating element with respect to a third-order or more approximate expression of a frequency temperature characteristic of the vibrating element is equal to or more than -150 ppb and equal to or less than +150 ppb.   An electronic device comprising the oscillator according to claim 1.   A moving object comprising the oscillator according to claim 1.

Images