Circuit device and oscillator

Abstract

To provide a circuit device and the like capable of realizing both proper temperature compensation of the oscillation frequency within a wide temperature range and control of the oscillation frequency with a frequency control voltage.SOLUTION: A circuit device 20 includes: an oscillation circuit 30 that oscillates a vibrator 10; a temperature compensation circuit 40 that outputs a temperature compensation voltage VCP for temperature compensation of the oscillation frequency of the oscillation circuit 30 on the basis of temperature detection results of a temperature sensor 48; and a frequency control circuit 50 that outputs a frequency control voltage VFC for the oscillation frequency. The oscillation circuit 30 includes: a first variable capacitance circuit 31 with a capacitance having positive change characteristics to a capacitance control voltage; and a second variable capacitance circuit with a capacitance having negative change characteristics to the capacitance control voltage. The temperature compensation circuit 40 supplies the temperature compensation voltage VCP to the first variable capacitance circuit 31 as the capacitance control voltage. The frequency control circuit 50 supplies the frequency control voltage VFC to the second variable capacitance circuit 32 as the capacitance control voltage.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a circuit device, an oscillator, and the like. [Background technology]

[0002] Circuit devices that oscillate a resonator such as a quartz crystal resonator include a variable capacitance circuit for adjusting the oscillation frequency. For example, Patent Document 1 discloses a voltage-controlled oscillator including an oscillator unit that oscillates the resonator, first and second variable capacitance circuits, first and second temperature-compensated voltage generation circuits, and a frequency-controlled voltage generation circuit. In this voltage-controlled oscillator, the first temperature-compensated voltage generation circuit generates a first temperature-compensated voltage that controls the capacitance of the first variable capacitance circuit based on a detection signal from a temperature sensor. The frequency-controlled voltage generation circuit generates a frequency-controlled voltage that controls the capacitance of the second variable capacitance circuit. The second temperature-compensated voltage correction circuit generates a second temperature-compensated voltage that corrects for changes in the temperature compensation amount caused by the frequency-controlled voltage. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2017-112557 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the voltage-capacitance characteristics of the variable capacitance circuits in the voltage-controlled oscillator of Patent Document 1 were all positive, which made it difficult to achieve both appropriate temperature compensation of the oscillation frequency over a wide temperature range and control of the oscillation frequency by the frequency control voltage. [Means for solving the problem]

[0005] One aspect of the present disclosure relates to a circuit device including an oscillation circuit that oscillates a vibrator, a temperature compensation circuit that outputs a temperature compensation voltage that temperature-compensates the oscillation frequency of the oscillation circuit based on the temperature detection result of a temperature sensor, and a frequency control circuit that outputs a frequency control voltage of the oscillation frequency, wherein the oscillation circuit includes a first variable capacitance circuit having a positive characteristic of change in capacitance with respect to the capacitance control voltage, and a second variable capacitance circuit having a negative characteristic of change in capacitance with respect to the capacitance control voltage, wherein the temperature compensation circuit supplies the temperature compensation voltage to the first variable capacitance circuit as the capacitance control voltage, and the frequency control circuit supplies the frequency control voltage to the second variable capacitance circuit as the capacitance control voltage.

[0006] Another aspect of the present disclosure relates to an oscillator including a vibrator and a circuit device, the circuit device including an oscillation circuit that causes the vibrator to oscillate, a temperature compensation circuit that outputs a temperature compensation voltage that temperature-compensates the oscillation frequency of the oscillation circuit based on a temperature detection result of a temperature sensor, and a frequency control circuit that outputs a frequency control voltage of the oscillation frequency, the oscillation circuit including a first variable capacitance circuit having a positive characteristic of change in capacitance with respect to a capacitance control voltage, and a second variable capacitance circuit having a negative characteristic of change in capacitance with respect to the capacitance control voltage, the temperature compensation circuit supplies the temperature compensation voltage to the first variable capacitance circuit as the capacitance control voltage, and the frequency control circuit supplies the frequency control voltage to the second variable capacitance circuit as the capacitance control voltage. [Brief explanation of the drawings]

[0007] [Figure 1] 1 shows an example of the configuration of a circuit device and an oscillator according to the present embodiment. [Figure 2] 3 shows a detailed configuration example of the circuit device and oscillator of the present embodiment. [Figure 3] FIG. 4 is a graph showing the positive voltage-capacitance characteristic of the first variable capacitance circuit. [Figure 4] FIG. 10 is a diagram illustrating the negative voltage-capacitance characteristic of the second variable capacitance circuit. [Figure 5] An example of the frequency-temperature characteristics of a vibrator. [Figure 6]10 shows an example of the temperature characteristics of the temperature-compensated voltage when a second variable capacitance circuit with negative characteristics is used. [Figure 7] 10 is an example of the temperature characteristic of the temperature-compensated voltage when a first variable capacitance circuit with a positive characteristic is used. [Figure 8] First example of oscillator circuit configuration. [Figure 9] 2. Second example of oscillator circuit configuration. [Figure 10] FIG. 3 is an explanatory diagram of a first variable capacitance circuit. [Figure 11] FIG. 4 is a diagram illustrating the voltage-capacitance characteristics of the first variable capacitance circuit. [Figure 12] FIG. 4 is a diagram illustrating the voltage-capacitance characteristics of the first variable capacitance circuit. [Figure 13] FIG. 4 is an explanatory diagram of a second variable capacitance circuit. [Figure 14] FIG. 4 is a diagram illustrating the voltage-capacitance characteristics of a second variable capacitance circuit. [Figure 15] FIG. 4 is a diagram illustrating the voltage-capacitance characteristics of a second variable capacitance circuit. [Figure 16] An example of a temperature compensation circuit configuration. [Figure 17] An example of a Class A amplifier circuit configuration. [Figure 18] An example of the configuration of an AB class amplifier circuit. [Figure 19] An example of a frequency control circuit configuration. [Figure 20] FIG. 3 is an explanatory diagram of the magnitude relationship between the capacitances of a first variable capacitance circuit and a second variable capacitance circuit. [Figure 21] FIG. 3 is an explanatory diagram of the magnitude relationship between the capacitances of a first variable capacitance circuit and a second variable capacitance circuit. [Figure 22] First example of oscillator structure. [Figure 23] Second example of oscillator structure. DETAILED DESCRIPTION OF THE INVENTION

[0008] The present embodiment will be described below. Note that the present embodiment described below does not unduly limit the content of the claims. Furthermore, not all of the configurations described in the present embodiment are necessarily essential components.

[0009] 1.Circuit device 1 shows an example of the configuration of a circuit device 20 according to this embodiment. The circuit device 20 according to this embodiment includes an oscillation circuit 30, a temperature compensation circuit 40, and a frequency control circuit 50. The oscillator 4 according to this embodiment includes a resonator 10 and the circuit device 20. The resonator 10 is electrically connected to the circuit device 20.

[0010] The vibrator 10 is an element that generates mechanical vibrations in response to an electrical signal. The vibrator 10 can be realized by a vibrating piece such as a quartz crystal vibrating piece. For example, the vibrator 10 can be realized by a quartz crystal vibrating piece that vibrates in a thickness-shear mode, such as an AT-cut or SC-cut cut angle, a tuning-fork type quartz crystal vibrating piece, or a double-ended tuning-fork type quartz crystal vibrating piece. For example, the vibrator 10 may be a vibrator built into a temperature-compensated crystal oscillator (TCXO) that does not have a thermostatic oven, or a vibrator built into an oven-controlled crystal oscillator (OCXO) that has a thermostatic oven. Note that the vibrator 10 of this embodiment can also be realized by various vibrating pieces, such as a vibrating piece other than a thickness-shear type, tuning-fork type, or double-ended tuning-fork type, or a piezoelectric vibrating piece made of a material other than quartz. For example, the vibrator 10 can be a surface acoustic wave (SAW) resonator or a micro-electromechanical systems (MEMS) resonator, which is a silicon vibrator formed using a silicon substrate.

[0011] The circuit device 20 is an integrated circuit device known as an IC (Integrated Circuit). For example, the circuit device 20 is an IC manufactured by a semiconductor process, and is a semiconductor chip in which circuit elements are formed on a semiconductor substrate. In FIG. 1, the circuit device 20 includes an oscillation circuit 30, a temperature compensation circuit 40, and a frequency control circuit 50, and may also include a temperature sensor 48. The oscillation circuit 30 includes a first variable capacitance circuit 31 and a second variable capacitance circuit 32.

[0012] The oscillator circuit 30 is a circuit that oscillates the resonator 10. For example, the oscillator circuit 30 generates an oscillation signal by oscillating the resonator 10. The oscillation signal is an oscillation clock signal. For example, the oscillator circuit 30 can be realized by an oscillation drive circuit electrically connected to one end and the other end of the resonator 10, and passive elements such as capacitors and resistors. The drive circuit can be realized by, for example, a CMOS inverter circuit or a bipolar transistor. The drive circuit is the core circuit of the oscillator circuit 30, and the drive circuit drives the resonator 10 with voltage or current, causing it to oscillate. Various types of oscillator circuits, such as inverter type, Pierce type, Colpitts type, or Hartley type, can be used as the oscillator circuit 30. Note that the connection in this embodiment is an electrical connection. An electrical connection is a connection that allows electrical signals to be transmitted, and is a connection that enables information to be transmitted via an electrical signal. The electrical connection may also be a connection via passive elements, etc.

[0013] The oscillator circuit 30 also includes a first variable capacitance circuit 31 and a second variable capacitance circuit 32. The first variable capacitance circuit 31 and the second variable capacitance circuit 32 are circuits that change the capacitance at least at one end or the other end of the vibrator 10, for example, and the oscillation frequency of the oscillator circuit 30 can be adjusted by adjusting the capacitance of the first variable capacitance circuit 31 and the second variable capacitance circuit 32. The first variable capacitance circuit 31 and the second variable capacitance circuit 32 can be realized by variable capacitance elements such as varactors. For example, each of the first variable capacitance circuit 31 and the second variable capacitance circuit 32 is configured by at least one variable capacitance element.

[0014] The temperature compensation circuit 40 is a circuit that performs temperature compensation for the oscillation frequency of the oscillation circuit 30. For example, the temperature compensation circuit 40 outputs a temperature compensation voltage VCP that temperature-compensates the oscillation frequency of the oscillation circuit 30 based on the temperature detection result of the temperature sensor 48. The temperature detection result is a temperature detection signal, such as a temperature detection voltage. Temperature compensation is a process that suppresses and compensates for fluctuations in the oscillation frequency due to temperature fluctuations, for example. In other words, the temperature compensation circuit 40 performs temperature compensation for the oscillation frequency of the oscillation circuit 30 so that the oscillation frequency remains constant even when temperature fluctuations occur.

[0015] The temperature sensor 48 is a sensor that detects temperature. Specifically, the temperature sensor 48 outputs a temperature-dependent voltage that changes depending on the environmental temperature as a temperature detection voltage. For example, the temperature sensor 48 generates the temperature detection voltage, which is a temperature detection signal, using a circuit element that has temperature dependency. Specifically, the temperature sensor 48 outputs a temperature detection voltage that changes depending on temperature, for example, by using the temperature dependency of the forward voltage of a PN junction. Note that while FIG. 1 shows the temperature sensor 48 provided in the circuit device 20, it is also possible to modify the circuit device 20 so that the temperature sensor 48 is provided externally to the circuit device 20 and the temperature compensation circuit 40 performs temperature compensation based on a temperature detection signal, such as a temperature detection voltage, input from the outside. It is also possible to modify the circuit device 20 so that the temperature sensor 48 uses a digital temperature sensor circuit. In this case, the temperature detection data is D / A converted to generate the temperature detection voltage.

[0016] The frequency control circuit 50 is a circuit that controls the oscillation frequency of the oscillation circuit 30. Specifically, the frequency control circuit 50 outputs a frequency control voltage VFC of the oscillation frequency. For example, the frequency control circuit 50 generates and outputs the frequency control voltage VFC based on a control voltage input from an external device. Alternatively, the frequency control circuit 50 may generate the frequency control voltage VFC based on a control voltage obtained by D / A converting control data input from an external device. By providing such a frequency control circuit 50, it becomes possible to realize control that sets the oscillation frequency of the oscillation circuit 30 to a desired frequency. For example, by providing the temperature compensation circuit 40 and the frequency control circuit 50, it becomes possible to set the oscillation frequency to a desired frequency according to the external control voltage and control data while performing temperature compensation for the oscillation frequency.

[0017] The oscillator circuit 30 includes a first variable capacitance circuit 31 having a positive characteristic of capacitance change with respect to the capacitance control voltage, and a second variable capacitance circuit 32 having a negative characteristic of capacitance change with respect to the capacitance control voltage. For example, the first variable capacitance circuit 31 and the second variable capacitance circuit 32 have different polarities of the positive and negative characteristic of the capacitance change with respect to the capacitance control voltage. A positive capacitance change is a change in which the capacitance increases as the capacitance control voltage increases, as will be described later in FIG. 3. A negative capacitance change is a change in which the capacitance decreases as the capacitance control voltage increases, as will be described later in FIG. 4. The capacitance can also be referred to as a capacitance value.

[0018] 1 , in this embodiment, the temperature compensation circuit 40 supplies the temperature compensation voltage VCP as a capacitance control voltage to the first variable capacitance circuit 31. The frequency control circuit 50 supplies the frequency control voltage VFC as a capacitance control voltage to the second variable capacitance circuit 32. Because the first variable capacitance circuit 31 is a variable capacitance circuit with a positive capacitance characteristic, when the temperature compensation voltage VCP from the temperature compensation circuit 40 increases, the capacitance of the first variable capacitance circuit 31 increases, and when the temperature compensation voltage VCP decreases, the capacitance of the first variable capacitance circuit 31 decreases. Because the second variable capacitance circuit 32 is a variable capacitance circuit with a negative capacitance characteristic, when the frequency control voltage VFC from the frequency control circuit 50 increases, the capacitance of the second variable capacitance circuit 32 decreases, and when the frequency control voltage VFC decreases, the capacitance of the second variable capacitance circuit 32 increases. By providing the first variable capacitance circuit 31 with a positive characteristic, to which the temperature-compensated voltage VCP from the temperature compensation circuit 40 is supplied as a capacitance control voltage, in the oscillator circuit 30, the capacitance of the first variable capacitance circuit 31 increases as the temperature rises, thereby decreasing the oscillation frequency of the oscillator circuit 30. As a result, when the oscillation frequency of the resonator 10 increases in a high-temperature region, the capacitance of the first variable capacitance circuit 31 increases, thereby achieving temperature compensation that offsets the increase in the oscillation frequency. Furthermore, providing the first variable capacitance circuit 31 with a positive characteristic in the oscillator circuit 30 also makes it possible to use, for example, a class A amplifier circuit as the output amplifier for the temperature-compensated voltage VCP of the temperature compensation circuit 40. Therefore, proper temperature compensation of the oscillation frequency over a wide temperature range is possible while achieving a smaller circuit size compared to when a class AB amplifier circuit is provided as the output amplifier. Furthermore, by providing the oscillator circuit 30 with the second variable capacitance circuit 32 having a negative characteristic to which the frequency control voltage VFC from the frequency control circuit 50 is supplied as a capacitance control voltage, when the frequency control voltage VFC increases, the capacitance of the second variable capacitance circuit 32 decreases, and the oscillation frequency of the oscillator circuit 30 increases. Therefore, the oscillation frequency can be variably controlled by the frequency control voltage VFC. As a result, it becomes possible to control the oscillation frequency based on the frequency control voltage VFC while achieving appropriate temperature compensation of the oscillation frequency over a wide temperature range by the temperature compensation circuit 40.For example, since it is not necessary to provide an amplifier circuit in the frequency control circuit 50, the circuit size can be reduced.

[0019] FIG. 2 shows a detailed configuration example of the circuit device 20 and oscillator 4 of this embodiment. In FIG. 2, the circuit device 20 includes an oscillation circuit 30, a temperature compensation circuit 40, a temperature sensor 48, a frequency control circuit 50, a logic circuit 60, a nonvolatile memory 70, an output circuit 80, and a power supply circuit 90. The oscillator 4 also includes a resonator 10 and the circuit device 20. The resonator 10 is electrically connected to the circuit device 20. For example, the resonator 10 and the circuit device 20 are electrically connected using internal wiring, bonding wires, metal bumps, or the like of a package that houses the resonator 10 and the circuit device 20. Note that the circuit device 20 and the oscillator 4 are not limited to the configuration shown in FIG. 2, and various modifications are possible, such as omitting some of the components, adding other components, or replacing some of the components with other components.

[0020] The circuit device 20 also includes pads PVDD, PGND, PX1, PX2, PVC, and PCK. The pads are terminals of the circuit device 20, which is a semiconductor chip. For example, in the pad area, a metal layer is exposed from a passivation film, which is an insulating layer, and this exposed metal layer forms the pads, which are terminals of the circuit device 20. The pads PVDD and PGND are a power pad and a ground pad, respectively. A power supply voltage VDD from an external power supply device is supplied to the pad PVDD. The pad PGND is a pad to which a ground voltage GND is supplied. GND can also be called VSS, and the ground voltage is, for example, the ground potential. In this embodiment, the ground is appropriately referred to as GND. For example, VDD corresponds to a high-potential power supply, and GND corresponds to a low-potential power supply. The pads PX1 and PX2 are pads for connecting the resonator 10. The pad PVC is a pad for inputting a control voltage VC, and the pad PCK is a pad for outputting a clock signal CK. The pads PVDD, PGND, PVC, and PCK are electrically connected to terminals TVDD, TGND, TVC, and TCK, respectively, which are external terminals for external connection of the oscillator 4. For example, each of these pads and each terminal is electrically connected using internal wiring of the package, bonding wires, metal bumps, or the like.

[0021] The oscillator circuit 30 is electrically connected to the vibrator 10 via pads PX1 and PX2. The pads PX1 and PX2 are pads for connecting the vibrator. A drive circuit for oscillation of the oscillator circuit 30 is provided between the pads PX1 and PX2. The oscillator circuit 30 includes a first variable capacitance circuit 31 and a second variable capacitance circuit 32. The first variable capacitance circuit 31 and the second variable capacitance circuit 32 are electrically connected to at least one of the pads PX1 and PX2, so that the load capacitance of the oscillator circuit 30 can be variably adjusted.

[0022] The temperature compensation circuit 40 performs analog temperature compensation using, for example, polynomial approximation. For example, when the temperature compensation voltage VCP that compensates for the frequency-temperature characteristics of the vibrator 10 is approximated by a polynomial, the temperature compensation circuit 40 performs analog temperature compensation based on coefficient information of the polynomial. Analog temperature compensation is temperature compensation achieved by, for example, adding analog signals such as current signals and voltage signals. For example, when the temperature compensation voltage VCP is approximated by a high-order polynomial, the zeroth-order coefficient, first-order coefficient, and higher-order coefficient of the polynomial are stored as zeroth-order correction data, first-order correction data, and higher-order correction data, respectively, in a storage unit realized by, for example, the nonvolatile memory 70. The high-order coefficients are, for example, coefficients of orders higher than first order, and the high-order correction data are correction data corresponding to the higher-order coefficients. For example, when the temperature-compensated voltage VCP is approximated by a third-order polynomial, the zeroth-order coefficient, first-order coefficient, second-order coefficient, and third-order coefficient of the polynomial are stored in a storage unit as zeroth-order correction data, first-order correction data, second-order correction data, and third-order correction data. The temperature compensation circuit 40 then performs temperature compensation based on the zeroth-order correction data to the third-order correction data. In this case, the second-order correction data and temperature compensation based on the second-order correction data may be omitted. For example, when the temperature-compensated voltage VCP is approximated by a fifth-order polynomial, the zeroth-order coefficient, first-order coefficient, second-order coefficient, third-order coefficient, fourth-order coefficient, and fifth-order coefficient of the polynomial are stored in a storage unit as zeroth-order correction data, first-order correction data, second-order correction data, third-order correction data, fourth-order correction data, and fifth-order correction data. The temperature compensation circuit 40 then performs temperature compensation based on the zeroth-order correction data to the fifth-order correction data. In this case, the second-order correction data or fourth-order correction data, or temperature compensation based on the second-order correction data or fourth-order correction data may be omitted. The degree of polynomial approximation may be any, and for example, polynomial approximation of a degree greater than 5 may be performed. The temperature sensor 48 may also perform zero-order correction.

[0023] An external control voltage VC is input to the frequency control circuit 50. For example, the control voltage VC from an external system implemented by a microcomputer or various ICs is input to the frequency control circuit 50 via the terminal TVC and the pad PVC. As an example, the oscillator circuit 30 of the circuit device 20 functions as a voltage-controlled oscillator, and a PLL feedback loop is formed by the external system. The frequency control circuit 50 then outputs a frequency control voltage VFC corresponding to the external control voltage VC. For example, the frequency control circuit 50 outputs a frequency control voltage VFC obtained by gain-adjusting the control voltage VC. Note that digital control data may be input to the circuit device 20 via an interface circuit (not shown), and the control data may be D / A converted to form a control voltage VC, which is then input to the frequency control circuit 50.

[0024] The logic circuit 60 is a control circuit that performs various control processes. For example, the logic circuit 60 performs overall control of the circuit device 20 and controls the operation sequence of the circuit device 20. The logic circuit 60 also performs various processes for controlling the oscillator circuit 30, controls the temperature sensor 48, the output circuit 80, or the power supply circuit 90, and controls the reading and writing of information from and to the non-volatile memory 70. The logic circuit 60 can be realized by an ASIC (Application Specific Integrated Circuit) circuit that is automatically placed and routed using a gate array or the like.

[0025] The nonvolatile memory 70 is a memory that retains information even without power supply. For example, the nonvolatile memory 70 is a memory that can retain information even without power supply and is rewritable. The nonvolatile memory 70 stores various information necessary for the operation of the circuit device 20. The nonvolatile memory 70 can be realized by an EEPROM (Electrically Erasable Programmable Read-Only Memory) realized by a FAMOS memory (Floating gate Avalanche injection MOS memory) or a MONOS memory (Metal-Oxide-Nitride-Oxide-Silicon memory). The nonvolatile memory 70 stores correction data such as primary correction data and higher-order correction data used for temperature compensation of the temperature compensation circuit 40.

[0026] The output circuit 80 outputs a clock signal CK based on the oscillation signal of the oscillation circuit 30. For example, the output circuit 80 buffers the oscillation signal, which is the oscillation clock signal from the oscillation circuit 30, and outputs it to the pad PCK as a clock signal CK. This clock signal CK is then output to the outside via the clock output terminal TCK of the oscillator 4. For example, the output circuit 80 outputs the clock signal CK in a single-ended CMOS signal format. Note that the output circuit 80 may also output the clock signal CK in a signal format other than CMOS. Furthermore, a clock signal generation circuit such as a PLL circuit that generates a clock signal CK with a frequency that is multiplied by the frequency of the oscillation signal may be provided downstream of the oscillation circuit 30, and the output circuit 80 may buffer and output the clock signal CK generated by this clock signal generation circuit.

[0027] The power supply circuit 90 receives a power supply voltage VDD from the pad PVDD and a ground voltage GND from the pad PGND, and supplies various power supply voltages for the internal circuits of the circuit device 20 to the internal circuits. For example, the power supply circuit 90 supplies a regulated power supply voltage obtained by regulating the power supply voltage VDD to each circuit of the circuit device 20, such as the oscillator circuit 30.

[0028] Fig. 3 is an explanatory diagram of the positive voltage-capacitance characteristic of the first variable capacitance circuit 31, and Fig. 4 is an explanatory diagram of the negative voltage-capacitance characteristic of the second variable capacitance circuit 32. The voltage-capacitance characteristic is the characteristic of the capacitance C relative to the capacitance control voltage VCC. Note that Figs. 3 and 4 show the voltage-capacitance characteristic schematically, and in reality, the characteristic is not a linear characteristic as shown in Figs. 3 and 4, but rather has an inflection point where the slope is maximum near the center of the change range.

[0029] As shown in Fig. 3, a temperature-compensated voltage VCP is input to the first variable capacitance circuit 31 as the capacitance control voltage VCC. In the positive voltage-capacitance characteristic of the first variable capacitance circuit 31, when the temperature-compensated voltage VCP increases, the capacitance C increases, which causes the oscillation frequency f of the oscillator circuit 30 to decrease. On the other hand, as shown in Fig. 4, a frequency-control voltage VFC is input to the second variable capacitance circuit 32 as the capacitance control voltage VCC. In the negative voltage-capacitance characteristic of the second variable capacitance circuit 32, when the frequency control voltage VFC increases, the capacitance C decreases, which causes the oscillation frequency f to increase.

[0030] FIG. 5 shows the frequency-temperature characteristics of the resonator 10. Specifically, this is the frequency-temperature characteristics of the resonator 10 made of, for example, an AT-cut quartz crystal. As shown in FIG. 5, the resonator 10 has a frequency-temperature characteristic that is approximated by a cubic curve. When adjusting the capacitance of such a resonator 10 using the second variable capacitance circuit 32 with a negative voltage-capacitance characteristic, the temperature compensation circuit 40 must output a temperature-compensated voltage VCP with a temperature characteristic such as that shown in FIG. 6. In this way, when the oscillation frequency of the resonator 10 increases in the high-temperature range as shown at A1 in FIG. 5, the temperature-compensated voltage VCP output from the temperature compensation circuit 40 decreases as shown at A2 in FIG. 6. This increases the capacitance of the second variable capacitance circuit 32 with a negative voltage-capacitance characteristic, offsetting the increase in the oscillation frequency of the resonator 10, thereby achieving temperature compensation that keeps the oscillation frequency constant.

[0031] However, in order to sufficiently reduce the temperature compensation voltage VCP in the high temperature range indicated by A2 in Fig. 6, it is necessary to widen the operating range on the low voltage side of the output amplifier of the temperature compensation circuit 40. For this reason, it is difficult to widen the operating range on the low voltage side with an amplifier circuit that operates in class A as shown in Fig. 17 (to be described later) as the output amplifier of the temperature compensation circuit 40, and it is necessary to use an amplifier circuit that operates in class AB as shown in Fig. 18 (to be described later), which complicates the circuit and increases the circuit size.

[0032] On the other hand, when adjusting the capacitance of the resonator 10 using the first variable capacitance circuit 31 with a positive voltage-capacitance characteristic, the temperature compensation circuit 40 may output a temperature compensation voltage VCP with a temperature characteristic such as that shown in Fig. 7. In this way, when the oscillation frequency of the resonator 10 rises in the high temperature range as shown at A1 in Fig. 5, the temperature compensation voltage VCP output from the temperature compensation circuit 40 increases as shown at A3 in Fig. 7. This increases the capacitance of the first variable capacitance circuit 31 with a positive voltage characteristic, offsetting the rise in the oscillation frequency of the resonator 10, thereby achieving temperature compensation that keeps the oscillation frequency constant.

[0033] In this case, in the high temperature range indicated by A3 in Fig. 7, the temperature compensation circuit 40 needs to expand the operating range on the high voltage side of its output amplifier in order to output a high temperature compensation voltage VCP. In this regard, even in the class A operation amplifier circuit shown in Fig. 17 (described later), if the P-type drive transistor constituting the output section is sufficiently turned on, it is possible to properly output a high temperature compensation voltage VCP such as that indicated by A3 in Fig. 7. Therefore, it is no longer necessary to use a class AB operation amplifier circuit such as that shown in Fig. 18 as the output amplifier of the temperature compensation circuit 40, making it possible to reduce the size and simplify the circuit.

[0034] As described above, the temperature compensation circuit 40 of this embodiment can include a class-A operation amplifier circuit that outputs a temperature-compensated voltage VCP. The class-A operation amplifier circuit includes, for example, a differential section having a differential input and an output section connected to the differential section, and the output section has a P-type drive transistor and a current source transistor connected in series between a high-potential power supply node and a low-potential power supply node. This configuration enables proper temperature compensation of the oscillation frequency over a wide temperature range to be achieved by the temperature compensation circuit 40 including a class-A operation amplifier circuit, which has a smaller circuit scale and a simpler configuration than a class-AB operation amplifier circuit, making it possible to achieve both proper temperature compensation and a smaller circuit size.

[0035] For example, the resonator 10 has a frequency-temperature characteristic that is approximated by a cubic curve as shown in Fig. 5. For example, the resonator 10 has a frequency-temperature characteristic that is approximated by a polynomial such as a cubic polynomial. In the resonator 10, in an untemperature-compensated state as shown in Fig. 5, the oscillation frequency fh at the upper limit of the operating temperature range shown in A1 is greater than the maximum value fa of the oscillation frequency shown in A4. The operating temperature range is a temperature range in which the oscillator 4 and the circuit device 20 can meet the specified characteristics.

[0036] For example, in the third-order frequency-temperature characteristic of the resonator 10 shown in FIG. 5, the oscillation frequency reaches a maximum value fa at temperature Ta as shown in A4, and reaches a minimum value fb at temperature Tb as shown in A5. The third-order frequency-temperature characteristic of the resonator 10 has an inflection point between temperatures Ta and Tb, for example, around 25°C. Therefore, the temperature range on the high-side of the operating temperature range is wider than the temperature range on the low-side. For example, when the operating temperature range is -40°C to 125°C, the temperature range on the high-side is 25°C to 125°C, which is wider than the temperature range on the low-side, -40°C to 25°C. The same is true when the operating temperature range is -40°C to 100°C. The oscillation frequency fh shown in A1 of FIG. 5 is the oscillation frequency at the upper limit of the operating temperature range, for example, the oscillation frequency at 125°C to 100°C. Therefore, in FIG. 5, the oscillation frequency fh at the upper limit of the operating temperature range is greater than the maximum value fa of the oscillation frequency. In this way, in vibrator 10 in which the oscillation frequency fh at the upper limit of the operating temperature range is greater than the maximum value fa of the oscillation frequency, the temperature range on the high temperature side is wider than the temperature range on the low temperature side.

[0037] Therefore, if the second variable capacitance circuit 32 with negative characteristic is used as the variable capacitance circuit to which the temperature compensation voltage VCP is input, the operating range on the low voltage side of the output amplifier of the temperature compensation circuit 40 must be widened in order to sufficiently reduce the temperature compensation voltage VCP at the upper limit of the operating temperature range, as shown at A2 in FIG. 6, and an amplifier circuit with class AB operation is required. In contrast, in this embodiment, the first variable capacitance circuit 31 with positive characteristic is used as the variable capacitance circuit to which the temperature compensation voltage VCP is input. Therefore, even if an amplifier circuit with class A operation is used as the output amplifier of the temperature compensation circuit 40, it is possible to sufficiently increase the temperature compensation voltage VCP at the upper limit of the operating temperature range, as shown at A3 in FIG. 7, making it possible to achieve both appropriate temperature compensation and a small circuit size.

[0038] 2. Oscillator circuit Next, the oscillator circuit 30 will be described in detail. FIG. 8 shows a first configuration example of the oscillator circuit 30. The oscillator circuit 30 in FIG. 8 includes a drive circuit DV, a resistor RA, a first variable capacitance circuit 31, and a second variable capacitance circuit 32. The oscillator circuit 30 may also include a capacitor CB5 provided between the supply node of the temperature compensation voltage VCP and a low-potential power supply node, and a capacitor CB6 provided between the supply node of the frequency control voltage VFC and the low-potential power supply node. The low-potential power supply node is, for example, a ground node. In the drive circuit DV, one end of the vibrator 10 is connected to node N1, which is its input node, via pad PX1, and the other end of the vibrator 10 is connected to node N2, which is its output node, via pad PX2. Resistor RA, which serves as a feedback element from the output to the input of the drive circuit DV, has one end connected to node N1 and the other end connected to node N2. 8, the first variable capacitance circuit 31 and the second variable capacitance circuit 32 are provided at both a node N1 to which one end of the vibrator 10 is connected via a pad PX1 and a node N2 to which the other end of the vibrator 10 is connected via a pad PX2. However, the first variable capacitance circuit 31 and the second variable capacitance circuit 32 may be provided at only one of the nodes N1 and N2.

[0039] In Fig. 8, the first variable capacitance circuit 31 is composed of a transistor TR1, and the second variable capacitance circuit 32 is composed of a transistor TR2. The transistors TR1 and TR2 are MOS (Metal Oxide Semiconductor) variable capacitance elements, also known as MOS varactors. In Fig. 8, the first variable capacitance circuit 31 and the second variable capacitance circuit 32 are composed of N-type transistors TR1 and TR2, respectively. A MOS-type variable capacitance element is a capacitance element in which the source and drain of a MOS transistor are short-circuited, and the capacitance generated between the short-circuited source and drain and the gate is variably controlled by a capacitance control voltage.

[0040] Note that the following description will mainly take as an example a case where each of the first variable capacitance circuit 31 and the second variable capacitance circuit 32 is configured with a single transistor that is a MOS-type variable capacitance element, but they may also be configured with two or more transistors connected in parallel. A modified embodiment is also possible in which P-type transistors are used as the transistors that make up the first variable capacitance circuit 31 and the second variable capacitance circuit 32. The following description will mainly take as an example the configurations of the first variable capacitance circuit 31 and the second variable capacitance circuit 32 provided at node N1. The first variable capacitance circuit 31 and the second variable capacitance circuit 32 connected to node N2 have similar configurations, so detailed description will be omitted.

[0041] The transistor TR1 of the first variable capacitance circuit 31 on the node N1 side has its gate supplied with the temperature compensation voltage VCP from the temperature compensation circuit 40, and its source and drain connected to node N1. This realizes a variable capacitance circuit with a positive voltage-to-capacitance characteristic as shown in FIG. 3. As the temperature compensation voltage VCP increases, the load capacitance of node N1 increases, and as the temperature compensation voltage VCP decreases, the load capacitance of node N1 decreases. Therefore, as the temperature compensation voltage VCP increases, the oscillation frequency decreases, and as the temperature compensation voltage VCP decreases, the oscillation frequency increases. As a result, for the third-order frequency-temperature characteristic of the resonator 10 shown in FIG. 5, the temperature compensation voltage VCP shown in FIG. 7 can offset increases or decreases in the oscillation frequency, thereby realizing temperature compensation that keeps the oscillation frequency constant.

[0042] The frequency control voltage VFC from the frequency control circuit 50 is supplied to the source and drain of the transistor TR2 of the second variable capacitance circuit 32 on the node N1 side, and the gate is connected to the node N1. This realizes a variable capacitance circuit with a negative voltage-to-capacitance characteristic as shown in FIG. 4, where an increase in the frequency control voltage VFC decreases the load capacitance of the node N1, and a decrease in the frequency control voltage VFC increases the load capacitance of the node N1. Therefore, an increase in the frequency control voltage VFC increases the oscillation frequency, and a decrease in the frequency control voltage VFC decreases the oscillation frequency. This makes it possible to realize a VC-TCXO, a voltage-controlled temperature-compensated oscillator that can control the oscillation frequency of the oscillation circuit 30 based on an external control voltage VC.

[0043] Fig. 9 shows a second configuration example of the oscillator circuit 30. Note that the oscillator circuit 30 is not limited to the configurations shown in Figs. 8 and 9, and various modifications are possible, such as omitting some of the components, adding other components, or replacing some of the components with other components.

[0044] In the second configuration example of Figure 9, the first variable capacitance circuit 31 on the node N1 side is composed of a transistor TR1, and the second variable capacitance circuit 32 on the node N1 side is composed of a transistor TR2. The first variable capacitance circuit 31 is electrically connected to the node N1 via a DC-blocking capacitor CB1, and the second variable capacitance circuit 32 is electrically connected to the node N1 via a DC-blocking capacitor CB2. Figure 9 also includes a reference voltage generation circuit 34 that generates reference voltages VR1 and VR2. The first variable capacitance circuit 31 and the second variable capacitance circuit 32 on the node N2 side are connected to the node N2 via capacitors CB3 and CB4, but these variable capacitance circuits have the same configuration as the first variable capacitance circuit 31 and the second variable capacitance circuit 32 on the node N1 side, so detailed description thereof will be omitted.

[0045] A transistor TR1 and a capacitor CB1, which are first variable capacitance elements, are connected in series between a node that supplies a reference voltage VR1 and a node N1. Specifically, one end of the capacitor CB1 is connected to the node N1, and the other end is connected to the gate of the transistor TR1, and the reference voltage VR1 is supplied to the source and drain of the transistor TR1. The temperature compensation circuit 40 supplies a temperature compensation voltage VCP to the connection node between the capacitor CB1 and the transistor TR1 via a resistor RB1.

[0046] A second variable capacitance element, a transistor TR2, and a capacitor CB2 are connected in series between a node that supplies a reference voltage VR2 and a node N1. Specifically, one end of the capacitor CB2 is connected to the node N1, and the other end is connected to the source and drain of the transistor TR2, and the reference voltage VR2 is supplied to the gate of the transistor TR2. The frequency control circuit 50 also supplies a frequency control voltage VFC to the connection node between the capacitor CB2 and the transistor TR2 via a resistor RB2.

[0047] 9, the first variable capacitance circuit 31 may be configured with multiple transistors TR1 connected in parallel, and the second variable capacitance circuit 32 may be configured with multiple transistors TR2 connected in parallel. In this case, multiple reference voltages VR1 with different voltages may be supplied to the sources and drains of the multiple transistors TR1 that make up the first variable capacitance circuit 31. Similarly, multiple reference voltages VR2 with different voltages may be supplied to the gates of the multiple transistors TR2 that make up the second variable capacitance circuit 32. By combining the different voltage-capacitance characteristics of the multiple transistors TR1, the linearity of the total capacitance of the first variable capacitance circuit 31 can be improved. Similarly, by combining the different voltage-capacitance characteristics of the multiple transistors TR2, the linearity of the total capacitance of the second variable capacitance circuit 32 can be improved.

[0048] As shown in FIG. 10, a temperature-compensated voltage VCP is supplied to the gate of transistor TR1 constituting first variable capacitance circuit 31, and a reference voltage VR1 is supplied to the source and drain. As a result, as shown in FIG. 11, the voltage-capacitance characteristic of first variable capacitance circuit 31 becomes a voltage-capacitance characteristic with a positive coefficient with respect to the gate-drain voltage VGD=VCP-VR1. Therefore, as shown in FIG. 12, the voltage-capacitance characteristic of first variable capacitance circuit 31 also becomes a voltage-capacitance characteristic with respect to temperature-compensated voltage VCP. Specifically, in FIG. 12, the voltage-capacitance characteristic becomes a positive coefficient shifted by the reference voltage VR1 as shown in B1 compared to FIG. 11.

[0049] In Figures 11 and 12, Vth is the threshold voltage of transistor TR1. As mentioned above, the slope of the voltage-capacitance characteristic is greatest near the center of the range of change, and in Figure 11, the slope of the voltage-capacitance characteristic is greatest when VGD = Vth. On the other hand, in Figure 12, the slope of the voltage-capacitance characteristic is greatest when VCP = Vth + VR1.

[0050] As shown in FIG. 13, the transistor TR2 constituting the second variable capacitance circuit 32 has its source and drain supplied with the frequency control voltage VFC and its gate supplied with the reference voltage VR2. As a result, as shown in FIG. 14, the voltage-capacitance characteristics of the second variable capacitance circuit 32 exhibit positive voltage-capacitance characteristics with respect to the gate-drain voltage VGD=VR2-VFC. In FIG. 14, Vth is the threshold voltage of the transistor TR2. Therefore, as shown in FIG. 15, the voltage-capacitance characteristics of the second variable capacitance circuit 32 exhibit negative voltage-capacitance characteristics with respect to the frequency control voltage VFC. Specifically, in FIG. 15, the polarity is reversed compared to FIG. 14, and the negative voltage-capacitance characteristics are shifted by the reference voltage VR2, as shown at B2.

[0051] 3.Temperature compensation circuit Fig. 16 shows an example configuration of the temperature compensation circuit 40. Note that the temperature compensation circuit 40 is not limited to the configuration shown in Fig. 16, and various modifications are possible, such as omitting some of the components, adding other components, or replacing some of the components with other components.

[0052] The temperature compensation circuit 40 is a circuit that outputs a temperature-compensated voltage VCP by polynomial approximation using temperature as a variable. This temperature compensation circuit 40 includes a current generation circuit 42 and a current-voltage conversion circuit 46. The current generation circuit 42 generates a function current based on the temperature detection result of a temperature sensor 48. For example, the current generation circuit 42 generates a function current for temperature compensation of the frequency-temperature characteristics of the resonator 10 as shown in FIG. 5 based on a temperature detection voltage VTS, which is the temperature detection result from the temperature sensor 48. The current-voltage conversion circuit 46 then converts the function current from the current generation circuit 42 into a voltage and outputs the temperature-compensated voltage VCP. Specifically, the current-voltage conversion circuit 46 outputs the temperature-compensated voltage VCP using an amplifier circuit AM that operates in class A.

[0053] The current generating circuit 42 includes a primary correction circuit 43 and a high-order correction circuit 44. The primary correction circuit 43 outputs a primary current that approximates a linear function based on the temperature detection voltage VTS. For example, the primary correction circuit 43 outputs a linear function current based on primary correction data corresponding to the linear coefficient of a polynomial in the polynomial approximation. The primary correction circuit 43 includes, for example, an operational amplifier, a first variable resistance circuit, a second variable resistance circuit, and a third variable resistance circuit. The operational amplifier, the first variable resistance circuit, and the second variable resistance circuit form a non-inverting amplifier circuit. The non-inverting amplifier circuit amplifies the temperature detection voltage VTS based on, for example, a reference voltage VRC. The non-inverting amplifier circuit outputs the primary current to the input node of the current-voltage conversion circuit 46 via the third variable resistance circuit.

[0054] The high-order correction circuit 44 outputs a high-order current that approximates a high-order function based on the temperature detection voltage VTS to the current-voltage conversion circuit 46. For example, the high-order correction circuit 44 outputs a high-order current based on high-order correction data corresponding to high-order coefficients of a polynomial in the polynomial approximation. As an example, the high-order correction circuit 44 outputs a cubic current that approximates a cubic function. In this case, the high-order correction circuit 44 includes a first differential circuit that performs a differential operation based on the temperature detection voltage VTS and a second differential circuit that performs a differential operation based on the output voltage of the first differential circuit and the temperature detection voltage VTS to output a cubic current. Note that in FIG. 16, the temperature sensor 48 performs offset correction of the temperature detection voltage VTS based on zero-order correction data corresponding to the zero-order coefficient of the polynomial. That is, the temperature sensor 48 adjusts the offset of the temperature detection voltage VTS by the amount indicated by the zero-order correction data. The offset correction of the temperature detection voltage VTS corresponds to zero-order correction in temperature compensation of the oscillation frequency. The high-order correction circuit 44 may further include a correction circuit that performs fourth-order or higher correction. For example, the high-order correction circuit 44 may further include a fourth-order correction circuit that outputs a fourth-order current that approximates a fourth-order function, and a fifth-order correction circuit that outputs a fifth-order current that approximates a fifth-order function.

[0055] The current-voltage conversion circuit 46 adds the primary current and the higher-order current and performs current-to-voltage conversion on the added current to output a temperature-compensated voltage VCP, thereby generating a temperature-compensated voltage VCP that approximates a polynomial function.

[0056] The current-voltage conversion circuit 46 includes an amplifier circuit AM, a resistor RC, and a capacitor CC. The amplifier circuit AM is realized by an operational amplifier. The resistor RC and the capacitor CC are connected in parallel between the output terminal and the inverting input terminal of the amplifier circuit AM. A reference voltage VRC is input to the non-inverting input terminal of the amplifier circuit AM. As a result, the current-voltage conversion circuit 46 outputs a temperature-compensated voltage VCP using, for example, the amplifier circuit AM operating in class A.

[0057] With the temperature compensation circuit 40 configured as described above, the function current generated by the current generation circuit 42 based on the temperature detection result of the temperature sensor 48 can be converted into a voltage by the current-voltage conversion circuit 46 and output as a temperature-compensated voltage VCP. Then, the current-voltage conversion circuit 46 outputs the temperature-compensated voltage by the amplifier circuit AM with class A operation, so that the temperature-compensated voltage VCP for performing appropriate temperature compensation of the oscillation frequency over a wide temperature range can be output by the amplifier circuit AM with class A operation, which has a small circuit scale and a simple configuration.

[0058] FIG. 17 shows an example configuration of a Class-A amplifier circuit AM. The amplifier circuit AM includes a differential section DP and an output section QP. The differential section DP includes transistors TD1 and TD2 that form a current mirror circuit, bipolar transistors BP1 and BP2 that form a differential pair, and a bipolar transistor BP3 that serves as a current source. Transistors TD1 and TD2 are P-type transistors with their gates connected in common. The inverting input terminal (base) of bipolar transistor BP1 receives voltage VCP0 from current generating circuit 43, and the non-inverting input terminal (base) of bipolar transistor BP2 receives reference voltage VRC. The output section QP includes a P-type driver transistor TD3 and a bipolar transistor BP4 that serves as a current source, both of which are connected in series between the VDD and GND nodes. The amplifier circuit AM also includes a resistor RD and a capacitor CD for phase compensation. Note that MOS transistors may be used instead of the bipolar transistors BP1 to BP4.

[0059] Meanwhile, Figure 18 shows an example configuration of an amplifier circuit AM that operates in class AB. What differs from Figure 17 is that the output section QP in Figure 18 includes a P-type drive transistor TD4 and an N-type drive transistor TD5 that are connected in series between the VDD node and the GND node. Also, Figure 18 includes a switch circuit SW and a bipolar transistor BP5 for controlling the gate of the drive transistor TD5.

[0060] As mentioned above, when using the second variable capacitance circuit 32 with a negative voltage-capacitance characteristic to temperature-compensate the frequency-temperature characteristic of the resonator 10 shown in FIG. 5 , the temperature compensation circuit 40 must output a temperature-compensated voltage VCP with the temperature characteristic shown in FIG. 6 . In this case, the amplifier circuit AM of the temperature compensation circuit 40 must output a sufficiently low voltage at the upper limit of the operating temperature range, as indicated by A2 in FIG. 6 . However, if a class-A amplifier circuit AM such as that shown in FIG. 17 is used as the output amplifier of the temperature compensation circuit 40, it becomes difficult to output a sufficiently low temperature-compensated voltage VCP, as indicated by A2 in FIG. 5 , using the bipolar transistor BP4, which serves as the current source transistor of the output section QP. In other words, because the bipolar transistor BP4, which serves as the current source, is a constant-current transistor, it is unable to draw a large current into the low-potential power supply, making it difficult to output a sufficiently low temperature-compensated voltage VCP. In this case, increasing the constant current makes it easier to output a low voltage, but increasing the constant current increases power consumption. Therefore, when using a second variable capacitance circuit 32 with a negative characteristic to temperature compensate for the frequency-temperature characteristic, it becomes necessary to use an amplifier circuit AM with class AB operation, such as the one shown in FIG. 18. With an amplifier circuit AM with class AB operation, the N-type drive transistor TD5 of the output section QP is fully turned on, allowing a low temperature-compensated voltage VCP to be output. However, using such an amplifier circuit AM with class AB operation can result in problems such as increased circuit complexity and size. For example, with an amplifier circuit AM with class AB operation, it is not possible to provide a filter circuit at the gate of the drive transistor of the output section QP. Furthermore, providing a filter circuit at the output node of the output section QP would prevent the Miller effect from working, necessitating a large-capacity capacitor to set the cutoff frequency to the same level as that of an amplifier circuit AM with class A operation, resulting in an increased circuit size.

[0061] In this regard, in this embodiment, a first variable capacitance circuit 31 with a positive voltage-capacitance characteristic is used to temperature compensate the frequency-temperature characteristic of the vibrator 10 shown in FIG. 5. Therefore, the temperature compensation circuit 40 outputs a temperature-compensated voltage VCP with the temperature characteristic shown in FIG. 7. In this case, as shown by A3 in FIG. 7, the amplifier circuit AM of the temperature compensation circuit 40 must output a sufficiently high voltage at the upper limit of the operating temperature range. Even when the amplifier circuit AM with class A operation shown in FIG. 17 is used as the output amplifier of the temperature compensation circuit 40, the P-type drive transistor TD3 of the output section QP is sufficiently turned on, making it possible to easily output a high voltage such as that shown by A3 in FIG. 7. Therefore, it is not necessary to use an amplifier circuit AM with class AB operation such as that shown in FIG. 18, which allows for simplification and miniaturization of the circuit.

[0062] 4. Frequency control circuit Next, the frequency control circuit 50 will be described in detail. Fig. 19 shows an example configuration of the frequency control circuit 50. Note that the frequency control circuit 50 is not limited to the configuration shown in Fig. 19, and various modifications are possible, such as omitting some of the components, adding other components, or replacing some of the components with other components.

[0063] The frequency control circuit 50 of this embodiment divides an externally input control voltage VC using at least one variable resistor, generating a voltage and outputting the generated voltage as the frequency control voltage VFC. For example, the frequency control circuit 50 generates the frequency control voltage VFC by dividing the control voltage VC using a variable resistor, without using an amplifier such as an operational amplifier. For example, using an amplifier to adjust the gain of the frequency control circuit 50 increases the circuit size, power consumption, and noise due to the increased number of transistors. In contrast, the frequency control circuit 50 of FIG. 19 divides the control voltage VC using a variable resistor and outputs the generated voltage as the frequency control voltage VFC. This allows the oscillation frequency to be controlled using the frequency control voltage VFC without using an amplifier with a large circuit size, high power consumption, and high noise, thereby enabling the circuit device 20 to be made smaller, with reduced power consumption and noise.

[0064] Specifically, the frequency control circuit 50 of FIG. 19 includes a first variable resistor RA1, a second variable resistor RA2, a third variable resistor RA3, and a fourth variable resistor RA4. The first variable resistor RA1 is provided between an input node NA1 of a control voltage VC and an output node NA2 of a frequency control voltage VFC. The second variable resistor RA2 has one end connected to the output node NA2 of the frequency control voltage VFC. The third variable resistor RA3 is provided between an input node NA3 of a reference voltage VREG and a connection node NA4 to which the other end of the second variable resistor RA2 is connected. The fourth variable resistor RA4 is provided between the connection node NA4 and a low-potential power supply node NA5. The low-potential power supply node NA5 is, for example, a GND node.

[0065] In the frequency control circuit 50 of FIG. 19, the currents IA1, IA2, IA3, and IA4 flowing through the first variable resistor RA1, the second variable resistor RA2, the third variable resistor RA3, and the fourth variable resistor RA4 are calculated by the following equations (1), (2), and (3).

[0066]

number

[0067] As a result, the voltage VM at the connection node NA4, which is the voltage division node of the third variable resistor RA3 and the fourth variable resistor RA4, is calculated as in the following equations (4) and (5).

[0068]

number

[0069] Therefore, the frequency control voltage VFC can be calculated using the following equations (6) and (7).

[0070]

number

[0071] The gain G=ΔVFC / ΔVC in the frequency control circuit 50 is expressed by the following equation (8).

[0072]

number

[0073] As shown in equation (8) above, the frequency control circuit 50 of this embodiment makes it possible to adjust the gain G of the frequency control voltage VFC relative to the control voltage VC with a small-scale circuit configuration that does not use an amplifier. For example, the gain G in the frequency control circuit 50 can be adjusted by adjusting the resistance values ​​of the first variable resistor RA1 to the fourth variable resistor RA4. Therefore, it is possible to adjust the gain G of the frequency control voltage VFC relative to the control voltage VC to any value without using an amplifier that has a large circuit scale, consumes a lot of power, and is noisy.

[0074] 5. Sensitivity settings In this embodiment, the absolute value of the frequency-voltage sensitivity by the first variable capacitance circuit 31 is set higher than the absolute value of the frequency-voltage sensitivity by the second variable capacitance circuit 32. For example, the frequency-voltage sensitivity, KV=ΔF / ΔV, is expressed by the following equation (9). CL is the overall load capacitance of the oscillation circuit 30, and C0 and C1 are the equivalent parallel capacitance and series capacitance of the vibrator 10.

[0075]

number

[0076] As is clear from equation (9), increasing the absolute value of the sensitivity KV increases the frequency change ΔF. Therefore, by increasing the absolute value of the sensitivity KV of the first variable capacitance circuit 31 for temperature compensation compared to the absolute value of the sensitivity KV of the second variable capacitance circuit 32 for frequency control, the frequency fluctuation range of the first variable capacitance circuit 31 for temperature compensation can be made wider than the frequency fluctuation range of the second variable capacitance circuit 32 for frequency control. For example, specifications require a frequency fluctuation range of approximately ±20 to 30 ppm on the temperature compensation side and approximately ±5 to 15 ppm on the frequency control side. Therefore, by increasing the absolute value of the sensitivity KV of the first variable capacitance circuit 31 compared to the absolute value of the sensitivity KV of the second variable capacitance circuit 32, the frequency fluctuation range on the temperature compensation side can be made wider than the frequency fluctuation range on the frequency control side, thereby satisfying specifications. The absolute value of the sensitivity of the variable capacitance circuit can be increased by increasing the size of the transistors that make up the variable capacitance circuit. Therefore, in order to make the absolute value of the sensitivity KV by the first variable capacitance circuit 31 higher than the absolute value of the sensitivity KV by the second variable capacitance circuit 32, the size of the transistor TR1 that constitutes the first variable capacitance circuit 31 should be larger than the size of the transistor TR2 that constitutes the second variable capacitance circuit 32. Note that hereinafter, the absolute value of the sensitivity will be referred to simply as sensitivity where appropriate.

[0077] For example, Figure 20 shows the voltage-capacitance characteristics of a variable capacitance circuit. In Figure 20, D2 has twice the slope of the voltage-capacitance characteristics compared to D1. In other words, the capacitance-voltage sensitivity of the variable capacitance circuit is doubled. However, even if the capacitance-voltage sensitivity, which is the slope of the voltage-capacitance characteristics of the variable capacitance circuit, is doubled, the sensitivity KV = ΔF / ΔV does not double, as shown in Figure 21. In other words, even if the slope of the voltage-capacitance characteristics of the sensitivity KV expressed by equation (9) above is doubled as shown in Figures D1 and D2 in Figure 20, it does not become twice the sensitivity shown in Figure 21 D3. Instead, the sensitivity decreases by the amount of the increase in load capacitance CL due to the increase in parasitic capacitance, as shown in Figure 24, resulting in the sensitivity shown in Figure D5.

[0078] For example, if the sensitivity KV of the second variable capacitance circuit 32 for frequency control is increased, the sensitivity KV of the first variable capacitance circuit 31 for temperature compensation will decrease as the load capacitance CL increases due to the parasitic capacitance of the second variable capacitance circuit 32. For this reason, in this embodiment, the sensitivity KV of the first variable capacitance circuit 31 for temperature compensation is preferentially increased, and the sensitivity KV of the second variable capacitance circuit 32 for frequency control is set lower than that of the temperature compensation side. In this way, the transistor size of the second variable capacitance circuit 32 can be reduced, thereby achieving a reduction in the circuit scale and also making it possible to suppress a decrease in the sensitivity KV of the first variable capacitance circuit 31 due to the parasitic capacitance of the second variable capacitance circuit 32.

[0079] 6. Oscillator FIG. 22 shows a first structural example of the oscillator 4 of this embodiment. The oscillator 4 has a resonator 10, a circuit device 20, and a package 15 that houses the resonator 10 and the circuit device 20. The package 15 is made of, for example, ceramic or the like, and has an internal housing space in which the resonator 10 and the circuit device 20 are housed. The housing space is hermetically sealed and is preferably in a reduced pressure state that is close to a vacuum. The package 15 can suitably protect the resonator 10 and the circuit device 20 from impact, dust, heat, moisture, and the like.

[0080] The package 15 has a base 16 and a lid 17. Specifically, the package 15 is composed of the base 16, which supports the resonator 10 and the circuit device 20, and the lid 17, which is bonded to the upper surface of the base 16 so as to form an accommodation space between the base 16 and the lid 17. The resonator 10 is supported via terminal electrodes on a stepped portion provided on the inside of the base 16. The circuit device 20 is disposed on the inside bottom surface of the base 16. Specifically, the circuit device 20 is disposed so that its active surface faces the inside bottom surface of the base 16. The active surface is the surface on which circuit elements of the circuit device 20 are formed. Bumps BMP are formed on the terminals of the circuit device 20. The circuit device 20 is supported on the inside bottom surface of the base 16 via conductive bumps BMP. The conductive bumps BMP are, for example, metal bumps, and the resonator 10 and the circuit device 20 are electrically connected via the bumps BMP, the internal wiring of the package 15, and the terminal electrodes. The circuit device 20 is also electrically connected to external terminals 18 and 19 of the oscillator 4 via bumps BMP and internal wiring of the package 15. The external terminals 18 and 19 are formed on the outer bottom surface of the package 15. The external terminals 18 and 19 are connected to an external device via external wiring. The external wiring is, for example, wiring formed on a circuit board on which the external device is mounted. This makes it possible to output a clock signal or the like to the external device.

[0081] 22, the circuit device 20 is flip-mounted so that the active surface of the circuit device 20 faces downward, but this embodiment is not limited to such mounting. For example, the circuit device 20 may be mounted so that the active surface of the circuit device 20 faces upward. In other words, the circuit device 20 is mounted so that the active surface faces the vibrator 10.

[0082] FIG. 23 shows a second structural example of the oscillator 4. The oscillator 4 includes a resonator 10, a circuit device 20, and a package 15 that houses the resonator 10 and the circuit device 20. The package 15 includes a base 16 and a lid 17. The base 16 includes a first substrate 6, which is an intermediate substrate; a second substrate 7 having a substantially rectangular frame shape and stacked on the top surface of the first substrate 6; and a third substrate 8 having a substantially rectangular frame shape and stacked on the bottom surface of the first substrate 6. The lid 17 is bonded to the top surface of the second substrate 7, and the resonator 10 is housed in a housing space S1 formed by the first substrate 6, the second substrate 7, and the lid 17. For example, the resonator 10 is hermetically sealed in the housing space S1, preferably in a reduced pressure state close to a vacuum. This allows the resonator 10 to be suitably protected from impact, dust, heat, moisture, and the like. The housing space S2 formed by the first substrate and the third substrate 8 houses a circuit device 20, which is a semiconductor chip. Furthermore, on the bottom surface of the third substrate 8, external terminals 18 and 19 are formed, which are electrode terminals for external connection of the oscillator 4.

[0083] In the accommodation space S1, the vibrator 10 is connected to a first electrode terminal and a second electrode terminal (not shown) formed on the upper surface of the first substrate 6 via conductive connection parts CDC1 and CDC2. The conductive connection parts CDC1 and CDC2 may be implemented by conductive bumps such as metal bumps or by a conductive adhesive. Specifically, for example, a first electrode pad (not shown) formed on one end of the tuning-fork-shaped vibrator 10 is connected to a first electrode terminal formed on the upper surface of the first substrate 6 via the conductive connection part CDC1. The first electrode terminal is then electrically connected to a pad PX1 of the circuit device 20. A second electrode pad (not shown) formed on the other end of the tuning-fork-shaped vibrator 10 is connected to a second electrode terminal formed on the upper surface of the first substrate 6 via the conductive connection part CDC2. The second electrode terminal is then electrically connected to a pad PX2 of the circuit device 20. This allows one end and the other end of the vibrator 10 to be electrically connected to the pads PX1 and PX2 of the circuit device 20 via the conductive connection parts CDC1 and CDC2. Furthermore, conductive bumps BMP are formed on a plurality of pads of the circuit device 20, which is a semiconductor chip, and these conductive bumps BMP are connected to a plurality of electrode terminals formed on the bottom surface of the first substrate 6. The electrode terminals connected to the pads of the circuit device 20 are then electrically connected to external terminals 18, 19 of the oscillator 4 via internal wiring or the like.

[0084] The oscillator 4 may be a wafer-level package (WLP) oscillator. In this case, the oscillator 4 includes a semiconductor substrate, a base having a through electrode penetrating between the first and second surfaces of the semiconductor substrate, a resonator 10 fixed to the first surface of the semiconductor substrate via a conductive bonding material such as a metal bump, and external terminals provided on the second surface of the semiconductor substrate via an insulating layer such as a relocation wiring layer. An integrated circuit serving as the circuit device 20 is formed on the first or second surface of the semiconductor substrate. In this case, a first semiconductor wafer having multiple bases on which the resonators 10 and the integrated circuits are arranged is bonded to a second semiconductor wafer having multiple lids, and the multiple bases and lids are then bonded together. The oscillators 4 are then individually separated using a dicing saw or the like. This allows for the realization of a wafer-level package oscillator 4, enabling high-throughput, low-cost manufacturing of the oscillators 4.

[0085] As described above, the circuit device of this embodiment includes an oscillation circuit that oscillates a vibrator, a temperature compensation circuit that outputs a temperature compensation voltage that temperature-compensates the oscillation frequency of the oscillation circuit based on the temperature detection result of the temperature sensor, and a frequency control circuit that outputs a frequency control voltage for the oscillation frequency. The oscillation circuit includes a first variable capacitance circuit whose capacitance change characteristic with respect to the capacitance control voltage is positive, and a second variable capacitance circuit whose capacitance change characteristic with respect to the capacitance control voltage is negative. The temperature compensation circuit supplies the temperature compensation voltage to the first variable capacitance circuit as a capacitance control voltage, and the frequency control circuit supplies the frequency control voltage to the second variable capacitance circuit as a capacitance control voltage.

[0086] By providing the oscillator circuit with a first variable capacitance circuit with a positive characteristic, to which the temperature compensation voltage from the temperature compensation circuit is supplied as a capacitance control voltage, the capacitance of the first variable capacitance circuit increases as the temperature rises, thereby decreasing the oscillation frequency of the oscillator circuit, and the capacitance of the first variable capacitance circuit decreases as the temperature drops, thereby increasing the oscillation frequency of the oscillator circuit. This makes it possible to achieve temperature compensation that offsets temperature-induced changes in oscillation frequency and keeps the oscillation frequency constant. Furthermore, by providing the oscillator circuit with a second variable capacitance circuit with a negative characteristic, to which the frequency control voltage from the frequency control circuit is supplied as a capacitance control voltage, the capacitance of the second variable capacitance circuit decreases as the frequency control voltage rises, thereby increasing the oscillation frequency of the oscillator circuit, and the capacitance of the second variable capacitance circuit increases as the frequency control voltage drops, thereby decreasing the oscillation frequency of the oscillator circuit. Therefore, it is possible to achieve control of the oscillation frequency based on the frequency control voltage while achieving appropriate temperature compensation of the oscillation frequency over a wide temperature range using the temperature compensation circuit.

[0087] In this embodiment, the temperature compensation circuit may include a class A operation amplifier circuit that outputs a temperature compensation voltage.

[0088] In this way, proper temperature compensation of the oscillation frequency over a wide temperature range can be achieved by a temperature compensation circuit including a class A operation amplifier circuit, which has a smaller circuit scale and a simpler configuration than a class AB operation amplifier circuit.

[0089] In addition, in this embodiment, the temperature compensation circuit includes a current generation circuit that generates a function current based on the temperature detection result of the temperature sensor, and a current-voltage conversion circuit that converts the function current into a voltage and outputs a temperature-compensated voltage, and the current-voltage conversion circuit may output the temperature-compensated voltage using an amplifier circuit that operates in class A.

[0090] In this way, the function current generated by the current generating circuit based on the temperature detection result of the temperature sensor can be converted into a voltage by the current-voltage conversion circuit and output as a temperature-compensated voltage.The current-voltage conversion circuit then outputs the temperature-compensated voltage using an amplifier circuit with class A operation, so that a temperature-compensated voltage for performing appropriate temperature compensation of the oscillation frequency over a wide temperature range can be output by an amplifier circuit with class A operation that has a small circuit scale and a simple configuration.

[0091] In addition, in this embodiment, the vibrator may have a frequency-temperature characteristic that is approximated by a cubic curve, and the vibrator may be one in which, in an untemperature-compensated state, the oscillation frequency at the upper limit of the operating temperature range is greater than the maximum value of the oscillation frequency.

[0092] In this manner, in a vibrator in which the oscillation frequency at the upper limit of the operating temperature range is greater than the maximum value of the oscillation frequency, the temperature range on the high temperature side is wider than the temperature range on the low temperature side, but in this embodiment, a first variable capacitance circuit with a positive characteristic is used as the variable capacitance circuit to which the temperature compensation voltage is supplied, so it is possible to sufficiently increase the temperature compensation voltage at the upper limit of the operating temperature range, and appropriate temperature compensation can be achieved.

[0093] In this embodiment, the frequency control circuit may also output, as the frequency control voltage, a voltage generated by dividing an externally input control voltage using at least one variable resistor.

[0094] In this way, it becomes possible to control the oscillation frequency using the frequency control voltage without using an amplifier that has a large circuit scale, consumes a lot of power, and produces a lot of noise, thereby making it possible to achieve a smaller circuit scale and lower power consumption.

[0095] In addition, in this embodiment, the frequency control circuit may include a first variable resistor arranged between the input node of the control voltage and the output node of the frequency control voltage, a second variable resistor having one end connected to the output node, a third variable resistor arranged between the input node of the reference voltage and a connection node to which the other end of the second variable resistor is connected, and a fourth variable resistor arranged between the connection node and a low-potential power supply node.

[0096] In this way, by adjusting the resistance values ​​of the first to fourth variable resistors, it is possible to adjust the gain of the frequency control voltage relative to the control voltage without using an amplifier with a large circuit scale, high power consumption, and high noise.

[0097] In this embodiment, the absolute value of the frequency-voltage sensitivity of the first variable capacitance circuit may be higher than the absolute value of the frequency-voltage sensitivity of the second variable capacitance circuit.

[0098] In this way, the frequency fluctuation width on the temperature compensation side can be made wider than the frequency fluctuation width on the frequency control side, thereby realizing appropriate temperature compensation.

[0099] The oscillator of this embodiment includes a resonator and a circuit device. The circuit device includes an oscillation circuit that oscillates the resonator, a temperature compensation circuit that outputs a temperature compensation voltage that temperature-compensates the oscillation frequency of the oscillation circuit based on the temperature detection result of the temperature sensor, and a frequency control circuit that outputs a frequency control voltage for the oscillation frequency. The oscillation circuit includes a first variable capacitance circuit whose capacitance change characteristic with respect to the capacitance control voltage is positive, and a second variable capacitance circuit whose capacitance change characteristic with respect to the capacitance control voltage is negative. The temperature compensation circuit supplies the temperature compensation voltage to the first variable capacitance circuit as a capacitance control voltage, and the frequency control circuit supplies the frequency control voltage to the second variable capacitance circuit as a capacitance control voltage.

[0100] Although the present embodiment has been described in detail above, those skilled in the art will readily understand that many modifications are possible without substantially departing from the novel features and advantages of the present disclosure. Therefore, all such modifications are intended to be included within the scope of the present disclosure. For example, a term described at least once in the specification or drawings together with a different term having a broader or equivalent meaning may be replaced with that different term anywhere in the specification or drawings. Furthermore, all combinations of the present embodiment and modifications are also included within the scope of the present disclosure. Furthermore, the configurations and operations of the circuit device and oscillator are not limited to those described in the present embodiment, and various modifications are possible. [Explanation of symbols]

[0101] 4...oscillator, 6...first substrate, 7...second substrate, 8...third substrate, 10...resonator, 15...package, 16...base, 17...lid, 18...external terminal, 19...external terminal, 20...circuit device, 30...oscillating circuit, 31...first variable capacitance circuit, 32...second variable capacitance circuit, 34...reference voltage generating circuit, 40...temperature compensation circuit, 42...current generating circuit, 43...first-order correction circuit, 44...high-order correction circuit, 46...current-voltage conversion circuit, 48...temperature sensor, 50...frequency control circuit, 60...logic circuit, 70...non-volatile memory, 80...output circuit, 90...power supply circuit, AM...amplifying circuit, BP1 to BP5...bipolar transistor, CB1 to CB6, CC, CD...capacitors, CK...clock signal, DP...differential section, DV...drive circuit, IA1 to IA4...current, PCK, PGND, PVC, PVDD, PX1, PX2...pad, QP...output section, RA, RB1, RB2, RC, RD...resistors, RA1 to RA4...first variable resistor to fourth variable resistor, S1, S2...accommodation space, TD1, TD2, TR1, TR2...transistors, TD3, TD4, TD5...drive transistor, TVDD, TGND, TVC, TCK...terminal, VC...control voltage, VCC...capacitance control voltage, VCP...temperature compensation voltage, VFC...frequency control voltage, VTS...temperature detection voltage

Claims

1. an oscillation circuit that causes the oscillator to oscillate; a temperature compensation circuit that outputs a temperature compensation voltage for temperature-compensating the oscillation frequency of the oscillation circuit based on a temperature detection result of a temperature sensor; a frequency control circuit that outputs a frequency control voltage of the oscillation frequency; Including, The oscillator circuit comprises: a first variable capacitance circuit having a capacitance change characteristic with respect to a capacitance control voltage that is a positive characteristic; a second variable capacitance circuit whose capacitance change characteristic with respect to the capacitance control voltage is negative; Including, The temperature compensation circuit supplying the temperature compensation voltage to the first variable capacitance circuit as the capacitance control voltage; The frequency control circuit supplying the frequency control voltage to the second variable capacitance circuit as the capacitance control voltage; The frequency control circuit a control voltage input from the outside is divided by at least one variable resistor to generate a voltage, and the voltage is output as the frequency control voltage; The frequency control circuit a first variable resistor provided between an input node of the control voltage and an output node of the frequency control voltage; a second variable resistor having one end connected to the output node; a third variable resistor provided between an input node of a reference voltage and a connection node to which the other end of the second variable resistor is connected; a fourth variable resistor provided between the connection node and a low potential power supply node; A circuit device comprising:

2. 2. The circuit device according to claim 1, The temperature compensation circuit a circuit device including a class A amplifier circuit that outputs the temperature compensated voltage;

3. 3. The circuit device according to claim 2, The temperature compensation circuit a current generating circuit that generates a function current based on the temperature detection result of the temperature sensor; a current-voltage conversion circuit that converts the function current into a voltage and outputs the temperature-compensated voltage; Including, The circuit device is characterized in that the current-voltage conversion circuit outputs the temperature-compensated voltage by the amplifier circuit operating in class A.

4. 4. The circuit device according to claim 1, the vibrator has a frequency-temperature characteristic that is approximated by a cubic curve, The circuit device is characterized in that the oscillator is an oscillator in which, in an uncompensated state, the oscillation frequency at the upper limit of the operating temperature range is greater than the maximum value of the oscillation frequency.

5. 5. The circuit device according to claim 1, A circuit device, characterized in that the absolute value of the frequency voltage sensitivity of the first variable capacitance circuit is higher than the absolute value of the frequency voltage sensitivity of the second variable capacitance circuit.

6. A vibrator and A circuit device; Including, The circuit device comprises: an oscillation circuit that causes the oscillator to oscillate; a temperature compensation circuit that outputs a temperature compensation voltage for temperature-compensating the oscillation frequency of the oscillation circuit based on a temperature detection result of a temperature sensor; a frequency control circuit that outputs a frequency control voltage of the oscillation frequency; Including, The oscillator circuit comprises: a first variable capacitance circuit having a capacitance change characteristic with respect to a capacitance control voltage that is a positive characteristic; a second variable capacitance circuit whose capacitance change characteristic with respect to the capacitance control voltage is negative; Including, The temperature compensation circuit supplying the temperature compensation voltage to the first variable capacitance circuit as the capacitance control voltage; The frequency control circuit supplying the frequency control voltage to the second variable capacitance circuit as the capacitance control voltage; The frequency control circuit a control voltage input from the outside is divided by at least one variable resistor to generate a voltage, and the voltage is output as the frequency control voltage; The frequency control circuit a first variable resistor provided between an input node of the control voltage and an output node of the frequency control voltage; a second variable resistor having one end connected to the output node; a third variable resistor provided between an input node of a reference voltage and a connection node to which the other end of the second variable resistor is connected; a fourth variable resistor provided between the connection node and a low potential power supply node; An oscillator comprising:

7. 7. The oscillator according to claim 6, The temperature compensation circuit an oscillator comprising a class A operation amplifier circuit that outputs the temperature compensated voltage;

8. 8. The oscillator according to claim 6 or 7, the vibrator has a frequency-temperature characteristic that is approximated by a cubic curve, The oscillator is designed to operate at the upper limit of its operating temperature range in an uncompensated state. An oscillator characterized in that the frequency of the oscillator is greater than the maximum value of the oscillation frequency.

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