Patent ID: 12244268

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, an embodiment will be described. The embodiment to be described below does not unduly limit contents described in the claims. In addition, all of the configurations described in the embodiment are not necessarily essential constituent elements.

1. Circuit Device

FIG.1is a diagram illustrating a configuration example of a circuit device20according to the embodiment. The circuit device20according to the embodiment includes an oscillation circuit30and a temperature compensation circuit40. An oscillator4according to the embodiment includes a resonator10and the circuit device20. The resonator10is electrically coupled to the circuit device20.

The resonator10is an element that generates mechanical oscillation according to an electrical signal. The resonator10can be implemented by, for example, a resonator element such as a quartz crystal resonator element. For example, the resonator10can be implemented by a quartz crystal resonator element that has a cut angle of AT cut, SC cut, or the like and that performs thickness-shear oscillation, a tuning fork type quartz crystal resonator element, or a double-tuning fork type quartz crystal resonator element. For example, the resonator10may be a resonator that is built in a temperature compensated crystal oscillator (TCXO) not provided with an oven, or may be a resonator that is built in an oven controlled crystal oscillator (OCXO) provided with an oven. The vibrator10according to the embodiment can be implemented by various resonator elements such as a resonator element other than a thickness-shear oscillating type, a tuning fork type, or a double-tuning fork type, and a piezoelectric resonator element formed of a material other than quartz crystal. For example, a surface acoustic wave (SAW) resonator, or a micro electro mechanical system (MEMS) resonator as a silicon resonator formed using a silicon substrate may be employed as the resonator10.

The circuit device20is an integrated circuit device called an integrated circuit (IC). For example, the circuit device20is an IC manufactured by a semiconductor process, and is a semiconductor chip in which a circuit element is formed on a semiconductor substrate. The circuit device20includes the oscillation circuit30and the temperature compensation circuit40.

The oscillation circuit30is a circuit configured to oscillate the resonator10. For example, the oscillation circuit30oscillates the resonator10to generate an oscillation signal. The oscillation signal is an oscillation clock signal. For example, the oscillation circuit30can be implemented by an oscillation drive circuit electrically coupled to one end and the other end of the resonator10, and a passive element such as a capacitor and a resistor. The drive circuit can be implemented by, for example, a CMOS inverter circuit or a bipolar transistor. The drive circuit is a core circuit of the oscillation circuit30, and the drive circuit oscillates the resonator10by driving the resonator10with a voltage or a current. As the oscillation circuit30, oscillation circuits of various types such as an inverter type, a Pierce type, a Colpitts type, and a Hartley type can be used. The oscillation circuit30may generate an oscillation signal using an element other than the resonator10. Note that coupling in the embodiment is electrical coupling. The electrical coupling is coupling in which electrical signals can be transmitted, and is coupling in which information can be transmitted by the electrical signals. The electrical coupling may be coupling established via a passive element or the like.

The temperature compensation circuit40is a circuit configured to perform temperature compensation for an oscillation frequency of the oscillation circuit30. For example, the temperature compensation circuit40outputs a temperature compensation signal for temperature compensating the oscillation frequency of the oscillation circuit30, based on a temperature detection signal from a temperature sensor (not illustrated). The temperature compensation is, for example, processing of performing compensation by reducing fluctuation of the oscillation frequency caused by temperature fluctuation. That is, the temperature compensation circuit40performs the temperature compensation for the oscillation frequency of the oscillation circuit30such that the oscillation frequency is constant even when temperature fluctuation occurs.

The temperature compensation circuit40includes a first reference current generation circuit41configured to generate a first reference current IRA and a second reference current generation circuit42configured to generate a second reference current IRB. The temperature compensation circuit40further includes a first compensation circuit51configured to perform temperature compensation for the oscillation frequency in a first temperature range based on the first reference current IRA, and a second compensation circuit52configured to perform temperature compensation for the oscillation frequency in a second temperature range, which is higher than the first temperature range in temperature, based on the second reference current IRB.

For example, the first compensation circuit51performs the temperature compensation for the oscillation frequency in the first temperature range, which is a low-temperature-side temperature range, based on the first reference current IRA from the first reference current generation circuit41and a temperature detection signal from the temperature sensor (not illustrated). For example, the first compensation circuit51generates a first temperature compensation signal based on the first reference current IRA and the temperature detection signal, and performs the temperature compensation for the oscillation frequency in the first temperature range in the oscillation circuit30based on the first temperature compensation signal. For example, the first compensation circuit51generates a first current as the first temperature compensation signal based on the first reference current IRA and the temperature detection signal, and performs the temperature compensation for the oscillation frequency based on a temperature compensation voltage obtained by subjecting the first current to current-voltage conversion. For example, the oscillation circuit30includes a variable capacitance circuit, and the temperature compensation for the oscillation frequency in the first temperature range is performed by controlling a capacitance of the variable capacitance circuit based on the temperature compensation voltage. Further, the second compensation circuit52generates a second temperature compensation signal based on the second reference current IRB and the temperature detection signal, and performs the temperature compensation for the oscillation frequency in the second temperature range in the oscillation circuit30based on the second temperature compensation signal. For example, the second compensation circuit52generates a second current as the second temperature compensation signal based on the second reference current IRB and the temperature detection signal, and performs the temperature compensation for the oscillation frequency based on a temperature compensation voltage obtained by subjecting the second current to current-voltage conversion. For example, the temperature compensation for the oscillation frequency in the second temperature range is performed by controlling the capacitance of the variable capacitance circuit of the oscillation circuit30based on the temperature compensation voltage.

In the embodiment, the first reference current generation circuit41reduces the first reference current IRA as a temperature rises. Alternatively, the second reference current generation circuit42reduces the second reference current IRB as the temperature drops. In this case, the first reference current generation circuit41may reduce the first reference current IRA as the temperature rises, and the second reference current generation circuit42may reduce the second reference current IRB as the temperature drops. The first reference current generation circuit41gradually reduces the first reference current IRA as the temperature rises, for example. For example, the first reference current IRA is monotonically reduced as the temperature rises. The second reference current generation circuit42gradually decreases the second reference current IRB as the temperature drops. For example, the second reference current IRB is monotonically decreased as the temperature drops.

As described, if the first reference current generation circuit41reduces the first reference current IRA, which is used for the temperature compensation for the oscillation frequency in the first temperature range, as the temperature rises, the first reference current IRA can be sufficiently reduced when the temperature is in the second temperature range on a higher temperature side than the first temperature range. Therefore, in the second temperature range in which the second compensation circuit52performs the temperature compensation for the oscillation frequency, it is possible to prevent the first reference current IRA and the current for temperature compensation based on the first reference current IRA from being wastefully consumed. If the second reference current generation circuit42reduces the second reference current IRB, which is used for the temperature compensation for the oscillation frequency in the second temperature range, as the temperature drops, the second reference current IRB can be sufficiently reduced when the temperature is in the first temperature range on a lower temperature side than the second temperature range. Therefore, in the first temperature range in which the first compensation circuit51performs the temperature compensation for the oscillation frequency, it is possible to prevent the second reference current IRB and the current for temperature compensation based on the second reference current IRB from being wastefully consumed. Accordingly, power consumption of the circuit device20can be reduced. In addition, since the first reference current generation circuit41reduces the first reference current IRA as the temperature rises and the second reference current generation circuit42reduces the second reference current IRB as the temperature drops, it is possible to prevent the first reference current IRA, the second reference current IRB, or the current for temperature compensation based on the reference current from being rapidly switched at a temperature in the vicinity of a boundary between the first temperature range and the second temperature range. Therefore, it is possible to prevent noise based on the switching from causing a noise characteristic of a clock signal to deteriorate.

FIG.2is a diagram illustrating a detailed configuration example of the circuit device20and the oscillator4according to the embodiment. InFIG.2, the circuit device20includes the oscillation circuit30, the temperature compensation circuit40, a temperature sensor48, a logic circuit60, a nonvolatile memory70, an output circuit80, and a power supply circuit90. The oscillator4includes the resonator10and the circuit device20. The resonator10is electrically coupled to the circuit device20. For example, the resonator10is electrically coupled to the circuit device20using an internal wiring of a package that accommodates the resonator10and the circuit device20, a bonding wire, or a metal bump. The circuit device20and the oscillator4are not limited to the configuration inFIG.2, and various modifications such as omitting a part of the components, adding other components, and replacing a part of the components with other components can be made.

The circuit device20includes pads PVDD, PGND, PX1, PX2, and PCK. The pad is a terminal of the circuit device20that is a semiconductor chip. For example, in a pad region, a metal layer is exposed from a passivation film that is an insulating layer, and the exposed metal layer forms the pad that is a terminal of the circuit device20. The pads PVDD and PGND are a power supply 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 GND, which is a ground voltage, is supplied. GND may be referred to as VSS, and the ground voltage is, for example, a ground potential. In the embodiment, the ground voltage is appropriately described as GND. For example, VDD corresponds to a high-potential-side power supply, and GND corresponds to a low-potential-side power supply. The pads PX1and PX2are pads for coupling to the resonator10. The pad PCK is an output pad of a clock signal CK. The pads PVDD, PGND and PCK are electrically coupled to terminals TVDD, TGND and TCK respectively, which are external terminals for external coupling to the oscillator4. For example, each pad is electrically coupled to a corresponding terminal using an internal wiring of a package, a bonding wire, or a metal bump.

The oscillation circuit30is electrically coupled to the resonator10via the pads PX1and PX2. The pads PX1and PX2are pads for coupling to the resonator. The oscillation drive circuit of the oscillation circuit30is provided between the pad PX1and the pad PX2. The oscillation circuit30includes a variable capacitance circuit32. The variable capacitance circuit32is a circuit configured to change a capacitance formed at least at one of the one end and the other end of the resonator10, for example. The oscillation frequency of the oscillation circuit30can be adjusted by adjusting the capacitance of the variable capacitance circuit32. That is, when the variable capacitance circuit32is electrically coupled to at least one of the pads PX1and PX2, a load capacitance of the oscillation circuit30can be variably adjusted. The variable capacitance circuit32can be implemented by a variable capacitance element such as a varactor. For example, the variable capacitance circuit32includes at least one variable capacitance element.

The temperature compensation circuit40performs analog temperature compensation using polynomial approximation, for example. For example, when a temperature compensation voltage VCP for compensating a frequency-temperature characteristic of the resonator10is approximated using a polynomial, the temperature compensation circuit40performs the analog temperature compensation based on coefficient information of the polynomial. The analog temperature compensation is, for example, temperature compensation implemented by addition processing of a current signal or a voltage signal that is an analog signal. For example, when the temperature compensation voltage VCP is approximated using a high-order polynomial, a zero-order coefficient, a linear coefficient, and a high-order coefficient of the polynomial are stored in a storage unit implemented by, for example, the nonvolatile memory70as zero-order correction data, linear correction data, and high-order correction data, respectively. The high-order coefficient is, for example, a coefficient of an order higher than the first order, and the high-order correction data is correction data corresponding to the high-order coefficient. For example, when the temperature compensation voltage VCP is approximated using a cubic polynomial, a zero-order coefficient, a linear coefficient, a quadratic coefficient, and a cubic coefficient of the polynomial are stored in the storage unit as zero-order correction data, linear correction data, quadratic correction data, and cubic correction data. The temperature compensation circuit40performs temperature compensation based on the zero-order correction data to the cubic correction data. In this case, the quadratic correction data and temperature compensation based on the quadratic correction data may be omitted. For example, when the temperature compensation voltage VCP is approximated using a quintic polynomial, a zero-order coefficient, a linear coefficient, a quadratic coefficient, a cubic coefficient, a quartic coefficient, and a quintic coefficient of the polynomial are stored in the storage unit as zero-order correction data, linear correction data, quadratic correction data, cubic correction data, quartic correction data, and quintic correction data. The temperature compensation circuit40performs temperature compensation based on the zero-order correction data to the quintic correction data. In this case, the quadratic correction data or the quartic correction data, and the temperature compensation based on the quadratic correction data or the quartic correction data may be omitted. The order of polynomial approximation may be any order. For example, polynomial approximation of an order higher than the fifth order may be executed. The zero-order correction may be executed by the temperature sensor48.

The temperature sensor48is a sensor configured to detect a temperature. Specifically, the temperature sensor48outputs, as a temperature detection voltage VTS, a temperature-dependent voltage that changes according to an environmental temperature. For example, the temperature sensor48generates the temperature detection voltage VTS, which is a temperature detection signal, using a circuit element having temperature dependency. Specifically, the temperature sensor48outputs the temperature detection voltage VTS, which changes depending on the temperature using, for example, temperature dependence of a forward voltage of a PN junction. A modification can also be made in which a digital temperature sensor circuit is used as the temperature sensor48. In this case, the temperature detection voltage VTS may be generated by performing D/A conversion on temperature detection data.

The logic circuit60is a control circuit and executes various types of control processing. For example, the logic circuit60controls the entire circuit device20or controls an operation sequence of the circuit device20. The logic circuit60executes various types of processing for controlling the oscillation circuit30, controls the temperature sensor48, the temperature compensation circuit40, the output circuit80, or the power supply circuit90, or controls reading and writing of information from and to the nonvolatile memory70.

The logic circuit60can be implemented by, for example, an application specific integrated circuit (ASIC) using automatic placement and routing such as a gate array.

The nonvolatile memory70is a memory that stores information even without power supply. For example, the nonvolatile memory70is a memory that can store information without power supply and in which information can be rewritten. The nonvolatile memory70stores various types of information necessary for operations of the circuit device20and the like. The nonvolatile memory70can be implemented by an electrically erasable programmable read-only memory (EEPROM) or the like that is implemented by a floating gate avalanche injection MOS memory (FAMOS memory) or a metal-oxide-nitride-oxide-silicon memory (MONOS memory). The nonvolatile memory70stores correction data such as linear correction data and high-order correction data used for temperature compensation of the temperature compensation circuit40.

The output circuit80outputs the clock signal CK based on an oscillation signal from the oscillation circuit30. For example, the output circuit80buffers an oscillation signal, which is an oscillation clock signal from the oscillation circuit30, and outputs the buffered oscillation signal as the clock signal CK to the pad PCK. The clock signal CK is output to the outside via the clock output terminal TCK of the oscillator4. For example, the output circuit80outputs the clock signal CK in a single-ended CMOS signal format. The output circuit80may output the clock signal CK in a signal format other than the CMOS signal format.

A clock signal generation circuit such as a PLL circuit that generates a clock signal CK having a frequency obtained by multiplying a frequency of an oscillation signal may be provided at a subsequent stage of the oscillation circuit30, and the output circuit80may buffer the clock signal CK generated by the clock signal generation circuit and output the buffered clock signal CK.

The power supply circuit90is supplied with the power supply voltage VDD from the pad PVDD and the ground voltage GND from the pad PGND, and supplies various power supply voltages for an internal circuit of the circuit device20to the internal circuit. For example, the power supply circuit90supplies a regulated power supply voltage obtained by regulating the power supply voltage VDD to circuits of the circuit device20such as the oscillation circuit30.

InFIG.2, the temperature compensation circuit40includes the first reference current generation circuit41, the second reference current generation circuit42, a current generation circuit50, and a current-voltage conversion circuit59. As described with reference toFIG.1, the first reference current generation circuit41generates the first reference current IRA for temperature compensation of the oscillation frequency in the first temperature range on the low temperature side. The second reference current generation circuit42generates the second reference current IRB for temperature compensation of the oscillation frequency in the second temperature range on the high temperature side. The current generation circuit50generates a function current for compensating the temperature characteristic of the oscillation frequency based on the first reference current IRA from the first reference current generation circuit41, the second reference current IRB from the second reference current generation circuit42, and the temperature detection voltage VTS that is a temperature detection signal from the temperature sensor48. Specifically, the current generation circuit50includes the first compensation circuit51and the second compensation circuit52that are described with reference toFIG.1. The current generation circuit50generates a function current for compensating the temperature characteristic of the oscillation frequency based on a first current IA and a second current IB. The first current IA is generated by the first compensation circuit51based on the first reference current IRA and the temperature detection signal, and the second current IB is generated by the second compensation circuit52based on the second reference current IRB and the temperature detection signal. Specifically, the first compensation circuit51, which is a first current generation circuit, generates the first current IA for temperature compensation of the oscillation frequency in the first temperature range based on the first reference current IRA and the temperature detection voltage VTS that is the temperature detection signal from the temperature sensor48.

The second compensation circuit52, which is a second current generation circuit, generates the second current IB for temperature compensation of the oscillation frequency in the second temperature range based on the second reference current IRB and the temperature detection voltage VTS that is the temperature detection signal from the temperature sensor48. Accordingly, a function current including the first current IA and the second current IB is output to the current-voltage conversion circuit59. The current-voltage conversion circuit59performs current-voltage conversion on the function current generated by the current generation circuit50, and outputs the temperature compensation voltage VCP for controlling the oscillation frequency to the oscillation circuit30. For example, the capacitance of the variable capacitance circuit32of the oscillation circuit30is controlled based on the temperature compensation voltage VCP, whereby the oscillation frequency is controlled and the temperature compensation, in which the oscillation frequency is made constant even when the temperature changes, is implemented.

According to the temperature compensation circuit40having such a configuration, when a function current including the first current IA generated by the first compensation circuit51based on the first reference current IRA and the temperature detection signal is subjected to current-voltage conversion performed by the current-voltage conversion circuit59, the temperature compensation voltage VCP for performing the temperature compensation in the first temperature range is generated. Further, when a function current including the second current IB generated by the second compensation circuit52based on the second reference current IRB and the temperature detection signal is subjected to current-voltage conversion performed by the current-voltage conversion circuit59, the temperature compensation voltage VCP for performing the temperature compensation in the second temperature range is generated. Accordingly, the temperature compensation for the oscillation frequency in the first temperature range and the second temperature range is implemented.

2. Temperature Compensation Circuit

FIG.3is a diagram illustrating in detail a first configuration example of the temperature compensation circuit40according to the embodiment.FIG.4is a diagram illustrating operations of the temperature compensation circuit40.FIG.3illustrates a specific circuit configuration example of the first reference current generation circuit41, the second reference current generation circuit42, the first compensation circuit51, and the second compensation circuit52. The configurations of the circuits in the embodiment are not limited to those illustrated inFIG.3, and various modifications can be made, such as omitting a part of the circuits or circuit elements, adding other circuits or circuit elements, or replacing a part of the circuits or circuit elements with other circuits or circuit elements.

InFIG.3, the first reference current generation circuit41generates the first reference current IRA, and the second reference current generation circuit42generates the second reference current IRB. Specifically, as illustrated inFIG.4, the first reference current generation circuit41generates the first reference current IRA whose value decreases according to an increase in temperature, and the second reference current generation circuit42generates the second reference current IRB whose value decreases according to a decrease in temperature. The first compensation circuit51generates the first current IA for performing the temperature compensation of the oscillation frequency in the first temperature range based on the first reference current IRA and the temperature detection voltage VTS. InFIG.3, the first current IA is a current obtained by adding a current IA1and a current IA2. The second compensation circuit52generates the second current IB for performing the temperature compensation of the oscillation frequency in the second temperature range based on the second reference current IRB and the temperature detection voltage VTS. InFIG.3, the second current IB is a current obtained by adding a current IB1and a current IB2.

Before describing the details of the temperature compensation circuit40inFIG.3, problems of the temperature compensation circuit40will be described.

FIG.5is a diagram illustrating a configuration example of a differential pair circuit used in the temperature compensation circuit40. The differential pair circuit includes bipolar transistors BP1and BP2, which are transistors of a differential pair, and a current source IS. Resistors are also provided between emitters of the bipolar transistors BP1and BP2and the current source IS. For example, inFIG.5, a reference voltage VL is input to a base of the bipolar transistor BP1. Accordingly, a current IL flows between a collector and the emitter of the bipolar transistor BP1. The temperature detection voltage VTS is input to a base of the bipolar transistor BP2. A current IQ, which is a collector current of the bipolar transistor BP2, is extracted from a current extraction port.

In the differential pair circuit inFIG.5, when a current flowing through the current source IS is defined as IRF, a relation of IRF=IL+IQ is established. Therefore, when the current IQ decreases, the current IL increases. Conversely, when the current IQ increases, the current IL decreases. For example, in a case where the temperature detection voltage VTS has a negative temperature characteristic that the voltage decreases with respect to an increase in temperature, as illustrated inFIG.6, as the temperature increases, the current IQ flowing through the bipolar transistor BP2to whose base the temperature detection voltage VTS is input decreases. Accordingly, based on the relation of IRF=IL+IQ, the current IL increases.

In the differential pair circuit inFIG.5, the currents satisfy IQ=IL at a point when the voltages satisfy VL=VTS. Therefore, a point of changing the current IQ can be set by setting the reference voltage VL, whereby a characteristic curve of a function current for the temperature compensation can be set. In a use temperature range in which the current IQ is increased, the current IL is small. In a temperature range in which the current IQ is not used, the current IQ is reduced, and thus the current IL is increased. Since the current IL is a current that is discarded without being extracted from the current extraction port, when the current IL is increased, power is wasted.

FIG.7is a diagram illustrating a configuration example of a temperature compensation circuit140according to a first comparative example of the embodiment. The temperature compensation circuit140includes a reference current generation circuit141, a first compensation circuit151, and a second compensation circuit152. The reference current generation circuit141generates a reference current IR. The first compensation circuit151performs temperature compensation for the oscillation frequency in the first temperature range, and the second compensation circuit152performs temperature compensation for the oscillation frequency in the second temperature range. The first compensation circuit151and the second compensation circuit152include a plurality of differential pair circuits described with reference toFIG.5. Reference currents IRF1and IRF2obtained by mirroring the reference current IR flow through the differential pair circuits of the first compensation circuit151. Reference currents IRG1and IRG2obtained by mirroring the reference current IR flow through the differential pair circuits of the second compensation circuit152. Then, a current IF=IF1+IF2for temperature compensation in the first temperature range is generated by the first compensation circuit151, and a current IG=IG1+IG2for temperature compensation in the second temperature range is generated by the second compensation circuit152. Since the reference current IR is a constant current, the reference current IRF1=IF1+IL1and the reference current IRF2=IF2+IL2, which flow through the differential pair circuits of the first compensation circuit151respectively, are also constant currents having constant current values. The reference current IRG1=IG1+IH1and the reference current IRG2=IG2+IH2, which flow through the differential pair circuits of the second compensation circuit152respectively, are also constant currents having constant current values.

In the first temperature range on the low temperature side, the current IF=IF1+IF2increases while the current IG=IG1+IG2decreases. When the current IG=IG1+IG2is decreased, since a relation that IRG1=IG1+IH1and IRG2=IG2+IH2are constant currents is established as illustrated inFIG.6, the currents IH1and IH2are increased. Therefore, in the first temperature range on the low temperature side, the currents IH1and IH2flowing in the second compensation circuit152used for the second temperature range are increased, and thus power is consumed wastefully.

On the other hand, in the second temperature range on the high temperature side, the current IG=IG1+IG2increases while the current IF=IF1+IF2decreases. When the current IF=IF1+IF2is decreased, since a relation that IRF1=IF1+IL1and IRF2=IF2+IL2are constant currents is established as illustrated inFIG.6, the currents IL1and IL2are increased. Therefore, in the second temperature range on the high temperature side, the currents IL1and IL2flowing in the first compensation circuit151used for the first temperature range are increased, and thus power is consumed wastefully. As described above, in the temperature compensation circuit140of the first comparative example inFIG.7, at a temperature in the first temperature range on the low temperature side, an unnecessary current may flow in the second compensation circuit152used for the second temperature range and power may be consumed. At a temperature in the second temperature range on the high temperature side, an unnecessary current may flow in the first compensation circuit151used for the first temperature range and power may be consumed.

FIG.8is a diagram illustrating a configuration example of the temperature compensation circuit140according to a second comparative example in which the problem of the first comparative example inFIG.7is solved. InFIG.8, switch circuits153and154are added to the first comparative example inFIG.7. In the first temperature range, the switch circuit153is turned on and the switch circuit154is turned off. Accordingly, it is possible to prevent an increase in power consumption caused due to unnecessary currents IH1and IH2flowing in the second compensation circuit152. On the other hand, in the second temperature range, the switch circuit153is turned off and the switch circuit154is turned on. Accordingly, it is possible to prevent an increase in power consumption caused due to unnecessary currents IL1and IL2flowing in the first compensation circuit151.

However, in the second comparative example inFIG.8, as illustrated inFIG.9, at temperatures in the vicinity of a boundary between the first temperature range and the second temperature range, noise is generated due to switching between on and off of the switch circuits153and154. When such noise is generated, a noise characteristic deteriorates such as that of phase noise of a clock signal output from the oscillator. For example, even when a method of slowly switching on and off the switch circuits153and154is employed, a gain at the time of switching of the transistor is large, and the deterioration of the noise characteristic cannot be avoided.

Therefore, in the embodiment, the temperature compensation circuit40configured as illustrated inFIG.3is employed. InFIG.3, as illustrated inFIG.4, the first reference current generation circuit41reduces the first reference current IRA as the temperature rises. In addition, the second reference current generation circuit42reduces the second reference current IRB as the temperature drops. The first compensation circuit51generates the first current IA for performing the temperature compensation for the oscillation frequency in the first temperature range on the low temperature side, based on the first reference current IRA that decreases according to an increase in temperature. On the other hand, the second compensation circuit52generates the second current IB for performing the temperature compensation for the oscillation frequency in the second temperature range on the high temperature side, based on the second reference current IRB that decreases according to a decrease in temperature.

For example, reference currents IRA1and IRA2obtained by mirroring the first reference current IRA flow through the differential pair circuits constituting the first compensation circuit51. As described with reference toFIGS.5and6, a relation of IRA1=IA1+IL1and IRA2=IA2+IL2is established. Therefore, as illustrated inFIG.4, when the first reference current IRA decreases as the temperature rises, IRA1=IA1+IL1and IRA2=IA2+IL2also decrease. Therefore, in the second temperature range on the high temperature side, IRA1=IA1+IL1and IRA2=IA2+IL2, which are currents flowing through the first compensation circuit51, are sufficiently small. Accordingly, when a temperature is in the second temperature range, a current is prevented from flowing wastefully through the first compensation circuit51used for the first temperature range, and the power consumption can be reduced as compared with the first comparative example inFIG.7. As illustrated inFIG.4, when the second reference current IRB decreases as the temperature drops, IRB1=IB1+IH1and IRB2=IB2+IH2also decrease. Therefore, in the first temperature range on the low temperature side, IRB1=IB1+IH1and IRB2=IB2+IH2, which are currents flowing through the second compensation circuit52, are sufficiently small. Accordingly, when the temperature is in the first temperature range, a current is prevented from flowing wastefully through the second compensation circuit52used for the second temperature range, and the power consumption can be reduced as compared with the first comparative example inFIG.7. Further, in the vicinity of the boundary between the first temperature range and the second temperature range, since switch noise as in the second comparative example inFIG.8is not generated, deterioration of a noise characteristic of a clock signal caused by the switch noise can be prevented. Therefore, according to the circuit device20in the embodiment, it is possible to achieve both a reduction in power consumption and prevention of deterioration of the noise characteristic at the same time.

Next, a detailed circuit configuration of the temperature compensation circuit40inFIG.3will be described. The first compensation circuit51includes a differential pair circuit having bipolar transistors BA2, BA3, and BA4and resistors, and a differential pair circuit having bipolar transistors BA5, BA6, and BA7and resistors. The bipolar transistors BA2and BA3are transistors constituting a differential pair, the temperature detection voltage VTS that is a temperature detection signal is input to a base of the bipolar transistor BA2, and a reference voltage VL1is input to a base of the bipolar transistor BA3. The bipolar transistor BA4is a transistor constituting a current source, and the reference current IRA1obtained by mirroring the first reference current IRA flows therethrough. Similarly, the bipolar transistors BA5and BA6are transistors constituting a differential pair, the temperature detection voltage VTS is input to a base of the bipolar transistor BA5, and a reference voltage VL2is input to a base of the bipolar transistor BA6. The bipolar transistor BA7is a transistor constituting a current source, and the reference current IRA2obtained by mirroring the first reference current IRA flows therethrough.

The second compensation circuit52includes a differential pair circuit having bipolar transistors BB2, BB3, and BB4and resistors, and a differential pair circuit having bipolar transistors BB5, BB6, and BB7and resistors. The bipolar transistors BB2and BB3are transistors constituting a differential pair, the temperature detection voltage VTS is input to a base of the bipolar transistor BB3, and a reference voltage VH1is input to a base of the bipolar transistor BB2. The bipolar transistor BB4is a transistor constituting a current source, and a reference current IRB1obtained by mirroring the second reference current IRB flows therethrough. Similarly, the bipolar transistors BB5and BB6are transistors constituting a differential pair, the temperature detection voltage VTS is input to a base of the bipolar transistor BB6, and a reference voltage VH2is input to a base of the bipolar transistor BB5. The bipolar transistor BB7is a transistor constituting a current source, and a reference current IRB2obtained by mirroring the second reference current IRB flows therethrough.

The temperature detection voltage VTS used in the first compensation circuit51and the temperature detection voltage VTS used in the second compensation circuit52may have, for example, temperature characteristics of the same polarity such as a negative temperature characteristic, and may have different voltage levels or the like.

Here, the temperature detection voltage VTS, which is a temperature detection signal, has, for example, a negative temperature characteristic, and the voltage decreases as the temperature rises. The reference voltages VL1and VL2are voltages for setting, for example, a point at which a characteristic of a function current for temperature compensation changes in the first temperature range on the low temperature side. The reference voltages VH1and VH2are voltages for setting, for example, a point at which a characteristic of a function current for temperature compensation changes in the second temperature range on the high temperature side.

According to the temperature compensation circuit40having such a configuration, in the first temperature range on the low temperature side, the first compensation circuit51can generate, as a function current, the first current IA=IA1+IA2having the characteristics illustrated inFIG.4using the first reference current IRA that decreases according to an increase in temperature. The subsequent current-voltage conversion circuit59illustrated inFIG.2performs current-voltage conversion on the function current to output the temperature compensation voltage VCP to the oscillation circuit30, and the capacitance of the variable capacitance circuit32is controlled according to, for example, the temperature compensation voltage VCP, whereby the temperature compensation for the oscillation frequency in the first temperature range can be implemented. On the other hand, in the second temperature range on the high temperature side, the second compensation circuit52can generate, as a function current, the second current IB=IB1+IB2having the characteristics illustrated inFIG.4using the second reference current IRB that decreases according to a decrease in temperature. The current-voltage conversion circuit59performs current-voltage conversion on the function current to output the temperature compensation voltage VCP to the oscillation circuit30, and the capacitance of the variable capacitance circuit32is controlled according to, for example, the temperature compensation voltage VCP, whereby the temperature compensation for the oscillation frequency in the second temperature range can be implemented.

As described above, the first compensation circuit51inFIG.3includes a first differential pair circuit. The first differential pair circuit includes first differential pair transistors a current flowing through one of which is controlled according to a temperature detection signal, and a first current source transistor that flows a reference current obtained by mirroring the first reference current IRA through the first differential pair transistors. The second compensation circuit52includes a second differential pair circuit. The second differential pair circuit includes second differential pair transistors a current flowing through one of which is controlled according to a temperature detection signal, and a second current source transistor that flows a reference current obtained by mirroring the second reference current IRB through the second differential pair transistors.

Here, the first differential pair circuit is a differential pair circuit including the bipolar transistors BA2, BA3, and BA4, or a differential pair circuit including the bipolar transistors BA5, BA6, and BA7. The first differential pair transistors of the first differential pair circuit are the bipolar transistors BA2and BA3or the bipolar transistors BA5and BA6. For example, the bipolar transistor BA2or the bipolar transistor BA5, which is one transistor of the first differential pair transistors, is controlled in current based on the temperature detection voltage VTS that is a temperature detection signal. The first current source transistor is the bipolar transistor BA4or the bipolar transistor BA7. For example, the bipolar transistor BA4is a current source transistor that flows the reference current IRA1obtained by mirroring the first reference current IRA through the bipolar transistors BA2and BA3that are the differential pair transistors. The bipolar transistor BA7is a current source transistor that flows the reference current IRA2obtained by mirroring the first reference current IRA through the bipolar transistors BA5and BA6that are the differential pair transistors.

The second differential pair circuit is a differential pair circuit including the bipolar transistors BB2, BB3, and BB4, or a differential pair circuit including the bipolar transistors BB5, BB6, and BB7. The second differential pair transistors of the second differential pair circuit are the bipolar transistors BB2and BB3or the bipolar transistors BB5and BB6.

For example, the bipolar transistor BB3or the bipolar transistor BB6, which is one transistor of the second differential pair transistors, is controlled in current based on the temperature detection voltage VTS that is a temperature detection signal. The second current source transistor is the bipolar transistor BB4or the bipolar transistor BB7. For example, the bipolar transistor BB4is a current source transistor that flows the reference current IRB1obtained by mirroring the second reference current IRB through the bipolar transistors BB2and BB3that are the differential pair transistors. The bipolar transistor BB7is a current source transistor that flows the reference current IRB2obtained by mirroring the second reference current IRB through the bipolar transistors BB5and BB6that are the differential pair transistors.

With such a configuration, the first current IA for the temperature compensation in the first temperature range can be generated by controlling a current flowing through one transistor of the first differential pair transistors based on a temperature detection signal while causing a reference current obtained by mirroring the first reference current IRA to flow through the first differential pair transistors of the first compensation circuit51. Further, the second current IB for the temperature compensation in the second temperature range can be generated by controlling a current flowing through one transistor of the second differential pair transistors based on a temperature detection signal while causing a reference current obtained by mirroring the second reference current IRB to flow through the second differential pair transistors of the second compensation circuit52.

The first reference current generation circuit41includes a first bipolar transistor BA1of an npn type, and a first resistor RA. In the first bipolar transistor BA1, a collector and a base thereof are coupled to each other, and an emitter thereof is coupled to a low-potential-side power supply node. The low-potential-side power supply node is, for example, a GND node. The first resistor RA is provided between a high-potential-side power supply node and the first bipolar transistor BA1, and one end of the first resistor RA on a high-potential-side power supply node side is set to a voltage having a negative temperature characteristic. The high-potential-side power supply node is, for example, a VDD node. The one end of the first resistor RA on the VDD node side is a node N1inFIG.3, and the node N1is set to a voltage having a negative temperature characteristic. Further, the first bipolar transistor BA1of an npn type is a diode-coupled bipolar transistor whose collector and base are coupled to each other, and a voltage of a node N2of the collector is set to VBE that is a base-to-emitter voltage of the first bipolar transistor BA1. In this way, the node N1at one end of the first resistor RA is set to the voltage having a negative temperature characteristic, and the node N2at the other end of the first resistor RA is set to the voltage VBE, whereby the first reference current IRA having a negative temperature characteristic can flow through the first resistor RA. Accordingly, the first reference current generation circuit41can generate the first reference current IRA that decreases according to an increase in temperature.

The first reference current generation circuit41includes a first operational amplifier OPA and a first transistor TA of a p-type. The first operational amplifier OPA and the first transistor TA constitute a first variable resistance circuit46. The temperature detection voltage VTS having a negative temperature characteristic is input to a non-inverting input terminal of the first operational amplifier OPA. The first transistor TA is provided between the VDD, which is the high-potential-side power supply node, and the first resistor RA. An output of the first operational amplifier OPA is input to a gate of the first transistor TA, and a drain of the first transistor TA is coupled to an inverting input terminal of the first operational amplifier OPA and one end of the first resistor RA. According to such a configuration, the node N1of the drain of the first transistor TA can be set to the temperature detection voltage VTS having a negative temperature characteristic by virtual ground of the first operational amplifier OPA. For example, when the temperature detection voltage VTS changes due to a temperature change, the gate of the first transistor TA is controlled by the first operational amplifier OPA, whereby on-resistance of the first transistor TA changes and the node N1of the drain of the first transistor TA is set to the temperature detection voltage VTS. Since the node N1at one end of the first resistor RA is set to the temperature detection voltage VTS having a negative temperature characteristic in this way, the first reference current generation circuit41can generate the first reference current IRA having a negative temperature characteristic.

The second reference current generation circuit42includes a second bipolar transistor BB1of an npn type and a second resistor RB. In the second bipolar transistor BB1, a collector and a base thereof are coupled to each other, and an emitter thereof is coupled to the GND node that is a low-potential-side power supply node. The second resistor RB is provided between the VDD node, which is the high-potential-side power supply node, and the second bipolar transistor BB1, and one end of the second resistor RB on the VDD node side is set to a voltage having a positive temperature characteristic. The one end of the second resistor RB on the VDD node side is a node N3inFIG.3, and the node N3is set to a voltage having a positive temperature characteristic. Further, the second bipolar transistor BB1of an npn type is a diode-coupled bipolar transistor whose collector and base are coupled to each other, and a voltage of a node N4of the collector is set to VBE that is a base-to-emitter voltage of the second bipolar transistor BB1. In this way, the node N3at one end of the second resistor RB is set to the voltage having a positive temperature characteristic, and the node N4at the other end of the second resistor RB is set to the voltage VBE, whereby the second reference current IRB having a positive temperature characteristic can flow through the second resistor RB.

Accordingly, the second reference current generation circuit42can generate the second reference current IRB that decreases according to a decrease in temperature.

The second reference current generation circuit42includes a second operational amplifier OPB and a second transistor TB of a p-type. The second operational amplifier OPB and the second transistor TB constitute a second variable resistance circuit47. A temperature detection voltage VTS2having a positive temperature characteristic is input to a non-inverting input terminal of the second operational amplifier OPB. The second transistor TB is provided between the VDD node, which is the high-potential-side power supply node, and the second resistor RB. An output of the second operational amplifier OPB is input to a gate of the second transistor TB, and a drain of the second transistor TB is coupled to an inverting input terminal of the second operational amplifier OPB and one end of the second resistor RB. According to such a configuration, the node N3of the drain of the second transistor TB can be set to the temperature detection voltage VTS2having a positive temperature characteristic by virtual ground of the second operational amplifier OPB. For example, when the temperature detection voltage VTS2changes due to a temperature change, the gate of the second transistor TB is controlled by the second operational amplifier OPB, whereby on-resistance of the second transistor TB is changed and the node N3of the drain of the second transistor TB is set to the temperature detection voltage VTS2. Since the node N3at one end of the second resistor RB is set to the temperature detection voltage VTS2having a positive temperature characteristic in this way, the second reference current generation circuit42can generate the second reference current IRB having a positive temperature characteristic.

As described above, inFIG.3, in the temperature compensation circuit40of the circuit device20that oscillates the resonator10, a reference current source of the first compensation circuit51and the second compensation circuit52that generate a function current for temperature compensation is divided into the first reference current generation circuit41on a low temperature side and the second reference current generation circuit42on a high temperature side. The first transistor TA of MOS is provided in the first reference current generation circuit41that is a reference current source on the low temperature side, and the first transistor TA is controlled by the first operational amplifier OPA to which the temperature detection voltage VTS having a negative temperature characteristic is input. On the other hand, the second transistor TB of MOS is provided in the second reference current generation circuit42that is a reference current source on the high temperature side, and the second transistor TB is controlled by the second operational amplifier OPB to which the temperature detection voltage VTS2having a positive temperature characteristic is input. Accordingly, it is possible to reduce current consumption while preventing an increase in circuit area and an increase in noise.

The configuration of the temperature compensation circuit40is not limited to that illustrated inFIG.3, and various modifications can be made such as replacing the bipolar transistor of the first compensation circuit51, the second compensation circuit52, the first reference current generation circuit41, and the second reference current generation circuit42with a MOS transistor. In this case, a diode-coupled transistor used for a current source can be implemented by coupling a drain and a gate of the MOS transistor. Further, in the embodiment, the case where two temperature ranges such as the first temperature range and the second temperature range are set has been described as an example. Alternatively, three or more temperature ranges may be set, and a reference current generation circuit may be provided for each of the three or more temperature ranges.

FIG.10is a graph illustrating a frequency-temperature characteristic and a temperature range. A temperature characteristic inFIG.10is a temperature characteristic of the oscillation frequency in a case where temperature compensation is not performed, and corresponds to, for example, a temperature characteristic of the AT-cut resonator10. InFIG.2, a capacitance change characteristic of the variable capacitance circuit32of the oscillation circuit30with respect to the temperature compensation voltage VCP that is a frequency control voltage is a positive characteristic. Accordingly, since a change characteristic of the oscillation frequency of the oscillation circuit30with respect to the temperature compensation voltage VCP is a negative characteristic, the temperature compensation voltage VCP and a function current used to generate the temperature compensation voltage VCP have the same temperature characteristic as illustrated inFIG.10.

InFIG.10, TT is a typical temperature, and is, for example, 25° C. This temperature TT corresponds to a temperature at an inflection point indicated by A1of a temperature characteristic of a cubic function inFIG.10. TL is the lowest operating temperature in a product specification, and is, for example, −40° C. TH is the maximum operating temperature in the product specification, and is, for example, 110° C. InFIG.10, a range of the temperatures TL to TT is defined as a first temperature range RT1, and a range of the temperatures TT to TH is defined as a second temperature range RT2. For example, temperature compensation in the first temperature range RT1is performed by the first compensation circuit51, and temperature compensation in the second temperature range RT2is performed by the second compensation circuit52.

As illustrated inFIG.10, the second temperature range RT2on a high temperature side is wider than the first temperature range RT1on a low temperature side. Therefore, in the second temperature range RT2on the high temperature side, it is necessary to adjust a function current in a wider range than in the first temperature range RT1on the low temperature side. Therefore, when adjusting the function current based on the reference current IR from one reference current generation circuit141as in the comparative example inFIG.7, it is necessary to increase a current adjustment amount in the second compensation circuit152on the high temperature side than in the first compensation circuit151on the low temperature side, which causes an increase in circuit area. That is, inFIG.7, the reference current in each compensation circuit is set according to a size ratio of the bipolar transistor of the current source of the reference current generation circuit141and the bipolar transistors of the current sources of the first compensation circuit151and the second compensation circuit152. For example, as will be described later with reference toFIG.12, when the bipolar transistor of the current source of the reference current generation circuit141is a unit transistor, the current source of each of the first compensation circuit151and the second compensation circuit152is implemented by arranging one or a plurality of unit transistors. Therefore, in the second compensation circuit152on the high temperature side where the temperature range is wide and the current adjustment amount is large, the number of unit transistors to be arranged is increased, which causes an increase in circuit area.

In this regard, in the temperature compensation circuit40according to the embodiment, unlike the comparative example inFIG.7, the first reference current generation circuit41on the low temperature side and the second reference current generation circuit42on the high temperature side are separately provided. Accordingly, the unit transistors serving as the bipolar transistors can be set separately on the low temperature side and the high temperature side. Furthermore, minimum current units set by resistance values of RA and RB can be set separately on the low temperature side and the high temperature side. Therefore, an increase in arrangement area due to an increase in the number of arranged unit transistors as in the comparative example inFIG.7can be prevented, and a reduction in the circuit area can be achieved.

Specifically, in the embodiment, inFIG.3, the resistance value of the second resistor RB of the second reference current generation circuit42on the high temperature side is made smaller than the resistance value of the first resistor RA of the first reference current generation circuit41on the low temperature side. For example, the reference currents of IRA and IRB increase as the resistance values of RA and RB decrease. Therefore, by making the resistance value of RB smaller than that of RA, even when the unit transistor of the same current source is used, the second reference current IRB can be set to a larger current value than the first reference current IRA. By setting the second reference current IRB to a large current value, it is possible to achieve the adjustment of the function current in the wide second temperature range RT2as illustrated inFIG.10while preventing an increase in circuit area due to the number of arranged unit transistors.

InFIG.10, the second reference current IRB at an upper limit of the second temperature range RT2is larger than the first reference current IRA at a lower limit of the first temperature range RT1. The first reference current IRA at the lower limit of the first temperature range RT1is a current at a point indicated by A2inFIG.10. The second reference current IRB at the upper limit of the second temperature range RT2is a current at a point indicated by A3inFIG.10. In this way, the second compensation circuit52adjusts the function current in the second temperature range RT2on the high temperature side that is wider with reference to the point A1of the typical temperature as compared with the first temperature range RT1on the low temperature side. Also in this case, in the embodiment, since the first reference current generation circuit41on the low temperature side and the second reference current generation circuit42on the high temperature side are separately provided, it is possible to achieve appropriate current adjustment in the first temperature range RT1and the second temperature range RT2while preventing an increase in circuit area.

FIG.11is a diagram illustrating a cross-sectional structure example of a bipolar transistor used in the temperature compensation circuit40according to the embodiment. The bipolar transistor inFIG.11is a bipolar transistor of an npn type. In a plan view orthogonal to a semiconductor substrate, a region of an emitter is formed by an N+ diffusion region positioned at a center, and a region of a base is formed by a P+ diffusion region in a manner of surrounding the region of the emitter. A region of a collector is formed by an N+ diffusion region in a manner of surrounding the region of the base.FIG.12is a diagram schematically illustrating a layout arrangement of the bipolar transistors of BA1, BA4, and BA7constituting the current sources inFIG.3. For example, the first bipolar transistor BA1of the current source of the first reference current generation circuit41is implemented by a unit transistor, the bipolar transistor BA4of the first compensation circuit51is implemented by a transistor corresponding to two unit transistors, and the bipolar transistor BA7is implemented by one unit transistor. In this way, the reference currents IRA1and IRA2obtained by mirroring the first reference current IRA can be generated.

FIG.13is a diagram illustrating in detail a second configuration example of the temperature compensation circuit40according to the embodiment. The second configuration example inFIG.13is different from the first configuration example inFIG.3in the configuration of the second reference current generation circuit42.

Specifically, the second reference current generation circuit42inFIG.13includes a second bipolar transistor BC2of an npn type, a third bipolar transistor BC3of an npn type, and the second resistor RB. In the second bipolar transistor BC2, a collector and a base thereof are coupled to each other, and an emitter thereof is coupled to the GND node that is a low-potential-side power supply node. In the third bipolar transistor BC3, a collector and a base thereof are coupled to each other, and an emitter thereof is coupled to the collector of the second bipolar transistor BC2. The second resistor RB is provided between the VDD node, which is a high-potential-side power supply node, and the third bipolar transistor BC3. For example, one end of the second resistor RB is coupled to the node N3, which is a collector node of the third bipolar transistor BC3, and the other end is coupled to the VDD node.

As described, the second bipolar transistor BC2of an npn type is a diode-coupled bipolar transistor whose collector and base are coupled to each other, and a voltage of the node N4of the collector is set to VBE that is a base-to-emitter voltage of the second bipolar transistor BC2. The third bipolar transistor BC3of an npn type is a diode-coupled bipolar transistor whose collector and base are coupled, and a voltage of the node N3of the collector is set to 2×VBE corresponding to a voltage obtained by adding the base-to-emitter voltage of the second bipolar transistor BC2and a base-to-emitter voltage of the third bipolar transistor BC3. Here, since the voltage VBE corresponds to a diode forward voltage, the voltage VBE has a negative temperature characteristic. Accordingly, the node N3is set to a voltage having a negative temperature characteristic. Therefore, in the second resistor RB whose one end is coupled to the node N3and the other end is coupled to the VDD node, a voltage difference between both ends increases as the temperature rises, and thus the second reference current IRB having a positive temperature characteristic flows. Therefore, the second reference current generation circuit42can generate the second reference current IRB having a positive temperature characteristic that the current decreases according to a decrease in temperature. For example,FIG.14illustrates a temperature characteristic of the second reference current IRB in a case where the bipolar transistor has a one-stage configuration, and a temperature characteristic of the second reference current IRB in a case where the bipolar transistor has a two-stage configuration as illustrated inFIG.13. By setting the bipolar transistor to have a two-stage configuration, it is possible to generate the second reference current IRB having a positive temperature characteristic with a larger inclination than in the case of the one-stage configuration. AlthoughFIG.13illustrates the configuration example in which the number of stages of the bipolar transistor is two, the number of stages of the bipolar transistor may be three or more.

As described, according to the temperature compensation circuit40having the configuration inFIG.13, it is possible to generate the appropriate second reference current IRB having a positive temperature characteristic by increasing the number of stages of the bipolar transistor of the reference current source as compared with the temperature compensation circuit40having the configuration inFIG.3. Since the second operational amplifier OPB and the second transistor TB that are provided in the configuration in FIG.3can be omitted, an advantage is exhibited that the appropriate second reference current IRB having a positive temperature characteristic can be generated while preventing an increase in circuit area.

FIG.15is a diagram illustrating an overall configuration example of the temperature compensation circuit40. As illustrated inFIG.15, the temperature compensation circuit40includes the current generation circuit50and the current-voltage conversion circuit59. The current generation circuit50generates a function current based on the first current IA and the second current IB. The first current IA is generated by the first compensation circuit51based on the first reference current IRA and the temperature detection voltage VTS, and the second current IB is generated by the second compensation circuit52based on the second reference current IRB and the temperature detection voltage VTS. That is, a function current including the first current IA and the second current IB is generated. The current-voltage conversion circuit59performs current-voltage conversion on the function current including the first current IA and the second current IB, and outputs the temperature compensation voltage VCP to the oscillation circuit30. Specifically, the current-voltage conversion circuit59includes an operational amplifier OPD1and a feedback circuit element. In the operational amplifier OPD1, a reference voltage VRC is input to a non-inverting input terminal thereof, and an output of the current generation circuit50is input to an inverting input terminal thereof. As a feedback circuit element, a resistor RD and a capacitor CD are provided in parallel between an output terminal and the inverting input terminal of the operational amplifier OPD1.

As illustrated inFIG.15, the temperature compensation circuit40is provided with a third reference current generation circuit43that generates a third reference current IRM, in addition to the first reference current generation circuit41and the second reference current generation circuit42. The current generation circuit50includes a k-th order component current generation circuit53and an m-th order component current generation circuit54. The k-th order component current generation circuit53includes the first compensation circuit51and the second compensation circuit52. Here, k>m, in which k and m are integers equal to or greater than 1. The k-th order component current generation circuit53generates, as k-th order component currents of a function current, the first current IA generated based on the first reference current IRA and the second current IB generated based on the second reference current IRB. For example, IA+IB is a k-th order component current of the function current. The m-th order component current generation circuit54generates IM, which is an m-th order component current of the function current, based on the third reference current IRM generated by the third reference current generation circuit43. The current-voltage conversion circuit59performs current-voltage conversion on the function current including IA+IB, which is the k-th order component current, and IM, which is the m-th order component current, to generate the temperature compensation voltage VCP. In this way, the k-th order component current of the function current is generated based on the first reference current IRA in the first temperature range, and is generated based on the second reference current IRB in the second temperature range. Accordingly, a reduction in power consumption can be achieved. On the other hand, the m-th order component current is not generated for each temperature range but, for example, is generated based on the third reference current IRM in all the temperature ranges. Accordingly, the power consumption of the entire temperature compensation circuit40can be reduced.

Specifically, the k-th order component current is a component current having a lower order than the m-th order component current. For example, the k-th order component current is a cubic component current of the function current, and the m-th order component current is a quartic component current or a quintic component current of the function current. For example, in the embodiment, the k-th order component current, which is a low-order component current, is generated in the first temperature range based on the first reference current IRA that decreases according to an increase in temperature, and is generated in the second temperature range based on the second reference current IRB that decreases according to a decrease in temperature.

Accordingly, when the temperature is in one of the first temperature range and the second temperature range, it is possible to prevent a current in the other temperature range from being wastefully consumed, and it is possible to achieve a reduction in power consumption. On the other hand, when a reference current is generated for each of the temperature ranges for the m-th order component current that is a high-order component current, there is a possibility that power consumption in the entire temperature compensation circuit40cannot be reduced due to power consumption in an operational amplifier or the like used for generation of the reference current, for example. In this regard, as illustrated inFIG.15, the m-th order component current, which is a high-order component current, is generated based on the third reference current IRM in all the temperature ranges, so that it is possible to reduce the power consumption in the entire temperature compensation circuit40.

Specifically, in the current generation circuit50, a cubic component current generation circuit is provided as the k-th order component current generation circuit53, and a quartic component current generation circuit and a quintic component current generation circuit are provided as the m-th order component current generation circuit54. The current generation circuit50is also provided with a linear component current generation circuit (not illustrated). The linear component current generation circuit, the cubic component current generation circuit, the quartic component current generation circuit, and the quintic component current generation circuit may be referred to as a linear correction circuit, a cubic correction circuit, a quartic correction circuit, and a quintic correction circuit, respectively. A zero-order correction circuit is implemented by, for example, the temperature sensor48.

For example,FIG.16illustrates a configuration example of a quartic component current generation circuit, which is one of the m-th order component current generation circuit54. In the quartic component current generation circuit, based on a reference current obtained by mirroring the third reference current IRM generated by the third reference current generation circuit43used for a quartic component and the temperature detection voltage VTS, a third compensation circuit55generates a quartic component current I4L in the first temperature range, and a fourth compensation circuit56generates a quartic component current I4H in the second temperature range. As described, in the quartic component current generation circuit inFIG.16, unlike the cubic component current generation circuit described with reference toFIGS.3and13, in the first temperature range and the second temperature range, the quartic component currents I4L and I4H of the function current are generated based on the third reference current IRM generated by the common third reference current generation circuit43. In this way, since it is not necessary to provide an operational amplifier or the like provided in the cubic component current generation circuit, a reduction in power consumption can be achieved. That is, since the quartic component current is about ¼ or less of the cubic component current, an effect of reducing power consumption by not providing the operational amplifier or the like is better than an effect of reducing power consumption by providing the reference current generation circuit for each temperature range.

FIG.17illustrates a configuration example of a quintic component current generation circuit, which is one of the m-th order component current generation circuits54. In the quintic component current generation circuit, based on a reference current obtained by mirroring the third reference current IRM generated by the third reference current generation circuit44used for a quintic component and the temperature detection voltage VTS, a fifth compensation circuit57generates a quintic component current I5L in the first temperature range, and a sixth compensation circuit58generates a quintic component current I5H in the second temperature range. As described, in the quintic component current generation circuit inFIG.17, unlike the cubic component current generation circuit described with reference toFIGS.3and13, in the first temperature range and the second temperature range, the quintic component currents I5L and I5H of the function current are generated based on the third reference current IRM generated by the common third reference current generation circuit44. In this way, since it is not necessary to provide an operational amplifier or the like provided in the cubic component current generation circuit, a reduction in power consumption can be achieved. That is, since the quintic component current is about 1/10 or less of the cubic component current, an effect of reducing power consumption by not providing the operational amplifier or the like is better than an effect of reducing power consumption by providing the reference current generation circuit for each temperature range.

3. Oscillator

FIG.18illustrates a first structure example of the oscillator4according to the embodiment. The oscillator4includes the resonator10, the circuit device20, and a package15that accommodates the resonator10and the circuit device20. The package15is made of, for example, ceramic, and has an accommodating space on an inner side. The resonator10and the circuit device20are accommodated in the accommodating space. The accommodating space is hermetically sealed, and is desirably in a depressurized state that is a state close to vacuum. With the package15, the resonator10and the circuit device20can be suitably protected from impact, dust, heat, moisture, and the like.

The package15includes a base16and a lid17. Specifically, the package15includes the base16that supports the resonator10and the circuit device20, and the lid17that is joined to an upper surface of the base16such that the accommodating space is defined between the base16and the lid17. The resonator10is supported by a step portion, which is provided at an inner side of the base16, via a terminal electrode.

The circuit device20is disposed at an inner bottom surface of the base16. Specifically, the circuit device20is disposed such that an active surface thereof faces the inner bottom surface of the base16. The active surface is a surface at which a circuit element of the circuit device20is formed. Bumps BMP are formed at terminals of the circuit device20. The circuit device20is supported by the inner bottom surface of the base16via the conductive bumps BMP. The conductive bumps BMP are, for example, metal bumps, and the resonator10is electrically coupled to the circuit device20via the bumps BMP, an internal wiring of the package15, the terminal electrode, and the like. The circuit device20is electrically coupled to external terminals18and19of the oscillator4via the bumps BMP and the internal wiring of the package15. The external terminals18and19are formed at an outer bottom surface of the package15. The external terminals18and19are coupled to an external device via an external wiring. The external wiring is, for example, a wiring formed at a circuit board on which the external device is mounted. Accordingly, a clock signal or the like can be output to the external device.

Although the circuit device20is flip mounted such that the active surface of the circuit device20faces downward inFIG.18, the embodiment is not limited to such mounting. For example, the circuit device20may be mounted such that the active surface of the circuit device20faces upward. That is, the circuit device20is mounted such that the active surface thereof faces the resonator10.

FIG.19illustrates a second structure example of the oscillator4. The oscillator4includes the resonator10, the circuit device20, and the package15that accommodates the resonator10and the circuit device20. The package15includes the base16and the lid17. The base16includes a first substrate6that is an intermediate substrate, a second substrate7having a substantially rectangular frame shape that is laminated at an upper surface side of the first substrate6, and a third substrate8having a substantially rectangular frame shape that is laminated at a bottom surface side of the first substrate6. The lid17is joined to an upper surface of the second substrate7, and the resonator10is accommodated in an accommodating space S1that is defined by the first substrate6, the second substrate7, and the lid17. For example, the resonator10is hermetically sealed in the accommodating space S1, and the accommodating space S1is desirably in a depressurized state that is a state close to vacuum. Accordingly, the resonator10can be suitably protected from impact, dust, heat, moisture, and the like. The circuit device20that is a semiconductor chip is accommodated in an accommodating space S2defined by the first substrate6and the third substrate8. The external terminals18and19that are external coupling electrode terminals of the oscillator4are formed at a bottom surface of the third substrate8.

In the accommodating space S1, the resonator10is coupled to, by conductive coupling portions CDC1and CDC2, a first electrode terminal and a second electrode terminal (not illustrated) formed at an upper surface of the first substrate6.

For example, the conductive coupling portions CDC1and CDC2may be implemented by conductive bumps such as metal bumps, or may be implemented by conductive adhesives.

Specifically, for example, a first electrode pad (not illustrated) formed at one end of the tuning fork type resonator10is coupled to, via the conductive coupling portion CDC1, the first electrode terminal formed at the upper surface of the first substrate6. The first electrode terminal is electrically coupled to the pad PX1of the circuit device20. A second electrode pad (not illustrated) formed at the other end of the tuning fork type resonator10is coupled to, via the conductive coupling portion CDC2, the second electrode terminal formed at the upper surface of the first substrate6. The second electrode terminal is electrically coupled to the pad PX2of the circuit device20. Accordingly, the one end and the other end of the resonator10can be electrically coupled to the pads PX1and PX2of the circuit device20via the conductive coupling portions CDC1and CDC2. The conductive bumps BMP are formed at a plurality of pads of the circuit device20that is a semiconductor chip, and these conductive bumps BMP are coupled to a plurality of electrode terminals formed at a bottom surface of the first substrate6. The electrode terminals coupled to the pads of the circuit device20are electrically coupled to the external terminals18and19of the oscillator4via an internal wiring or the like.

The oscillator4may be an oscillator of a wafer level package (WLP). In this case, the oscillator4includes: a base that includes a semiconductor substrate and a penetration electrode penetrating between a first surface and a second surface of the semiconductor substrate; the resonator10that is fixed to the first surface of the semiconductor substrate via a conductive joining member such as a metal bump; and an external terminal that is provided at a second surface side of the semiconductor substrate via an insulating layer such as a re-wiring layer. An integrated circuit serving as the circuit device20is formed at the first surface or the second surface of the semiconductor substrate. In this case, by bonding a first semiconductor wafer disposed with a plurality of bases, each having the resonator10and an integrated circuit, to a second semiconductor wafer formed with a plurality of lids, the plurality of bases are joined to the plurality of lids, and then dicing of the oscillators4is performed using a dicing saw or the like. In this way, the oscillator4of the wafer level package can be implemented, and the oscillator4can be manufactured with high throughput and low cost.

As described above, the circuit device according to the embodiment includes an oscillation circuit configured to generate an oscillation signal and a temperature compensation circuit configured to perform temperature compensation for an oscillation frequency of the oscillation signal. The temperature compensation circuit includes a first reference current generation circuit configured to generate a first reference current, a second reference current generation circuit configured to generate a second reference current, a first compensation circuit configured to perform temperature compensation for the oscillation frequency in a first temperature range based on the first reference current, and a second compensation circuit configured to perform temperature compensation for the oscillation frequency in a second temperature range, which is higher than the first temperature range in temperature, based on the second reference current. The first reference current generation circuit reduces the first reference current as a temperature rises, or the second reference current generation circuit reduces the second reference current as the temperature drops.

According to the embodiment, the first reference current generation circuit reduces the first reference current as the temperature rises. Accordingly, when the temperature is in the second temperature range on a higher temperature side than the first temperature range, it is possible to sufficiently reduce the first reference current, and it is possible to prevent a current for temperature compensation based on the first reference current or the first reference current from being wastefully consumed. Alternatively, the second reference current generation circuit reduces the second reference current as the temperature drops. Accordingly, when the temperature is in the first temperature range on a low temperature side, it is possible to sufficiently reduce the second reference current, and it is possible to prevent a current for temperature compensation based on the second reference current or the second reference current from being wastefully consumed. Accordingly, a reduction in power consumption of the circuit device and the like can be achieved.

In the embodiment, the first reference current generation circuit may include a first bipolar transistor of an npn type in which a collector and a base are coupled to each other and an emitter is coupled to a low-potential-side power supply node, and a first resistor that is provided between a high-potential-side power supply node and the first bipolar transistor and whose one end on a high-potential-side power supply node side is set to a voltage having a negative temperature characteristic.

As described, since a node at the one end on the high-potential-side power supply node side of the first resistor is set to the voltage having a negative temperature characteristic, a reference current having a negative temperature characteristic can flow through the first resistor, and the first reference current that decreases as the temperature rises can be generated.

In the embodiment, the first reference current generation circuit may include a first operational amplifier to whose non-inverting input terminal a temperature detection voltage having a negative temperature characteristic is input, and a first transistor of a P type that is provided between the high-potential-side power supply node and the first resistor, to whose gate an output of the first operational amplifier is input, and whose drain is coupled to an inverting input terminal of the first operational amplifier and the one end of the first resistor.

In this way, a node of the drain of the first transistor can be set to the temperature detection voltage having a negative temperature characteristic by virtual ground of the first operational amplifier, and the first reference current generation circuit can generate the first reference current having a negative temperature characteristic.

In the embodiment, the second reference current generation circuit may include a second bipolar transistor of an npn type in which a collector and a base are coupled to each other and an emitter is coupled to the low-potential-side power supply node, and a second resistor that is provided between the high-potential-side power supply node and the second bipolar transistor and whose one end on the high-potential-side power supply node side is set to a voltage having a positive temperature characteristic.

As described, since a node at the one end on the high-potential-side power supply node side of the second resistor is set to the voltage having a positive temperature characteristic, a reference current having a positive temperature characteristic can flow through the second resistor, and the second reference current that decreases as the temperature drops can be generated.

In the embodiment, the second reference current generation circuit may include a second operational amplifier to whose non-inverting input terminal a temperature detection voltage having a positive temperature characteristic is input, and a second transistor of a P type that is provided between the high-potential-side power supply node and the second resistor, to whose gate an output of the second operational amplifier is input, and whose drain is coupled to an inverting input terminal of the second operational amplifier and the one end of the second resistor.

In this way, a node of the drain of the second transistor can be set to the temperature detection voltage having a positive temperature characteristic by virtual ground of the second operational amplifier, and the second reference current generation circuit can generate the second reference current having a positive temperature characteristic.

In the embodiment, the second reference current generation circuit may include a second bipolar transistor of an npn type in which a collector and a base are coupled to each other and an emitter is coupled to the low-potential-side power supply node, a third bipolar transistor in which a collector and a base are coupled to each other and an emitter is coupled to the collector of the second bipolar transistor, and a second resistor provided between the high-potential-side power supply node and the third bipolar transistor.

In this way, by setting a bipolar transistor serving as a reference current source in multiple stages, it is possible to generate the appropriate second reference current having a positive temperature characteristic while preventing an increase in circuit area.

In the embodiment, a resistance value of the second resistor may be smaller than a resistance value of the first resistor.

Since the resistance value of the second resistor is made smaller than the resistance value of the first resistor as described, the second reference current can be set to a larger current value than the first reference current, and current adjustment in the second compensation circuit can be implemented while preventing an increase in circuit area.

In the embodiment, the second reference current at an upper limit of the second temperature range may be larger than the first reference current at a lower limit of the first temperature range.

In this way, the current adjustment in the second temperature range on a high temperature side, which is wider than the first temperature range on a low temperature side, is performed by the second compensation circuit. Also in this case, in the embodiment, since the first reference current generation circuit on the low temperature side and the second reference current generation circuit on the high temperature side are separately provided, it is possible to achieve appropriate current adjustment in the first temperature range and the second temperature range while preventing an increase in circuit area.

In the embodiment, the first compensation circuit may include a first differential pair circuit. The first differential pair circuit may include first differential pair transistors a current flowing through one of which is controlled according to a temperature detection signal, and a first current source transistor that flows a reference current obtained by mirroring the first reference current through the first differential pair transistors. The second compensation circuit may include a second differential pair circuit. The second differential pair circuit may include second differential pair transistors a current flowing through one of which is controlled according to the temperature detection signal, and a second current source transistor that flows a reference current obtained by mirroring the second reference current through the second differential pair transistors.

In this way, a first current for temperature compensation in the first temperature range can be generated by controlling the current flowing through one transistor of the first differential pair transistors based on the temperature detection signal while causing the reference current obtained by mirroring the first reference current to flow through the first differential pair transistors of the first compensation circuit. Further, a second current for temperature compensation in the second temperature range can be generated by controlling the current flowing through one transistor of the second differential pair transistors based on the temperature detection signal while causing the reference current obtained by mirroring the second reference current to flow through the second differential pair transistors of the second compensation circuit.

In the embodiment, the temperature compensation circuit may include a current generation circuit configured to generate, based on a first current and a second current, a function current for compensating a temperature characteristic of the oscillation frequency, the first current being generated by the first compensation circuit based on the first reference current and a temperature detection signal and the second current being generated by the second compensation circuit based on the second reference current and the temperature detection signal. Further, the temperature compensation circuit may include a current-voltage conversion circuit configured to perform current-voltage conversion on the function current to output a temperature compensation voltage for controlling the oscillation frequency to the oscillation circuit.

In this way, the function current, which includes the first current generated by the first compensation circuit based on the first reference current and the temperature detection signal, is subjected to the current-voltage conversion performed by the current-voltage conversion circuit, so that a temperature compensation voltage for performing temperature compensation in the first temperature range is generated. Further, the function current, which includes the second current generated by the second compensation circuit based on the second reference current and the temperature detection signal is subjected to the current-voltage conversion performed by the current-voltage conversion circuit, so that a temperature compensation voltage for performing temperature compensation in the second temperature range is generated.

In the embodiment, a third reference current generation circuit configured to generate a third reference current may be provided.

The current generation circuit may include a k-th order component current generation circuit configured to generate, as a k-th order component current of the function current, the first current generated based on the first reference current and the second current generated based on the second reference current, and an m-th order component current generation circuit configured to generate an m-th order component current of the function current based on the third reference current.

In this way, the k-th order component current of the function current is generated based on the first reference current in the first temperature range, and is generated based on the second reference current in the second temperature range. Accordingly, a reduction in power consumption can be achieved. On the other hand, the m-th order component current is generated based on the third reference current, so that the power consumption of the entire temperature compensation circuit can be reduced.

In the embodiment, the k-th order component current may be a component current having a lower order than the m-th order component current.

In this way, when the temperature is in one of the first temperature range and the second temperature range, it is possible to prevent a current in the other temperature range from being wastefully consumed, and the m-th order component current that is a higher-order component current is generated based on the third reference current, so that it is possible to reduce the power consumption in the entire temperature compensation circuit.

An oscillator according to the embodiment includes a resonator and a circuit device. The circuit device includes an oscillation circuit configured to oscillate the resonator to generate an oscillation signal, and a temperature compensation circuit configured to perform temperature compensation on an oscillation frequency of the oscillation signal. The temperature compensation circuit includes a first compensation circuit configured to perform temperature compensation for the oscillation frequency in a first temperature range, a second compensation circuit configured to perform temperature compensation for the oscillation frequency in a second temperature range, which is higher than the first temperature range in temperature, a first reference current generation circuit configured to generate a first reference current serving as a reference current of the first compensation circuit, and a second reference current generation circuit configured to generate a second reference current serving as a reference current of the second compensation circuit. The first reference current generation circuit reduces the first reference current as a temperature rises, or the second reference current generation circuit reduces the second reference current as the temperature drops.

Although the embodiment has been described in detail above, it will be easily understood by those skilled in the art that many modifications can be made without substantially departing from the novel matters and effects according to the present disclosure. Therefore, all such modifications are intended to be included within the scope of the present disclosure. For example, a term cited with a different term having a broader meaning or the same meaning at least once in the specification or in the drawings can be replaced with the different term at any place in the specification or in the drawings. In addition, all combinations of the embodiment and the modifications are also included in the scope of the present disclosure. The configurations, operations, and the like of the circuit device and the oscillator are not limited to those described in the embodiment, and various modifications can be made.