Oscillator, electronic device, and vehicle

An oscillator includes a resonator and an integrated circuit, the integrated circuit includes an oscillation circuit that oscillates the resonator, a temperature sensor, a temperature compensation circuit that compensates for temperature characteristics of the resonator based on an output signal of the temperature sensor, an output circuit that receives a signal output from the oscillation circuit and outputs an oscillation signal, and a heat generating circuit, and in the heat generating circuit, a current flows in a first period after supply of a power supply voltage from the outside is started to generate heat and no current flows in the second period after the first period ends.

The present application is based on, and claims priority from JP Application Serial Number 2019-013421, filed Jan. 29, 2019, the disclosure of which is hereby incorporated by reference herein in its entirety.

BACKGROUND

1. Technical Field

The present disclosure relates to an oscillator, an electronic device, and a vehicle.

2. Related Art

In JP-A-2015-126286, a temperature compensated oscillator capable of adjusting a temperature compensation circuit in a state close to that during normal operation by allowing a current equivalent to a current flowing through an output circuit during normal operation to flow through a heat generating circuit because the output circuit stops operating when the temperature compensation circuit is adjusted.

In general, when a power supply voltage is applied to a temperature compensated oscillator, an integrated circuit that oscillates a resonator operates to generate heat and the heat is transmitted to the resonator, so that the temperature compensated oscillator enters a thermal equilibrium state in which the heat of the integrated circuit and the heat of the resonator are stable. In the temperature compensated oscillator described in JP-A-2015-126286, a frequency deviation can be reduced by performing temperature compensation in such a thermal equilibrium state. However, immediately after the oscillator is started, the integrated circuit becomes a heat generation source, and thus temperature of the resonator changes with a delay following a temperature change of the integrated circuit. That is, when the oscillator is started, thermal equilibrium may be lost because the temperature change of the resonator occurs with a delay with respect to the temperature change of the temperature sensor provided in the integrated circuit and the frequency deviation may increase due to the frequency of the oscillation signal deviating from the frequency in the thermal equilibrium state.

SUMMARY

An oscillator according to an aspect of the present disclosure includes a resonator and an integrated circuit, in which the integrated circuit includes an oscillation circuit that oscillates the resonator, a temperature sensor, a temperature compensation circuit that compensates for temperature characteristics of the resonator based on an output signal of the temperature sensor, an output circuit that receives a signal output from the oscillation circuit and outputs an oscillation signal, and a heat generating circuit, and in the heat generating circuit, a current flows in a first period after supply of a power supply voltage from the outside is started to generate heat and no current flows in a second period after the first period ends.

In the oscillator according to the aspect, the output circuit may stop operating in the first period and operate in the second period and power consumed by the heat generating circuit per unit time in the first period may be larger than power consumed by the output circuit per unit time in the second period.

In the oscillator according to the aspect, the current flowing through the heat generating circuit in the first period may be variable.

In the oscillator according to the aspect, a length of the first period may be variable.

In the oscillator according to the aspect, the integrated circuit may include an amplitude detection circuit that detects an amplitude of the signal output from the oscillation circuit and outputs a detection signal, and the first period may be set based on the detection signal.

In the oscillator according to the aspect, the integrated circuit may include a plurality of external connection terminals including a first external connection terminal electrically coupled to one end of the resonator and a second external connection terminal electrically coupled to the other end of the resonator, and, among the plurality of external connection terminals, the first external connection terminal or the second external connection terminal may be closest to the heat generating circuit.

In the oscillator according to the aspect, among the plurality of external connection terminals, the first external connection terminal or the second external connection terminal may be farthest from the temperature sensor.

An oscillator according to another aspect of the present disclosure includes a resonator and an integrated circuit, in which the integrated circuit generates heat with a first heat generation amount per unit time in a first period after supply of a power supply voltage from the outside is started, and generates heat with a second heat generation amount per unit time in a second period after the first period ends, and the first heat generation amount is larger than the second heat generation amount.

An electronic device according to another aspect of the present disclosure includes the oscillator according to the aspect.

A vehicle according to another aspect of the present disclosure includes the oscillator according to the aspect.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, exemplary embodiments of the present disclosure will be described in detail with reference to the drawings. The embodiments described below do not unduly limit contents of the present disclosure described in the claims. Also, not all of the configurations described below are essential constituent requirements of the present disclosure.

1-1. First Embodiment

FIGS. 1 and 2are diagrams illustrating an example of a structure of an oscillator1of the embodiment of the present disclosure.FIG. 1is a perspective view of the oscillator1andFIG. 2is a cross-sectional view taken along line II-II ofFIG. 1.

The oscillator1of the embodiment of the present disclosure is a temperature compensated oscillator, and as illustrated inFIGS. 1 and 2, the oscillator1includes an integrated circuit2, a resonator3, a package4, a lid5, and a plurality of external terminals6. In the embodiment of the present disclosure, the resonator3is a quartz crystal resonator using quartz crystal as a substrate material, and is, for example, an AT cut quartz crystal resonator, a tuning fork type quartz crystal resonator, or the like. The resonator3may be a surface acoustic wave (SAW) resonator or a micro electromechanical systems (MEMS) resonator. As the substrate material of the resonator3, in addition to quartz crystal, piezoelectric single crystals such as lithium tantalate and lithium niobate, piezoelectric materials such as piezoelectric ceramics such as lead zirconate titanate, or silicon semiconductor materials can be used. As an excitation unit of the resonator3, one using a piezoelectric effect may be used, or electrostatic drive using a Coulomb force may be used. The integrated circuit2is a circuit that oscillates the resonator3and outputs an oscillation signal.

The package4accommodates the integrated circuit2and the resonator3in the same space. Specifically, the package4is provided with a recess, and the recess is covered with the lid5to form an accommodation chamber7. On the inside of the package4or the surface of the recess, wirings (not illustrated) for electrically coupling two terminals of the integrated circuit2, specifically, an XI terminal and an XO terminal inFIG. 3to be described later, and two excitation electrodes3aand3bof the resonator3, respectively, are provided. On the inside of the package4or the surface of the recess, wiring (not illustrated) for electrically coupling each terminal of the integrated circuit2and each external terminal6provided on the bottom surface of the package4is provided. The package4is not limited to a configuration in which the integrated circuit2and the resonator3are accommodated in the same space. For example, a so-called H-type package in which the integrated circuit2is mounted on one surface of a package substrate and the resonator3is mounted on the other surface thereof may be used.

The resonator3includes metal excitation electrodes3aand3bon the front and back surfaces thereof, respectively, and oscillates at a desired frequency according to the shape and mass of the resonator3including the excitation electrodes3aand3b.

FIG. 3is a functional block diagram of the oscillator1according to the first embodiment. As illustrated inFIG. 3, the oscillator1of the first embodiment includes the integrated circuit2and the resonator3. The integrated circuit2includes a VDD terminal, a GND terminal, an OUT terminal, a VC terminal, the XI terminal, and the XO terminal as external connection terminals. The VDD terminal, the GND terminal, the OUT terminal, and the VC terminal are electrically coupled to T1 to T4 terminals, which are the plurality of external terminals6of the oscillator1illustrated inFIG. 2, respectively. The XI terminal is electrically coupled to one end of the resonator3and the terminal XO terminal is electrically coupled to the other end of the resonator3.

In this embodiment, the integrated circuit2includes an oscillation circuit10, an amplitude control circuit20, an output circuit30, a temperature compensation circuit40, a temperature sensor42, a regulator circuit50, a memory60, a switch circuit70, a serial interface circuit80, an amplitude detection circuit90, and a heat generation period control circuit92. The integrated circuit2of this embodiment may have a configuration in which some of these elements are omitted or changed, or other elements are added.

The oscillation circuit10is a circuit that oscillates the resonator3, and amplifies an output signal of the resonator3and feeds the output signal back to the resonator3. The oscillation circuit10outputs an oscillation signal VOSC based on oscillation of the resonator3.

The temperature sensor42detects the temperature of the integrated circuit2and outputs a temperature signal having a voltage corresponding to the temperature, and is realized by, for example, a circuit using temperature characteristics of a band gap reference circuit.

The temperature compensation circuit40is a circuit that compensates for the temperature characteristics of the resonator3based on the output signal of the temperature sensor42. In this embodiment, the temperature compensation circuit40generates a temperature compensation voltage VCOMP based on the temperature signal output from the temperature sensor42and a coefficient value corresponding to frequency-temperature characteristics of the resonator3stored in the memory60. The temperature compensation voltage VCOMP is applied to one end of a variable capacitance element (not illustrated) that functions as a load capacitance of the oscillation circuit10to control the oscillation frequency. The temperature compensation circuit40is a circuit that compensates for the temperature characteristics of the resonator3by converting the frequency of the oscillation signal VOSC output from the oscillation circuit10according to the temperature characteristics of the resonator3. Such a circuit is realized by, for example, a fractional N-PLL circuit.

The output circuit30receives the oscillation signal VOSC, which is a signal output from the oscillation circuit10, as an input and outputs an oscillation signal VOUT. For example, when the oscillator1is used as an oscillator for GPS used in a cellular or the like, a high frequency-temperature compensation accuracy of, for example, ±0.5 ppm is required. Therefore, in this embodiment, the regulator circuit50stabilizes an output voltage amplitude of the output circuit30, and from the viewpoint of reducing current consumption, the output circuit30outputs the oscillation signal VOUT having a clipped sine waveform with the output amplitude suppressed.

The amplitude control circuit20is a circuit for controlling the amplitude of the oscillation signal VOUT output from the output circuit30.

The regulator circuit50generates a constant voltage Vreg as a power supply voltage or a reference voltage for the oscillation circuit10, the temperature compensation circuit40, the output circuit30, and the like, based on a power supply voltage supplied from the VDD terminal.

The memory60includes a register (not illustrated) and a non-volatile memory such as a metal oxide nitride oxide silicon (MONOS) type memory or an electrically erasable programmable read-only memory (EEPROM), and is configured to be able to perform read and write for the non-volatile memory or the register through the serial interface circuit80from the external terminal6of the oscillator1. In this embodiment, since the integrated circuit2coupled to the external terminal6of the oscillator1has only four terminals of VDD, GND, OUT, and VC, for example, when the voltage at the VDD terminal is higher than a threshold value, the serial interface circuit80may receive a clock signal externally input from the VC terminal and a data signal externally input from the OUT terminal, and may perform read and write of data for a non-volatile memory or internal register (not illustrated). The serial interface circuit80may be, for example, an interface circuit of a 2-wire bus such as an inter-integrated circuit (I2C) bus, or may be an interface circuit of a 3-wire bus such as a serial peripheral interface (SPI) bus or a 4-wire bus.

The switch circuit70is a circuit for switching electrical connection between the temperature compensation circuit40and the OUT terminal that is electrically coupled to an output side of the output circuit30.

In this embodiment, in an inspection process before shipment of the oscillator1, a low-level or high-level test signal TP can be input to the VC terminal, and after the inspection process is completed, the VC terminal is grounded and the test signal TP is fixed at the low level. When the test signal TP input to the VC terminal is at the low level, the switch circuit70does not electrically couple the temperature compensation circuit40and the OUT terminal, and the oscillation signal VOUT output from the output circuit30is output to the OUT terminal. When the test signal TP is at the high level, the switch circuit70electrically couples the temperature compensation circuit40and the OUT terminal, output of the oscillation signal VOUT from the output circuit30is stopped, and the temperature compensation voltage VCOMP is output to the OUT terminal.

The memory60stores oscillation stage current adjustment data IADJ for adjusting and selecting an oscillation stage current of the oscillation circuit10in accordance with the frequency of the resonator3. The memory60stores frequency division switching data DIV for selecting whether or not to divide and output the oscillation signal VOSC by a frequency dividing circuit provided inside the output circuit30. The memory60also stores output level adjustment data VADJ for adjusting an amplitude level of the oscillation signal VOUT of clipped sine wave output from the output circuit30.

These data are stored in the non-volatile memory included in the memory60in the manufacturing process of the oscillator1. In the manufacturing process of the oscillator1, coefficient values such as zero-order, first order, third order (not illustrated) corresponding to the frequency-temperature characteristics of the resonator3are also stored in the non-volatile memory. Each data stored in the non-volatile memory is written from the non-volatile memory to each register immediately after the start of the oscillator1, that is, immediately after the supply of the power supply voltage to the VDD terminal is started.

The amplitude detection circuit90detects the amplitude of the oscillation signal VOSC, which is a signal output from the oscillation circuit10, and outputs a detection signal VDET. In this embodiment, the detection signal VDET is at a low level when the amplitude of the oscillation signal VOSC is smaller than a predetermined threshold, and is at a high level when the amplitude of the oscillation signal VOSC is larger than the predetermined threshold.

The heat generation period control circuit92outputs a heat generation control signal HTCTL based on the detection signal VDET output from the amplitude detection circuit90. In this embodiment, when the detection signal VDET is at a low level, the heat generation control signal HTCTL is at a low level. The heat generation control signal HTCTL changes from the low level to the high level in synchronization with the timing when the detection signal VDET changes from the low level to the high level. That is, a period during which the heat generation control signal HTCTL is at the low level is set based on the detection signal VDET. For example, the heat generation control signal HTCTL may change from the low level to the high level immediately after the detection signal VDET changes from the low level to the high level, or the heat generation control signal HTCTL may change from the low level to the high level when a predetermined time elapses from the timing when the detection signal VDET changes from the low level to the high level. Immediately after the oscillator1is started, the amplitude of the oscillation signal VOSC is smaller than the threshold value, and thus the detection signal VDET is at the low level, and the heat generation control signal HTCTL is also at the low level. Thereafter, when the amplitude of the oscillation signal VOSC becomes larger than the threshold value, the detection signal VDET changes from the low level to the high level, and as a result, the heat generation control signal HTCTL also changes from the low level to the high level.

As will be described later, the amplitude control circuit20includes a heat generating circuit, and heat generation of the heat generating circuit is controlled based on the heat generation control signal HTCTL and the test signal TP. In this embodiment, the heat generating circuit is controlled to generate heat when the heat generation control signal HTCTL is at the low level or when the test signal is at the high level.

Configuration of Oscillation Circuit

FIG. 4is a diagram illustrating a configuration example of the oscillation circuit10ofFIG. 3. InFIG. 4, although the oscillation stage current adjustment data IADJ is 4 bits, but may be 2 bits or less, or 5 bits or more. As illustrated inFIG. 4, the oscillation circuit10includes an oscillation unit11and a current source circuit12. The oscillation unit11is coupled to the resonator3to constitute a Pierce-type oscillation circuit. In the oscillation unit11, varicap diodes VCD1and VCD2which are variable capacitance elements are connected in series with each other and in parallel with the resonator3, a capacitance value of the oscillation unit11is changed with respect to the temperature by applying the temperature compensation voltage VCOMP to the varicap diodes VCD1and VCD2, and the oscillation signal VOSC in which the frequency-temperature characteristics of the resonator3is compensated is output.

The current source circuit12generates a current Iref serving as a reference for an oscillation stage current Iosc by a current adjustment unit in which a differential amplifier AMP1, a PMOS transistor M2, a bipolar transistor Q2, a resistor R1, and a plurality of resistors R2are connected in parallel. The reference current Iref is adjusted by the oscillation stage current adjustment data IADJ. A size of a gate width of the PMOS transistor M1and a size of a gate width of the PMOS transistor M2have a ratio of 10:1, for example. A size of a gate width of a PMOS transistor M3and a size of a gate width of a PMOS transistor M4have the same size ratio. For example, when Iref=20 μA, 200 μA, which is 10 times Iref, is supplied to the oscillation unit11as the oscillation stage current Iosc. The circuit configured by a differential amplifier AMP2, the PMOS transistor M4, a current source for supplying a bias current Ibias, and PMOS transistors M5and M6is a circuit for further suppressing power supply dependence of the oscillation stage current Iosc flowing through the cascode-connected PMOS transistors M1and M3. This circuit is a gain enhanced cascode circuit that further reduces the power source dependence of the current output from the current source compared to the cascode circuit in a TCXO that requires high frequency accuracy. This cascode circuit monitors a source voltage of the PMOS transistor M4on a reference side and, controls gate voltages of the PMOS transistors M3and M4by the differential amplifier AMP2when the power supply voltage supplied from the VDD terminal fluctuates to further suppress change in potential difference between the source and drain of the PMOS transistors M1and M2. Output resistance of the current source circuit12further increases by a gain multiple of the differential amplifier AMP2. The oscillation stage current Iosc is stabilized against fluctuations in the power supply voltage, and fluctuations in the oscillation frequency of the oscillation unit11can be suppressed.

Configuration of Output Circuit

FIG. 5is a diagram illustrating a configuration example of the output circuit30inFIG. 3. As illustrated inFIG. 5, the output circuit30is supplied with the output voltage Vreg of the regulator circuit50and a clip voltage Vclip for obtaining the clipped sine wave output generated by the amplitude control circuit20. The output circuit30includes a frequency dividing circuit, and is configured to be able to select whether or not to divide the oscillation signal VOSC output from the oscillation circuit10by two, based on a value of the frequency division switching data DIV. In this embodiment, when the value of the frequency division switching data DIV is 0, the oscillation signal VOSC is not frequency-divided, the polarity thereof is inverted by an inverter configured by the MOS transistors M1to M4, and a signal at a node VBUF1is transmitted to a NOR circuit NOR1. On the other hand, when the value of the frequency division switching data DIV is 1, the oscillation signal VOSC is divided to ½ by the frequency dividing circuit, and the signal of the node VBUF1is transmitted to the NOR circuit NOR1.

As described above, since the heat generation control signal HTCTL is at the low level immediately after the oscillator1is started, the MOS transistors M2and M3are turned off, an output node VBUF2of the NOR circuit NOR1and an output node VBUF3of a NOR circuit NOR2are both set to the ground potential, and the NMOS transistors M5and M6are both turned off. As a result, the output circuit30enters an operation stop state. Thereafter, when the heat generation control signal HTCTL changes from the low level to the high level, the output circuit30becomes operable, and the oscillation signal VOSC is clipped at a voltage amplitude level determined by the clip voltage Vclip and is output as the oscillation signal VOUT.

In the manufacturing process of the oscillator1, when adjusting the temperature compensation circuit40ofFIG. 3, the test signal TP is set to the high level. With this configuration, the MOS transistors M2and M3are turned off, the output node VBUF2of the NOR circuit NOR1and the output node VBUF3of the NOR circuit NOR2are both set to the ground potential, and the NMOS transistors M5and M6are both turned off. As a result, the output circuit30enters an operation stop state.

Configuration of Amplitude Control Circuit

FIG. 6is a diagram illustrating a configuration example of the amplitude control circuit20inFIG. 3. As illustrated inFIG. 6, the amplitude control circuit20includes a heat generating circuit21, a replica circuit22, and a decoder23. InFIG. 6, NMOS transistors M1, M2, and M3are depletion-type MOS transistors, and the other MOS transistors are enhancement-type MOS transistors.

As represented in the following expression (1), the clip voltage Vclip that determines an output amplitude level of the output circuit30is a voltage obtained by subtracting a gate-source voltage VgsM2of the MOS transistor M2from the output voltage Vg of the differential amplifier AMP included in the replica circuit22.
Vclip=Vg−VgsM2(1)

The output voltage Vg of the differential amplifier AMP is obtained from an analog voltage Vdac D/A converted by a D/A converter DAC based on data given by the output level adjustment data VADJ by the following expression (2).

By substituting the expression (2) into the expression (1), a relationship of the following expression (3) is established. That is, the clip voltage Vclip is determined by Vdac·(R1/R2+1), which is a voltage obtained by amplifying the output voltage Vdac of the D/A converter DAC by the differential amplifier AMP.

As described above, the waveform of the oscillation signal VOUT output from the output circuit30is a clipped sine wave, and the peak value of the clipped sine wave decreases as the output frequency increases, and thus the output level adjustment data VADJ corresponding to the output frequency is stored in the memory60.

Since the test signal TP is fixed at a low level in the shipped oscillator1, a switch circuit SW1is in an on state and an NMOS switch SW2is in an off state. With this configuration, the amplitude control circuit20enters an operating state, and outputs the clip voltage Vclip represented by the expression (1).

Immediately after the oscillator1is started, the heat generation control signal HTCTL is at the low level, and thus a MOS transistor M3B included in the heat generating circuit21is turned on and the heat generating circuit21enters an operating state. With this configuration, a direct current Iht flows through the heat generating circuit21to generate heat. Thereafter, when the heat generation control signal HTCTL changes from the low level to the high level, the MOS transistor M3B changes from the on state to the off state, and the heat generating circuit21enters an operation stop state. As such above, in this embodiment, the heat generating circuit21generates heat immediately after the start of the oscillator1, and the generated heat is transmitted to the resonator3through the XI terminal and the XO terminal, so that temperature rise of the resonator3is accelerated, and then the heat generating circuit21stops heat generation and the temperature rise of the resonator3is suppressed. With this configuration, the time required to reach a thermal equilibrium state in which the temperature of the integrated circuit2and the temperature of the resonator3coincide with each other can be shortened.

On the other hand, in the manufacturing process of the oscillator1, when the temperature compensation circuit40is adjusted, the test signal TP is set to a high level. For that reason, the switch circuit SW1is turned off, the NMOS switch SW2is turned on, and the NMOS transistor M2enters a cut-off state. The MOS transistor M3B is turned on, and the heat generating circuit21enters an operating state.

The decoder23controls the direct current Iht flowing through the heat generating circuit21based on the test signal TP, the oscillation stage current adjustment data IADJ, and the frequency division switching data DIV. Specifically, when the test signal TP is at the high level, the decoder23controls a resistance value of the variable resistor VR according to the oscillation stage current adjustment data IADJ and the frequency division switching data DIV. With this configuration, the current Iht flowing through the heat generating circuit21when the test signal TP is at the high level changes in conjunction with the value of the oscillation stage current adjustment data IADJ, the value of the frequency division switching data DIV, and the value of the output level adjustment data VADJ and approaches a current corresponding to the current consumed by the output circuit30when the test signal TP is at the low level. As a result, a difference between the consumption current of the integrated circuit2when the test signal TP is at the low level and the consumption current of the integrated circuit2when the test signal TP is at the high level is reduced. That is, the difference between the current consumption of the integrated circuit2when the output circuit30is in the operating state and the current consumption of the integrated circuit2when the output circuit30is in the stopped state is reduced.

When the test signal TP is at the low level, the decoder23controls the variable resistor VR included in the heat generating circuit21to a predetermined resistance value. The greater the resistance value of the variable resistor VR, the greater the DC current Iht that flows through the heat generating circuit21when the heat generation control signal HTCTL is at the low level. The resistance value of the variable resistor VR may be set so that the time required for the integrated circuit2and the resonator3to reach the thermal equilibrium state is as short as possible. When the test signal TP is at the low level, the variable resistor VR is controlled to a predetermined resistance value regardless of the logic level of the heat generation control signal HTCTL, but when the heat generation control signal HTCTL is at the high level, the direct current Iht does not flow through the heat generating circuit21.

Relationship Between Temperature of Integrated Circuit and Resonator

The oscillator1of this embodiment can shorten the time required for the integrated circuit2and the resonator3to reach a thermal equilibrium state by causing the direct current Iht to flow through the heat generating circuit21immediately after the start, compared to the oscillator of the comparative example in which the direct current Iht does not flow through the heat generating circuit21.

FIG. 7is a diagram illustrating an example of the operation of the oscillator of the comparative example.FIG. 8is a diagram illustrating an example of the operation of the oscillator1of this embodiment. InFIGS. 7 and 8, A1indicates a change in the power supply voltage supplied to the VDD terminal, A2indicates a waveform of the oscillation signal VOSC, and A3indicates a waveform of the oscillation signal VOUT. A4indicates power consumption of the integrated circuit2, A5indicates temperature of the integrated circuit2and the temperature of the resonator3, and A6indicates frequency deviation of the oscillation frequency. In A5, the solid line represents the temperature change of the integrated circuit2, and the broken line represents the temperature change of the resonator3.

As indicated by A1inFIGS. 7 and 8, when the supply of the power supply voltage to the VDD terminal is started at time t0, the resonator3oscillates and the amplitude of the oscillation signal VOSC gradually increases, as indicated by A2. When the amplitude of the oscillation signal VOSC becomes larger than the threshold value, the oscillation signal VOUT is generated at time t1, as indicated by A3. Thereafter, the supply of the power supply voltage to the VDD terminal is completed at time t4, and the operation of the oscillator1is stopped.

In the oscillator of the comparative example, as indicated by A4inFIG. 7, in a first period P1from time t0to time t1, the output circuit30stops its operating, and thus a consumption current is I0, whereas in a second period P2from time t1to time t4, the output circuit30operates, and thus the consumption current becomes I1larger than I0. For that reason, the amount of heat generated in the first period P1is smaller than the amount of heat generated in the second period P2, and as indicated by A5, the temperature of the integrated circuit2rises slowly and the temperature of the resonator3also rises gradually following the temperature of the integrated circuit2. Then, at time t3in the second period P2, the integrated circuit2and the resonator3reach a thermal equilibrium state, and the oscillation frequency deviation becomes substantially zero as indicated by A6.

In contrast, in the oscillator1according to this embodiment, in the first period P1after the supply of the power supply voltage from the outside is started, a current flows through the heat generating circuit21to generate heat and no current flows in the second period P2after the first period P1ends. The first period P1is a period during which the heat generation control signal HTCTL is at the low level, and is set based on the detection signal VDET output from the amplitude detection circuit90as described above. Although the output circuit30stops operating in the first period P1and operates in the second period P2, in this embodiment, the power consumed by the heat generating circuit21per unit time in the first period P1is larger than the power consumed by the output circuit30per unit time in the second period P2. Accordingly, as indicated by A4inFIG. 8, a consumption current I2in the first period P1is larger than the consumption current I1in the second period P2. As a result, the integrated circuit2generates heat with a first heat generation amount per unit time in the first period P1, generates heat with a second heat generation amount per unit time in the second period P2after the first period P1ends, and the first heat generation amount is larger than the second heat generation amount. For that reason, in the first period P1, the temperature of the integrated circuit2rises sharply, and the temperature of the resonator3also rises sharply following the temperature of the integrated circuit2. Then, at time t2earlier than time t3of the second period P2, the integrated circuit2and the resonator3reach a thermal equilibrium state and the deviation of the oscillation frequency becomes substantially zero, as indicated by A6. As such, in the oscillator1of this embodiment, the time until the integrated circuit2and the resonator3reach the thermal equilibrium state is shortened compared to the oscillator of the comparative example.

In the oscillator1of this embodiment, even if the power consumed by the heat generating circuit21per unit time in the first period P1is smaller than the power consumed by the output circuit30per unit time in the second period P2, since the consumption current I0in the first period P1is larger than that of the oscillator of the comparative example, the time until the integrated circuit2and the resonator3reach a thermal equilibrium state is shortened.

Layout of Integrated Circuit

In this embodiment, a layout of the integrated circuit2is devised so that heat generated by the integrated circuit2is easily transmitted to the resonator3.FIG. 9is a plan view of a semiconductor substrate100on which elements are formed in the integrated circuit2. As illustrated inFIG. 9, in this embodiment, the shortest distance d1between the heat generating circuit21and the XI terminal is shorter than the shortest distance d3between the heat generating circuit21and the VC terminal, the shortest distance d4between the heat generating circuit21and the VDD terminal, the shortest distance d5between the heat generating circuit21and the VSS terminal, and the shortest distance d6between the heat generating circuit21and the OUT terminal. Similarly, the shortest distance d2between the heat generating circuit21and the XO terminal is shorter than the shortest distance d3between the heat generating circuit21and the VC terminal, the shortest distance d4between the heat generating circuit21and the VDD terminal, the shortest distance d5between the heat generating circuit21and the VSS terminal, and the shortest distance d6between the heat generating circuit21and the OUT terminal. That is, the heat generating circuit21has the shortest distance from the XI terminal or the XO terminal among the plurality of external connection terminals of the integrated circuit2. In other words, among the plurality of external connection terminals of the integrated circuit2, the XI terminal or the XO terminal is closest to the heat generating circuit21. Accordingly, the heat generated by the heat generating circuit21is efficiently transmitted to the resonator3through the XI terminal and the XO terminal, the temperature rise of the resonator3is accelerated, and the time until the integrated circuit2and the resonator3reach a thermal equilibrium state is shortened.

As illustrated inFIG. 9, in this embodiment, the shortest distance d7between the temperature sensor42and the XI terminal is longer than the shortest distance d9between the temperature sensor42and the VC terminal, the shortest distance d10between the temperature sensor42and the VDD terminal, and the shortest distance d11between the temperature sensor42and the VSS terminal, and the shortest distance d12between the temperature sensor42and the OUT terminal. Similarly, the shortest distance d8between the temperature sensor42and the XO terminal is longer than the shortest distance d9between the temperature sensor42and the VC terminal, the shortest distance d10between the temperature sensor42and the VDD terminal, the shortest distance d11between the temperature sensor42and the VSS terminal, and the shortest distance d12between the temperature sensor42and the OUT terminal. That is, the temperature sensor42has the longest distance from the XI terminal or the XO terminal among the plurality of external connection terminals of the integrated circuit2. In other words, among the plurality of external connection terminals of the integrated circuit2, the XI terminal or the XO terminal is farthest from the temperature sensor42. Accordingly, since the temperature sensor42is away from the heat generating circuit21, the temperature sensor42detects a temperature lower than the temperature of the heat generating circuit21, and thus the difference between the temperature detected by the temperature sensor42and the temperature of the resonator3is reduced and the frequency deviation when the output of the oscillation signal VOSC is started can be reduced.

The shortest distance d1between the heat generating circuit21and the XI terminal is smaller than the shortest distance d7between the temperature sensor42and the XI terminal. Similarly, the shortest distance d2between the heat generating circuit21and the XO terminal is smaller than the shortest distance d8between the temperature sensor42and the XO terminal. Accordingly, the heat generated by the heat generating circuit21is more easily transmitted to the resonator3through the XI terminal and the XO terminal than the temperature sensor42, and thus the difference between the temperature detected by the temperature sensor42and the temperature of the resonator3is reduced.

The XI terminal is an example of a “first external connection terminal”, and the XO terminal is an example of a “second external connection terminal”.

Operational Effects

As described above, in the oscillator1of the first embodiment, since the heat generating circuit21generates heat during the first period P1from the start, power consumption of the integrated circuit2in the second period P2is larger than the power consumption of the integrated circuit2in the second period P2after the first period P1, in the integrated circuit2. As a result, the heat generation amount of the integrated circuit2in the first period P1becomes larger than the heat generation amount of the integrated circuit2in the second period P2, and the heat from the integrated circuit2is efficiently transmitted to the resonator3. For that reason, the temperature rise of the resonator3is accelerated, the time until the integrated circuit2and the resonator3reach a thermal equilibrium state is shortened, and the frequency deviation when the output of the oscillation signal VOSC is started is reduced. Accordingly, according to the oscillator1of the first embodiment, it is possible to reduce the frequency deviation of the oscillation signal at the time of start.

Also, according to the oscillator1of the first embodiment, when the temperature compensation circuit40is adjusted, the current flowing through the heat generating circuit21can be changed in conjunction with the oscillation stage current adjustment data, the output level adjustment data VADJ, and the frequency division switching data DIV to accurately generate the current corresponding to the current consumed by the output circuit30during normal operation, and thus frequency temperature compensation can be performed with high accuracy by reducing the differential current. In the oscillator1of the first embodiment, a circuit area of the integrated circuit2is reduced by using the heat generating circuit21in the first period P1and at the time of adjusting the temperature compensation circuit40.

1-2. Second Embodiment

Hereinafter, for the oscillator1of a second embodiment, the same reference numerals are given to the same configurations as those of the first embodiment, the description similar to the first embodiment is omitted or simplified, and the contents different from the first embodiment will be mainly described.

FIG. 10is a functional block diagram of the oscillator1according to the second embodiment. As illustrated inFIG. 10, in the oscillator1according to the second embodiment, heat generation control current adjustment data IADJ2for adjusting and selecting the current flowing through the heat generating circuit21in the first period P1is stored in the memory60of the integrated circuit2. The heat generation control current adjustment data IADJ2is stored in a non-volatile memory included in the memory60in the manufacturing process of the oscillator1. The heat generation control current adjustment data IADJ2stored in the non-volatile memory is written from the non-volatile memory to the register immediately after the start of the oscillator1, that is, immediately after the supply of the power supply voltage to the VDD terminal is started.

The amplitude control circuit20adjusts and selects the current that flows through the heat generating circuit21in the first period P1based on the heat generation control current adjustment data IADJ2.

FIG. 11is a diagram illustrating a configuration example of the amplitude control circuit20ofFIG. 10. As illustrated inFIG. 11, in the amplitude control circuit20, the decoder23controls the direct current Iht flowing through the heat generating circuit21based on the test signal TP, the oscillation stage current adjustment data IADJ, the frequency division switching data DIV, and the heat generation control current adjustment data IADJ2. Specifically, when the test signal TP is at the high level, the decoder23controls the resistance value of the variable resistor VR according to the oscillation stage current adjustment data IADJ and the frequency division switching data DIV, similarly as in the first embodiment.

When the test signal TP is at the low level, the decoder23controls the variable resistor VR included in the heat generating circuit21to a value corresponding to the heat generation control current adjustment data IADJ2in the first period P1when the heat generation control signal HTCTL is at the low level. Then, the direct current Iht corresponding to the resistance value of the variable resistor VR flows through the heat generating circuit21. That is, in the oscillator1of the second embodiment, the current flowing through the heat generating circuit21in the first period P1is variable.

FIG. 12is a diagram illustrating an example of the operation of the oscillator1according to the second embodiment. InFIG. 12, B1indicates the change in the power supply voltage supplied to the VDD terminal, B2indicates the waveform of the oscillation signal VOSC, and B3indicates the waveform of the oscillation signal VOUT. B4indicates the power consumption of the integrated circuit2, B5indicates the temperature of the integrated circuit2and the temperature of the resonator3, and B6indicates the frequency deviation of the oscillation frequency. In B5, the solid line represents the temperature change of the integrated circuit2, and the broken line represents the temperature change of the resonator3.

As illustrated by B1inFIG. 12, when the supply of the power supply voltage to the VDD terminal is started at time t0, the resonator3oscillates and the amplitude of the oscillation signal VOSC gradually increases, as indicated by B2. When the amplitude of the oscillation signal VOSC becomes larger than the threshold value, the oscillation signal VOUT is generated at time t1, as indicated by B3. Thereafter, the supply of the power supply voltage to the VDD terminal is completed at time t4, and the operation of the oscillator1is stopped.

In the oscillator1of the second embodiment, the current corresponding to the heat generation control current adjustment data IADJ2flows through the heat generating circuit21to generate heat in the first period P1, and no current flows in the second period P2after the first period P1ends. That is, in this embodiment, the consumption current I2in the first period P1can be adjusted, as indicated by B4. Although the output circuit30stops operating in the first period P1and operates in the second period P2, in this embodiment, the power consumed by the heat generating circuit21per unit time in the first period P1is larger than the power consumed by the output circuit30per unit time in the second period P2. Accordingly, as indicated by B4, the consumption current I2in the first period P1is larger than the consumption current I1in the second period P2. As a result, the integrated circuit2generates heat with a first heat generation amount per unit time in the first period P1, generates heat with a second heat generation amount per unit time in the second period P2after the first period P1ends, and the first heat generation amount is larger than the second heat generation amount. For that reason, in the first period P1, the temperature of the integrated circuit2rises sharply, and the temperature of the resonator3also rises sharply following the temperature of the integrated circuit2. Then, at time t2of the second period P2, the integrated circuit2and the resonator3reach a thermal equilibrium state and the deviation of the oscillation frequency becomes substantially zero, as indicated by B6. As such, according to the oscillator1of the second embodiment, similarly as in the first embodiment, the time until the integrated circuit2and the resonator3reach the thermal equilibrium state is shortened compared to the oscillator of the comparative example described above. Furthermore, according to the oscillator1of the second embodiment, since the current flowing through the heat generating circuit21in the first period P1can be adjusted according to an individual difference of the oscillator1, even if there is an individual difference of the oscillator1, the time until the integrated circuit2and the resonator3reach a thermal equilibrium state can be reliably shortened.

Hereinafter, for the oscillator1of a third embodiment, the same reference numerals are given to the same configurations as those of the first embodiment, the description similar to the first embodiment is omitted or simplified, and the contents different from the first embodiment will be mainly described.

FIG. 13is a functional block diagram of the oscillator1according to the third embodiment. As illustrated inFIG. 13, in the oscillator1according to the third embodiment, heat generation period adjustment data TADJ for adjusting and selecting the length of the first period P1during which the current flows through the heat generating circuit21is stored in the memory60of the integrated circuit2. The heat generation period adjustment data TADJ is stored in a non-volatile memory included in the memory60in the manufacturing process of the oscillator1. The heat generation period adjustment data TADJ stored in the non-volatile memory is written from the non-volatile memory to the register immediately after the start of the oscillator1, that is, immediately after the supply of the power supply voltage to the VDD terminal is started.

The heat generation period control circuit92outputs the heat generation control signal HTCTL based on the detection signal VDET output from the amplitude detection circuit90and the heat generation period adjustment data TADJ. In this embodiment, when the detection signal VDET is at the low level, the heat generation control signal HTCTL is at the low level. When the time set according to the heat generation period adjustment data TADJ elapses from the timing when the detection signal VDET changes from the low level to the high level, the heat generation control signal HTCTL changes from the low level to the high level. Specifically, the heat generation period control circuit92counts the number of pulses of the oscillation signal VOSC from the timing when the detection signal VDET changes from the low level to the high level, and changes the heat generation control signal HTCTL from the low level to the high level when the count value corresponding to the heat generation period adjustment data TADJ is reached. As such, in the oscillator1according to the third embodiment, the length of the first period P1is variable.

FIG. 14is a diagram illustrating an example of the operation of the oscillator1according to the third embodiment. InFIG. 14, C1indicates the change in the power supply voltage supplied to the VDD terminal, C2indicates the waveform of the oscillation signal VOSC, and C3indicates the waveform of the oscillation signal VOUT. C4indicates the power consumption of the integrated circuit2, C5indicates the temperature of the integrated circuit2and the temperature of the resonator3, and C6indicates the frequency deviation of the oscillation frequency. In C5, the solid line represents the temperature change of the integrated circuit2, and the broken line represents the temperature change of the resonator3.

As illustrated by C1inFIG. 14, when the supply of the power supply voltage to the VDD terminal is started at time t0, the resonator3oscillates and the amplitude of the oscillation signal VOSC gradually increases, as indicated by C2. When the amplitude of the oscillation signal VOSC becomes larger than the threshold value, the oscillation signal VOUT is generated at time t1, as indicated by C3. Thereafter, the supply of the power supply voltage to the VDD terminal is completed at time t4, and the operation of the oscillator1is stopped.

In the oscillator1of the second embodiment, the current flows through the heat generating circuit21to generate heat in the first period P1, and no current flows in the second period P2after the first period P1ends. In this embodiment, the length of the first period P1can be adjusted, as indicated by C4. Although the output circuit30stops operating in the first period P1and operates in the second period P2, in this embodiment, the power consumed by the heat generating circuit21per unit time in the first period P1is larger than the power consumed by the output circuit30per unit time in the second period P2. Accordingly, as indicated by C4, the consumption current I2in the first period P1is larger than the consumption current I1in the second period P2. As a result, the integrated circuit2generates heat with a first heat generation amount per unit time in the first period P1, generates heat with a second heat generation amount per unit time in the second period P2after the first period P1ends, and the first heat generation amount is larger than the second heat generation amount. For that reason, in the first period P1, the temperature of the integrated circuit2rises sharply, and the temperature of the resonator3also rises sharply following the temperature of the integrated circuit2. Then, at time t2of the second period P2, the integrated circuit2and the resonator3reach a thermal equilibrium state and the deviation of the oscillation frequency becomes substantially zero, as indicated by C6. As such, according to the oscillator1of the third embodiment, similarly as in the first embodiment, the time until the integrated circuit2and the resonator3reach the thermal equilibrium state is shortened compared to the oscillator of the comparative example described above. Furthermore, according to the oscillator1of the third embodiment, since the length of the first period P1during which the temperature of the integrated circuit2rises sharply can be adjusted according to the individual difference of the oscillator1, even if there is an individual difference of the oscillator1, the time until the integrated circuit2and the resonator3reach a thermal equilibrium state can be reliably shortened.

1-4. Modification Example

The second embodiment and third embodiment described above may be combined. That is, in the oscillator1, both the length of the first period P1and the current flowing through the heat generating circuit21in the first period P1may be variable.

In the third embodiment, although the first period P1ends when the time set according to the heat generation period adjustment data TADJ elapses from the timing when the detection signal VDET changes from the low level to the high level, the first period P1may end when a time set according to the heat generation period adjustment data TADJ elapses immediately after the oscillator1is started. For example, the heat generation period control circuit92counts the number of pulses of the oscillation signal VOSC immediately after the oscillator1is started, and may end the first period P1by changing the heat generation control signal HTCTL from the low level to the high level when the count value corresponding to the heat generation period adjustment data TADJ is reached.

In each of the embodiments described above, although the heat generating circuit21is used in both the first period P1and at the time of adjusting the temperature compensation circuit40, a heat generating circuit that generates heat during the first period P1and a heat generating circuit that generates heat during adjustment of the temperature compensation circuit40may be provided separately.

In each of the embodiments described above, although the heat generating circuit21generates heat when the first period P1and the temperature compensation circuit40are adjusted, the present disclosure can also be applied to an oscillator that does not generate heat when the temperature compensation circuit40is adjusted.

In each of the embodiments described above, although the integrated circuit2includes the heat generating circuit21, an element having a heater function such as a Peltier element may be provided instead of the heat generating circuit21or together with the heat generating circuit21, and the element may generate heat in the first period P1.

The oscillator1of each of the above embodiments is an oscillator including a temperature compensation function such as a voltage controlled temperature compensated crystal oscillator (TCXO), but may be an oscillator having a temperature compensation function and a frequency control function such as a voltage controlled temperature compensated crystal oscillator (VC-TCXO).

2. Electronic Device

FIG. 15is a functional block diagram illustrating an example of a configuration of an electronic device of the embodiment of the present disclosure.FIG. 16is a diagram illustrating an example of the appearance of a smartphone that is an example of an electronic device of the embodiment of the present disclosure.

An electronic device300according to the embodiment of the present disclosure is configured to include an oscillator310, a central processing unit (CPU)320, an operation unit330, a read only memory (ROM)340, a random access memory (RAM)350, a communication unit360, and a display unit370. The electronic device of the embodiment of the present disclosure may have a configuration in which some of constitutional elements inFIG. 15are omitted or changed, or other constitutional elements are added.

An oscillator310includes an integrated circuit312and a resonator313. The integrated circuit312oscillates the resonator313and generates an oscillation signal. The oscillation signal is output from an external terminal of the oscillator310to the CPU320.

The CPU320is a processing unit that performs various calculation processing and control processing using an oscillation signal input from the oscillator310as a clock signal in accordance with a program stored in the ROM340or the like. Specifically, the CPU320performs various processing according to operation signals from the operation unit330, processing for controlling the communication unit360to perform data communication with an external device, and processing for transmitting a display signal for displaying various types of information on the display unit370, and the like.

The operation unit330is an input device including operation keys, button switches, and the like, and outputs an operation signal corresponding to an operation by a user to the CPU320.

The ROM340is a storage unit that stores programs, data, and the like for the CPU320to perform various calculation processing and control processing.

The RAM350is used as a work area of the CPU320, and is a storage unit that temporarily stores programs and data read from the ROM340, data input from the operation unit330, operation results executed by the CPU320according to various programs, and the like.

The communication unit360performs various controls for establishing data communication between the CPU320and the external device.

The display unit370is a display device configured by a liquid crystal display (LCD) or the like, and displays various types of information based on the display signal input from the CPU320. The display unit370may be provided with a touch panel that functions as the operation unit330.

By applying, for example, the oscillator1of each embodiment described above as the oscillator310the frequency deviation of the oscillation signal at the time of start can be reduced, so that a highly reliable electronic device can be realized.

Various electronic devices are conceivable as such an electronic device300, and examples thereof include a personal computer such as a mobile-type computer, a laptop-type computer, and a tablet-type computer, a mobile terminal such as a smartphone and a mobile phone, a digital camera, an ink jet ejection device such as an ink jet printer, a storage area network device such as a router and a switch, local area network equipment, mobile terminal base station equipment, a TV, a video camera, a video recorder, a car navigation device, a real-time clock device, a pager, an electronic notebook, an electronic dictionary, a calculator, an electronic game device, a game controller, a word processor, a workstation, a video phone, a crime prevention TV monitor, electronic binoculars, a POS terminal, medical equipment such as an electronic thermometer, a blood pressure monitor, a blood glucose meter, an electrocardiogram measuring device, an ultrasonic diagnostic device, and an electronic endoscope, a fish finder, various measuring instruments, instruments for a vehicle, an aircraft, a ship, and the like, a flight simulator, a head mounted display, a motion tracing device, a motion tracking device, a motion controller, and a pedestrian dead reckoning (PDR) device.

As an example of the electronic device300of the embodiment of the present disclosure, a transmission apparatus that functions as a terminal base station apparatus or the like that performs communication with a terminal in a wired or wireless manner using the oscillator310described above as a reference signal source may be included. As the oscillator310, for example, by applying the oscillator1of each of the embodiments described above, it is also possible to realize the electronic device300that can be used for, for example, a communication base station and that is desired to have high frequency accuracy, high performance, and high reliability at a lower cost than in the past.

Another example of the electronic device300according to the embodiment of the present disclosure may be a communication apparatus including a frequency control unit in which the communication unit360receives an external clock signal and the CPU320controls the frequency of the oscillator310based on the external clock signal and an output signal of the oscillator310. The communication apparatus may be, for example, a backbone network device such as Stratum 3 or a communication device used for a femtocell.

FIG. 17is a diagram illustrating an example of a vehicle according to the embodiment of the present disclosure. A vehicle400illustrated inFIG. 17is configured to include an oscillator410, controllers420,430, and440that perform various controls for an engine system, a brake system, a keyless entry system, and the like, a battery450, and a backup battery460. The vehicle according to the embodiment of the present disclosure may have a configuration in which some of the constitutional elements inFIG. 17are omitted or other components are added.

The oscillator410includes an integrated circuit (not illustrated) and a resonator, and the integrated circuit oscillates the resonator and generates an oscillation signal. This oscillation signal is output from the external terminal of the oscillator410to the controllers420,430, and440and used as, for example, a clock signal.

The battery450supplies power to the oscillator410and the controllers420,430, and440. The backup battery460supplies power to the oscillator410and the controllers420,430, and440when an output voltage of the battery450falls below a threshold value.

By applying, for example, the oscillator1of each of embodiment described above as the oscillator410, the frequency deviation of the oscillation signal at the time of start can be reduced, so that a highly reliable vehicle can be realized.

As such a vehicle400, various vehicles are conceivable, and examples thereof may include automobiles such as electric cars, airplanes such as jets and helicopters, ships, rockets, and artificial satellites.

The present disclosure is not limited to the embodiment of the present disclosure, and various modification examples may be made thereto within the scope of the gist of the present disclosure.

The embodiments and modification example described above are merely examples, and the present disclosure is not limited thereto. For example, it is possible to appropriately combine each embodiment and each modification example.

The present disclosure includes configurations that are substantially the same as the configurations described in the embodiments, for example, configurations that have the same functions, methods, and results, or configurations that have the same purposes and effects. The present disclosure includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. The present disclosure includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. The present disclosure includes a configuration in which a known technique is added to the configuration described in the embodiment.