JP2006166393A - Temperature compensated oscillation circuit comprising temperature compensation circuit, and electronic apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature compensated oscillation circuit comprising a temperature compensation circuit capable of highly accurately performing temperature compensation by logical operation. <P>SOLUTION: The temperature compensated oscillation circuit comprising the temperature compensation circuit includes: a temperature detection unit 22 that measures the ambient temperature of a piezoelectric vibrator 12 and outputs, as a digital signal, the result of the measurement; a conversion processing unit 28 that logically operates the digital signal and outputs the result of the operation as a compensation signal for compensating for frequency/temperature characteristics of the piezoelectric vibrator 12; the piezoelectric vibrator 12 that oscillates at a predetermined frequency; and a frequency adjustment means for adjusting the oscillation frequency of the piezoelectric vibrator 12 by changing element values in accordance with the compensation signal. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a temperature-compensated oscillation circuit and an electronic apparatus having a temperature compensation circuit, and more particularly to a digital temperature compensation type oscillation circuit.

  An oscillation circuit including a temperature compensation circuit can constitute a temperature compensated piezoelectric oscillator or a real time clock. As shown in FIG. 18, the temperature compensated piezoelectric oscillator 1 includes an oscillation circuit 3 connected to the piezoelectric vibrator 2, a control circuit 4 that controls the oscillation circuit 3, and an analog / analog connected to the previous stage of the control circuit 4. This is a configuration including a digital (A / D) converter 5 and a temperature sensor 6 connected to the preceding stage of the A / D converter 5. The oscillation circuit 3 connected to the piezoelectric vibrator 2 includes a capacitor array for changing the oscillation frequency. A storage unit 7 is connected to the control circuit 4. The storage unit 7 stores data (correction value) representing the capacitance value of the capacitance array with respect to the temperature within the operating temperature range of the temperature compensated piezoelectric oscillator 1. The correction value is obtained by changing the ambient temperature in a state where the piezoelectric oscillator 1 is oscillated after the piezoelectric oscillator 1 is accommodated in the thermostatic bath.

  The temperature sensor 6 measures the ambient temperature of the piezoelectric vibrator 2 and outputs the measurement result to the A / D converter 5 as an analog signal. The A / D converter 5 converts the analog signal into a digital signal, and then outputs the digital signal to the control circuit 4. After inputting the digital signal, the control circuit 4 reads a correction value corresponding to the value of the digital signal from the storage unit 7 and outputs it to the oscillation circuit 3. The oscillation circuit 3 adjusts and outputs the oscillation frequency by a method such as changing the capacitance value of the capacitance array according to the input correction value.

For example, Patent Documents 1 to 3 are disclosed as temperature compensated piezoelectric oscillators. The temperature compensated piezoelectric oscillator disclosed in Patent Document 2 halves the temperature interval for temperature compensation control by interpolating a known control value between two adjacent points of the temperature to be controlled using a simple average value. The accuracy of the frequency temperature compensation control is increased without narrowing and increasing the capacity of the memory circuit. In addition, the temperature compensated piezoelectric oscillator disclosed in Patent Document 3 reduces the memory consumption capacity by sequentially storing not the absolute value of compensation data but the difference with adjacent data in a memory.
Japanese Patent Laid-Open No. 48-25463 (see FIG. 9) JP-A-5-152846 JP-A-8-130411

  By the way, the correction value stored in the storage unit must be acquired by changing the ambient temperature in a state where the piezoelectric oscillator is oscillated after the piezoelectric oscillator is accommodated in the thermostat. There was such a problem.

  In addition, since it is necessary to increase the data in order to perform high-precision temperature compensation, the storage capacity of the storage unit composed of a memory (EPROM) capable of erasing data must be increased, and the data writing time is increased. There was a problem such as becoming longer.

An object of the present invention is to provide a temperature compensated oscillation circuit including a temperature compensation circuit that can perform temperature compensation with high accuracy without using a storage unit for temperature compensation.
It is another object of the present invention to provide an electronic device equipped with a temperature compensated oscillation circuit provided with this temperature compensation circuit.

  In order to achieve the above object, a temperature compensated oscillation circuit including a temperature compensation circuit according to the present invention is an oscillation circuit that is connected to a piezoelectric vibrator and outputs an oscillation signal having a predetermined frequency. A temperature detection unit that outputs the measurement data of the ambient temperature as a digital signal; a conversion processing unit that performs a logical operation on the digital signal and outputs the calculation result as a compensation signal that compensates for the frequency temperature characteristics of the piezoelectric vibrator; Frequency adjustment means for adjusting the oscillation frequency of the piezoelectric vibrator in accordance with the compensation signal, and the conversion processing unit inputs the digital signal and outputs the digital signal larger than the center temperature of the operating temperature range. A folding circuit that performs inversion processing and a signal from the folding circuit are input, and the signal is suppressed if the signal is within a range including the center temperature of the operating temperature range. Outputs the compensation signal of the equivalence, a conversion logic circuit comprising a suppression circuit for outputting the signal as the compensation signal if the signal out of the range, and is characterized in that.

  A temperature compensated oscillation circuit including a temperature compensation circuit according to the present invention is an oscillation circuit that is connected to a piezoelectric vibrator and outputs an oscillation signal having a predetermined frequency. A temperature detection unit that outputs a digital signal; a logical operation of the digital signal; a conversion processing unit that outputs the calculation result as a compensation signal that compensates for a frequency temperature characteristic of the piezoelectric vibrator; A frequency adjusting means for changing an oscillation signal, and the conversion processing unit receives the digital signal and inverts the digital signal larger than the center temperature of the operating temperature range; If the signal is within the range including the center temperature of the operating temperature range, the signal is suppressed and the compensation signal having the same value is output. Wherein the suppression circuit for outputting the signal as the compensation signal if the signal is a conversion logic circuit with, is characterized in that the.

  In the temperature compensated oscillation circuit provided with the temperature compensation circuit, the value of the compensation signal and the element value of the frequency adjustment means are associated one-to-one, so that the frequency adjustment means can be controlled according to the compensation signal, The frequency temperature characteristic of the piezoelectric vibrator can be temperature compensated. The temperature compensated oscillation circuit including the temperature compensation circuit according to the present invention can obtain data (computation result) for temperature compensation of the frequency temperature characteristics of the piezoelectric vibrator by logical operation. Therefore, since a compensation signal can be obtained only by a logical operation, data for controlling the frequency adjusting means can be obtained in a short time. Further, since there is no step of storing all the data at the time of manufacture, the time for writing this data can be reduced.

  The suppression circuit suppresses the output signal to the same value if the value of the input signal is within a certain range including the center temperature, and forms a flat region in the signal waveform output from the conversion processing unit. That is, since the conversion processing unit makes the signal waveform of the output compensation signal trapezoidal by a logical operation, if the value of the digital signal is within a flat region, the compensation signal having the same value is output. Therefore, the frequency temperature characteristic after temperature compensation becomes a shape that follows the frequency temperature characteristic of the piezoelectric vibrator in the flat region, and the frequency deviation becomes a value close to zero outside the flat region, so that temperature compensation can be performed with high accuracy. In addition, since the conversion processing unit can configure the folding circuit and the suppression circuit with simple logic circuits, it can have a small circuit configuration and can reduce power consumption. In addition, the manufacturing cost of the logic circuit can be reduced. Therefore, the temperature compensated oscillation circuit including the temperature compensation circuit can be reduced in size, reduced in power consumption, and reduced in manufacturing cost.

  The folding circuit includes exclusive ORs EXORn-1 to EXOR0 for inputting the most significant digit INn of the digital signal and the second and lower digits INn-1,. A NAND circuit that inputs the upper 3 digits of the signal output from the folding circuit (output signal of the exclusive OR EXORn-1,... EXORn-3) and the upper 4 bits of the signal output from the folding circuit. It is characterized by comprising ANDs ANDn-4 to AND0 for inputting digits after the digit (exclusive logical product EXORn-4,... EXOR0) and the output of the negative logical product NAND. As a result, the digital signal can be inverted by exclusive OR, and trapezoidal processing can be performed by NAND and AND.

  The folding circuit includes exclusive ORs EXORn-1 to EXOR0 for inputting the most significant digit INn of the digital signal and the second and lower digits INn-1,. The signal output from the folding circuit and a preset suppression value are input to compare and determine which is greater, a magnitude comparator that outputs the determination result, and the signal output from the folding circuit; And a selector that inputs the suppression value set in advance and outputs either the signal or the suppression value based on the determination result output from the magnitude comparator. . As a result, the digital signal can be inverted by exclusive OR, and trapezoidal processing can be performed by the selector and the magnitude comparator.

  The temperature detection unit includes a temperature sensor that measures an ambient temperature of the piezoelectric vibrator, and an analog / digital converter that converts an analog signal output from the temperature sensor into a digital signal. The analog / digital converter Is a comparator for inputting the analog signal and the output signal of the digital / analog converter, the successive approximation register connected to the comparator, and the digital / analog for inputting the reference signal and the output signal of the successive approximation register. A successive approximation type comprising a converter, wherein the digital / analog converter inputs a first reference signal and a second reference signal having different potentials as the reference signal, and the first reference signal and the analog signal Selection means for selecting one of the first reference signal and the second reference signal according to the result of comparing It is characterized in that. Since different reference signals are used for the reference signal used to determine the most significant digit and the reference signal used to determine other digits, the signal waveform output from the analog / digital converter The slope can be changed at the midpoint. Since this intermediate point corresponds to the center temperature of the operating temperature range of the temperature compensated oscillation circuit provided with the temperature compensation circuit, the slope of the signal waveform output from the analog / digital converter is changed between the lower temperature side and the higher temperature side than the center temperature. Can be changed. This makes it possible to perform temperature compensation that matches the asymmetric frequency temperature characteristics of the piezoelectric vibrator.

  The temperature detection unit includes a temperature sensor that measures an ambient temperature of the piezoelectric vibrator, and an analog / digital converter that converts an analog signal output from the temperature sensor into a digital signal. The analog / digital converter Is a double integration type comprising an integration circuit for inputting the analog signal, a discharge circuit connected to the integration circuit, and a counter connected to the discharge circuit. A current adjustment circuit that adjusts the discharge current accordingly is provided in the subsequent stage. Since the discharge current is changed by the most significant digit, the slope of the signal waveform output from the analog / digital converter can be changed at the intermediate point. Since this intermediate point corresponds to the center temperature of the operating temperature range of the temperature compensated oscillation circuit provided with the temperature compensation circuit, the slope of the signal waveform output from the analog / digital converter is changed between the lower temperature side and the higher temperature side than the center temperature. Can be changed. This makes it possible to perform temperature compensation that matches the asymmetric frequency temperature characteristics of the piezoelectric vibrator.

  The frequency adjusting means is a capacitance array in which a plurality of circuits in which capacitors and switches are connected in series are connected in parallel. In this capacity slow / fast method, the capacitance value of the capacitor array is changed according to the compensation signal to adjust the oscillation frequency of the piezoelectric vibrator. As a result, it is possible to compensate for the frequency temperature of the piezoelectric vibrator.

  The frequency adjusting means is a logic slow / fast circuit provided with a frequency divider. In this logical slow / fast method, the frequency division ratio of the frequency divider is changed according to the compensation signal to change the frequency of the oscillation signal. Thereby, temperature compensation of the frequency temperature characteristic of the piezoelectric vibrator can be performed.

  A temperature measuring circuit is provided at the output stage of the oscillation frequency of the temperature-compensated piezoelectric vibrator. Since this clock circuit can display and output a clock and calendar, a real-time clock can be configured.

  A latch is provided between the conversion processing unit and the frequency adjusting means for inputting information on the compensation signal and storing and holding the information until a new compensation signal is input. Even if the temperature detection unit and the conversion processing unit connected to the preceding stage of the latch are operated intermittently, the compensation signal can be continuously output from the latch. Therefore, the power consumption can be reduced by intermittently operating the temperature detection unit and the conversion processing unit.

  The piezoelectric vibrator has a frequency temperature characteristic approximated by a quadratic function. As a result, the temperature compensated oscillation circuit having the temperature compensation circuit can accurately perform temperature compensation when the above-described temperature compensation is applied to the frequency temperature characteristic of the piezoelectric vibrator approximated by a quadratic function.

  In the following, a best embodiment of a temperature-compensated oscillation circuit and an electronic device including a temperature compensation circuit will be described. A temperature compensated oscillation circuit including a temperature compensation circuit can constitute a temperature compensated piezoelectric oscillator or a real time clock. Therefore, in the following embodiment, a configuration in which a temperature compensated piezoelectric oscillator is configured will be described.

  First, the first embodiment will be described. FIG. 1 is a block diagram of a temperature compensated piezoelectric oscillator. FIG. 2 is an explanatory diagram of the conversion logic circuit. FIG. 3 is an explanatory diagram of the capacitor array. The temperature compensated piezoelectric oscillator 10 according to the first embodiment includes a piezoelectric vibrator 12 having frequency temperature characteristics approximated by a quadratic function. The piezoelectric vibrator 12 may be, for example, a tuning fork type piezoelectric vibrator, a surface acoustic wave resonator, a BT cut piezoelectric vibrator, or the like. An oscillation circuit 14 for oscillating the vibrator 12 is connected to the piezoelectric vibrator 12. The oscillation circuit 14 is provided with a capacitor array 16 serving as a frequency adjusting means for adjusting the oscillation frequency of the piezoelectric vibrator 12. The capacitor array 16 includes a plurality of capacitors 18 having different capacitance values connected in parallel, and switches 20 connected to the capacitors 18.

  The temperature compensated piezoelectric oscillator 10 includes a temperature detection unit 22 that measures the ambient temperature of the piezoelectric vibrator 12 and outputs the measurement result as a temperature detection signal. Specifically, the temperature detection unit 22 measures the ambient temperature of the piezoelectric vibrator 12, outputs a measurement result as an analog signal, and converts the input analog signal into a digital signal and outputs the analog signal. / Digital (A / D) converter 26. Therefore, the temperature detection signal output from the temperature detection unit 22 is a digital signal.

  A conversion processing unit 28 for temperature compensating the frequency temperature characteristic of the piezoelectric vibrator 12 within the operating temperature range of the temperature compensated piezoelectric oscillator 10 is connected to the subsequent stage of the temperature detecting unit 22. The conversion processing unit 28 is constituted by a conversion logic circuit 30 and performs a logical operation on the temperature detection signal to output a temperature compensation signal (compensation signal). The conversion logic circuit 30 has a number of inputs corresponding to the number of output bits of the A / D converter 26, and a folding circuit 32 constituted by an exclusive OR for inputting the most significant digit and the lower digits. And a suppression circuit 34 composed of a negative logical product and a logical product for inputting a signal output from the folding circuit 32.

  Specifically, the folding circuit 32 has inputs IN0 to IN5 corresponding to the number of output bits of the A / D converter 26, and exclusively inputs the most significant digit IN5 and lower digits IN4, IN3,. Logical ORs EXOR0 to EXOR4. Then, the suppression circuit 34 receives a negative logical product NAND that inputs the output signals of the exclusive logical sums EXOR2 to EXOR4, a logical product AND0 that inputs the output signal of the negative logical product NAND and the output signal of the exclusive logical sum EXOR0, A logical product AND1 for inputting an output signal of the negative logical product NAND and an output signal of the exclusive logical sum EXOR1 is provided. Although the 6-bit conversion logic circuit 30 is shown in the present embodiment, the number of bits is not limited to 6 bits.

  Such a folding circuit 32 inverts a signal larger than the center temperature of the operating temperature range of the temperature compensated piezoelectric oscillator 10, and the suppression circuit 34 has a predetermined range including the center temperature of the operating temperature range. The signal inside is suppressed.

  The temperature compensation circuit includes a temperature detection unit 22 and a conversion processing unit 28. The subsequent stage of the conversion processing unit 28 is connected to the oscillation circuit 14, and the compensation signal performs ON / OFF control of each switch 20 provided in the capacitor array 16 to change the capacitance value (element value) of the capacitor array 16. Let The value of the compensation signal and the value for controlling ON / OFF of each switch 20 of the capacitor array 16 (capacity value of the capacitor array 16) are associated with each other on a one-to-one basis.

  Next, the operation of the temperature compensated piezoelectric oscillator 10 according to the first embodiment will be described. FIG. 4 is an explanatory diagram of signal waveforms showing the relationship between input signals and output signals of the A / D converter 26, the folding circuit 32, and the suppression circuit 34. Note that the input signals shown on the horizontal axes of FIGS. 4B and 4C represent the input signals to the conversion logic circuit 30. FIG. First, the temperature sensor 24 measures the ambient temperature of the piezoelectric vibrator 12 and outputs the measurement result as an analog signal. The A / D converter 26 converts an analog signal into a digital signal. At this time, the operating temperature range of the temperature compensated piezoelectric oscillator 10 is divided into predetermined steps by A / D conversion, and is divided into 64 steps in this embodiment. At this time, the relationship between the input signal and the output signal in the A / D converter 26 is as shown in FIG. For example, when the operating temperature range of the temperature compensated piezoelectric oscillator 10 is −30 ° C. to 80 ° C. and the center temperature is 25 ° C., when this is divided by 6 bits, it becomes about 1.7 ° C. per step. In the case where there is a variation in the relationship between the measured temperature and the output signal in the temperature sensor 24, an A / D converter 26 is provided with an offset circuit or a full scale circuit for adjusting the variation of the temperature sensor 24. It is possible to eliminate variations in the output from the device 26.

  The digital signal output from the A / D converter 26 is input to the folding circuit 32 of the conversion logic circuit 30. By this folding circuit 32, as shown in FIG. 4B, a signal larger than the center temperature in the operating temperature range of the temperature compensated piezoelectric oscillator 10 is inverted. For example, if the operating temperature range of the temperature compensated piezoelectric oscillator 10 is −30 ° C. to 80 ° C. and the center temperature is 25 ° C., a decimal number of a signal larger than 25 ° C., that is, a digital signal A / D converted by 6 bits An input value larger than 32 is reversed. Therefore, the relationship between the input signal and the output signal of the folding circuit 32 is axisymmetric about the input value 32, and the shape is a triangle.

  The signal output from the folding circuit 32 is input to the suppression circuit 34. As shown in FIG. 4C, the suppression circuit 34 suppresses (flattens) signals within a predetermined temperature range (in the input value range) including the center temperature of the operating temperature range. For example, when the operating temperature range of the temperature-compensated piezoelectric oscillator 10 is −30 ° C. to 80 ° C. and the center temperature is 25 ° C., the center temperature after A / D conversion with 6 bits is 32 in decimal notation. If the temperature range (input value range) is 28 to 35 in decimal notation, the same value is output when a signal in this 28 to 35 range is input. As described above, the suppression circuit 34 suppresses so as to output a certain value when a signal within a predetermined temperature range is input. Therefore, the relationship between the input signal and the output signal of the suppression circuit 34 is the predetermined temperature range. Becomes flat (flat region) and becomes a trapezoid as a whole.

  The signal output from the suppression circuit 34 is a compensation signal output from the conversion logic circuit 30. The compensation signal is an address value of the capacitance array 16, that is, a control signal for obtaining a desired capacitance value by turning on / off each switch 20 of the capacitance array 16. Then, by adjusting the capacitance value of the capacitor array 16 according to the compensation signal, the oscillation frequency of the piezoelectric vibrator 12 is adjusted, and temperature compensation is performed so that the frequency deviation of the frequency temperature characteristic becomes zero.

  FIG. 5 shows frequency temperature characteristics of the temperature compensated piezoelectric oscillator 10. The solid line in FIG. 5 is the frequency temperature characteristic of the temperature compensated piezoelectric oscillator 10, and the broken line is the frequency temperature characteristic of the piezoelectric vibrator 12. As shown in FIG. 4C, the compensation signal outputs a signal having the same value as the input signal in the flat region, so that the capacitance value of the capacitor array 16 is the same. Therefore, the frequency temperature characteristic of the piezoelectric oscillator has the same shape as the frequency temperature characteristic of the piezoelectric vibrator 12 in the flat region.

  Since the capacitance value is adjusted according to the compensation signal outside the flat region, the frequency temperature characteristic of the piezoelectric vibrator 12 is temperature compensated according to the capacitance value. Since the temperature compensation is performed by the digital method outside the flat region, the frequency temperature characteristic of the temperature compensated piezoelectric oscillator 10 is cut for each step in which the operating temperature range of the temperature compensated piezoelectric oscillator 10 is divided into a plurality of steps. That is, the frequency temperature characteristics after temperature compensation are not continuous, but are fragmented at each step. If the number of bits that divide the operating temperature range of the temperature compensated piezoelectric oscillator 10 is increased, the amplitude for each step of the bits is reduced.

  As described above, the temperature compensated piezoelectric oscillator 10 according to the first embodiment can adjust the capacitance value of the capacitor array 16 according to the temperature measured by the temperature sensor 24 by using the simple conversion logic circuit 30. . Since the conversion logic circuit 30 can be formed by a small scale integrated circuit (IC) chip, the manufacturing cost of the IC chip can be reduced. In addition, since it is not necessary to store the correspondence between the temperature measured by the temperature sensor and the capacitance value of the capacitance array in the memory in order to perform temperature compensation, it is possible to reduce the writing time of the associated data. Therefore, the manufacturing cost of the temperature compensated piezoelectric oscillator 10 can also be reduced. Furthermore, since the conversion logic circuit 30 can be reduced in size, the temperature compensated piezoelectric oscillator 10 can also be reduced in size.

In addition, since the temperature compensated piezoelectric oscillator 10 according to the present embodiment does not need to obtain temperature compensation data for associating the temperature with the capacitance value, the time for obtaining the temperature compensation data can be reduced.
Furthermore, since the temperature compensated piezoelectric oscillator 10 according to this embodiment is a simple conversion logic circuit 30, it can reduce power consumption.

  In order to improve the temperature compensation of the temperature compensated piezoelectric oscillator 10, the number of bits of the digital signal input to the conversion processing unit 28 may be increased. That is, the operating temperature range of the temperature compensated piezoelectric oscillator 10 may be divided in fine steps. For this purpose, the conversion logic circuit may be configured as follows. FIG. 6 is an explanatory diagram of a conversion logic circuit in which the number of bits is increased. When the number of bits is increased, the conversion logic circuit 30 may increase the exclusive OR and the logical product below the conversion logic circuit 30 shown in FIG. Specifically, the conversion logic circuit 30 includes a folding circuit 32 and a suppression circuit 34. The folding circuit 32 has a number of inputs IN0 to INn corresponding to the number of output bits of the A / D converter 26, and includes the most significant digit INn and lower digits INn-1, INn-2,. Input exclusive ORs EXOR0 to EXORn-1 are provided. The suppression circuit 34 inputs the output signal of the exclusive logical sums EXORn-3 to EXORn-1, and outputs the negative logical product NAND and one of the digits of the exclusive logical products EXORn-4 to EXOR0. AND AND0 to ANDn-4 are input. The suppression circuit 34 outputs compensation signals OUT0 to OUTn-1. By configuring the conversion logic circuit 30 in this way, the conversion processing unit 28 can increase the number of bits, and the temperature compensation of the temperature compensated piezoelectric oscillator 10 can be made highly accurate.

  Next, a second embodiment will be described. In the second embodiment, a modification of the temperature compensated oscillator according to the first embodiment will be described. Specifically, the temperature-compensated piezoelectric oscillator according to the second embodiment is different from the temperature-compensated piezoelectric oscillator according to the first embodiment in the configuration of the conversion logic circuit. The configuration will be described. In addition, the same number is attached | subjected to the part of the same structure as the temperature compensation piezoelectric oscillator which concerns on 1st Embodiment, and the description is abbreviate | omitted or simplified. The temperature compensated piezoelectric oscillator 10 according to the second embodiment includes a temperature detection unit 22 including a temperature sensor 24 and an A / D converter 26, a conversion processing unit 28 including a conversion logic circuit 80, and the piezoelectric vibrator 12. (See FIG. 1).

  FIG. 7 is an explanatory diagram of a conversion logic circuit according to the second embodiment. The conversion logic circuit 80 includes a folding circuit 32 and a suppression circuit 82. The folding circuit 32 receives the temperature detection signal (digital signal) output from the temperature detection unit 22 and inverts the digital signal having a value larger than the center temperature in the operating temperature range of the temperature compensated piezoelectric oscillator 10. is there. The suppression circuit 82 receives the signal output from the folding circuit 32, and suppresses the signal and outputs a compensation signal having the same value if the signal is within a predetermined range including the center temperature of the operating temperature range. If this signal is out of range, the signal is output as a compensation signal.

  Specifically, the folding circuit 32 has inputs IN0 to IN5 corresponding to the number of output bits of the A / D converter 26, and inputs the most significant digit IN5 and the lower digits IN4, IN3,. Exclusive ORs EXOR0 to EXOR4 are provided. The suppression circuit 82 includes a selector 84 for inputting a signal output from the folding circuit 32 and a magnitude comparator 86. The suppression circuit 82 is preset with suppression values e0 to e4 so as to output the same value within a predetermined range including the center temperature of the operating temperature range. This suppression value is selected by the selector 84 and the magnitude. Input to the comparator 86.

  The magnitude comparator 86 receives the signal output from the folding circuit 32 and the suppression value, compares and determines which value is larger, and outputs the determination result to the selector 84. The selector 84 receives the determination result from the magnitude comparator 86 and outputs either the signal or the suppression value based on the determination result. Although the 6-bit conversion logic circuit 80 is shown in the present embodiment, the number of bits is not limited to 6 bits.

  Next, the operation of the conversion logic circuit 80 will be described. The temperature compensation signal (digital signal) output from the A / D converter 26 is input to the folding circuit 32 of the conversion logic circuit 80. The folding circuit 32 inverts the digital signal having a value larger than the center temperature in the operating temperature range of the temperature compensated piezoelectric oscillator 10 (see FIG. 4B).

  The signal output from the folding circuit 32 is input to the suppression circuit 82. That is, the signal is input to the selector 84 and the magnitude comparator 86. In addition, a suppression value is set in advance in the suppression circuit 82, and this suppression value is also input to the selector 84 and the magnitude comparator 86. The suppression value is the output value α shown in FIG. 4C and is the output value of the suppression circuit 82 in the flat region. Therefore, the magnitude comparator 86 compares the signal output from the folding circuit 32 with the suppression value, and if the signal is smaller than the suppression value, outputs the determination result to the selector 84 so as to select the signal. To do. The selector 84 selects the signal from the input signal and the suppression value based on the determination result, and outputs this as output signals OUT0 to OUT4 of the suppression circuit 82. Further, the magnitude comparator 86 compares the signal with the suppression value, and if the signal is larger than the suppression value, outputs the determination result to the selector 84 so as to select the suppression value. The selector 84 selects a suppression value from the input signal and the suppression value based on the determination result, and outputs this as output signals OUT0 to OUT4 of the suppression circuit 82.

  In such a conversion logic circuit 80, since the suppression value can be set to an arbitrary value, the values of the output signals OUT0 to OUT4 of the conversion logic circuit 80 in the flat region can be set arbitrarily, and the flat region The width can also be set arbitrarily. Therefore, since the output signals OUT0 to OUT4 of the conversion logic circuit 80 can be set finely, temperature compensation can be performed with high accuracy according to the frequency temperature characteristics of the piezoelectric vibrator 12.

  When the number of output bits of the A / D converter is an arbitrary number, the conversion logic circuit 80 may be configured as follows. FIG. 8 is an explanatory diagram of a conversion logic circuit to which an arbitrary number of bits is input. When the conversion logic circuit 80 inputs a signal having an arbitrary number of bits from the A / D converter 26, the conversion logic circuit 80 may set a bit number suppression value corresponding to the number of bits of the signal output from the folding circuit 32.

Specifically, the folding circuit 32 includes exclusive ORs EXORn-1 to EXOR0 for inputting the most significant digit INn of the digital signal and the digits INn-1,. . The suppression circuit 82 includes a magnitude comparator 86 and a selector 84 for inputting the signals bn-1 to b0 output from the folding circuit 32 and the suppression values en-1 to e0 set to the same number of bits as this signal. ing. The magnitude comparator 86 compares the signals bn-1 to b0 with the suppression values en-1 to e0, and if the signals bn-1 to b0 are smaller than the suppression values en-1 to e0, the selector 84 The determination result is output so as to select the signals bn-1 to b0. The selector 84 selects the signals bn-1 to b0 based on the determination result and outputs them as the output signals OUTn-1 to OUT0 of the conversion logic circuit 80. The magnitude comparator 86 compares the signals bn-1 to b0 with the suppression values en-1 to e0, and if the signals bn-1 to b0 are larger than the suppression values en-1 to e0, the selector 84 The determination result is output so as to select the suppression values en-1 to e0. The selector 84 selects the suppression values en−1 to e0 based on the determination result and outputs them as output signals OUTn−1 to OUT0 of the conversion logic circuit 80.
By adopting such a configuration of the conversion logic circuit 80, the conversion logic circuit 80 corresponds to the temperature compensation signals INn to IN0 of any number of bits output from the A / D converter 26, so that the compensation signal OUTn− 1 to OUT0 can be output.

  Next, a third embodiment will be described. In the third embodiment, since a modified example of the temperature compensated piezoelectric oscillator according to the first and second embodiments will be described, a part having the same configuration as the temperature compensated piezoelectric oscillator according to the first and second embodiments is included. The same reference numerals are assigned, and the description thereof is omitted or simplified. Usually, the frequency temperature characteristic of the piezoelectric vibrator 12 is a bilateral curve that is asymmetrical with respect to the vertex temperature, and the frequency temperature characteristic on the low temperature side (the left curve) with respect to the vertex temperature is the frequency temperature characteristic on the high temperature side. It is gentler than the curve on the right. Therefore, the temperature compensated piezoelectric oscillator 10 according to the third embodiment is configured to perform temperature compensation in accordance with the frequency temperature characteristics of the left-right asymmetric piezoelectric vibrator 12 in order to perform temperature compensation with higher accuracy. . That is, the temperature compensated piezoelectric oscillator 10 according to the third embodiment includes a temperature detection unit 22 including a temperature sensor 24 and an A / D converter 42, a conversion processing unit 28 including conversion logic circuits 30 and 80, and a piezoelectric element. It is the structure provided with the oscillation circuit 14 provided with the vibrator | oscillator 12 (refer FIG. 1). The temperature sensor 24, the conversion logic circuits 30 and 80, the piezoelectric vibrator 12 and the oscillation circuit 14 may have the same configuration as that described in the first and second embodiments. In order to perform temperature compensation in accordance with the frequency temperature characteristics of the piezoelectric vibrator 12, the successive approximation A / D converter 42a or the double integration A / D converter 42b may be used as the A / D converter 42. .

  Next, the successive approximation A / D converter 42a will be described. FIG. 9 is an explanatory diagram of a successive approximation A / D converter. The successive approximation A / D converter 42 a includes a sample / hold (S / H) circuit 44 that inputs an analog signal output from the temperature sensor 24. A comparator 48 for inputting the signal output from the S / H circuit 44 and the output signal of the digital / analog (D / A) converter 46 is provided at the subsequent stage of the S / H circuit 44. At the subsequent stage of the comparator 48, there is provided a successive approximation register 50 for inputting the signal output from the comparator 48 and outputting the most significant digit to the least significant digit of the bits. At the subsequent stage of the successive approximation register 50, a D / A converter 46 for inputting the signal output from the successive approximation register 50 and the first reference signal Vr0 and the second reference signal Vr1 having different potentials as reference signals. Is provided.

  The D / A converter 46 includes a circuit for inputting the first reference signal Vr0 and the second reference signal Vr1, and selects either the first reference signal Vr0 or the second reference signal Vr1 at the tip of these circuits. A selection means 52 is provided. The selection means 52 selects either the first reference signal Vr0 or the second reference signal Vr1 according to the signal of the most significant digit d5 output from the successive approximation register 50. Specifically, the selection means 52 selects the first reference signal Vr0 when the most significant digit d5 is “0” in binary notation, and selects the first reference signal Vr0 when the most significant digit d5 is “1” in binary notation. The second reference signal Vr1 is selected. A resistor R is connected in parallel to the circuit of the first reference signal Vr0 in the previous stage of the selection means 52. Further, a plurality of resistors 2R, 4R, 8R, 16R, and 32R having different resistance values are connected in parallel at the subsequent stage of the selection means 52. A switch 54 that is ON / OFF controlled in accordance with a signal output from the successive approximation register 50 is provided in a stage preceding each of the resistors R to 32R. Specifically, the switch 54 is open when each digit d0 to d5 is “0” in binary notation, and is short-circuited when each digit d0 to d5 is “1” in binary notation. It is. The number of resistors is not limited to the above-described form. Further, an integrator 56 is provided at the subsequent stage of these resistors R to 32R.

  Next, the conversion operation of the successive approximation A / D converter 42a will be described. First, an analog signal output from the temperature sensor 24 is input to the comparator 48 via the S / H circuit 44. Then, the most significant digit d5 is set to “1”, and a signal of “100000” in binary notation is input to the D / A converter 46. With this signal, the selection means 52 selects the second reference signal Vr1, and the switch 54 controlled by the most significant digit d5 is short-circuited. The switch 54 controlled by the signals of the digits d0 to d4 output from the successive approximation register 50 is opened. The signal Vc output from the D / A converter 46 is a potential signal of Vc = Vr0. The output signal Vc is compared with the potential of the analog signal. If the potential of the analog signal is higher than the output signal Vc, the most significant digit d5 becomes “1”, and if it is lower, it becomes “0”.

  Next, the digit d4 output from the successive approximation register 50 is set to “1”, and “110000” or “010000” is input to the D / A converter 46 in binary notation. In this case, “110000” is input when the most significant digit d5 is “1”, and “010000” is input when the most significant digit d5 is “0”. When “110000” is input in binary notation, the selection means 52 selects the second reference signal Vr1, and the switch 54 controlled by the signals of the digits d5 and d4 output from the successive approximation register 50 is short-circuited. The The signal Vc output from the D / A converter 46 is a potential signal of Vc = Vr0 + (d4 / 2) × Vr1. The output signal Vc is compared with the potential of the analog signal. If the potential of the analog signal is higher than the output signal Vc, the digit d4 becomes “1”, and if it is lower, it becomes “0”. When “010000” is input in binary notation, the selection unit 52 selects the first reference signal Vr0 and opens the switch 54 controlled by the signal of the digit d5 output from the successive approximation register 50. The switch 54 controlled by the signal of the digit d4 is short-circuited. The signal Vc output from the D / A converter 46 is a potential signal of Vc = (d4 / 2) × Vr0. The output signal Vc is compared with the potential of the analog signal. If the potential of the analog signal is higher than the output signal Vc, the digit d4 becomes “1”, and if it is lower, it becomes “0”. For the digits d3 to d0 below this, “0” or “1” is determined in the same manner as described above.

  Next, an example of a specific operation of the successive approximation A / D converter 42a will be described. FIG. 10 is a diagram for explaining an example of the successive approximation type A / D conversion operation. The vertical axis in FIG. 10 represents the potential of the output signal Vc of the D / A converter 46, and the horizontal axis represents each digit of the digital signal. When an analog signal is input to the comparator 48, a signal “100000” is output from the successive approximation register 50, and thus a potential signal of the output signal Vc = Vr 0 is output from the D / A converter 46. When this analog signal is compared with the output signal Vc, since the analog signal is larger than the output signal Vc, the most significant digit d5 is determined to be “1”. Next, a signal of “110000” is output from the successive approximation register 50, and a potential signal of output signal Vc = Vr0 + (d4 / 2) × Vr1 is output from the D / A converter 46. At this time, since the analog signal is smaller than the output signal Vc, the digit d4 output from the successive approximation register 50 becomes “0”. When such an operation is repeated, the digits d3 to d0 are sequentially determined, and in the case shown in FIG. 10, “100101” is obtained.

  As described above, when the first reference signal Vr0 and the second reference signal Vr1 having different potentials are used, the potential of the output signal Vc differs depending on whether the most significant digit d5 is “0” or “1”. That is, the potential used as a comparison reference for the analog signal differs between the case where the selection unit 52 selects the first reference signal Vr0 and the case where the second reference signal Vr1 is selected. The position where the output signal Vc = Vr0 is the center point of the signal input to the A / D converter 42a (the center temperature in the operating temperature range of the temperature compensated piezoelectric oscillator 10). Therefore, the relationship between the input signal and output signal of the A / D converter 42a is a signal waveform as shown by the solid line in FIG.

  Next, the double integration type A / D converter 42b will be described. FIG. 12 is an explanatory diagram of a double integration type A / D converter. The double integration type A / D converter 42 b includes an integration circuit 60 that inputs an analog signal output from the temperature sensor 24. If the integrating circuit 60 is an RC integrating circuit 60 as shown in FIG. 12, for example, a switch 62 is provided at the subsequent stage of the resistor R, and the capacitor C is always in conduction with a circuit connected at the subsequent stage of the integrating circuit 60. ing. Further, a discharge circuit 68 including a switch 64 and a current adjustment circuit 66 and a comparator 70 are connected to the integration circuit 60 in parallel. At the subsequent stage of the comparator 70, there is provided a counter 72 for inputting a clock signal and outputting each digit d5 to d0 from the most significant digit to the least significant digit of the bit. The circuit that outputs the most significant digit d5 is connected to the current adjustment circuit 66.

  Next, the conversion operation of the above-mentioned double integration type A / D converter 42b will be described. FIG. 13 is an explanatory diagram of a double integration type A / D conversion operation. First, when the switch 62 provided in the integration circuit 60 is short-circuited for a certain time and the switch 64 provided in the discharge circuit 68 is opened, the analog signal output from the temperature sensor 24 is integrated. At this time, a charge proportional to the input voltage and time is stored in the capacitor C of the integrating circuit 60. Then, after a predetermined time has elapsed, the switch 62 provided in the integrating circuit 60 is opened. At the same time as the switch 64 provided in the discharge circuit 68 is short-circuited, the counter 72 starts counting. As a result, the electric charge charged in the capacitor C of the integrating circuit 60 flows to the discharge circuit 68 with the constant current I1, and the capacitor C is discharged. By counting the discharge time with the counter 72, the digits d0 to d5 of each bit are determined. At this time, when the discharge time exceeds 1/2 of the full scale FSR, the most significant digit d5 is determined to be “1”, but when this most significant digit is determined, the discharge current is switched to the constant current I2. That is, when the most significant digit d5 is determined to be “1”, the signal output from the counter 72 is input to the current adjustment circuit 66 of the discharge circuit 68, and the constant current I1 is switched to the constant current I2. In FIG. 13, the full scale FSR indicates the discharge time when the discharge is continued with the constant current I1. The current adjustment circuit 66 only needs to have an operation of switching current, and may be constituted by a current mirror circuit, for example. As a result, the electric charge charged in the capacitor C flows to the discharge circuit 68 with the constant current I2, and the capacitor C is discharged. When the discharge of the capacitor C is completed, the counter 72 stops counting and each digit d0 to d5 is determined.

  Thus, when the count of the counter 72 exceeds 1/2 of the full scale FSR (see the solid line in FIG. 13), the capacitor C is discharged with the constant current I1 and the constant current I2, and the count of the counter 72 is the full scale FSR. Is not exceeded (see the broken line in FIG. 13), the capacitor C is discharged only by the constant current I1. Further, the position that is ½ of the full scale FSR is the center point of the signal input to the A / D converter 42b (the center temperature in the operating temperature range of the temperature compensated piezoelectric oscillator 10). Therefore, the relationship between the input signal and the output signal of the A / D converter 42b is a signal waveform as shown by the solid line in FIG. 11, as in the successive approximation type A / D converter 42a.

Next, the operation of the conversion processing unit 28 will be described. The digital signal output from the successive approximation type or double integration type A / D converter 42 is input to conversion logic circuits 30 and 80 provided in the conversion processing unit 28. The conversion logic circuits 30 and 80 have the same configuration as the conversion logic circuit described in the first and second embodiments, and include a folding circuit 32 and suppression circuits 34 and 82. FIG. 14 is a diagram showing the relationship between the input signal and the output signal of the folding circuit 32 and the suppression circuits 34 and 82. As shown by the solid line in FIG. 14A, the folding circuit 32 has a value greater than the center temperature of the operating temperature range of the temperature compensated piezoelectric oscillator 10, that is, the center temperature of the signal input to the A / D converter 42. The signal is inverted. Further, as shown by the solid line in FIG. 14B, the suppression circuits 34 and 82 suppress (flatten) signals within a predetermined temperature range (input value range) including the center temperature of the operating temperature range. .
When the capacitance value of the capacitance array is adjusted according to the compensation signal output from the conversion processing unit 28, temperature compensation in accordance with the left-right asymmetric frequency temperature characteristic of the piezoelectric vibrator 12 becomes possible.

As described above, the temperature compensated piezoelectric oscillator 10 according to the third embodiment has an inclination of the signal waveform between the low temperature side and the high temperature side of the center temperature of the operating temperature range in the temperature detection signal output from the A / D converter 42. Therefore, temperature compensation suitable for each of the high temperature portion and the low temperature portion of the frequency temperature characteristic of the left-right asymmetric piezoelectric vibrator 12 can be performed.
The temperature compensated piezoelectric oscillator 10 according to the third embodiment can achieve the same effects as the temperature compensated piezoelectric oscillator 10 according to the first and second embodiments.

  Next, a fourth embodiment will be described. In the fourth embodiment, an example in which a temperature compensated piezoelectric oscillator is configured by a temperature compensated oscillation circuit provided with a temperature compensation circuit will be described. FIG. 15 is an explanatory diagram of a temperature compensated piezoelectric oscillator according to the fourth embodiment. The temperature compensated piezoelectric oscillator 100 according to the fourth embodiment has the same configuration as the temperature compensated piezoelectric oscillator according to the first to third embodiments, but includes the conversion logic circuits 30 and 80 and the oscillation circuit 14 (capacitance array 16). ) In that a latch 102 is provided. That is, the temperature compensated piezoelectric oscillator 100 according to the fourth embodiment includes an oscillation including a temperature sensor 24, A / D converters 26 and 42, conversion logic circuits 30 and 80, a latch 102, a piezoelectric vibrator 12, and a capacitor array 16. A circuit 14 and a control logic circuit 104 are provided.

  The latch 102 receives information on the compensation signal output from the conversion logic circuits 30 and 80 and stores and holds the information until a new compensation signal is input from the conversion logic circuits 30 and 80. That is, when the compensation signal is input once from the conversion logic circuits 30 and 80, the latch 102 continues to output the compensation signal input for the first time to the oscillation circuit 14 (capacitance array 16) until the next compensation signal is input. Is.

Therefore, the temperature compensated piezoelectric oscillator 100 controls the temperature sensor 24, the A / D converters 26 and 42, and the conversion logic circuits 30 and 80 by the control logic circuit 104, and measures the ambient temperature of the piezoelectric vibrator 12 by the temperature sensor 24. Then, the measurement result is converted into a digital signal by the A / D converters 26 and 42, and the digital signal is logically operated by the conversion logic circuits 30 and 80, and the operation of outputting the compensation signal to the latch 102 is intermittently performed. However, since the previous compensation signal is continuously output until a new compensation signal is input to the latch 102, it is possible to continuously output the frequency signal that has been temperature compensated according to the compensation signal.
When the temperature sensor 24, the A / D converters 26 and 42, and the conversion logic circuits 30 and 80 are operated, power is consumed. However, the power consumption can be reduced by making the operation intermittent. .

  Next, a fifth embodiment will be described. In the fifth embodiment, an example in which a real-time clock is configured by a temperature-compensated oscillation circuit including a temperature compensation circuit will be described. FIG. 16 is an explanatory diagram of a real-time clock according to the fifth embodiment. The real-time clock 110 according to the fifth embodiment has a configuration in which a timer circuit 112 is provided at the subsequent stage of the temperature compensated piezoelectric oscillator 100 according to the fourth embodiment. That is, the real-time clock 110 includes a temperature sensor 24, A / D converters 26 and 42, conversion logic circuits 30 and 80, a latch 102, a piezoelectric vibrator 12, an oscillation circuit 14 including a capacitor array 16, and a control logic circuit 104. A clock circuit 112 is provided at the subsequent stage of the oscillation circuit 14.

  The timer circuit 112 includes a frequency divider 114 and a clock / calendar circuit 116. The frequency divider 114 divides the frequency signal output from the oscillation circuit 14 by a predetermined frequency division ratio. The clock / calendar circuit 116 displays or outputs a clock or calendar based on an output signal from the frequency divider 114.

  The operation of the real time clock 110 is as follows. That is, the control logic circuit 104 controls the temperature sensor 24, the A / D converters 26 and 42, and the conversion logic circuits 30 and 80, and the ambient temperature of the piezoelectric vibrator 12 is measured by the temperature sensor 24. The measurement result is converted into a digital signal by the A / D converters 26 and 42, the digital signal is logically operated by the conversion logic circuits 30 and 80, and a compensation signal is output to the capacitor array 16 via the latch 102. The capacitance array 16 changes the capacitance value based on the compensation signal to compensate the temperature of the piezoelectric vibrator 12. As a result, a frequency signal is output from the oscillation circuit 14, and a clock or calendar is displayed or output by the time measuring circuit 112.

  Such a rapid and slow capacity real-time clock 110 can display and output a clock and a calendar using the frequency signal temperature-compensated with high accuracy. Since the real-time clock 110 includes the latch 102 and the control logic circuit 104, the temperature sensor 24, the A / D converters 26 and 42, and the conversion logic circuits 30 and 80 are continuously operated even if they are intermittently operated. A frequency signal can be output, and power consumption can be reduced.

  Next, a sixth embodiment will be described. In the sixth embodiment, an example in which a real-time clock is configured by a temperature compensated oscillation circuit including a temperature compensation circuit will be described. FIG. 17 is an explanatory diagram of a real-time clock according to the sixth embodiment. The real-time clock 120 according to the sixth embodiment includes a temperature sensor 24, A / D converters 26 and 42, conversion logic circuits 30 and 80, a latch 102, and a control logic circuit 104. The real-time clock 120 includes an oscillation circuit 14 to which the piezoelectric vibrator 12 is connected, and a timing circuit 122 is provided at a stage subsequent to the oscillation circuit 14 and a stage subsequent to the latch 102.

  The timing circuit 122 includes a logic slow / fast circuit 124 and a clock / calendar circuit 126, and the logic slow / fast circuit 124 is connected to the rear stage of the latch 102 and the rear stage of the oscillation circuit 14. The logic slow / fast circuit 124 includes a frequency divider, and changes the frequency division ratio based on the compensation signal output from the latch 102 to change the frequency of the oscillation signal output from the oscillation circuit 14. . That is, the logic slow / fast circuit 124 compensates the temperature of the piezoelectric vibrator 12 by changing the frequency division ratio.

  The operation of the real time clock 120 is as follows. That is, the control logic circuit 104 controls the temperature sensor 24, the A / D converters 26 and 42, and the conversion logic circuits 30 and 80, and the ambient temperature of the piezoelectric vibrator 12 is measured by the temperature sensor 24. The measurement result is converted into a digital signal by the A / D converters 26 and 42, the digital signal is logically operated by the conversion logic circuits 30 and 80, and the compensation signal is output to the logic slow / fast circuit 124 via the latch 102. . The logic slow / fast circuit 124 changes the frequency division ratio based on the compensation signal to compensate the temperature of the oscillation frequency of the piezoelectric vibrator 12. Thus, the oscillation frequency of the piezoelectric vibrator 12 is compensated for temperature, and the frequency signal is input to the timepiece / calendar circuit 126 to display or output the timepiece or calendar.

  Such a logic slow / fast real-time clock 120 can display and output a clock and a calendar using the frequency signal temperature-compensated with high accuracy. Since the real-time clock 120 includes the latch 102 and the control logic circuit 104, even if the temperature sensor 24, the A / D converters 26 and 42, and the conversion logic circuits 30 and 80 are operated intermittently, the real-time clock 120 is continuously compensated. A signal can be output, and power consumption can be reduced.

The temperature-compensated piezoelectric oscillators 10 and 100 and the real-time clocks 110 and 120 described above can be mounted, for example, in electronic devices such as computers and servers that require time management as signal sources for clock signals.
The real-time clocks 110 and 120 can also have an integration counter, an alarm function, a timer interrupt function, and the like.

It is a block diagram of a temperature compensation piezoelectric oscillator. It is explanatory drawing of a conversion logic circuit. It is explanatory drawing of a capacity | capacitance array. It is explanatory drawing of the signal waveform which shows the relationship between the input signal and output signal of an A / D converter, a folding circuit, and a suppression circuit. It is a frequency temperature characteristic of a temperature compensation piezoelectric oscillator. It is explanatory drawing of the conversion logic circuit which increased the number of bits. It is explanatory drawing of the conversion logic circuit which concerns on 2nd Embodiment. It is explanatory drawing of the conversion logic circuit into which arbitrary number of bits are input. It is explanatory drawing of a successive approximation type A / D converter. It is a figure explaining an example of a successive approximation type A / D conversion operation. It is a figure which shows the relationship between the input signal and output signal of an A / D converter in 3rd Embodiment. It is explanatory drawing of a double integral type A / D converter. It is explanatory drawing of a double integral type A / D conversion operation. It is a figure which shows the relationship between the input signal and output signal of a folding circuit and a suppression circuit in 3rd Embodiment. It is explanatory drawing of the temperature compensation piezoelectric oscillator which concerns on 4th Embodiment. It is explanatory drawing of the real-time clock which concerns on 5th Embodiment. It is explanatory drawing of the real-time clock which concerns on 6th Embodiment. It is a block diagram of the temperature compensation piezoelectric oscillator which concerns on a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ......... Temperature compensation piezoelectric oscillator, 12 ......... Piezoelectric vibrator, 14 ......... Oscillation circuit, 22 ......... Temperature detection unit, 24 ......... Temperature sensor, 26 ......... Analog / digital (A / D) ) Converter 28... Conversion processing unit 30... Conversion logic circuit 32... Folding circuit 34 34 Suppression circuit 42 a ... Successive comparison A / D converter 42 b ... Double integration type A / D converter, 80 ... Conversion logic circuit, 82 ... Suppression circuit.

Claims (12)

An oscillation circuit that is connected to a piezoelectric vibrator and outputs an oscillation signal having a predetermined frequency,
A temperature detector for outputting the measurement data of the ambient temperature of the piezoelectric vibrator as a digital signal;
A logical processing of the digital signal, a conversion processing unit for outputting the calculation result as a compensation signal for compensating the frequency temperature characteristics of the piezoelectric vibrator;
Frequency adjusting means for adjusting the oscillation frequency of the piezoelectric vibrator according to the compensation signal;
The conversion processing unit
A folding circuit that inputs the digital signal and inverts the digital signal that is greater than the center temperature of the operating temperature range;
If the signal from the folding circuit is input and the signal is within the range including the center temperature of the operating temperature range, the signal is suppressed and the compensation signal having the same value is output. A suppression circuit that outputs the signal as the compensation signal;
A conversion logic circuit comprising:
A temperature compensated oscillation circuit comprising a temperature compensation circuit characterized by the above. An oscillation circuit that is connected to a piezoelectric vibrator and outputs an oscillation signal having a predetermined frequency,
A temperature detector for outputting the measurement data of the ambient temperature of the piezoelectric vibrator as a digital signal;
A logical processing of the digital signal, a conversion processing unit for outputting the calculation result as a compensation signal for compensating the frequency temperature characteristics of the piezoelectric vibrator;
Frequency adjusting means for changing the oscillation signal according to the compensation signal,
The conversion processing unit
A folding circuit that inputs the digital signal and inverts the digital signal that is greater than the center temperature of the operating temperature range;
If the signal from the folding circuit is input and the signal is within the range including the center temperature of the operating temperature range, the signal is suppressed and the compensation signal having the same value is output. A suppression circuit that outputs the signal as the compensation signal;
A conversion logic circuit comprising:
A temperature compensated oscillation circuit comprising a temperature compensation circuit characterized by the above. The folding circuit includes an exclusive OR for inputting the most significant digit of the digital signal and the second digit or less from the higher order,
The suppression circuit is
NAND of inputting the upper 3 digits of the signal output from the folding circuit;
A logical product for inputting an upper 4th digit of the signal output from the folding circuit and an output of a negative logical product;
A temperature-compensated oscillation circuit comprising the temperature compensation circuit according to claim 1 or 2. The folding circuit includes an exclusive OR for inputting the most significant digit of the digital signal and the second and lower digits from the upper order,
The suppression circuit is
A magnitude comparator that inputs the signal output from the folding circuit and a preset suppression value and compares which is greater, and outputs the determination result;
The signal output from the folding circuit and the preset suppression value are input, and either the signal or the suppression value is output based on the determination result output from the magnitude comparator. With a selector,
A temperature-compensated oscillation circuit comprising the temperature compensation circuit according to claim 1 or 2. The temperature detection unit includes a temperature sensor that measures the ambient temperature of the piezoelectric vibrator, and an analog / digital converter that converts an analog signal output from the temperature sensor into a digital signal,
The analog / digital converter includes a comparator for inputting the analog signal and the output signal of the digital / analog converter, the successive approximation register connected to the comparator, a reference signal and an output signal of the successive approximation register. A successive approximation type comprising the digital / analog converter for input;
The digital / analog converter inputs a first reference signal and a second reference signal having different potentials as the reference signal, and according to a result of comparison between the first reference signal and the analog signal, Selecting means for selecting either a reference signal or the second reference signal;
A temperature compensated oscillation circuit comprising the temperature compensation circuit according to claim 1 or 2. The temperature detection unit includes a temperature sensor that measures the ambient temperature of the piezoelectric vibrator, and an analog / digital converter that converts an analog signal output from the temperature sensor into a digital signal,
The analog / digital converter is a double integration type comprising an integration circuit for inputting the analog signal, a discharge circuit connected to the integration circuit, and a counter connected to the discharge circuit,
The discharge circuit includes a current adjustment circuit that adjusts a discharge current according to an output signal of the counter in a subsequent stage.
A temperature compensated oscillation circuit comprising the temperature compensation circuit according to claim 1 or 2.   2. The temperature compensated oscillation circuit with a temperature compensation circuit according to claim 1, wherein the frequency adjusting means is a capacitance array in which a plurality of circuits in which capacitors and switches are connected in series are connected in parallel.   3. The temperature compensated oscillation circuit with a temperature compensation circuit according to claim 2, wherein the frequency adjusting means is a logic slow / fast circuit having a frequency divider.   3. A temperature compensated oscillation circuit comprising a temperature compensation circuit according to claim 1, further comprising: a timer circuit at an output stage of the oscillation frequency of the temperature-compensated piezoelectric vibrator.   A latch is provided between the conversion processing unit and the frequency adjusting means for inputting the information of the compensation signal and storing and holding the information until a new compensation signal is input. A temperature compensated oscillation circuit comprising the temperature compensation circuit according to Item 1 or 2.   The temperature-compensated oscillation circuit having a temperature compensation circuit according to claim 1, wherein the piezoelectric vibrator has a frequency temperature characteristic approximated by a quadratic function.   An electronic device comprising a temperature compensated oscillation circuit including the temperature compensation circuit according to claim 1.

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