Circuit device and oscillator

Abstract

To facilitate and to shorten the time for frequency measurement for a plurality of oscillators, in a case where oscillation signals outputted from oscillators are measured and frequencies are obtained outside the oscillators.SOLUTION: A circuit device includes: an oscillation control circuit for controlling oscillation of an oscillator; a measurement part for measuring information corresponding to a frequency of the oscillation signal outputted form the oscillation control circuit; and an interface. When a first signal determining measurement period from outside, the measurement part measures information corresponding to the frequency for the oscillation signal outputted during the measurement period, and the interface outputs a measurement result of the information corresponding to the frequency.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a circuit device and an oscillator.

Background Art

[0002] Conventionally, a technique for measuring the frequency of an oscillator is known. The measured frequency is used, for example, to generate temperature compensation data for making a plurality of order components of the frequency-temperature characteristic approach zero, as disclosed in Patent Document 1.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Conventionally, it has been necessary to measure the frequency by measuring the oscillation signal output from the oscillator outside the oscillator. In such a configuration, the work for measuring the frequencies of a plurality of oscillators becomes very complicated and time-consuming.

Means for Solving the Problems

[0005] A circuit device according to an embodiment includes an oscillation control circuit that controls the oscillation of a vibrator, a measurement unit that measures information corresponding to the frequency of the oscillation signal output from the oscillation control circuit, and an interface. The measurement unit measures information corresponding to the frequency of the oscillation signal output during the measurement period when a first signal for determining the measurement period is input from the outside, and the interface outputs the measurement result of the information corresponding to the frequency.

[0006] Further, an oscillator according to an embodiment includes a vibrator, an oscillation control circuit that controls the oscillation of the vibrator, a measurement unit that measures information corresponding to the frequency of an oscillation signal output from the oscillation control circuit, and an interface. When a first signal for determining a measurement period is input from the outside, the measurement unit measures the information corresponding to the frequency output during the measurement period, and the interface outputs a measurement result of the information corresponding to the frequency.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0008] Here, embodiments of the present invention will be described in the following order. (1) Configuration of the oscillator: (2) Frequency adjustment processing: (3) Other embodiments:

[0009] (1) Configuration of the oscillator: Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Note that the embodiments described below do not unduly limit the content of the present invention described in the claims. Also, not all of the configurations described below are essential constituent elements of the present invention.

[0010] FIG. 1 is a functional block diagram of the oscillator 1. The oscillator 1 according to the present embodiment is housed in a package (not shown) and includes a circuit device 2 and a vibrator 3. External terminals are formed on the outer surface of the package. Each external terminal is electrically connected to a corresponding terminal formed on the circuit device 2. In the present embodiment, each terminal includes a power supply terminal VDD, a ground terminal GND, a terminal TS1 to which a first signal for determining a frequency measurement period is input, terminals SCL and SDA for serial communication, and an output terminal OUT. In the present embodiment, the terminal TS1, which is an input terminal for receiving the first signal, is provided in the oscillator 1 separately from the terminals SCL and SDA for serial communication, but these terminals may be common terminals.

[0011] As the vibrator 3, for example, a crystal oscillator, a SAW (Surface Acoustic Wave) resonator, other piezoelectric vibrators, MEMS (Micro Electro Mechanical Systems) vibrators, etc. can be used. As the substrate material of the vibrator 3, piezoelectric single crystals such as quartz, lithium tantalate, and lithium niobate, piezoelectric materials such as piezoelectric ceramics such as lead zirconate titanate, or silicon semiconductor materials, etc. can be used. As the excitation means of the vibrator 3, those based on the piezoelectric effect may be used, or electrostatic drive based on Coulomb force may be used. Note that the circuit device 2 and the vibrator 3 are electrically connected via XO terminals and XI terminals.

[0012] In the present embodiment, the circuit device 2 is configured to include an oscillation control circuit 10, an output circuit 20, a measurement unit 30, a correction unit 40, a temperature sensor 50, a regulator circuit 60, a storage unit 70, and a serial interface (I / F) circuit 80, a digital control circuit 90. Note that the circuit device 2 of the present embodiment may be configured by omitting or changing some of these elements, or adding other elements.

[0013] The regulator circuit 60 generates a constant voltage that serves as the power supply voltage or reference voltage for some or all of the oscillation control circuit 10, output circuit 20, measurement unit 30, correction unit 40, digital control circuit 90, etc., based on the power supply voltage supplied from the VDD terminal. The serial interface circuit 80 is a circuit that serves as an interface for communication between the external device and the oscillator 1. In the present embodiment, the serial interface circuit 80 is a circuit that performs I2C communication, but of course, the communication method is not limited to the I2C method.

[0014] The storage unit 70 has a non-volatile memory 72 and a register 74. The register 74 can store the information transmitted by the external device via the terminal SDA and the serial interface circuit 80. Also, the register 74 can output the information stored in the register 74 to the external device via the terminal SDA and the serial interface circuit 80.

[0015] The non-volatile memory 72 is a storage unit for storing various control data. For example, it may be various rewritable non-volatile memories such as EEPROM (Electrically Erasable Programmable Read-Only Memory) or flash memory, or it may be various non-volatile memories that cannot be rewritten, such as one-time P ROM (One Time Programmable Read Only Memory). The digital control circuit 90 can store the information stored in the register 74 in the non-volatile memory 72, and can also store the information stored in the non-volatile memory 72 in the register 74.

[0016] In this embodiment, the non-volatile memory 72 stores temperature compensation data (zeroth-order temperature compensation data, ···, nth-order temperature compensation data) for controlling the correction unit 40 that corrects the temperature characteristics of the oscillator 3. Note that since the zeroth-order temperature compensation data is data that does not depend on temperature, the frequency at the reference temperature is adjusted by the zeroth-order temperature compensation data. n is a positive integer value. Further, the non-volatile memory 72 may store data for controlling the output circuit 20 and the like.

[0017] The temperature compensation data (zeroth-order temperature compensation data, ···, nth-order temperature compensation data) is data for correcting the frequency-temperature characteristics of the oscillator 1, which is calculated in the temperature compensation adjustment process of the oscillator 1. For example, it is a value for causing the correction unit 40 to output a voltage corresponding to each order component of the zeroth to nth orders of the frequency-temperature characteristics of the oscillation signal CLK. For example, if the oscillator 3 is an AT-cut crystal oscillator, since the frequency-temperature characteristics exhibit a third-order curve, an integer value of 3 or more is selected as n. Note that the temperature compensation data may include compensation data for all orders from zeroth to nth, or may include only compensation data for some orders from zeroth to nth.

[0018] Various data including the temperature compensation data stored in the non-volatile memory 72 is transferred from the non-volatile memory 72 to the register 74 when the circuit device 2 is powered on (when the voltage of the VDD terminal rises from 0V to a desired voltage) and is held in the register 74. Then, the temperature compensation data (zeroth-order temperature compensation data, ···, nth-order temperature compensation data) held in the register 74 is input to the correction unit 40.

[0019] When the frequency of the oscillation signal CLK of the oscillator 1 is measured, the number of pulses, which is information corresponding to the frequency, is written into the register 74. The data written into the register 74 is written into the non-volatile memory 72. Also, when readout is performed from an external device, the number of pulses is output to the external device via the terminal SDA and the serial interface circuit 80.

[0020] The oscillation control circuit 10 is a circuit that controls the oscillation of the oscillator 3. Specifically, the oscillation control circuit 10 amplifies the output signal of the oscillator 3 and feeds it back to the oscillator 3 to oscillate the oscillator 3, and outputs an oscillation signal CLK based on the oscillation of the oscillator 3. In the present embodiment, the oscillation control circuit 10 includes a variable capacitance element for temperature adjustment, and the frequency of the oscillation signal CLK output from the oscillation control circuit 10 can be changed by changing the applied voltage to the variable capacitance element. The output voltage of the correction unit 40 is configured to be applied to the variable capacitance element, and by applying a voltage that cancels out the frequency change of the oscillation signal CLK due to temperature to the variable capacitance element, temperature compensation is performed so that the frequency does not change with respect to a temperature change within a predetermined range.

[0021] The temperature sensor 50 is a temperature-sensitive element that outputs a signal (for example, a voltage corresponding to the temperature) according to the temperature around it. The temperature sensor 50 may have a positive polarity in which the output voltage increases as the temperature increases, or a negative polarity in which the output voltage decreases as the temperature increases. Note that as the temperature sensor 50, it is desirable that the output voltage changes as linearly as possible with respect to temperature change within a desired temperature range in which the operation of the oscillator 1 is guaranteed. In the present embodiment, the output voltage corresponding to the temperature detected by the temperature sensor 50 is input to the digital control circuit 90 via an analog-digital conversion circuit (not shown).

[0022] The digital control circuit 90 is a processor that performs various digital processes. The various digital processes include a control process for the correction unit 40 and a process for measuring the frequency of the oscillation signal CLK.

[0023] In the control process for the correction unit 40, the digital control circuit 90 outputs a control signal for instructing the 0th-order temperature compensation voltage to the nth-order temperature compensation voltage based on the 0th-order temperature compensation data to the nth-order temperature compensation data stored in the register 74. Based on the control signal from the digital control circuit 90, the correction unit 40 generates a voltage (temperature compensation voltage) for compensating the frequency-temperature characteristic of the vibrator 3 and applies it to one end of a variable capacitance element (not shown) that functions as the load capacitance of the oscillation control circuit 10. Thereby, the oscillation frequency of the oscillation control circuit 10 is controlled to be substantially constant regardless of temperature. In the present embodiment, the correction unit 40 includes a 0th-order voltage generation circuit 40-0 to an nth-order voltage generation circuit 40-n and an addition circuit 42.

[0024] The 0th-order voltage generation circuit 40-0 to the nth-order voltage generation circuit 40-n each generate a 0th-order temperature compensation voltage to an nth-order temperature compensation voltage for compensating the 0th-order component to the nth-order component of the frequency-temperature characteristic of the vibrator 3 in response to a control signal from the digital control circuit 90. The addition circuit 42 adds and outputs the 0th-order temperature compensation voltage to the nth-order temperature compensation voltage generated by the 0th-order voltage generation circuit 40-0 to the nth-order voltage generation circuit 40-n, respectively. The output voltage of this addition circuit 42 becomes the output voltage (temperature compensation voltage) of the correction unit 40.

[0025] The output circuit 20 receives the oscillation signal CLK output by the oscillation control circuit 10, generates an oscillation signal CLK for external output, and outputs it to the outside via the OUT terminal. For example, the division ratio and output level of the oscillation signal CLK in the output circuit 20 may be controlled by the control data held in the register 74.

[0026] The oscillator 1 configured as described above functions as a voltage-controlled temperature-compensated oscillator (if the vibrator 3 is a crystal oscillator, it is a VC-TCXO (Voltage Controlled Temperature Compensated Crystal Oscillator)) that outputs an oscillation signal CLK with a constant frequency regardless of temperature within a desired temperature range.

[0027] In the manufacturing process of oscillator 1, generally, a large number of oscillators 1 with the same configuration are manufactured in parallel. FIG. 2 is a diagram schematically showing a state in which a plurality of oscillators 1 are formed on a wafer and not diced. In the present embodiment, it is assumed that in this state, the temperature characteristics of the oscillation signal CLK of each oscillator 1 are measured, and temperature compensation data is generated for each oscillator 1. Note that FIG. 2 schematically shows a plurality of oscillators 1 formed on a wafer, and the number of oscillators 1 is not limited. The size of oscillator 1 on its largest surface is, for example, a size such as 1 mm × 0.8 mm, and in an actual manufacturing process, tens of thousands of oscillators 1 can be formed on one surface of a wafer.

[0028] In such a configuration, when attempting to output the oscillation signal CLK from oscillator 1 and measure the frequency of the oscillation signal CLK of each oscillator 1 with an external device, it becomes difficult to simultaneously measure the frequencies of the oscillation signals CLK of all oscillators 1. For example, in order to simultaneously measure the oscillation signals CLK output from each of tens of thousands of oscillators 1, tens of thousands of frequency counters would be required outside oscillator 1, which is practically impossible.

[0029] Therefore, in the present embodiment, the configuration is such that oscillator 1 is provided with a circuit for measuring information corresponding to the frequency inside, and the information corresponding to the frequency is output from oscillator 1 to an external device, and the external device calculates the frequency. That is, if the configuration is such that information corresponding to tens of thousands of frequencies is processed as digital data, it can be easily processed by a general-purpose computer or the like, and it is possible to simultaneously measure the frequencies even for tens of thousands of oscillators 1.

[0030] To realize such frequency measurement, the circuit device 2 of oscillator 1 according to the present embodiment includes a measurement unit 30. The measurement unit 30 is a circuit that measures information corresponding to the frequency of the oscillation signal CLK output from the oscillation control circuit 10. In the present embodiment, the measurement unit 30 is constituted by a counter. Also, in the present embodiment, the information corresponding to the frequency of the oscillation signal CLK is the number of pulses Np of the oscillation signal CLK.

[0031] The measurement unit 30 is a counter that counts the number of pulses of the oscillation signal CLK, and can be realized by, for example, a known circuit in which frequency division circuits are connected in series. The number of connected frequency division circuits may be any number necessary to represent the number of bits indicating the count value. The oscillation signal CLK and the first signal S1 input from the terminal TS1 are input to the measurement unit 30. In the present embodiment, the first signal S1 is a signal having a pulse width of a length indicating the time length of the measurement period. When the first signal S1 that determines the measurement period of the oscillation signal CLK is input from the outside via the terminal TS1, the measurement unit 30 counts the number of pulses Np of the oscillation signal CLK output during the measurement period.

[0032] That is, the measurement unit 30 includes a circuit in which the oscillation signal CLK is input to the frequency division circuit during the period when the first signal S1 is input to the measurement unit 30 (the period when it is at a high level), and the oscillation signal CLK is not input to the frequency division circuit during the period when the first signal S1 is not input to the measurement unit 30. Such a circuit can be realized by various known configurations. In addition, each frequency division circuit included in the measurement unit 30 is configured to reset the count value to 0 by the reset signal RS. The output of each frequency division circuit becomes a bit value indicating the count value.

[0033] FIG. 3 is a timing chart showing examples of the input signals and output signals of the measurement unit 30. The oscillation signal CLK is a pulse signal that repeats a high level and a low level at regular intervals. In the present embodiment, the frequency is calculated by counting the number of pulses (the number of times it becomes a high level) within the measurement period Tm indicated by the first signal S1.

[0034] In order to perform the counting of the number of pulses, when the counting starts, a reset signal RS is output from the digital control circuit 90 and input to the measurement unit 30. When the reset signal RS is input to each frequency division circuit, the output value of each frequency division circuit, that is, each bit value of the count value, is reset to 0.

[0035] After being reset, when the first signal S1 is input to the measurement unit 30, the counting by the frequency division circuit starts. In FIG. 3, the outputs of the respective frequency division circuits are shown as Q0 to QN. The numerical values added to Q are natural numbers and correspond to the bits of the count value. That is, in the example shown in FIG. 3, the count value is represented by an (N + 1)-digit value from the value Q0 of the first bit to the value QN of the (N + 1)-bit. The value of N is not limited, but in the present embodiment, it is set to a sufficient number of values to count the number of pulses Np within the measurement period Tm.

[0036] The number of pulses Np is counted over the period during which the first signal S1 is at a high level. When the first signal S1 changes to a low level after the measurement period has elapsed, the digital control circuit 90 acquires the number of pulses Np from the measurement unit 30 and stores it in the register 74. In the present embodiment, when the number of pulses Np is stored in the register 74, the number of pulses Np is stored in the non-volatile memory 72. According to this configuration, the measured number of pulses Np is held in the storage unit 70 even when the power supply of the oscillator 1 is turned off, and the number of pulses Np can be read out when the power supply is turned on again.

[0037] When the number of pulses Np is stored in the register 74 and the non-volatile memory 72, the user can connect an external device to the oscillator 1, read out the number of pulses Np at an arbitrary timing, and store it in the external device. In the present embodiment, the external device can be realized by, for example, a general-purpose computer or the like. The user can connect the external device to the terminals SCL and SDA formed in each of the plurality of oscillators 1 formed on the wafer, and read out the number of pulses Np measured in each of the plurality of oscillators 1 with a single external device.

[0038] That is, in response to an output instruction from an external device, the digital control circuit 90 acquires the number of pulses Np stored in the register 74 and outputs the number of pulses Np to the external device via the terminal SDA and the serial interface circuit 80. According to the above configuration, in the external device, by calculating the frequencies of the oscillation signals CLK in the plurality of oscillators 1, the frequencies of the oscillation signals CLK in the plurality of oscillators 1 can be measured very easily.

[0039] (2) Frequency adjustment process: When using the oscillator 1 as described above, the frequencies of the oscillation signals CLK in the plurality of oscillators 1 can be measured in parallel, and based on the measurement results, the temperature characteristics of each vibrator 3 included in the oscillator 1 can be corrected. FIG. 4 is a flowchart showing the frequency adjustment process. Before executing the frequency adjustment process, the user connects the plurality of oscillators 1 formed on the wafer to an external device. Further, the user prepares a temperature adjustment device for setting the plurality of oscillators 1 formed on the wafer to a desired temperature and a temperature sensor for measuring the temperature of the plurality of oscillators 1. The user starts the frequency adjustment process in this state.

[0040] The oscillator 1 according to the present embodiment has a normal mode and a test mode. The normal mode is a mode in which an oscillation signal CLK or a signal generated based on the oscillation signal CLK is output from the OUT terminal of the oscillator 1. The test mode is a mode for performing frequency measurement and the like. When the measurement unit 30 of each oscillator 1 is instructed to enter the test mode from an external device, it measures the number of pulses Np, which is information corresponding to the frequency.

[0041] Therefore, first, the external device sets the oscillator 1 to the test mode (step S100). The test mode is entered, for example, according to the procedure shown in FIG. 5. FIG. 5 is an example of a timing chart showing the voltage waveforms of the terminals related to the mode setting. When the oscillator 1 is used, first, a power supply voltage is supplied to the VDD terminal of the oscillator 1, and the GND terminal is set to the ground level. In the example shown in FIG. 1, the voltage of the VDD terminal rises from the 0 level to the predetermined level, and at time t1, the voltage of the VDD terminal becomes the power supply voltage. At this time, the digital control circuit 90 transfers and stores various information stored in the non-volatile memory 72 in the register 74.

[0042] In a predetermined period after time t1, the digital control circuit 90 becomes capable of receiving an entry code. If the entry code, which is a predetermined voltage waveform, is not input to the SDA terminal during the predetermined period, the digital control circuit 90 starts operating in the normal mode. If the entry code, which is a predetermined voltage waveform, is input to the SDA terminal during the predetermined period, the digital control circuit 90 starts operating in the interface mode. The interface mode is a mode in which communication using the serial interface circuit 80 is possible, and in this embodiment, a configuration in which I2C communication is possible is assumed.

[0043] In the example shown in FIG. 1, the operation as the interface mode starts at time t2. In the interface mode, the SCL terminal is used as the serial clock terminal, and the SDA terminal is used as the serial data terminal. Therefore, in the interface mode, a serial clock signal is supplied to the SCL terminal. Various commands synchronized with the serial clock signal are supplied to the SDA terminal. The digital control circuit 90 can execute various operations according to the commands. In the present embodiment, the commands include a transition command for instructing a transition to the test mode. The commands can be in various forms. In the present embodiment, it is assumed that a configuration is such that when a predetermined value is written to a predetermined address of the register 74, the test mode is entered. Therefore, the command for writing a predetermined value to a predetermined address is the transition command.

[0044] When the transition command is input to the SDA terminal, the digital control circuit 90 starts the test mode. In the test mode, when the digital control circuit 90 receives, for example, a command for reading the information of the address where the number of pulses Np is stored, it outputs the number of pulses Np to an external device via the serial interface circuit 80. As described above, in the present embodiment, when receiving commands related to the test mode, that is, the entry code and the transition command, from the external device, it transitions from the normal mode to the test mode.

[0045] In the state where the test mode is being executed, the external device initializes the variable x for specifying the temperature to 1 (step S105). In the present embodiment, the frequency of the oscillation signal CLK is measured at a plurality of temperatures. The variable x is a value for specifying any one of the plurality of temperatures. For example, when the measured temperatures are 0°C, 25°C, 50°C, and 95°C, when x is 1, 2, 3, and 4 respectively, the temperature Tx means 0°C, 25°C, 50°C, and 95°C respectively.

[0046] Next, the external device sets the temperature to Tx (step S110). That is, the external device can control a temperature adjustment device for adjusting the temperature of the oscillator 1 formed on the wafer and can acquire the detection result of the temperature sensor. The external device controls the temperature adjustment device based on the detection result of the temperature sensor to set the temperature of each oscillator 1 to Tx.

[0047] When the temperature of each oscillator 1 formed on the wafer reaches Tx, the external device initializes the variable y for specifying the measurement conditions to 1 (step S115). In the present embodiment, the frequency is measured under a plurality of measurement conditions at the same temperature, and the variable y is a value for specifying any one of the measurement conditions.

[0048] The measurement condition Cy corresponds to the correction state in the correction unit 40. When the measurement condition Cy is different, the presence or absence of application of temperature compensation data by the correction unit 40 and the degree of correction are different. Specifically, when the measurement condition Cy is different, whether or not a voltage is applied to the variable capacitance element of the oscillation control circuit 10 by the 0th-order voltage generation circuit 40-0 to the nth-order voltage generation circuit 40-n is different, and when the voltage is applied, the magnitude is different.

[0049] FIG. 6 is a diagram showing an example of the measurement condition Cy. In FIG. 6, an example in which the correction unit 40 includes the 0th-order voltage generation circuit 40-0 to the 3rd-order voltage generation circuit 40-3 is assumed. The 0th to 3rd orders shown in FIG. 6 indicate the presence or absence of correction and the magnitude of correction in the 0th-order voltage generation circuit 40-0 to the 3rd-order voltage generation circuit 40-3.

[0050] For example, for the order indicated by "-" in FIG. 6, no correction is performed. Therefore, in the case of measurement condition C1, no correction is performed in any of the 0th-order voltage generation circuit 40-0 to the 3rd-order voltage generation circuit 40-3. In this case, the number of pulses Np is the number of pulses Np within the measurement period Tm when the oscillator 1 reaches the temperature Tx without correction. In FIG. 6, for the order indicated by "maximum", it indicates that correction is performed with the maximum value of the voltage that can be output by the voltage generation circuit of that order. For example, in the case of measurement condition C2, the maximum value of the voltage that can be output is output from the 0th-order voltage generation circuit 40-0, and no correction is performed in the 1st-order voltage generation circuit 40-1 to the 3rd-order voltage generation circuit 40-3.

[0051] In FIG. 6, for the order indicated by "minimum", it indicates that correction is performed with the minimum value of the voltage that can be output by the voltage generation circuit of that order. For example, in the case of measurement condition C5, the minimum value of the voltage that can be output is output from the 1st-order voltage generation circuit 40-1, and no correction is performed in the 0th-order voltage generation circuit 40-0, the 2nd-order voltage generation circuit 40-2, and the 3rd-order voltage generation circuit 40-3. As described above, in the present embodiment, conditions for not performing correction in all of the 0th-order voltage generation circuit 40-0 to the 3rd-order voltage generation circuit 40-3, conditions for correcting only any one with the maximum value of the voltage, and conditions for correcting only any one with the minimum value of the voltage are defined, and a total of 9 measurement conditions Cy, that is, measurement conditions C1 to C9 are defined. Hereinafter, the frequency adjustment process will be described according to the example shown in FIG. 6.

[0052] In step S120, the external device sets the measurement conditions to Cy (step S120). Specifically, the external device outputs a command for operating the correction unit 40 based on the presence or absence and magnitude of correction corresponding to the measurement conditions Cy. The digital control circuit 90 acquires the command via the SDA terminal and the serial interface circuit 80, and controls the correction unit 40 based on the command so that the presence or absence and magnitude of correction corresponding to the measurement conditions Cy are obtained. That is, the digital control circuit 90 instructs, by the command, the correction unit 40 to perform correction with the temperature compensation data corresponding to the measurement conditions Cy, and the correction unit 40 operates the 0th-order voltage generation circuit 40-0 to the nth-order voltage generation circuit 40-n so as to operate with the instructed temperature compensation data. According to the above configuration, measurement by the measurement unit 30 becomes possible in a state where correction by the correction unit 40 is performed according to the measurement conditions Cy.

[0053] Next, the external device causes the digital control circuit 90 to output a reset signal RS (step S125). Specifically, the external device outputs a command for outputting the reset signal Rs to the oscillator 1. The digital control circuit 90 acquires the command via the SDA terminal and the serial interface circuit 80, and outputs the reset signal RS to the measurement unit 30. As a result, as shown at time Tr in FIG. 3, the reset signal RS is output, and all outputs of the frequency division circuit included in the measurement unit 30 become low level (0).

[0054] Next, the external device outputs a first signal S1 (step S130). Specifically, the external device outputs a first signal S1 having a pulse width of a predetermined time length to the oscillator 1. The first signal S1 is supplied to the measurement unit 30 via the terminal TS1. As a result, as in the example shown in FIG. 3, when the first signal S1 changes from low level to high level, measurement by the measurement unit 30 is started. Each time a falling edge of the oscillation signal CLK occurs in the frequency division circuit of the measurement unit 30, a signal is transmitted to the subsequent stage. As a result, Q0 to QN indicate, in 2 bits, the number of falling edges of the oscillation signal CLK that have occurred after the input of the first signal S1, that is, the number of pulses.

[0055] The time length of the first signal S1 is a predetermined length. When the first signal S1 changes from a high level to a low level, the number of pulses Np is acquired by the digital control circuit 90 and stored in a predetermined address of the register 74. Further, the number of pulses Np stored in the register 74 is stored in the non-volatile memory 72. The above processing is performed for each of the plurality of oscillators 1 connected to the external device. That is, the number of pulses Np, which is the measurement result of the measurement condition Cy at the same temperature Tx, is acquired in each oscillator 1 and stored in the register and the non-volatile memory 72 of each oscillator 1.

[0056] In the present embodiment, the pulse width of the first signal S1, that is, the measurement period Tm, is accurately determined by an internal clock having a known frequency in the external device. Therefore, in the present embodiment, it is possible to accurately specify the frequency by the number of pulses Np / the measurement period Tm. Note that since the frequency of the oscillator 1 is not accurately specified before the measurement in the test mode, it is difficult to accurately specify the frequency of the oscillation signal CLK using the signal inside the oscillator 1. However, in the present embodiment, since the measurement period Tm accurately determined by the external device is used, it is easy to accurately measure the frequency of the oscillation signal CLK.

[0057] Next, the external device determines whether the measurements have been completed under all measurement conditions (step S140). If it is determined in step S140 that the measurements have not been completed under all measurement conditions, the external device increments the variable y (step S135) and repeats the processing after step S120. According to the above configuration, the number of pulses Np corresponding to the frequency of the oscillation signal CLK is measured under each measurement condition. That is, the measurement unit 30 measures the number of pulses Np for each of the measurement conditions C1 to C9 at the temperature Tx. Then, the digital control circuit 90 stores the measurement results at predetermined addresses in the register 74 and the non-volatile memory 72. In the present embodiment, the addresses at which the measurement results for each temperature and measurement condition are stored are determined in advance, and the external device can acquire the measurement results for any temperature and measurement condition by specifying the address to be read.

[0058] If it is determined in step S140 that the measurements have been completed under all measurement conditions, the external device determines whether the measurements have been completed at all temperatures (step S145). If it is determined in step S145 that the measurements have not been completed at all temperatures, the external device increments the variable x (step S150) and repeats the processing after step S110.

[0059] If it is determined in step S145 that the measurements have been completed at all temperatures, the external device acquires the number of pulses Np for each temperature and measurement condition (step S155). Since the number of pulses Np for each temperature and measurement condition is stored at a predetermined address in the register 74 of the oscillator 1, the external device specifies the address to read these numbers of pulses Np. The digital control circuit 90 of the oscillator 1 acquires the number of pulses Np stored at the addressed read and outputs it to the external device via the serial interface circuit 80. The read number of pulses Np is stored in a storage medium (not shown) of the external device with the temperature and measurement conditions associated therewith. The external device acquires the number of pulses Np for all temperatures and measurement conditions for all of the plurality of oscillators 1.

[0060] Next, the external device converts the number of pulses into a frequency (step S160). Specifically, the external device obtains the frequency by dividing the number of pulses Np by the measurement period Tm. Here too, the external device obtains the frequencies for all of the plurality of oscillators 1 under all temperatures and measurement conditions.

[0061] Next, the external device obtains the 0th-order coefficient to 3rd-order coefficient (step S165). Specifically, in this example, the relationship between the frequency of the oscillation signal CLK and the temperature is considered to be expressed by a cubic equation. For this reason, the external device considers the frequency F to be expressed as a function of the temperature T as in Equation (1). F = aT 3 + bT 2 + cT + d ··· (1) Note that a, b, c, and d are the 3rd-order coefficient, 2nd-order coefficient, 1st-order coefficient, and 0th-order coefficient, respectively.

[0062] Based on the frequency obtained from the number of pulses Np measured under each measurement condition and the temperature, the external device obtains a cubic equation that approximates the relationship between the frequency and the temperature. FIG. 7 is a graph plotting the frequencies of temperatures T1 to T4 under the measurement condition C1. Note that in the graph shown in FIG. 7, the horizontal axis is the temperature and the vertical axis is the frequency. The measurement condition C1 is the temperature characteristic of the frequency of the oscillation signal CLK in a state where correction by the correction unit 40 is not performed. For this reason, by using the frequencies for the four temperatures measured under the measurement condition C1 and using a known approximation, a cubic equation can be specified and regarded as the temperature characteristic of the frequency of the oscillation signal CLK.

[0063] When each coefficient of the cubic equation obtained by the approximation is expressed as a1, b1, c1, and d1, the cubic equation of the frequency F is expressed as in Equation (2). F = a1T 3 + b1T 2 + c1T + d1 ··· (2) The solid line shown in FIG. 7 shows the result of plotting Equation (2) on the graph.

[0064] Under measurement condition C1, since the frequency of the oscillation signal CLK has a temperature characteristic as shown in Equation (2), if the correction unit 40 can provide the oscillation control circuit 10 with the inverse characteristic of the said characteristic, that is, the characteristic as shown in Equation (3), the temperature characteristic of Equation (2) can be cancelled out. F=-a1T 3 -b1T 2 -c1T-d1···(3)

[0065] The external device determines the correction coefficient for performing the above cancellation. That is, the external device regards -d1 of Equation (3) specified based on the measurement result of measurement condition C1 as the zero-order coefficient, -c1 as the first-order coefficient, -b1 as the second-order coefficient, and -a1 as the third-order coefficient. The external device acquires the zero-order coefficient to the third-order coefficient for all of the plurality of oscillators 1.

[0066] Next, the external device generates zero-order temperature compensation data to third-order temperature compensation data and stores them in the oscillator 1 (step S170). Specifically, the external device specifies the temperature compensation voltage for realizing each of the zero-order coefficient to the third-order coefficient, and specifies the temperature compensation data for outputting the said temperature compensation voltage.

[0067] Therefore, the external device specifies the temperature compensation voltage for realizing each of the zero-order coefficient to the third-order coefficient by using the measurement results of measurement conditions C2 to C9. Specifically, the external device specifies the zero-order temperature compensation voltage by using measurement conditions C2 and C3. The measurement result of measurement condition C2 is the maximum value of the voltage that can be output by the zero-order voltage generation circuit 40-0, and is the measurement result in a state where no correction is performed in the first-order voltage generation circuit 40-1 to the third-order voltage generation circuit 40-3. The measurement result of measurement condition C3 is the minimum value of the voltage that can be output by the zero-order voltage generation circuit 40-0, and is the measurement result in a state where no correction is performed in the first-order voltage generation circuit 40-1 to the third-order voltage generation circuit 40-3.

[0068] Therefore, if an approximation similar to Equation (3) is performed based on the frequency obtained from the number of pulses, which is the measurement result under measurement condition C2, the correction coefficient dmax in the state where the maximum value of the voltage that can be output by the zero-order voltage generation circuit 40-0 is output can be obtained. Also, if an approximation similar to Equation (3) is performed based on the frequency obtained from the number of pulses, which is the measurement result under measurement condition C3, the correction coefficient dmin in the state where the minimum value of the voltage that can be output by the zero-order voltage generation circuit 40-0 is output can be obtained.

[0069] According to these correction coefficients dmax and dmin, the range of the correction coefficient that can be changed by the zero-order voltage generation circuit 40-0 can be specified. That is, it can be said that the range of the correction coefficient that can be changed by the zero-order voltage generation circuit 40-0 is the range of dmin to dmax. The zero-order temperature compensation data is a numerical value within a predetermined range, and when the zero-order temperature compensation data is changed within the range from the maximum value to the minimum value, the correction coefficient can be changed within the range of dmax to dmin. Also, the change in the correction coefficient with respect to the change in the zero-order temperature compensation data can be regarded as a linear change. Therefore, by comparing the above-described zero-order coefficient "-d1" with the range of the correction coefficient dmin to dmax, the zero-order temperature compensation data required to output the zero-order temperature compensation voltage corresponding to the zero-order coefficient "-d1" can be specified.

[0070] The external device performs the same processing as the above processing for the first-order coefficient to the third-order coefficient. That is, the external device specifies the first-order temperature compensation data using measurement conditions C4 and C5, specifies the second-order temperature compensation data using measurement conditions C6 and C7, and specifies the third-order temperature compensation data using measurement conditions C8 and C9.

[0071] As described above, when the 0th-order temperature compensation data to the 3rd-order temperature compensation data are acquired, the external device writes each temperature compensation data to the predetermined address of the oscillator 1. That is, the external device outputs a command for storing each temperature compensation data to the predetermined address to the oscillator 1. The digital control circuit 90 acquires the command via the SDA terminal and the serial interface circuit 80, and stores each temperature compensation data at the address indicated by the command. The external device executes the above processing for all of the plurality of oscillators 1 formed on the wafer.

[0072] According to the above configuration, the frequencies of the plurality of oscillators 1 can be measured simultaneously and accurately. In a configuration in which the frequencies of the plurality of oscillators 1 are measured sequentially, the measurement is performed at different timings between the oscillator 1 measured first and the oscillator 1 measured thereafter. This time lag increases as the number of oscillators 1 to be measured increases. As the time lag increases, it becomes difficult to maintain the temperature at the same temperature during measurement, and temperature management becomes difficult. Also, when measured at different temperatures, approximate processing using different temperatures for each oscillator 1 is required, and the processing becomes complicated. However, according to the present embodiment, since it is possible to measure the frequencies of the plurality of oscillators 1 simultaneously, the temperatures of the plurality of oscillators 1 can be regarded as the same, temperature management becomes simple, and approximate processing also becomes simple. Therefore, it is possible to easily execute the measurement of the frequencies of the plurality of oscillators 1.

[0073] Furthermore, since the oscillator 1 includes the measurement unit 30 inside the oscillator 1, there is no need to provide a counter for the pulses of the oscillation signal CLK or a frequency measurement function in the external device in order to measure the frequency of the oscillator 1. For this reason, it is possible to measure the frequencies of the plurality of oscillators 1 simultaneously using a simple external device.

[0074] When the frequency adjustment process is completed, it is preferable to test the temperature characteristics of the oscillator 1. That is, the frequency of the oscillator 1 is measured at a plurality of temperatures, and it is confirmed whether the change in frequency due to temperature is below a predetermined standard. For the oscillator 1 in which the change in frequency due to temperature is not below the predetermined standard, the frequency adjustment process shown in FIG. 4 is performed again. In the present embodiment, since the temperature management of the oscillator 1 is simple and the approximation process is simple, compared with the configuration in which the frequencies of a plurality of oscillators 1 are measured in order, the load when repeating the execution of the frequency adjustment process and the test of the temperature characteristics is very small.

[0075] (3) Other embodiments: The above-described embodiment is an example for implementing the present invention, and various other embodiments can be adopted. For example, the oscillator 1 may be an oscillator including a PLL circuit. Further, the application target of the oscillator 1 according to an embodiment of the present invention is not limited, and it can be used for various targets, for example, various electronic devices, vehicle electrical components, and the like.

[0076] The oscillation control circuit only needs to be able to control the oscillation of the vibrator. That is, it only needs to be able to control the oscillation of the vibrator to output the oscillation signal CLK. Therefore, the oscillation control circuit may be realized in various modes, and for example, may include an oscillation circuit using an RC circuit or an LC circuit, a multivibrator, a ring oscillator, or the like. Further, the oscillation control circuit may include a PLL circuit.

[0077] The measurement unit only needs to be able to measure information corresponding to the frequency of the oscillation signal output from the oscillation control circuit. That is, the measurement unit only needs to be able to measure information for specifying the frequency of the oscillation signal. The information corresponding to the frequency of the oscillation signal is not limited to the number of pulses within the measurement period as in the above-described embodiment. For example, the measurement period may be included in the information corresponding to the frequency of the oscillation signal, or the information corresponding to the frequency of the oscillation signal may be information indicating the frequency itself.

[0078] Furthermore, when a first signal for determining the measurement period is input from the outside, the measurement unit only needs to be able to measure information corresponding to the frequency of the oscillation signal output during the measurement period. That is, the measurement period is specified by the first signal from the outside, and the measurement unit performs measurement during the measurement period. The first signal only needs to be able to specify the measurement period, and various configurations may be adopted other than the configuration that specifies the measurement period by the pulse length. For example, the measurement period may be specified by a digital signal, and the measurement period may be specified based on an external clock or the like in each part (such as the measurement unit) in the circuit device, and the measurement may be configured to be enabled during the measurement period.

[0079] The interface only needs to be able to output at least the measurement result of the information corresponding to the frequency. Therefore, the interface may be provided in the circuit device for outputting the measurement result, or the output of the measurement result and the interface for other uses may be shared.

[0080] The storage unit only needs to be able to store the measurement result of the information corresponding to the frequency measured by the measurement unit. That is, it only needs to be able to hold the measurement result so that the measurement result can be used at any timing. Therefore, the storage circuit is preferably the above-mentioned non-volatile memory so that the operation setting information is held even when the power supply is stopped and restarted. However, if the operation setting information is stored during power-on and referred to by the control circuit, a volatile memory may also be used. Of course, the type of memory is not limited.

[0081] Furthermore, the terminal as an interface for receiving the first signal S1 in the oscillator 1 may be shared with other terminals. For example, the first signal S1 may be input from an external device to the oscillator 1 using a terminal electrically connected to the serial interface circuit 80. For example, in the configuration shown in FIG. 1, after the oscillator 1 shifts to the test mode, a configuration may be adopted in which the first signal S1 is received via the SDA terminal and the serial interface circuit 80.

[0082] This configuration can be realized, for example, by a configuration in which, after a command for transmitting the first signal S1 to the oscillator 1 is output from an external device, the first signal S1 having a predetermined time length is output from the external device to the oscillator 1. In this case, the serial interface circuit 80 supplies the first signal S1 to the measurement unit 30, and the measurement unit 30 executes counting of the number of pulses by the frequency division circuit based on the first signal S1. According to the above configuration, it is not necessary to provide the terminal TS1 only for the first signal S1 to the oscillator 1, and the oscillator 1 can be realized with a simple configuration.

Explanation of symbols

[0083] 1…Oscillator, 2…Circuit device, 3…Vibrator, 10…Oscillation control circuit, 20…Output circuit, 30…Measurement unit, 40…Correction unit, 40-0 to 40-n…Voltage generation circuit 42…Addition circuit, 50…Temperature sensor, 60…Regulator circuit, 70…Storage unit, 72…Non-volatile memory, 74…Register, 80…Serial interface circuit, 90…Digital control circuit

Claims

1. An oscillation control circuit for controlling the oscillation of an oscillator, A measurement unit for measuring information corresponding to the frequency of the oscillation signal output from the oscillation control circuit, An interface, and when a first signal for determining a measurement period is input from the outside, the measurement unit measures information corresponding to the frequency of the oscillation signal output during the measurement period, the interface outputs the measurement result of the information corresponding to the frequency, A circuit device.

2. Further comprising a storage unit for storing the measurement result of the information corresponding to the frequency measured by the measurement unit, the interface outputs the measurement result stored in the storage unit to the outside, The circuit device according to claim 1.

3. Having a normal mode and a test mode, when the test mode is instructed from the outside, the measurement unit measures information corresponding to the frequency, The circuit device according to claim 1.

4. The interface receives a command related to the test mode from the outside and shifts from the normal mode to the test mode, The circuit device according to claim 3.

5. The measurement unit measures information corresponding to the frequency for each different temperature, the storage unit stores the measurement results for each temperature, The circuit device according to claim 2.

6. Further comprising a correction unit for correcting the temperature characteristics of the oscillator, the interface receives temperature compensation data used for the correction performed by the correction unit, The measurement unit measures information corresponding to the frequency in a state where the correction unit corrects the temperature characteristics using the received temperature compensation data. The storage unit stores the measurement results for each correction coefficient. The circuit device according to claim 2.

7. The interface receives the first signal after transitioning to the test mode. The circuit device according to claim 3.

8. Separate from the interface, an input terminal for receiving the first signal is provided. The circuit device according to claim 1.

9. An oscillator and An oscillation control circuit that controls the oscillation of the oscillator, A measurement unit that measures information corresponding to the frequency of the oscillation signal output from the oscillation control circuit, An interface, and is provided with When a first signal for determining a measurement period is input from the outside, the measurement unit measures information corresponding to the frequency output during the measurement period. The interface outputs the measurement result of the information corresponding to the frequency. Oscillator.

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