HK1076933B - Temperature compensation type oscillator - Google Patents

Description

Temperature compensation type oscillator

Technical Field

The present invention relates to a temperature compensation oscillator that keeps the frequency of an output signal substantially constant regardless of the ambient temperature, and more particularly, to a temperature compensation oscillator that can disable the temperature compensation function.

Background

Temperature compensated oscillators (TCXOs) have been used in a variety of fields, but have been widely used in recent years in portable mobile communication devices such as mobile phones. In general, such a temperature compensation oscillator is configured by an oscillation circuit using an AT cut quartz plate (oscillator) of 10MHz band as a vibration source, and a temperature compensation circuit using a frequency variable device is provided therein, and a quartz oscillator in which an oscillation frequency is stabilized by eliminating a 3-order curve temperature characteristic of the AT cut quartz plate is often used.

The structure of such a temperature compensation circuit is roughly classified into an analog temperature compensation oscillator and a digital temperature compensation oscillator.

Such a temperature compensation oscillator is required to have stability of an oscillation output signal and also to be small, light and inexpensive.

Fig. 8 illustrates a package structure of a temperature compensation type oscillator for ultra-small surface mounting.

The temperature compensation oscillator includes a package (container) 10 including a package body 11, a solder ring 12, and a lid 13, and a quartz piece (vibrator) 15, a MOS IC (integrated circuit) chip 16 constituting an oscillation circuit and a temperature compensation circuit described later, and a circuit element 17 such as a chip capacitor are hermetically mounted in the package.

The circuit configuration of such a temperature compensation type oscillator is shown in fig. 9. The oscillation circuit 20 is connected in parallel with the quartz piece 15, the inverter 21, and the feedback resistor 22, and the two connection points are grounded via the dc cut capacitors Cc and Cd and the voltage control variable capacitors 23 and 24 of the oscillation capacitor, respectively, to form an inverter oscillation circuit.

An output line 25 for outputting a signal based on the oscillation output is drawn from a connection point on the output side of the inverter 21 and is connected to an output terminal 26. In addition, other piezoelectric elements may be used as the vibrator instead of the quartz plate.

Also provided with: a temperature detection circuit 18 for detecting a temperature state in the vicinity of the quartz piece 15 in the oscillation circuit 20 by a thermistor or the like; the compensation circuit 30 is used to keep the frequency of the signal outputted to the output line 25 of the oscillation circuit 20 constant according to the temperature detection signal of the temperature detection circuit 18.

The temperature compensation circuit 30 includes: a compensation data storage circuit (nonvolatile memory) 31 that stores compensation data for temperature compensation; a D/A conversion circuit 32 for generating a control voltage based on the compensation data and the temperature detection signal from the temperature detection circuit 18.

The control voltage output from the D/a conversion circuit 32 is applied to the positive electrodes of the voltage-controlled variable capacitors 23 and 24 (the respective connection points to which the dc cut capacitors Cc and Cd are connected) via the resistors R1 and R2 provided in the oscillation circuit 20, respectively, and the capacitance values of the voltage-controlled variable capacitors 23 and 24 are changed in accordance with the voltage. Thereby, the oscillation frequency of the oscillation circuit 20 is controlled to keep the frequency of the output signal substantially constant.

In such a temperature compensation type oscillator, the oscillation circuits 20 formed in the quartz plate 15 and the IC chip 16 cannot be all manufactured completely uniformly due to variations in manufacturing and the like and each have different temperature-frequency characteristics. It is not possible to temperature compensate all oscillator circuits 20 from the same reference.

For this purpose, it is necessary to create different compensation data for each oscillation circuit and store the compensation data in the storage circuit 31. However, if the deviation of the characteristics of the quartz plate 15 is large and cannot be completely compensated, it is necessary to adjust in advance so that the characteristics of the quartz plate 15 are as uniform as possible.

Thus, the adjustment work has been conventionally performed in the following steps.

First, only piezoelectric elements such as a quartz plate 15 are mounted in the package (package body 11 in fig. 8).

② holding the package at a reference temperature (generally, room temperature: 25 ℃), monitoring the resonance frequency of the piezoelectric element by a network analyzer, and removing an electrode film on the surface of the piezoelectric element by an ion beam or the like to adjust to a desired frequency.

And installing the IC chip forming the oscillation circuit and the temperature compensation circuit in the package.

And fourthly, the package is exposed to a plurality of temperature states, the oscillation frequency is measured in the various temperature states, and the difference between the oscillation frequency and the expected oscillation frequency fo is measured.

Forming temperature compensation data based on the measured value, and writing the temperature compensation data into a compensation data storage circuit (nonvolatile memory) of the IC chip.

Accordingly, in the conventional method for adjusting a temperature compensated oscillator, when adjusting the characteristics of a piezoelectric element such as a quartz plate, an IC chip constituting an oscillation circuit is not mounted, the piezoelectric element is resonated from the outside by a network analyzer or the like to monitor the resonant frequency, and an electrode film on the surface of the piezoelectric element is removed so that the resonant frequency becomes a desired value.

Therefore, there is a problem that when an IC chip is mounted in a package to form an oscillation circuit together with a piezoelectric element and the oscillation circuit oscillates, a deviation occurs between an oscillation frequency and a resonance frequency adjusted in advance. In addition, the number of adjustment steps will be increased, requiring additional adjustment costs.

For this purpose, it is conceivable to mount the piezoelectric element and the IC chip in a package, operate an oscillation circuit, monitor the resonance frequency, adjust the resonance frequency of the piezoelectric element at room temperature in a state close to an actual use state, and form compensation data thereafter. In this case, the temperature compensation circuit also operates. In addition, when the temperature compensation data storage circuit is in the initial state, the compensation data is not stored, and the initial value cannot be determined in the case where all bits of the register for storing this data are "0" and the case where all bits are "1". And thus has problems that the resonance frequency of the piezoelectric element such as a quartz plate cannot be appropriately adjusted and the subsequent compensation data cannot be appropriately formed.

Disclosure of Invention

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to simplify and improve the accuracy of the adjustment process of a temperature compensated oscillator, in which the temperature characteristic of a piezoelectric element itself can be accurately adjusted by operating an oscillation circuit in a state where the piezoelectric element such as a quartz plate, an IC chip, and the like are mounted in a package to constitute the temperature compensated oscillator, and the subsequent formation of compensation data and the storage of the data in a compensation data storage circuit can be continuously and appropriately performed.

The present invention provides a temperature compensation type oscillator, comprising: an oscillation circuit having an oscillation capacitance, an oscillation frequency varying with a temperature variation; an output line that outputs a signal based on an oscillation output of the oscillation circuit; a temperature detection circuit for detecting a temperature state in the vicinity of the oscillation circuit; a temperature compensation circuit for maintaining a frequency of a signal output from the output line at a constant value based on an output from the temperature detection circuit, the temperature compensation oscillator being characterized in that: a selection device for selecting whether a temperature compensation function of the temperature compensation circuit is enabled or disabled is provided, the oscillation circuit and the temperature compensation circuit being mounted in a package, the selection device including: and a selection circuit configured to fix a capacitance value of the oscillation capacitor of the oscillation circuit to a predetermined constant capacitance value independent of temperature when the temperature compensation function is disabled, and to change the capacitance value of the oscillation capacitor of the oscillation circuit in accordance with the temperature detected by the temperature detection circuit when the temperature compensation function is enabled.

In the temperature compensated oscillator, the oscillation circuit includes an oscillation capacitor, and the selection means changes a capacitance value of the oscillation capacitor in accordance with the temperature detected by the temperature detection circuit in the temperature compensation circuit when the temperature compensation function of the temperature compensation circuit is in an active state, and fixes the capacitance value of the oscillation capacitor to a predetermined capacitance value when the temperature compensation function is in an inactive state.

The oscillation capacitor has a variable capacitor whose capacitance value changes in accordance with an applied voltage, and the temperature compensation circuit has a device for changing the capacitance value of the oscillation capacitor by changing the voltage applied to the variable capacitor.

In the above case, when the capacitance value of the oscillation capacitor is fixed to a predetermined capacitance value, the selection means may have means for fixing the voltage applied to the variable capacitor to a predetermined value.

Alternatively, the oscillation capacitor may have a plurality of fixed capacitors, and the temperature compensation circuit may change a connection state of the plurality of fixed capacitors to change a capacitance value of the oscillation capacitor.

In the above case, the selection means may have separation means for making the variable capacitance not included in the oscillation capacitance when the oscillation capacitance is fixed to a predetermined capacitance value.

The temperature compensation oscillator may be provided with a selection information storage circuit that stores control information for controlling a selection state of the selection device.

Further, it is preferable that a compensation data storage circuit for storing temperature compensation data of the temperature compensation circuit is provided.

Both the selection information storage circuit and the compensation data storage circuit may be provided, and in this case, the two circuits may be configured by an integrated storage circuit (for example, a single nonvolatile memory).

A control information input terminal for inputting control information for controlling the selection state of the selection device from the outside may be provided. The control information input terminal may be an external terminal provided on a package constituting the temperature compensation type oscillator.

The selection information storage circuit is composed of a predetermined conductive pattern, and by cutting off the conductive pattern, information for controlling the selection state of the selection device can be stored.

Drawings

Fig. 1 is a circuit block diagram showing a configuration of a first embodiment of a temperature compensated oscillator according to the present invention.

Fig. 2 is a circuit diagram showing another example of the oscillation circuit.

Fig. 3 is a circuit diagram showing still another different example of the oscillation circuit.

Fig. 4 is a circuit block diagram showing a configuration of a second embodiment of the temperature compensation oscillator according to the present invention.

Fig. 5 is a block diagram showing an example of the variable frequency division circuit in fig. 4.

Fig. 6 illustrates the relationship of the frequency division data M, N of the above-described variable frequency division circuit with the frequency division ratio (a gradual change multiple) and the output signal frequency.

Fig. 7 is a circuit block diagram showing a configuration of a third embodiment of the temperature compensated oscillator according to the present invention.

Fig. 8 is a schematic cross-sectional view illustrating a package of the temperature compensation oscillator.

Fig. 9 is a circuit block diagram showing an example of a conventional temperature compensation oscillator configuration.

Detailed Description

In order to describe the present invention in more detail, the best mode of carrying out the invention is explained below with reference to the accompanying drawings.

[ first embodiment ]

Fig. 1 is a circuit block diagram showing the configuration of a first embodiment of the temperature compensation oscillator of the present invention, and the same reference numerals are attached to the same parts in fig. 8 and 9, and the description thereof is omitted.

The temperature compensated oscillator shown in fig. 1 includes: an oscillation circuit 20 having an output line 25 and an output terminal 26 similar to those of the conventional example shown in fig. 9, a temperature detection circuit 18, and a temperature compensation circuit 30. The present embodiment is unique to the present embodiment and further includes a selection circuit 40 for selecting a device, a selection information storage circuit (nonvolatile memory) 50 for storing control information for controlling the selection state, and a constant voltage generation circuit 51 for outputting a constant voltage Vk.

In addition to the selection information storage circuit 50, an external terminal 52 is provided outside the package 10 shown in fig. 8 as a control information input terminal for inputting control information for controlling the selection state of the selection circuit 40. The control information input terminal may be provided inside the package body 11.

The selection circuit 40 includes a pair of transmission gates 41, 42, a three-input NAND circuit, and two inverters ("not" circuits) 44, 45.

The output of the temperature compensation circuit 30, i.e. the control voltage Vc, can be applied to the common connection point of the resistors R1, R2 of the oscillator circuit 20, as shown in fig. 9, via a transmission gate 41. The output of the constant voltage generating circuit 51, i.e., the constant voltage Vk, is applied to the common connection point of the resistors R1, R2 of the same oscillation circuit 20 through another transmission gate 42.

The selection information storage circuit 50 outputs 3 bits of selection information, and the output of bit 1 becomes two inputs of the three-input NAND circuit 43 as the output of bit 3, and the output of bit 2 is inverted by the inverter 44 to become the remaining one input of the NAND circuit 43. Therefore, when the selection information output from the selection information storage circuit 50 is only "101", the output thereof becomes "0" since all of the three inputs of the NAND circuit 43 are "1".

The output of this NAND circuit 43 is applied directly to the gates on the negative logic side of transmission gate 41 and the gates on the positive logic side of transmission gate 42; and inverted by inverter 45 to be applied to the gate on the positive logic side of transmission gate 41 and the gate on the negative logic side of transmission gate 42.

Therefore, only when the selection information outputted from the selection information storage circuit 50 is "101", the transfer gate 41 is turned on and the transfer gate 42 is turned off, so that the control voltage Vc outputted from the temperature compensation circuit 30 is applied to the oscillation circuit 20 through the transfer gate 41 and is applied to the voltage control type variable capacitors 23 and 24 through the resistors R1 and R2 shown in fig. 9, and the capacitance value of the oscillation capacitor changes with temperature, thereby keeping the oscillation rate of the oscillation circuit 20 constant and performing temperature compensation.

When the information output from the selection information storage circuit 50 is not "101", the transmission gate 42 is turned on and the transmission gate 41 is turned off, so that the constant voltage Vk output from the constant voltage generation circuit 51 is applied to the oscillation circuit 20 via the transmission gate 42 and is applied to the voltage control type variable capacitors 23 and 24 via the resistors R1 and R2 shown in fig. 9, and the capacitance value of the oscillation capacitor is thereby fixed to a predetermined capacitance value corresponding to the constant voltage, and the oscillation frequency of the oscillation circuit 20 is not temperature-compensated.

In this way, the selection circuit 40 supplies the control voltage Vc from the temperature compensation circuit 30 to the oscillation circuit 20 based on the 3-bit selection information outputted from the selection information storage circuit 50 to enable the temperature compensation function, or supplies the constant voltage Vk from the constant voltage generation circuit to select to disable the temperature compensation function.

The selection circuit 40 can be switched by applying a high level "1" signal (voltage) or a low level "0" signal as control information to the external terminal 52.

When a control information input terminal such as the external terminal 52 is provided, the NAND circuit 43 and the inverter 44 in the selection information storage circuit 50 and the selection circuit 40 in fig. 1 may be omitted.

According to this temperature compensated oscillator, initial adjustment of the quartz piece of the oscillation circuit 20 and formation, storage, and adjustment of temperature compensation data can be performed, and the oscillation circuit 20 can be operated in a state where the temperature compensated oscillator is completed by mounting the IC chip and the like constituting the quartz piece, the oscillation circuit, the temperature compensation circuit, and the like in a package. In this adjustment, the selection information of the selection information storage circuit 50 is set to be other than "101", and the temperature compensation function is deactivated to cause the oscillation circuit 20 to perform the oscillation operation with a predetermined oscillation capacitance.

The steps of this adjustment operation are as follows.

First, IC chips constituting the oscillation circuit 20 and the circuits shown in fig. 11 are mounted in a package (for example, a package body 11 shown in fig. 8), and then a quartz piece is mounted.

② holding the package at a reference temperature (generally, room temperature: 25 ℃), making the temperature compensation function of the temperature compensation type oscillator ineffective and operating as a simple oscillator, monitoring the oscillation frequency by a network analyzer or the like, removing the electrode film on the surface of the quartz piece by an ion beam or the like, and adjusting to a desired oscillation frequency fo.

And thirdly, covering the package, and hermetically sealing the quartz plate.

And fourthly, measuring the oscillation frequency of the sealing device in various temperature states, and measuring the difference between the oscillation frequency and the desired frequency fo.

Forming temperature compensation data based on the measured value, and writing the temperature compensation data into a compensation data storage circuit (nonvolatile memory) of the IC chip.

After the adjustment, if the selection information of the selection information storage circuit 50 is "101", the temperature compensation function is effective, and the temperature compensation oscillator can be normally operated, thereby completing the ultra-small temperature compensation oscillator.

Thus, the oscillation circuit oscillates in the same manner as in the actual use state, the temperature characteristic of the crystal piece can be accurately adjusted without being affected by the temperature compensation circuit, and the operations of forming compensation data and storing the compensation data in the storage circuit can be appropriately continued, whereby the adjustment procedure of the temperature compensation type oscillator can be simplified and made highly accurate.

In step II, the package may be adjusted in an oven in order to maintain the package at a reference temperature (generally, room temperature: 25 ℃ C.).

In step (iv), the set temperature of the oven may be sequentially varied to expose the package to a plurality of temperature conditions. The package may be sequentially placed in a plurality of incubators set to different temperatures, and the measured temperature range of the package is an operation guaranteed temperature range of the oscillator, and is set to, for example, an appropriate temperature point (e.g., about 11 temperature points) between-40 ℃ and +100 ℃.

When the reference frequency of the quartz plate is adjusted, a metal film such as silver is deposited on the surface of the quartz plate in advance to form a film thickness (thickness) such that the harmonic oscillation frequency is lower than the reference frequency, and for this purpose, an electrode film on the surface of the quartz plate is irradiated with an ion beam by an ion gun, sputter-etched, or the like, or the mass of the electrode film can be reduced only.

As the vibrator of the oscillation circuit, other piezoelectric elements may be used instead of the quartz plate.

Since the temperature characteristic curve of the oscillation circuit using the AT quartz plate as the oscillator is basically a 3-order curve, even if the oscillation frequency AT the reference temperature is adjusted to the desired frequency fo, the oscillation frequency is shifted when the ambient temperature changes. Therefore, the temperature is actually changed from the lower limit to the upper limit of the use guaranteed temperature range, and the actual oscillation frequency of the oscillation circuit, that is, the frequency of the signal output to the output terminal 26 is measured in each temperature state (temperature measurement point), and the difference from the desired oscillation frequency fo is measured.

The calculated temperature compensation circuit 30 is temperature compensation data necessary for generating the control voltage Vc for making the difference 0, and writes the temperature data into a compensation data storage circuit (nonvolatile memory) 31 shown in fig. 9 in association with the temperature data.

Although high-precision temperature compensation data can be formed when the temperature measuring points are many, the measuring time is increased. For this purpose, a cubic curve of the temperature characteristic of the oscillation circuit may be estimated from the measurement results in a suitable number of temperature states (for example, about 11 temperature measurement points), or temperature compensation data with respect to temperature may be interpolated between the temperature measurement points and written in the compensation data storage circuit.

[ different example 1 of Oscillating Circuit ]

Fig. 2 and 3 show different examples of the oscillation circuit, in particular, different examples of the oscillation capacitor and the capacitance varying device.

The oscillation circuit shown in fig. 2 is similar to the oscillation circuit 20 shown in fig. 9 in that a quartz piece 15, an inverter 21, and a feedback resistor 22 are connected in parallel, and both connection points are grounded via oscillation capacitors, respectively, to form an inverted oscillation circuit. However, the oscillation capacitor may be a parallel circuit of a plurality of fixed capacitors instead of the voltage-controlled variable capacitor.

Specifically, a first capacitor array 27 in which capacitors C1 to C5 are connected in parallel to each other through switches S1 to S5 is provided between the input side of the inverter 21 and the ground, and a second capacitor array 28 in which capacitors C6 to C10 are connected in parallel to each other through switches S7 to S10 is provided between the output side of the inverter 21 and the ground. The switches S1 to S10 may be switching elements such as MOS-FETs.

In the above case, a circuit for reading out the compensation data corresponding to the temperature detection data of the temperature detection circuit 18 from the compensation data storage circuit 31 and outputting the variable switch control signal for controlling the on/off states of the oscillation circuit switches S1 to S10 is provided instead of the D/a conversion circuit shown in fig. 9 instead of the temperature compensation circuit.

The constant voltage generation circuit 51 shown in fig. 1 is modified to include a circuit for generating a fixed switch control signal, and a predetermined switch (for example, switches S1 to S3 and S6 to S8) among the switches S1 to S10 of the oscillation circuit is turned on and the other switches are turned off. One of the fixed switch control signal and the variable switch control signal generated by the temperature compensation circuit is selected by a selection device, and applied to the control electrodes of the switches S1 to S10 of the oscillation circuit to control on/off thereof.

Thus, when the temperature compensation function is disabled at the time of initial adjustment, the fixed switch control signal is selected by the selection means and input to the oscillation circuit, and for example, the switches S1 to S3 and S6 to S8 are turned on and the other switches are turned off. Thus, the capacitance value of the first capacitive array 27 is fixed to the capacitance value of the parallel circuit of capacitors C1-C3, and the capacitance value of the second capacitive array 28 is fixed to the capacitance value of the parallel circuit of capacitors C6-C8. Accordingly, the capacitance value of the oscillation capacitor becomes a constant value regardless of temperature change.

After the initial adjustment, when the temperature compensation function is enabled, the variable switch control signal is selected from the temperature compensation circuit by the selection means and inputted to the oscillation circuit, and the switches S1 to S5 of the first capacitor array 27 and the switches S6 to S10 of the second capacitor array 28 are selectively turned on to 1 or more, respectively. Thereby changing the effective capacitor combination (connection state) of the first and second capacitance arrays 27 and 28. The capacitance value (oscillation capacitance) of each capacitor array 27, 28 is changed in accordance with a change in temperature.

For example, as described above, when the switches S1 to S3 of the first capacitor array 27 and S6 to S8 of the second capacitor array 28 are turned on and the capacitors C1 to C3 and the capacitors C6 to C8 are connected in parallel as the reference state, and the switches S1, S2, or both are turned off from this state, the capacitance values of the first capacitor array 27 and the second capacitor array 28 are decreased when the switches S6, S7, or both are turned off. In addition, when the switch S4 or S5 or both are turned on, and the switch S9 or S10 or both are turned on, the capacitance of each of the first capacitor array 27 and the second capacitor array 28 increases.

Furthermore, by appropriately selecting the number of capacitors constituting the first capacitor array 27 and the second capacitor array 28 and the capacitance value of each capacitor and changing the connection state, the capacitance value of the oscillation capacitor can be controlled very finely to perform temperature compensation of the oscillation frequency.

[ different example 2 of oscillation Circuit ]

The oscillation circuit shown in fig. 3 is a series circuit in which switches S11 and S12 are inserted in series in voltage-controlled variable capacitors 23 and 24 of oscillation circuit 20 shown in fig. 9, respectively, and a series circuit in which capacitor Ca and switch S13 are connected in parallel with each other, and a series circuit in which capacitor Cb and switch S14 are connected in parallel with each other. The capacitors Ca and Cb are fixed capacitors. Cc. Cd is the dc partial cut-off capacitance.

When the temperature compensation function is disabled at the time of initial adjustment, the switches S11 and S12 are turned off by the selection circuit, the switches S13 and S14 are turned on, and the capacitance value of the oscillation capacitance is fixed to the capacitance values of the capacitors Ca and Cb, and the voltage-controlled variable capacitors 23 and 24 at this time are turned off and are not included in the oscillation capacitance.

After the initial adjustment, when the temperature compensation function is enabled, the switches S11 and S12 are turned on and the switches S13 and S14 are turned off by the selection circuit, whereby the voltage-controlled variable capacitors 23 and 24 become oscillation capacitors, and the control voltage from the temperature compensation circuit is applied through the resistors R1 and R2, whereby the capacitance values change with temperature change, and temperature compensation of the oscillation frequency can be performed.

In the above-described oscillation circuit, other piezoelectric elements may be used as the vibrator instead of the quartz plate.

[ second embodiment ]

A second embodiment of the temperature compensated oscillator of the present invention is explained with reference to fig. 4. In fig. 4, the same portions as those in fig. 1 and 9 are denoted by the same reference numerals and the description thereof is omitted, but the compensation data storage circuit 31 and the selection information storage circuit 50 of the temperature compensation circuit in the present embodiment are integrated storage circuits, which also serve as 1 nonvolatile memory 19, and most of the storage area is used as the compensation data storage circuit 31 and part is used as the selection information storage circuit 50.

The temperature compensated oscillator shown in fig. 4 includes a variable frequency divider circuit 60 between the oscillator circuit 20 and the output line 25, and a first selector circuit 40A and a second selector circuit 40B as selection means. The first and second selection circuits 40A and 40B have the same circuit configuration, and are constituted by digital gate circuits 47 and 48, a 3-input and circuit 46, and two inverters ("not" circuits) 44 and 49, as shown in the second selection circuit 40B.

The outputs of bit 1 and bit 3 of the 3-bit selection information output from the selection information storage circuit 50 directly become two inputs of the 3-input and circuit 46, and the output of bit 2 is inverted by an inverter into the remaining one input of the and circuit 46. Therefore, only when the selection information outputted from the selection information storage circuit 50 is "101", all three inputs of the and circuit 46 are "1", and the output thereof is "1". When the selection information output from the selection information storage circuit 50 is other than "101", the output of the and circuit 46 becomes "0".

The output of AND circuit 46 is applied directly to control terminal C of digital gate 47, while the control terminal C to digital gate 48 is applied by inversion through inverter 49.

Then, the second selection circuit 40B selects the variable-divided data Dc input from the compensation data output circuit 33 of the temperature compensation circuit 30' and outputs the selected data Dc to the variable-divided circuit 60 only when the selection information output from the selection information storage circuit 50 is "101", because the digital gate circuit 47 is on and the digital gate circuit 48 is off, and selects the fixed-divided data Dk input from the ROM52 and outputs the selected data Dk to the variable-divided circuit 60 when the selection information output from the selection information storage circuit 50 is other than "101", because the digital gate circuit 48 is on and the digital gate circuit 47 is off.

The first selection circuit 40 has the same configuration as described above except that the switching control data Sc and Sk is selected and the oscillation circuit 20 is the target of output of the selected switching control data.

The compensation data output circuit 33 of the temperature compensation circuit 30' refers to the compensation data stored in the compensation data storage circuit 31 in accordance with the temperature data detected by the temperature detection circuit 18, outputs a variable switch control signal (digital data) Sc and frequency division data Dc for temperature compensation, and inputs the signals to the digital gate circuits 47 of the first and second selection circuits 40A and 40B, respectively.

On the other hand, the ROM52 prestores fixed switching control signals (digital data) Sk and frequency-divided data Dk, reads the data by a readout circuit not shown in the figure, and inputs the data to the digital circuits 48 of the first and second selection circuits 40A and 40B, respectively.

Accordingly, the first selection circuit 40A selects the variable control signal Sc input from the compensation data output circuit 33 of the temperature compensation circuit 30' to output to the oscillation circuit 20 when the selection information output from the selection information storage circuit 50 is only "101", and selects the fixed switching control signal Sk input from the ROM52 to output to the oscillation circuit 20 when the selection information output from the selection information storage circuit 50 is a result other than "101".

The oscillation circuit 20 is a circuit employing, as an oscillation capacitor, first and second capacitor arrays 27 and 28 in which a plurality of capacitors are connected in parallel by switches, for example, as shown in fig. 2, and on/off of the switches S1 to S10 is controlled by a switch control signal (digital data) Sc or Sk output from the first selection circuit 40A, whereby the capacitance value of the oscillation capacitor is controlled to change the resonance frequency. Electronic switches that can be turned on/off by 1-bit digital signals such as MOS analog switches can be used as the switches S1 to S10 shown in fig. 2.

The frequency conversion circuit 60 is a well-known circuit, and an example thereof will be described with reference to fig. 5. The variable frequency dividing circuit 60 includes a reference frequency divider 61, a phase comparator 62, a low pass filter (hereinafter simply referred to as "LPF") 63, a voltage controlled oscillation circuit (hereinafter simply referred to as "VCO") 64, and a feedback frequency divider 65 to output a buffer 66.

The oscillation output signal from the oscillation circuit 20 is divided by the reference frequency divider 61 and input to the phase comparator 62 as a reference signal. On the other hand, the oscillation signal of the VCO64 is divided by the feedback frequency divider 65 and input to the phase comparator 62 as a comparison signal. The phase comparator 62 outputs a voltage corresponding to the phase difference between the two input signals, and supplies the voltage to the VCO64 via the LPF63 to control the oscillation frequency of the VCO64, and the oscillation signal of the VCO is output to the output line 25 via the output buffer 66.

Both the reference divider 61 and the feedback divider 65 are programmable dividers that can be divided by variable integer values.

When the frequency of the oscillation output signal of the oscillation circuit 20 is fc, the frequency fo of the output signal of the variable frequency divider circuit 60 is determined by the frequency division number M of the reference frequency divider 61 and the frequency division number N of the feedback frequency divider 65 according to the following relational expression:

fo＝fc×N/M

the reference frequency divider 61 divides the frequency of the input signal by 1/M and outputs the divided frequency, and the feedback frequency divider 65 divides the frequency of the input signal by 1/N and outputs the divided frequency.

N/M is a frequency division variable (in this case, a multiple of a step change), and can be arbitrarily set according to the values of the frequencies M and N. For example, by changing the values of the division numbers M and N as shown in fig. 6 with M-N-100 as a reference value, the division ratio (the gradient multiple) can be increased or decreased from 1.000 by 0.005.

Therefore, when the frequency fc of the oscillation output signal from the oscillation circuit 20 is 20MHz, the frequency fo of the output signal increases and decreases by 0.1MHz with respect to 20 MHz.

Then, assuming that the fixed frequency-divided data Dk stored in the ROM52 shown in fig. 4 is formed of M and N and M is 100 and the variable frequency-divided data Dc output from the compensation data output circuit 33 is also formed of the frequency division numbers M and N, when the second selection circuit 40B shown in fig. 4 selects the fixed frequency-divided data Dk from the ROM52 and inputs it to the variable frequency-dividing circuit 60 as shown in fig. 6, the frequency division ratio becomes 1.000 because M is 100, and the frequency fo of the output signal becomes the same as the frequency fc of the oscillation output signal of the oscillation circuit 20 (20 MHz in the example of fig. 6).

When the second selection circuit 40B in fig. 4 selects the division number data Dc to be outputted from the compensation data output circuit 33 and inputs the data to the variable division circuit 60, the division ratio can be variously changed by the values of the division numbers M and N constituting the division number data Dc, and when the division ratio (the incremental change multiple) is increased or decreased from 1.000 by 0.005 as illustrated in fig. 6, the frequency fo of the output signal can be increased or decreased by 0.1MHz with reference to 20 MHz.

The minimum variable width (width) and the maximum variable range of the frequency dividing ratio (the gradient multiple) can be arbitrarily set by selecting the frequency dividing numbers M and N.

In this embodiment, at the initial adjustment time when the resonance frequency of the quartz plate of the oscillation circuit 20 is adjusted to form the compensation data and store the compensation data in the compensation data storage circuit 31, the 3-bit selection information of the selection information storage circuit 50 is also in a state other than "101".

Therefore, the first selection circuit 40A selects the fixed switch control signal Sk input from the ROM52 to output to the oscillation circuit 20, and the second selection circuit 40B selects the fixed division number data Dk input from the ROM52 to output to the variable division circuit 60.

Thus, the oscillation circuit 20 turns on only the switches S1 to S3 and S6 to S8 shown in fig. 2 and turns off the other switches by the fixed switch control signal Sk.

To this end, the capacitance of the first capacitor array 27 is fixed to the capacitance of the parallel circuit of capacitors C1-C3, and the capacitance of the second capacitor array 28 is fixed to the capacitance of the parallel circuit of capacitors C6-C8. This is a standard state, the oscillation capacitance is constant regardless of temperature change, and the frequency fc of the oscillation output signal is not temperature-compensated although it fluctuates somewhat due to the temperature characteristic of the quartz plate 15.

On the other hand, since the fixed division number data Dk has M ═ N ═ 100, the division ratio is fixed to 1.000, and the frequency fo of the signal output to the output line is the same as the frequency fc of the oscillation circuit 20, and temperature compensation is not performed in this case. That is, the temperature compensation function at this time becomes ineffective, and the temperature compensation oscillator shown in fig. 4 functions only as an oscillator.

After the adjustment operation is completed, when the last compensation data is written in the compensation data storage circuit 31 or immediately thereafter, "101" is written as selection information in the selection information storage circuit 50 in the same nonvolatile memory 19.

Accordingly, the selection information outputted from the selection information storage circuit 50 becomes "101", the first selection circuit 40A selects the variable switch control signal Sc from the compensation data output circuit 33 of the temperature compensation circuit 30' and outputs it to the oscillation circuit 20, and the second selection circuit 40B also selects the variable frequency-divided data Dc from the compensation data output circuit 33 and outputs it to the variable frequency-divided circuit 60.

The oscillation circuit 20 turns on the switches S1 to S5 of the first capacitor array 27 and the switches S6 to S10 of the second capacitor array 28, each of which is 1 or more, for example, as shown in fig. 2, by the variable switch control signal Sc. Thus, the effective capacitor combination (connection state) of the first capacitor array 27 and the second capacitor array 28 is changed, so that the capacitance value (oscillation capacitance) of each capacitor array 27, 28 changes with the temperature change, and the frequency fc of the oscillation signal of the oscillation circuit 20 is adjusted to compensate for the temperature-induced variation.

The variable frequency division circuit 60 changes the frequency division ratio in accordance with the values of the frequency division numbers M and N constituting the input frequency division number data Dc, and outputs the frequency fo of the output signal as fc × N/M. In the example shown in fig. 6, the frequency of the output signal is increased or decreased by 0.1MHz with reference to 20 MHz.

When the temperature compensation function is enabled, the oscillation frequency variation due to the temperature characteristic of the quartz piece can be compensated by adjusting the value of the oscillation capacitor of the oscillation circuit 20 in combination with the adjustment of the division ratio (the gradual change multiple) of the variable frequency division circuit 60, and an output signal of a constant frequency can be always output to the output terminal 26.

In this embodiment, another piezoelectric element may be used as the vibrator of the vibration circuit 20 instead of the quartz plate.

[ third embodiment ]

A third embodiment of the present invention will be described with reference to fig. 7. In fig. 7, the same portions as those in fig. 1 are given the same reference numerals and the description thereof is omitted.

In the temperature compensation oscillator shown in fig. 7, a selection circuit 40' is a circuit in which a NAND circuit 43 and an inverter 44 are removed from the selection circuit 40 shown in fig. 1, and a selection information storage circuit 55 using a predetermined conductive pattern 56 is provided instead of the selection information storage circuit 50 of the nonvolatile memory in the temperature compensation oscillator shown in fig. 1. Further, the external terminal 52 in fig. 1 is not provided.

This conductive pattern 56 is formed, for example, on an insulating substrate provided at a portion which can be operated from the outside at the end of initial adjustment inside or outside the package body 11 shown in fig. 8. And then connected to the positive power supply line 57 at one end thereof and grounded at the other end via the resistor 58. The voltage level at the point P of the connection point of this conductive pattern 56 and the resistor 58 is output as 2-valued selection information to the selection circuit 40', which is inverted as shown in the figure, directly or through the inverter 45, and applied to each of the transfer gates 41, 42.

In the initial state, the conductive pattern 56 of the selection information storage circuit 55 is turned on, the voltage level at the point P is high level "1", the transfer gate 42 of the selection circuit 40' is turned on, and the transfer gate 41 is turned off. Therefore, the constant voltage generation circuit 51 outputs the constant voltage Vk and supplies the constant voltage Vk to the oscillation circuit 20 through the transmission gate 42, and the temperature compensation function is disabled because the oscillation capacitance value of the oscillation circuit 20 is fixed to a predetermined capacitance value.

When the conductive pattern 56 of the selection information storage circuit 55 is cut off after the initial adjustment is completed, the voltage level of the point P becomes a low level "0" which is a ground level, and the transfer gate 41 of the selection circuit 40' is turned on and the transfer gate 42 is turned off. Then, the temperature compensation circuit 30 supplies the control voltage VC outputted from the temperature detection signal of the temperature detection circuit 18 to the oscillation circuit 20 through the transmission gate 41, so that the capacitance value of the oscillation capacitor of the oscillation circuit 20 changes with the temperature change.

Thus, even if the ambient temperature fluctuates, the oscillation frequency, that is, the frequency of the signal output to the output terminal 26 through the output line 25 is kept constant, and the temperature compensation function can be effectively affected.

[ modification of embodiment ]

In the first and second embodiments described above, the temperature compensation function is enabled by setting the selection information of the selection information storage circuit 50 to "101", but the present invention is not limited to this, and any data may be used as the selection information, and the number of bits of the data may be arbitrary. However, in general, since the probability that all data in the initial state of the nonvolatile memories and the like constituting the selection information storage circuit 50 are "1" or "0" is high, it is preferable to avoid setting "111" or "000" as the selection information.

As described above, in the temperature compensated oscillator of the present invention, in a state in which the temperature compensated oscillator is configured by mounting the piezoelectric element such as the quartz plate and the IC chip in the package, the oscillation circuit thereof is operated to accurately adjust the temperature characteristic of the piezoelectric element itself.

Further, the subsequent operations of forming the compensation data and storing the compensation data in the memory circuit can be continued appropriately, so that the adjustment step can be simplified and the accuracy can be improved.

This makes it possible to improve the performance of a portable mobile communication device or the like in which such an oscillator is mounted without increasing the cost.

Claims (17)

1. A temperature compensated oscillator comprising:

an oscillation circuit having an oscillation capacitance, an oscillation frequency varying with a temperature variation;

an output line that outputs a signal based on an oscillation output of the oscillation circuit;

a temperature detection circuit for detecting a temperature state in the vicinity of the oscillation circuit;

a temperature compensation circuit for maintaining the frequency of the signal output from the output line at a constant value based on the output from the temperature detection circuit,

the temperature compensation type oscillator is characterized in that:

a selection device for selecting the temperature compensation function of the temperature compensation circuit to be in an effective state or an ineffective state,

the oscillation circuit and the temperature compensation circuit are mounted in a package,

the selection device includes:

and a selection circuit configured to fix a capacitance value of the oscillation capacitor of the oscillation circuit to a predetermined constant capacitance value independent of temperature when the temperature compensation function is disabled, and to change the capacitance value of the oscillation capacitor of the oscillation circuit in accordance with the temperature detected by the temperature detection circuit when the temperature compensation function is enabled.

2. The temperature-compensated oscillator according to claim 1, comprising:

a switch for setting the temperature compensation function to an active state;

a switch for making the temperature compensation function in an invalid state.

3. The temperature-compensated oscillator of claim 2, wherein:

the switch for setting the temperature compensation function to the inactive state is a device for fixing the capacitance value of the oscillation capacitor to the constant capacitance value, and when the switch for setting the temperature compensation function to the active state is turned on, input of a signal from the device for fixing the capacitance value of the oscillation capacitor to the constant capacitance value is prohibited, and when the switch for setting the temperature compensation function to the inactive state is turned on, input of a signal from the temperature compensation circuit to the oscillation circuit is prohibited.

4. The temperature-compensated oscillator of claim 1, wherein:

the oscillation capacitor has a variable capacitor whose capacitance value is changed in accordance with an applied voltage, and the temperature compensation circuit has a device for changing the capacitance value of the oscillation capacitor by changing the voltage applied to the variable capacitor.

5. The temperature-compensated oscillator of claim 4, wherein:

the selection means has means for fixing the voltage applied to the variable capacitor to a constant voltage independent of temperature when the capacitance value of the oscillation capacitor is fixed to the constant capacitance value.

6. The temperature-compensated oscillator of claim 5, wherein:

the constant voltage is supplied from a constant voltage generating circuit.

7. The temperature-compensated oscillator of claim 1, wherein:

a selection information storage circuit is provided, and the selection means selects whether the temperature compensation function of the temperature compensation circuit is in an active state or in an inactive state by a signal from the selection information storage circuit.

8. The temperature-compensated oscillator of claim 7, wherein:

the selection information storage circuit is configured by a multi-bit memory, and the selection device enables the temperature compensation function of the temperature compensation circuit when the values of the bits of the multi-bit memory are in a predetermined combination.

9. The temperature-compensated oscillator of claim 7, wherein:

the selection information storage circuit is composed of a conductive pattern, and the selection device enables the temperature compensation function of the temperature compensation circuit to be in an active state by cutting off the conductive pattern.

10. The temperature-compensated oscillator of claim 1, wherein:

the oscillation capacitor has a plurality of fixed capacitors, and the temperature compensation circuit has a device for changing the connection state of the plurality of fixed capacitors to change the capacitance value of the oscillation capacitor.

11. The temperature-compensated oscillator of claim 1, wherein:

a variable frequency dividing circuit is provided between the oscillation circuit and the output line,

the selection means may be configured to change the frequency division ratio of the variable frequency divider circuit in accordance with the temperature detected by the temperature detector circuit in the temperature compensation circuit when the temperature compensation function of the temperature compensation circuit is in an active state, and to fix the frequency division ratio of the variable frequency divider circuit at a predetermined value when the temperature compensation function is in an inactive state.

12. The temperature-compensated oscillator of claim 4, wherein:

the selection means includes separation means for making the variable capacitor not included in the oscillation capacitor when the capacitance value of the oscillation capacitor is fixed to the constant capacitance value.

13. The temperature-compensated oscillator according to any one of claims 1 to 12, wherein:

a compensation data storage circuit is provided for storing temperature compensation data of the temperature compensation circuit.

14. The temperature-compensated oscillator according to claim 7 or 8, wherein:

a compensation data storage circuit for storing temperature compensation data of the temperature compensation circuit is provided, wherein the selection information storage circuit and the compensation data storage circuit are integrated.

15. The temperature-compensated oscillator of claim 11, wherein:

the temperature compensation circuit includes a selection information storage circuit for storing control information for controlling a selection state of the selection device and a compensation data storage circuit for storing temperature compensation data of the temperature compensation circuit, wherein the selection information storage circuit and the compensation data storage circuit are integrated.

16. The temperature-compensated oscillator of any one of claims 1 to 6, wherein:

a control information input terminal is provided for inputting control information for controlling the selection state of the selection device from the outside.

17. The temperature-compensated oscillator of claim 16, wherein:

the control information input terminal is an external terminal provided on a package constituting the temperature compensation oscillator.