JP2007151196A - Temperature compensation type oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make adjusting process simplified and highly accurate by accurately adjusting the temperature characteristics of a quartz element itself, while operating an oscillation circuit and thereafter consecutively carrying out the work of generating compensation data and storing thereof, under the condition where the quartz element, an IC chip, and the like are mounted inside a package. <P>SOLUTION: A temperature compensation type oscillator is provided with an oscillation circuit 20, a temperature detection circuit 18, and a temperature compensation circuit 30 for keeping the output signal frequency of the oscillation circuit 20 at a substantially constant value based on the temperature detection signal, and a selection circuit 40 for selecting whether the temperature compensation function of the temperature compensation circuit 30 is to be set in a valid or invalid state. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

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

Temperature compensated oscillators (TCXO) are used in various fields, but in recent years, they are widely used in portable mobile communication devices such as mobile phones. This type of temperature-compensated oscillator generally includes an oscillation circuit using a 10 MHz band AT-cut crystal piece (vibrator) as a vibration source, and is provided with a temperature-compensation circuit using some frequency variable means. Quartz oscillators that stabilize the oscillation frequency by canceling the temperature characteristics of the cubic curve are frequently used.
The temperature compensation circuit is roughly divided into an analog temperature compensation oscillator and a digital temperature compensation oscillator.

For this type of temperature-compensated oscillator, there is a demand for reduction in size, weight and cost as well as stability of the oscillation output signal.
FIG. 8 shows a package configuration example of an ultra-compact surface mounting temperature compensated oscillator.
In this temperature-compensated oscillator, a package (container) 10 is constituted by a package main body 11, a welding ring 12 and a cover 13, and a crystal piece 15 and a MOS which constitutes an oscillation circuit and a temperature compensation circuit which will be described later. A type IC (integrated circuit) chip 16 and a circuit element 17 such as a chip capacitor are attached and sealed.

The circuit configuration of this temperature compensated oscillator is as shown in FIG. In the oscillation circuit 20, a crystal piece 15, an inverter 21, and a feedback resistor 22 are connected in parallel, and the connection points thereof are DC cut capacitors Cc and Cd, and a voltage controlled variable capacitor (capacitor) 23 that is an oscillation capacitor, respectively. , 24 to form an inverter oscillation circuit. An output line 25 that outputs a signal based on the oscillation output is drawn from a connection point on the output side of the inverter 21 and connected to the output terminal 26. In addition, it is also possible to use another piezoelectric element instead of the crystal piece 15 as a vibrator.
Further, a temperature detection circuit 18 that detects a temperature state in the vicinity of the crystal piece 15 in the oscillation circuit 20 by a thermistor or the like, and an output signal from the temperature detection circuit 18 is output to the output line 25 of the oscillation circuit 20. A temperature compensation circuit 30 is provided to keep the frequency of the signal constant.

  The temperature compensation circuit 30 is based on a compensation data storage circuit (non-volatile memory) 31 for storing compensation data for performing temperature compensation, and an output signal indicating the detected temperature from the compensation data and the temperature detection circuit 18. And a D / A conversion circuit 32 for generating a control voltage. The control voltage output from the D / A conversion circuit 32 is supplied to the positive side of each voltage controlled variable capacitor 23, 24 via the resistors R1, R2 provided in the oscillation circuit 20 (DC cut capacitors Cc, Cd and And the oscillation capacity of each of the voltage-controlled variable capacitors 23 and 24 is changed according to 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 compensated oscillator, the oscillation circuit 20 formed in the crystal piece 15 and the IC chip 16 cannot be made completely the same due to manufacturing variations or the like. Will have. Therefore, it is not possible to compensate the temperature of all the oscillation circuits 20 with the same reference. Therefore, it is necessary to create different compensation data for each oscillation circuit and store it in the compensation data storage circuit 31. However, if the variation in the characteristics of the crystal piece 15 is large, it cannot be compensated. Therefore, it is necessary to adjust in advance so that the characteristics of the crystal piece 15 are made as uniform as possible.

Conventionally, adjustment work has been performed in the following steps.
Step 1: Mount only a piezoelectric element such as the crystal piece 15 in the package (package body 11 in FIG. 8).
Step 2: Keep the package at a reference temperature (generally room temperature: 25 ° C.), monitor the resonance frequency of the piezoelectric element with a network analyzer or the like, and remove the electrode film on the surface of the piezoelectric element with an ion beam or the like to obtain the desired frequency Adjust so that
Step 3: Mount an IC chip constituting an oscillation circuit and a temperature compensation circuit on the package.
Step 4: subjecting the package to a plurality of temperature conditions, by measuring the oscillation frequency at the respective temperature conditions, to measure the difference between the desired oscillation frequency f _0.
Step 5: Create temperature compensation data based on the measured value, and write it into the compensation data storage circuit (nonvolatile memory) of the IC chip.

As described above, in the adjustment method of the conventional temperature compensated oscillator, when adjusting the characteristics of the piezoelectric element such as the crystal piece, the IC chip constituting the oscillation circuit is not mounted, but the piezoelectric element is externally connected with a network analyzer or the like. The resonance frequency is monitored and the resonance frequency is monitored, and the electrode film on the surface of the piezoelectric element is removed so that the frequency becomes a desired value.
Therefore, there is a problem that a deviation occurs between the oscillation frequency when the IC chip is also mounted on the package and the oscillation circuit is configured with the piezoelectric element to perform the oscillation operation and the resonance frequency adjusted in advance. In addition, the number of adjustment steps is increased, resulting in an extra adjustment cost.

  Therefore, the piezoelectric element and IC chip are mounted in the package, the oscillation circuit is operated, the oscillation frequency is monitored, and the adjustment of the resonance frequency of the piezoelectric element at room temperature and the subsequent creation of compensation data are performed. Although it is conceivable to continue the operation in a state close to the use state, in that case, the temperature compensation circuit also operates. In addition, although the compensation data is not stored in the temperature compensation data storage circuit in the initial state, all the bits of the register for storing it are “0” and all are “1”. The initial value is unknown. Therefore, there is a problem that the resonance frequency of a piezoelectric element such as a crystal piece cannot be adjusted appropriately, and the subsequent creation of compensation data cannot be made properly.

  The present invention has been made to solve such a problem. In a state where a temperature-compensated oscillator is configured by mounting a piezoelectric element such as a crystal piece and an IC chip in a package, the oscillation circuit is formed. The temperature compensated oscillator is made to be able to accurately adjust the temperature characteristics of the piezoelectric element itself by operating it, and to make subsequent compensation data creation and storing it in the compensation data storage circuit appropriately. The purpose is to simplify and improve the accuracy of the adjustment process.

The present invention includes an oscillation circuit whose oscillation frequency changes with a temperature change, an output line for outputting a signal based on the oscillation output, a temperature detection circuit for detecting a temperature state in the vicinity of the oscillation circuit, and a temperature detection signal thereof In order to achieve the above object, the temperature compensation function of the temperature compensation circuit is effective in a temperature compensation oscillator having a temperature compensation circuit for keeping the frequency of the signal output to the output line at a substantially constant value based on Selection means for selecting whether the state is set or the invalid state is provided.
Further, a variable frequency dividing circuit is provided between the oscillation circuit and the output line, and the selecting means has the variable compensator added to the temperature compensation circuit when the temperature compensation function of the temperature compensation circuit is to be enabled. When the frequency division ratio of the frequency divider circuit is changed depending on the temperature change, and the temperature compensation function is disabled, the frequency division ratio of the variable frequency divider circuit is fixed to a predetermined value. You may do it.

In these temperature-compensated oscillators, the oscillation circuit has an oscillation capacitance, and the selection means sets an oscillation capacitance value in the temperature compensation circuit when the temperature compensation function of the temperature compensation circuit is enabled. If the temperature compensation function is changed depending on the temperature change, and the temperature compensation function is disabled, a means for fixing the oscillation capacitance to a predetermined capacitance value may be provided.
The oscillation capacitor has a variable capacitor whose capacitance value changes in accordance with the applied voltage, and the temperature compensation circuit preferably has means for changing the value of the oscillation capacitor by changing the voltage applied to the variable capacitor.
In this case, the selection means may include means for fixing the voltage applied to the variable capacitor to a predetermined value when the oscillation capacitor is fixed to a predetermined capacitance value.

Alternatively, the oscillation capacitor may have a plurality of fixed capacitors, and the temperature compensation circuit may have means for changing the oscillation capacitance by changing the connection state of the plurality of fixed capacitors.
In this case, the selection means may include means for separating the variable capacitor so as not to be included in the oscillation capacitor when the oscillation capacitor is fixed to a predetermined capacitance value.
In these temperature compensation oscillators, a selection information storage circuit for storing control information for controlling the selection state of the selection means may be provided.
It is desirable to provide a compensation data storage circuit for storing temperature compensation data of the temperature compensation circuit.
The compensation data storage circuit and the selection information storage circuit can be configured as an integrated storage circuit (for example, one nonvolatile memory).
You may provide the control information input terminal for inputting the control information which controls the selection state of the said selection means from the outside. The control information input terminal may be an external terminal provided in a package constituting the temperature compensated oscillator.
The selection information storage circuit may be formed of a predetermined conductive pattern, and may store information for controlling the selection state of the selection means by cutting the conductive pattern.

  The temperature compensated oscillator according to the present invention configured as described above is a piezoelectric element in which a piezoelectric element such as a crystal piece and an IC chip are mounted in a package and the temperature compensated oscillator is configured to operate the oscillation circuit. The temperature characteristic of itself can be adjusted accurately. Further, the subsequent creation of compensation data and the operation of storing the compensation data in the compensation data storage circuit can be appropriately performed continuously, and the adjustment process can be simplified and highly accurate.

Preferred embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a block circuit diagram showing the configuration of the first embodiment of the temperature compensated oscillator according to the present invention. The same parts as those in FIG. 8 and FIG. To do.
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 the conventional example shown in FIG. 9, a temperature detection circuit 18, and a temperature compensation circuit 30. Further, as specific to this embodiment, a selection circuit 40 as selection means, a selection information storage circuit (nonvolatile memory) 50 for storing control information for controlling the selection state, and a constant voltage Vk are output. And a constant voltage generating circuit 51.

In addition to the selection information storage circuit 50, a control information input terminal for inputting control information for controlling the selection state of the selection circuit 40 is provided as an external terminal 52 outside the package 10 shown in FIG. . This control information input terminal may be provided inside the package body 11.
The selection circuit 40 includes a pair of transmission gates 41 and 42, a three-input NAND circuit 43, and two inverters (NOT circuits) 44 and 45. The control voltage Vc, which is the output of the temperature compensation circuit 30, is applied to the common connection point of the resistors R1 and R2 shown in FIG. The constant voltage Vk, which is the output of the constant voltage generation circuit 51, is applied to the common connection point of the resistors R1 and R2 of the oscillation circuit 20 through the other transmission gate 42.

The selection information storage circuit 50 outputs 3-bit selection information, and the outputs of the bit 1 and the bit 3 become the two inputs of the 3-input NAND circuit 43 as it is, and the output of the bit 2 is inverted by the inverter 44 to be the NAND circuit. The remaining 43 inputs. Therefore, only when the selection information output from the selection information storage circuit 50 is “101”, all three inputs of the NAND circuit 43 become “1”, so that the output becomes “0”.
The output of the NAND circuit 43 is directly applied to the gate on the negative logic side of the transmission gate 41 and the gate on the positive logic side of the transmission gate 42, and the gate on the positive logic side of the transmission gate 41 and the negative gate of the transmission gate 42. Inverted by the inverter 45 and applied to the gate on the logic side.

Therefore, only when the selection information output from the selection information storage circuit 50 is “101”, the transmission gate 41 is turned on and the transmission gate 42 is turned off, so that the control voltage Vc output from the temperature compensation circuit 30 is Since the voltage is applied to the oscillation circuit 20 through the transmission gate 41 and applied to the voltage controlled variable capacitors 23 and 24 via the resistors R1 and R2 shown in FIG. 9, the value of the oscillation capacitance depends on the temperature. The temperature is compensated so that the oscillation frequency of the oscillation circuit 20 is kept constant.
When the selection information output from the selection information storage circuit 50 is other than “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 the transmission gate. 42 is applied to the oscillation circuit 20 and applied to the voltage-controlled variable capacitors 23 and 24 via the resistors R1 and R2 shown in FIG. 9, and the value of the oscillation capacitance corresponds to the constant voltage. The fixed capacitance value is fixed, and temperature compensation of the oscillation frequency of the oscillation circuit 20 is not performed.

Accordingly, 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 output from the selection information storage circuit 50, thereby enabling the temperature compensation function. Or a constant (fixed) voltage Vk from the constant voltage generation circuit is selected 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 (voltage) as control information to the external terminal 52. .
When a control information input terminal such as the external terminal 52 is provided, the selection information storage circuit 50, the NAND circuit 43, and the inverter 44 in FIG. 1 may be omitted.

  According to this temperature-compensated oscillator, initial adjustment of the crystal piece of the oscillation circuit 20 and adjustment work for creating and storing temperature compensation data are performed in an IC chip that constitutes the crystal piece, the oscillation circuit, the temperature compensation circuit, and the like in the package. Can be performed by operating the oscillation circuit 20 in a state in which the temperature compensation oscillator is completed. At the time of the adjustment, the selection information in the selection information storage circuit 50 is set to other than “101”, thereby invalidating the temperature compensation function and causing the oscillation circuit 20 to oscillate with a predetermined oscillation capacity.

The steps of the adjustment work are as follows.
Step 1: In the package (for example, the package body 11 shown in FIG. 8), the oscillation circuit 20 and an IC chip constituting each circuit shown in FIG. 1 are mounted, and then a crystal piece is mounted.
Step 2: Keep the package at a reference temperature (generally room temperature: 25 ° C), disable the temperature compensation function of the temperature-compensated oscillator, operate as a simple oscillator, and monitor the oscillation frequency with a network analyzer etc. by removing the electrode film of the crystal piece surface with a beam or the like is adjusted to a desired oscillation frequency f _0.
Step 3: A cover is attached to the package, and the crystal piece is hermetically sealed.
Step 4: subjecting the package to a plurality of temperature, by measuring the oscillation frequency at the respective temperature conditions, to measure the difference between the desired oscillation frequency f _0.
Step 5: Create temperature compensation data based on the measured value, and write it into the compensation data storage circuit (nonvolatile memory) of the IC chip.

After this adjustment, if the selection information in the selection information storage circuit 50 is set to “101”, the temperature compensation function becomes effective, and it becomes possible to operate normally as a temperature compensation oscillator, and an ultra-compact temperature compensation oscillator is completed. .
Therefore, while the oscillation circuit oscillates in the same manner as the actual use state, the temperature characteristics of the crystal piece can be accurately adjusted without being affected by the temperature compensation circuit, and the subsequent creation of compensation data and the compensation data storage circuit The work to be stored in can also be performed appropriately. Therefore, the adjustment process of the temperature compensated oscillator can be simplified and highly accurate.

In step 2, the package is maintained at a reference temperature (generally room temperature: 25 ° C.) by adjusting the package in a thermostatic bath.
In step 4, the package is exposed to a plurality of temperature states by changing the set temperature of the thermostat in order or by sequentially storing the packages in a plurality of thermostats set at different temperatures. The measurement temperature range is an operation guarantee temperature range of the oscillator, and is set to an appropriate point (for example, about 11 points) between −40 ° C. and + 100 ° C.
To adjust the reference frequency of the crystal piece, a metal film such as silver is vapor-deposited on the surface of the crystal piece in advance to form a film thickness (thick) that makes the resonance frequency lower than the reference frequency. This is performed by irradiating the electrode film with an ion beam using an ion gun or performing sputter etching to reduce the mass of the electrode film little by little.
The same applies to the case where another piezoelectric element is used in place of the crystal piece as the oscillator of the oscillation circuit.

Since the temperature characteristics of the oscillation frequency of an oscillation circuit using an AT-cut quartz crystal as a vibrator is almost a cubic curve, the ambient temperature changes even if the oscillation frequency is adjusted to the desired frequency f ₀ at the reference temperature. Then the oscillation frequency will shift. Therefore, by actually changing the temperature between the lower limit and the upper limit of the guaranteed temperature range, the actual oscillation frequency of the oscillation circuit, that is, the frequency of the signal output to the output terminal 26 in each temperature state (measurement point). measured, to measure the difference between the desired oscillation frequency f _0.
Then, the temperature compensation data necessary to generate the control voltage Vc for making the difference 0 is generated in the temperature compensation circuit 30, and the temperature is stored in the compensation data storage circuit (nonvolatile memory) 31 shown in FIG. Write corresponding to the data.
Although more accurate temperature compensation data can be created with a larger number of measurement points, the measurement time becomes longer, so the temperature characteristics of the oscillation circuit are determined from the measurement results in an appropriate number (for example, about 11 points) of temperature conditions. It is advisable to estimate the cubic curve and to create temperature compensation data with respect to the temperature between the measurement points by interpolating it and write it to the compensation data storage circuit.

Next, different examples of the oscillation circuit, in particular, different examples of the oscillation capacitance and the capacitance variable means are shown in FIGS.
In the oscillation circuit shown in FIG. 2, similarly to the oscillation circuit 20 shown in FIG. 9, a crystal piece 15, an inverter 21 and a feedback resistor 22 are connected in parallel, and both connection points are grounded via oscillation capacitors. Thus, an inverter oscillation circuit is configured. However, in place of the voltage-controlled variable capacitor, a plurality of fixed-capacitor parallel circuits are used as the oscillation capacitor.
That is, a first capacitor array 27 in which capacitors C1 to C5 are connected in parallel via switches S1 to S5, respectively, is provided between the input side of the inverter 21 and the ground, and capacitors C6 to C10 are connected to switches S7 to S10, respectively. The second capacitor array 28 is connected in parallel with each other, and is provided between the output side of the inverter 21 and the ground. A switching element such as a MOS-FET may be used for each of the switches S1 to S10.

In this case, instead of the D / A conversion circuit shown in FIG. 9, the temperature compensation circuit reads compensation data corresponding to the temperature detection data from the temperature detection circuit 18 from the compensation data storage circuit 31, and switches the oscillation circuit switch S1. A circuit for outputting a variable switch control signal for controlling the ON / OFF state of S10 is provided.
Further, in place of the constant voltage generation circuit 51 shown in FIG. 1, predetermined switches (for example, switches S1 to S3 and S6 to S8) among the switches S1 to S10 of the oscillation circuit are turned on, and the other switches are turned off. A circuit for generating a fixed switch control signal is provided, and either the fixed switch control signal or the variable switch control signal generated by the temperature compensation circuit described above is selected by the selection means, and the switch S1 of the oscillation circuit is selected. Applied to each control electrode of S10 to control ON / OFF thereof.

When the temperature compensation function is invalidated at the time of initial adjustment, the fixed switch control signal is selected by the selection means and is input to the oscillation circuit. For example, the switches S1 to S3 and S6 to S8 are turned on and the other switches are selected. Switch off. Thereby, the capacitance value of the first capacitance array 27 is fixed to the capacitance value of the parallel circuit of the capacitors C1 to C3, and the capacitance value of the second capacitance array 28 is fixed to the capacitance value of the parallel circuit of the capacitors C6 to C8. The Therefore, the oscillation capacity is constant regardless of the temperature change.
When the temperature compensation function is enabled after the initial adjustment, the variable switch control signal from the temperature compensation circuit is selected by the selection means and input to the oscillation circuit, and the switches S1 to S5 and the second capacitor array 27 of the first capacitor array 27 are input. At least one of the switches S6 to S10 of the capacitor array 28 is selectively turned on. Thereby, the effective combination (connection state) of the capacitors of the first capacitor array 27 and the second capacitor array 28 is changed, and the capacitance values (oscillation capacitors) of the capacitor arrays 27 and 28 are changed depending on the temperature change. Let

For example, as described above, 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. In the reference state, when the switch S1 and / or S2 is turned off from that state, and when the switch S6 and / or S7 is turned off, the capacitance values of the first capacitor array 27 and the second capacitor array 28 decrease. To do. Further, when the switch S4 and / or S5 is turned on and the switch S9 and / or S10 is turned on from the standard state, the capacitance values of the first capacitor array 27 and the second capacitor array 28 increase.
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 oscillation capacitance can be controlled considerably finely. Temperature compensation of the oscillation frequency can be performed.

The oscillation circuit shown in FIG. 3 has switches S11 and S12 inserted in series with the voltage controlled variable capacitors 23 and 24 in the oscillation circuit 20 shown in FIG. 9, and a series circuit of a capacitor Ca and a switch S13 in parallel with them. , And a series circuit of the capacitor Cb and the switch S14. Capacitors Ca and Cb are fixed capacitors. Cc and Cd are direct current component cut capacities.
When disabling the temperature compensation function during initial adjustment, the switches S11 and S12 are turned off and the switches S13 and S14 are turned on by the selection circuit, so that the oscillation capacitance is fixed to the capacitance values of the capacitors Ca and Cb. Is done. At this time, the voltage-controlled variable capacitors 23 and 24 are separated so as not to be included in the oscillation capacitor.

When the temperature compensation function is enabled after the initial adjustment, the voltage control variable capacitors 23 and 24 become oscillation capacitors by turning on the switches S11 and S12 and turning off the switches S13 and S14 by the selection circuit. Since the control voltage from the circuit is applied via the resistors R1 and R2, and each capacitance value changes depending on the temperature change, temperature compensation of the oscillation frequency can be performed.
In these oscillation circuits as well, other piezoelectric elements can be used as the vibrator instead of the crystal piece.

Next, a second embodiment of the temperature compensated oscillator according to the present invention will be described with reference to FIG. 4, parts that are the same as those in FIGS. 1 and 9 are given the same reference numerals, and descriptions thereof are omitted. However, the compensation data storage circuit 31 and the selection information storage circuit 50 of the temperature compensation circuit in this embodiment are an integral storage circuit, which also serves as one nonvolatile memory 19, and most of the storage area is the compensation data storage circuit. 31 is used, and a part thereof is used as the selection information storage circuit 50.
In the temperature compensated oscillator shown in FIG. 4, a variable frequency dividing circuit 60 is provided between the oscillation circuit 20 and the output line 25, and a first selection circuit 40A and a second selection circuit 40B are provided as selection means. ing. The first and second selection circuits 40A and 40B have the same circuit configuration, and, as shown in the second selection circuit 40B, digital gate circuits 47 and 48.
And a three-input AND circuit 46 and two inverters (NOT circuits) 44 and 49.

Of the 3-bit selection information output from the selection information storage circuit 50, the output of bit 1 and bit 3 is directly used as two inputs of the 3-input AND circuit 46, and the output of bit 2 is inverted by the inverter 44 and is AND circuit 46. Is the remaining input. Therefore, only when the selection information output from the selection information storage circuit 50 is “101”, all three inputs of the AND circuit 46 become “1”, so the output becomes “1”. When the selection information output from the selection information storage circuit 50 is other than “101”, the output of the AND circuit 46 is “0”.
The output of the AND circuit 46 is directly applied to the control terminal C of the digital gate circuit 47, and is inverted and applied to the control terminal C of the digital gate circuit 48 by the inverter 49.

Therefore, in the second selection circuit 40B, the digital gate circuit 47 is turned on and the digital gate circuit 48 is turned off only when the selection information output from the selection information storage circuit 50 is “101”. The variable frequency division number data Dc input from the compensation data output circuit 33 of the compensation circuit 30 ′ is selected and output to the variable frequency dividing circuit 60, and the selection information output from the selection information storage circuit 50 is other than “101”. In some cases, the digital gate circuit 48 is turned on and the digital gate circuit 47 is turned off, so that the fixed frequency division number data Dk input from the ROM 52 is selected and output to the variable frequency dividing circuit 60.
The first selection circuit 40A has the same configuration as this, except that the switch control data Sc and Sk are selected and the output destination of the selected switch control data is the oscillation circuit 20.

The compensation data output circuit 33 of the temperature compensation circuit 30 ′ is a variable switch for performing temperature compensation with reference to the compensation data of the compensation data storage circuit 31 according to the temperature data detected by the temperature detection circuit 18. A control signal (digital data) Sc and frequency division number data Dc are output and input to the digital gate circuit 47 of the first and second selection circuits 40A and 40B, respectively.
On the other hand, the ROM 52, which is a read-only memory, stores a fixed switch control signal (digital data) Sk and frequency division number data Dk in advance, and each data is read by a read circuit (not shown). Are input to the digital gate circuits 48 of the first and second selection circuits 40A and 40B, respectively.

Therefore, the first selection circuit 40A can change the variable switch control signal Sc input from the compensation data output circuit 33 of the temperature compensation circuit 30 'only when the selection information output from the selection information storage circuit 50 is "101". Is selected and output to the oscillation circuit 20. When the selection information output from the selection information storage circuit 50 is other than “101”, the fixed switch control signal Sk input from the ROM 52 is selected and output to the oscillation circuit 20. .
For example, as shown in FIG. 2, the oscillation circuit 20 is a circuit using first and second capacitor arrays 27 and 28 in which a large number of capacitors are provided in parallel via switches as oscillation capacitors. By controlling ON / OFF of S1 to S10 by the switch control signal (digital data) Sc or Sk output from the first selection circuit 40A, the oscillation capacity can be controlled and the oscillation frequency can be varied. As the switches S1 to S10 shown in FIG. 2, an electronic switch that can be controlled ON / OFF by a 1-bit digital signal such as a MOS type analog switch is used.

A known circuit is used as the variable frequency dividing circuit 60, and an example thereof will be described with reference to FIG. The variable frequency dividing circuit 60 includes a reference divider 61, a phase comparator 62, a low-pass filter (hereinafter abbreviated as “LPF”) 63, a voltage-controlled oscillation circuit (hereinafter abbreviated as “VCO”) 64, a feedback divider 65, And an output buffer 66.
The oscillation output signal from the oscillation circuit 20 is divided by the reference divider 61 and input to the phase comparator 62 as a reference signal. On the other hand, the oscillation signal of the VCO 64 is divided by the feedback divider 65 and input as a comparison signal to the phase comparator 62. The phase comparator 62 outputs a voltage corresponding to the phase difference between the two input signals, which is supplied to the VCO 64 via the LPF 63 and controls the oscillation frequency of the VCO 64. The oscillation signal of the VCO is output to the output line 25 via the output buffer 66.
The reference divider 61 and the feedback divider 65 are both programmable dividers that can divide by a variable integer value.

The frequency fo of the output signal of the variable frequency dividing circuit 60 is determined by the frequency division number M of the reference divider 61 and the frequency division number N of the feedback divider 65, where the frequency of the oscillation output signal from the oscillation circuit 20 is fc. The relationship is shown by the following equation.
fo = fc × N / M
The reference divider 61 divides the frequency of the input signal by 1 / M and outputs it, and the feedback divider 65 divides the frequency of the input signal by 1 / N and outputs it.
N / M is a frequency division ratio (in this case, a multiplication number), and can be arbitrarily set according to the values of the frequency division numbers M and N. For example, by using M = N = 100 as a reference value and changing the values of frequency division numbers M and N as shown in FIG. 6, the frequency division ratio (multiplication number) is increased from 1.000 to 0.005. Can be reduced or decreased.
Therefore, when the frequency fc of the oscillation output signal from the oscillation circuit 20 is 20 MHz, the frequency fo of the output signal can be increased or decreased in increments of 0.1 MHz with reference to 20 MHz.

Accordingly, the fixed frequency division number data Dk stored in the ROM 52 shown in FIG. 4 is composed of the frequency division numbers M and N, M = N = 100, and variable frequency division number data output from the compensation data output circuit 33. If Dc is also constituted by the frequency dividing numbers M and N and as shown in FIG. 6, the second selecting circuit 40B in FIG. 4 selects the fixed frequency dividing number data Dk from the ROM 52 and the variable frequency dividing circuit. 60, since M = N = 100, the frequency division ratio is 1.000, and the frequency fo of the output signal is the same as the frequency fc of the oscillation output signal from the oscillation circuit 20 (example in FIG. 6). 20 MHz).
When the second selection circuit 40B in FIG. 4 selects the variable frequency division number data Dc output from the compensation data output circuit 33 and inputs it to the variable frequency division circuit 60, the frequency division constituting the frequency division number data Dc. Depending on the values of the numbers M and N, the dividing ratio can be changed variously. In the example shown in FIG. 6, the dividing ratio (multiplication number) is increased or decreased from 1.000 to 0.005. In other words, the frequency fo of the output signal can be increased or decreased in increments of 0.1 MHz with 20 MHz as a reference.

The minimum variable width (step size) and the maximum variable range of the frequency division ratio (multiplication number) can be arbitrarily set by selecting the frequency division numbers M and N.
Also in this embodiment, the 3-bit selection information of the selection information storage circuit 50 is adjusted at the time of initial adjustment until the resonance frequency of the crystal piece of the oscillation circuit 20 is adjusted and the compensation data is generated and stored in the compensation data storage circuit 31. Is in a state other than “101”.
Therefore, the first selection circuit 40A selects the fixed switch control signal Sk input from the ROM 52 and outputs it to the oscillation circuit 20. The second selection circuit 40B also selects fixed frequency division number data Dk input from the ROM 52 and outputs it to the variable frequency dividing circuit 60.

Accordingly, the oscillation circuit 20 is turned on only by the switches S1 to S3 and S6 to S8 shown in FIG. 2, for example, and the other switches are turned off by the fixed switch control signal Sk. Therefore, the capacitance value of the first capacitance array 27 is fixed to the capacitance value of the parallel circuit of the capacitors C1 to C3, and the capacitance value of the second capacitance array 28 is fixed to the capacitance value of the parallel circuit of the capacitors C6 to C8. . This is the standard state, and the oscillation capacity is constant regardless of the temperature change, and the frequency fc of the oscillation output signal varies somewhat depending on the temperature characteristics of the crystal piece 15, but temperature compensation is not performed.
On the other hand, in the variable frequency dividing circuit 60, the frequency dividing ratio is fixed to 1.000 by M = N = 100 of the fixed frequency dividing number data Dk, and the frequency fo of the signal output to the output line is the oscillation of the oscillation circuit 20. This is the same as the frequency fc of the output signal, and temperature compensation is not performed here either. That is, at this time, the temperature compensation function is disabled, and the temperature compensated oscillator shown in FIG. 4 operates as a simple oscillator.

When the adjustment work is completed, “101” is written as selection information in the selection information storage circuit 50 in the same nonvolatile memory 19 at the time of writing the last compensation data in the compensation data storage circuit 31 or immediately after that.
As a result, the selection information output from the selection information storage circuit 50 becomes “101”, and 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 ′. Output to the oscillation circuit 20. The second selection circuit 40B also selects the variable frequency division number data Dc from the compensation data output circuit 33 and outputs it to the variable frequency division circuit 60.

The oscillation circuit 20 selects, for example, one or more of the switches S1 to S5 of the first capacitor array 27 and the switches S6 to S10 of the second capacitor array 28 shown in FIG. 2 according to the variable switch control signal Sc. ON. Therefore, the effective combination (connection state) of the capacitors of the first capacitor array 27 and the second capacitor array 28 is changed, and the capacitance values (oscillation capacitors) of the capacitor arrays 27 and 28 are changed depending on the temperature change. The frequency fc of the oscillation signal of the oscillation circuit 20 is adjusted so as to compensate for fluctuations due to temperature.

Further, the variable frequency dividing circuit 60 changes the frequency dividing ratio according to the values of the frequency dividing numbers M and N constituting the input frequency dividing number data Dc, and sets the frequency fo of the output signal to fc × N / M. Output. In the example shown in FIG. 6, the frequency of the output signal can be increased or decreased in increments of 0.1 MHz with 20 MHz as a reference.
As described above, when the temperature compensation function is enabled, the temperature characteristic of the crystal piece is adjusted by the combination of the adjustment of the oscillation capacitance value in the oscillation circuit 20 and the adjustment of the frequency division ratio (multiplication number) in the variable frequency divider circuit 60. The output signal having a constant frequency can always be output to the output terminal 26 by compensating for the fluctuation of the oscillation frequency based on it.
Also in this embodiment, as the vibrator of the oscillation circuit 20, another piezoelectric element can be used instead of the crystal piece.

Next, a third embodiment of the temperature compensated oscillator according to the present invention will be described with reference to FIG. 7, parts that are the same as in FIG. 1 are given the same reference numerals, and descriptions thereof are omitted.
In the temperature compensated oscillator shown in FIG. 7, the selection circuit 40 'is a circuit obtained by removing the NAND circuit 43 and the inverter 44 from the selection circuit 40 shown in FIG. A selection information storage circuit 55 using a predetermined conductive pattern 56 is provided instead of the selection information storage circuit 50 using a volatile memory. Note that the external terminal 52 in FIG. 1 is not provided.

  The conductive pattern 56 is formed, for example, on an insulating substrate provided in a portion that can be operated from the outside in the package main body 11 shown in FIG. One end thereof is connected to the positive power supply line 57, and the other end is grounded via a resistor 58. The voltage level at the point P, which is the connection point between the conductive pattern 56 and the resistor 58, is output to the selection circuit 40 'as binary selection information, which is directly or directly applied to each gate of the transmission gates 41 and 42 as shown in the figure. Inverted by the inverter 45 and applied.

  In the initial state, the conductive pattern 56 of the selection information storage circuit 55 is conductive, and the voltage level at the point P is high “1”, so that the transmission gate 42 of the selection circuit 40 ′ is turned on and the transmission gate 41 is turned off. It has become. Therefore, the constant voltage Vk output from the constant voltage generation circuit 51 is supplied to the oscillation circuit 20 through the transmission gate 42, and the value of the oscillation capacitance of the oscillation circuit 20 is fixed to a predetermined capacitance value, so that the temperature compensation function is disabled.

  When the conductive pattern 56 of the selection information storage circuit 55 is cut after the initial adjustment is completed, the voltage level at the point P becomes the ground level, that is, low “0”, so that the transmission gate 41 of the selection circuit 40 ′ is turned ON. The transmission gate 42 is turned off. Therefore, the control voltage Vc output from the temperature compensation circuit 30 according to the temperature detection signal from the temperature detection circuit 18 is supplied to the oscillation circuit 20 through the transmission gate 41, and the oscillation capacitance value of the oscillation circuit 20 depends on the temperature change. Change. As a result, the temperature compensation function effectively works so that the oscillation frequency, that is, the frequency of the signal output to the output terminal 26 through the output line 25 is kept constant even when the environmental temperature varies.

  In the first and second embodiments described above, the temperature compensation function is enabled by setting the selection information in the selection information storage circuit 50 to “101”. However, the present invention is not limited to this, and any data is available. May be used as the selection information, and the number of digits of the data is arbitrary. However, since the non-volatile memory or the like constituting the selection information storage circuit 50 generally has a high probability that the data in the initial state is all “1” or all “0”, the above-mentioned selection information includes “111” and “ It is preferable to avoid 000 ".

  The present invention can be used for various temperature-compensated oscillators (TCXO) in which the frequency of an output signal is kept substantially constant regardless of a change in ambient temperature, and is particularly frequently used for portable mobile communication devices such as cellular phones. It can be applied to a temperature compensated oscillator.

1 is a block circuit diagram showing a configuration of a first embodiment of a temperature compensated oscillator according to the present invention. FIG. It is a circuit diagram which shows the example from which the oscillation circuit differs. It is a circuit diagram which shows the further different example of an oscillation circuit similarly. FIG. 3 is a block circuit diagram showing a configuration of a second embodiment of a temperature compensated oscillator according to the present invention. FIG. 5 is a block diagram illustrating an example of a variable frequency dividing circuit in FIG. 4. It is a figure which similarly shows an example of the relationship between the frequency dividing numbers M and N by the variable frequency dividing circuit, frequency dividing ratio (multiplication number), and output frequency. It is a block circuit diagram which shows the structure of 3rd Embodiment of the temperature compensation type | mold oscillator by this invention. It is a schematic sectional drawing which shows an example of the package of a temperature compensation type | mold oscillator. It is a block circuit diagram which shows the structural example of the conventional temperature compensation type | mold oscillator.

Explanation of symbols

10: Package (container) 11: Package body 12: Welding ring 13: Cover 15: Crystal piece (vibrator)
16: IC (integrated circuit) 17: Circuit element such as a chip capacitor 18: Temperature detection circuit 19: Non-volatile memory 20: Oscillator circuit 21: Inverter 22: Feedback resistor 23, 24: Voltage-controlled variable capacitor 25: Output line 26 : Output terminal 27: first capacitor array 28: second capacitor array 30, 30 ': temperature compensation circuit 31: compensation data storage circuit 32: D / A conversion circuit 33: compensation data output circuit 40, 40': selection Circuit (selection means)
40A: first selection circuit 40B: second selection circuit 41, 42: transmission gate 47, 48: digital gate circuit 50: selection information storage circuit 51: constant voltage generation circuit 52: external terminal (control information input terminal) 55 : Selection information storage circuit 56: Conductive pattern 57: Positive power supply line 58: Resistor 60: Variable frequency dividing circuit

Claims (13)

An oscillation circuit whose oscillation frequency changes with temperature change, an output line for outputting a signal based on the oscillation output of the oscillation circuit, a temperature detection circuit for detecting a temperature state in the vicinity of the oscillation circuit, and the temperature detection circuit In a temperature compensated oscillator having a temperature compensation circuit for keeping the frequency of a signal output to the output line based on an output from a substantially constant value,
A temperature-compensated oscillator comprising selection means for selecting whether to enable or disable the temperature compensation function of the temperature compensation circuit. The temperature compensated oscillator according to claim 1, wherein
A variable frequency divider is provided between the oscillation circuit and the output line,
When the temperature compensation function of the temperature compensation circuit is enabled, the selection unit causes the temperature compensation circuit to change a frequency division ratio of the variable frequency divider circuit depending on a temperature change, and A temperature-compensated oscillator having means for fixing a frequency division ratio of the variable frequency dividing circuit to a predetermined value when the compensation function is disabled. The temperature compensated oscillator according to claim 1 or 2,
The oscillation circuit has an oscillation capacitor,
The selection means, when enabling the temperature compensation function of the temperature compensation circuit, causes the temperature compensation circuit to change the value of the oscillation capacitance depending on a temperature change, and invalidates the temperature compensation function. A temperature compensated oscillator having means for fixing the oscillation capacitance to a predetermined capacitance value when the state is set.   The oscillation capacitor has a variable capacitor whose capacitance value changes in accordance with an applied voltage, and the temperature compensation circuit has means for changing the value of the oscillation capacitor by changing the voltage applied to the variable capacitor. The temperature-compensated oscillator according to claim 3.   4. The oscillation capacitor according to claim 3, wherein the oscillation capacitor has a plurality of fixed capacitors, and the temperature compensation circuit has means for changing the oscillation capacitance by changing a connection state of the plurality of fixed capacitors. Temperature compensated oscillator.   5. The temperature compensated oscillator according to claim 4, wherein the selection means includes means for fixing the voltage applied to the variable capacitor to a predetermined value when the oscillation capacitor is fixed to a predetermined capacitance value. .   5. The temperature compensated oscillator according to claim 4, wherein the selection means includes means for separating the variable capacitor so as not to be included in the oscillation capacitor when the oscillation capacitor is fixed to a predetermined capacitance value. . The temperature compensated oscillator according to any one of claims 1 to 7,
A temperature compensated oscillator comprising a selection information storage circuit for storing control information for controlling a selection state of the selection means. The temperature compensated oscillator according to any one of claims 1 to 8,
A temperature compensation oscillator comprising a compensation data storage circuit for storing temperature compensation data of the temperature compensation circuit. The temperature compensated oscillator according to any one of claims 1 to 7,
A selection information storage circuit for storing control information for controlling a selection state of the selection means; a compensation data storage circuit for storing temperature compensation data of the temperature compensation circuit; and the selection information storage circuit and the compensation data storage. A temperature-compensated oscillator, wherein the circuit is an integrated memory circuit. The temperature compensated oscillator according to any one of claims 1 to 10,
A temperature-compensated oscillator comprising a control information input terminal for inputting control information for controlling the selection state of the selection means from the outside.   12. The temperature compensated oscillator according to claim 11, wherein the control information input terminal is an external terminal provided in a package constituting the temperature compensated oscillator.   9. The selection information storage circuit includes a predetermined conductive pattern, and stores information for controlling a selection state of the selection unit by cutting the conductive pattern. Temperature compensated oscillator.

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