JPH09102713A - Crystal oscillator device and its control method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve frequency control accuracy for a crystal oscillator device and its control method. SOLUTION: A control circuit includes a temperature sensor 30, a temperature detection part 32 which is electrically connected to the sensor 30, a memory 36 which is electrically connected to the part 32, an amplification part 31 where the sensor 30 is electrically connected to the memory 36, a 1st D/A conversion part 38 which is electrically placed between the memory 36 and the sensor 30, and a 2nd D/A conversion part 37 which is electrically placed between the memory 36 and the part 31. The part 31 includes a polarity inverting circuit 33 which is connected to the sensor 30, a variable attenuator 34 which is connected to the circuit 33, an offset control circuit 100, and an amplifier circuit 35. Then the memory 36 has the control voltage setting groups of 8 pieces or less which really operate.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a crystal oscillator having a temperature compensation function and a method of adjusting the same.

[0002]

2. Description of the Related Art A crystal oscillating device is provided with a crystal oscillator, and the oscillating frequency of this crystal oscillator fluctuates greatly with temperature fluctuations.

For this reason, conventionally, in order to reduce the oscillation frequency fluctuation of the crystal oscillator due to the temperature fluctuation, a voltage applied to a varactor diode used as a frequency adjusting element of the crystal oscillator is controlled by a control circuit.

The configuration of the conventional control circuit is as follows.
130 ° C from low to high, for example -35 ° C to 95 ° C
If temperature compensation is performed between the
The temperature compensation data for each 4 ° C. is stored in a memory.

In this case, the compensation data in the above-mentioned conventional example requires data relating to a precise slope, a temperature bias point, a polarity, a coarse slope, and a fixed offset for each of the 4 ° C. Thirty-two groups were stored in the memory as control voltage setting groups.

That is, the data of one control voltage setting group is selectively output from the memory according to the temperature detected by the temperature sensor, thereby stabilizing the oscillation frequency of the crystal oscillator irrespective of the fluctuation of the ambient temperature. It is.

[0007]

The problem with the prior art is that the size of the memory is increased and the size of the semiconductor integrated circuit including the memory and the control circuit is increased. It meant that the power would also increase.

That is, in the conventional example, the temperature is from -35.degree.
The temperature compensation data for each 4 ° C. is stored in the control voltage setting group of the memory in order to compensate the temperature up to 4 ° C. every 4 ° C. Therefore, this memory has a large capacity having 32 control voltage setting groups. In order to control such a large-capacity memory having as many as 32 control voltage setting groups, the control circuit is also complicated and easy to increase in size. As a result, a semiconductor integrated circuit comprising the memory and the control circuit is required. It was enlarged.

Further, a control circuit for controlling a memory having 32 control voltage setting groups tends to consume a large amount of power.

Therefore, an object of the present invention is to provide a semiconductor integrated circuit including a memory and a control circuit, which can be easily downsized, the power consumption can be easily reduced, and the frequency adjustment accuracy can be easily increased.

[0011]

According to the present invention, there is provided a crystal oscillator, a frequency adjusting element electrically connected to the crystal oscillator, and a control circuit for controlling a voltage applied to the frequency adjusting element. A temperature sensor, a temperature detector electrically connected to the temperature sensor, a memory electrically connected to the temperature detector, the memory and the temperature. An amplifying unit to which a sensor is electrically connected; a first D / A conversion unit electrically interposed between the memory and the temperature detecting unit; and an electrically connecting unit between the memory and the amplifying unit. The second D /
An A conversion unit, wherein the amplification unit includes a polarity inversion circuit connected to the temperature sensor, a variable attenuator, an offset adjustment circuit, and an amplification circuit sequentially connected to the polarity inversion circuit; Has eight or less control voltage setting groups that actually operate, and each control voltage setting group
The temperature detection data, the amplification degree setting data, and the offset voltage data are stored. By doing so, the size is reduced and the frequency adjustment accuracy is increased.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the invention of claim 1 of the present invention, a memory in which temperature detection data, amplification degree setting data, and offset voltage data are included in one control voltage setting group is actually operated. Since it has 8 or less, the memory capacity is small, and even a control circuit for a memory having actually 8 or less control voltage setting groups is simple in configuration and easily miniaturized. As a result, the memory and control circuit are This facilitates miniaturization of the semiconductor integrated circuit included therein.

If the memory capacity is small and the control circuit is simple, the power consumption can be easily reduced. Further, in the amplifying section, the polarity is set by the polarity inverting circuit, and then the control voltage, the slope of which is set by the variable attenuator, is adjusted by the offset adjusting circuit, then amplified by the amplifying circuit, and applied to the frequency adjusting element. Therefore, the frequency adjustment accuracy is high.

FIG. 2 is a block diagram of a mobile phone. Reference numeral 1 denotes an antenna. Between the antenna 1 and the receiver 2, an antenna duplexer 3, an amplifier 4, a bandpass filter 5, a mixer 6, A bandpass filter 7, a mixer 8, a bandpass filter 9, a demodulator 10, and a received signal processing circuit 11 are provided. Further, a transmission signal processing circuit 13, a modulator 14, a bandpass filter 15, a power amplification unit 16, and an isolator 17 are provided between the transmitter 12 and the antenna duplexer 3 from the transmitter 12 side. . The mixer 6 is connected to the VCO via the bandpass filter 18.
/ Synthesizer 19, and this VCO / synthesizer 19 is also connected to the modulator 14. The VCO / synthesizer 19 is connected to a control circuit 20 and a closed circuit of a temperature-compensated crystal oscillator (hereinafter referred to as TCXO) 21. Further, the control circuit 20 includes the reception / transmission signal processing circuit 1
1, 13 and the key / display panel 22 are connected.
Note that a crystal oscillator 23 is connected to the mixer 8.

That is, the signal generated by the TCXO 21 is multiplied by the VCO / synthesizer 19 and output to the reception mixer 6 via the band-pass filter 18 and to the modulator 14 of the direct transmission system. This block diagram is well known. Now, the configuration of the TCXO 21 in this embodiment is shown in FIGS. In FIG. 3, reference numeral 23 denotes a substrate, on which a crystal unit 24 and a semiconductor integrated circuit (hereinafter referred to as IC) 25 are mounted, and in this state, a metal case mounted on the substrate 23 It is sealed and held by 26. As shown in FIG. 1, the Vcc terminal 27 of the IC 25 is connected to the battery 28 of the mobile phone shown in FIG. A power supply regulator 29 for stabilizing the power supply is connected to the Vcc terminal 27.

The power supply regulator 29 stably supplies power to each section shown in FIG. Well IC
A temperature sensor 30 provided in the unit 25 is connected to an amplification unit 31 and a temperature detection unit 32 so as to supply a detected temperature signal to both. The temperature sensor 30 is composed of a semiconductor diode, and its resistance value gradually decreases linearly from a low temperature to a high temperature, whereby the output voltage further decreases linearly.

The amplifying unit 31 includes a polarity inversion circuit 33 connected to the temperature sensor 30 and a variable attenuator 3 connected to the polarity inversion circuit 33 in order.
4, an offset adjustment circuit 100 and an amplification circuit 35. The polarity reversing circuit 33, the offset adjusting circuit 100, and the memory 36 are connected to the variable attenuator 34. Further, a second D / A converter 37 is connected to the offset adjustment circuit 100.

The amplifier circuit 35 further includes a memory 36,
Offset adjustment circuit 100 and second D / A converter 37
Is connected. Further, a first D / A converter 38 is interposed between the memory 36 and the temperature detector 32.

Further, an adder 39 is connected to the amplifying circuit 35 of the amplifying section 31, and the control circuit 20 of the portable telephone shown in FIG. 2 is connected to the adder 39 via a Vc terminal 40.

The output of the adder 39 is supplied to a voltage controlled crystal oscillator 42 via a sample hold circuit 41, and the output of this voltage controlled crystal oscillator 42 is Vout terminal 4.
2 to the VCO / synthesizer 19 shown in FIG.

In FIG. 1, reference numeral 44 denotes the TCXO 21
Is a power supply controller for intermittently operating as described later, and 45 is a GND terminal.

The operation of the TCXO 21 shown in FIG. 1 will be described later in detail, but the overall operation will be briefly described here for easy understanding.

That is, the memory 36 stores a maximum of eight groups of temperature detection data, amplification degree setting data, and offset voltage data as one control voltage setting group.

Therefore, when the temperature detected by the temperature sensor 30 is transmitted as a first signal to the temperature detecting section 32, the temperature detection data in the eight control voltage setting groups stored in the memory 36 is converted to the first signal. Are sequentially supplied as second signals to the temperature detection unit 32 via the D / A conversion unit 38, where the first and second signal comparisons are performed.

From the comparison, it is determined that the amplification degree setting data and the offset voltage data of any of the eight control voltage setting groups in the memory 36 are supplied to the amplifier 31 and the second D / A converter 37. Be executed.

By performing this operation, an operation for suppressing the oscillation frequency fluctuation due to the temperature fluctuation is performed, and this point will be described in detail later.

Next, the voltage controlled crystal oscillator 42 shown in FIG.
Will be described with reference to FIG. In the voltage controlled crystal oscillator 42, a stable DC voltage is supplied to the amplifier circuits 46 and 47 from the power supply regulator 29 of FIG.

As is well known, an oscillation circuit is formed by a resistor 48 connected in parallel with the amplification circuit 46, and the crystal oscillator 24
Will be oscillated by this oscillation circuit.

The oscillation output is supplied to the amplifier circuit 47, Vou
The signal is output to the VCO / synthesizer 19 of FIG.

In FIG. 4, what adjusts the oscillation frequency is a plurality of varactor diodes 49 provided as frequency adjusting elements on the input side and the output side of the crystal unit 24.
That is, the capacitance of these varactor diodes 49 is adjusted according to the level of the DC voltage applied to the cathode of the varactor diode 49 via the sample and hold circuit 41 of FIG. 1, so that the oscillation frequency is adjusted. It is becoming.

In this embodiment, the quartz oscillator 2
The total capacity of the plurality of varactor diodes 49 provided on the input side of No. 4 is equal to or larger than the total capacity of the varactor diode 49 on the output side. The reason for this is
This is to reduce the power consumption. If the capacity is increased on the output side, a large current flows easily, and the power consumption increases.

Next, returning to FIG. 1, the amplifying section 31 will be described. As described above, the amplifying section 31 is composed of a series connection of the polarity inverting circuit 33, the variable attenuator 34, the offset adjusting circuit 100, and the amplifying circuit 35, the details of which are shown in FIG.

That is, the polarity inversion circuit 33 is
0, an amplifier circuit 101 for buffering between the amplifier circuit 50 and the temperature sensor 30, and two switching elements 51 and 52.
And an amplifier circuit 102 for a buffer.
The switching elements 51 and 52 are designed to perform opposing switching operations.
Of the temperature sensor 30 and the output from the temperature sensor 30 via the amplifier circuit 101 is input to the inverting input terminal of the amplifier circuit 50.

The ON / OFF of the switching elements 51 and 52 is determined by the digital data from the memory 36.

That is, when the switching element 51 is turned on and 52 is turned off by the digital data from the memory 36, the output from the temperature sensor 30 bypasses the amplifier circuit 50 and passes through the switching element 51, and the amplifier circuit 102.
And is output to the variable attenuator 34 as it is.

On the contrary, when the switching element 51 is off and 52 is on, the output from the temperature sensor 30 is inverted by the amplifier circuit 50 and output to the variable attenuator 34 via the amplifier circuit 102. .

The variable attenuator 34 having received the output from the polarity inverting circuit 33 generates the slope before the time in consideration of the slope obtained as a result of finally being amplified by the amplifier circuit 35. belongs to.

That is, the variable attenuator 34 is connected to the serially connected 1
It has six resistors 54 and two sets of a plurality of switching elements 57 and 58 for leading the voltage between both ends of the selected resistor 54 to the amplifier circuits 55 and 56. The switching elements 57 and 58 are turned on at the same time.

The selection of one set of these two switching elements 57 and 58 is determined by the digital data from the memory 36 which of the plurality of NAND elements 59 is selected.

The selected switching element 57,
One of the voltages across the resistor 54 selected by turning on 58 is output to the amplifier 55 and the other is output to the amplifier 56.

16 resistors 60 are connected in series between the outputs of the amplifier circuits 55 and 56. Which of the resistors 60 is selected depends on the digital data from the memory 36 which upper end of the resistor 60 is selected. It is determined by whether the NAND element 61 is selected. Then, the voltage at the upper end of the selected resistor 60 is output to the amplifier circuit 62.

That is, the primary voltage selection is performed in the upper part of the variable attenuator 34 in FIG. 5, for example, 8/16 * V and 7 /
16 * V is selected, and then, in the lower part of FIG. 5, a secondary voltage selection, that is, a value between 8/16 * V and 7/16 * V is determined by 16 resistors 60. Is determined by the selection of

Thus, for example, 7.5 / 16 * V
Is supplied to the offset adjustment circuit 100 via the amplifier circuit 62, and then the offset adjustment circuit 100 performs the offset adjustment.
3 will be supplied.

First, the offset operation in the offset adjustment circuit 100 will be described.

The voltage from the amplifier circuit 62 has a gain of -1.
It is supplied to an inverting input terminal of an offset adjustment circuit 100 composed of a double amplification circuit. On the other hand, this offset adjustment circuit 1
An offset voltage from the second D / A converter 37 is supplied to the non-inverting input terminal of 00, and the offset adjustment is performed by the supply of the offset voltage. The offset voltage is obtained by supplying the offset voltage data in the selected control voltage setting group in the memory 36 to the second D / A conversion unit 37, whereby the offset voltage is, for example, 1.5. If it is a bolt, the following offset adjustment is performed.

That is, in this offset adjustment circuit 100, if the inverting input is Vin and the non-inverting input is VREF,
The output Vout is as follows.

Vout = (Vin-VREF) *-1 + VREF Therefore, as Vin in this equation, 7.5 / 16 *
The result of substituting the above 1.5V as V and VREF is Vout
Becomes

The offset voltage (Vout) thus adjusted is supplied to the inverting input terminal of the amplifier circuit 53.

The amplification degree of the amplification circuit 53 is fixed to, for example, eight times. Since the output from the offset adjustment circuit 100 is input to the inverting input terminal, the amplification circuit 53 outputs -8 times. As a result, the slope of the polarity set by the polarity inversion circuit 33 is set by the amplification circuit 53.

An analog voltage is also supplied from the second D / A converter 37 to the non-inverting input terminal of the amplifier circuit 53. The reason is that the offset adjusted by the offset adjusting circuit 100 is
This is to prevent an offset shift in the case of double amplification, and the offset shift can be prevented if the reference voltages of the amplifier circuit 53 and the offset adjustment circuit 100 are the same.

The voltage thus polarized, inclined, and offset by the amplifier 31 is output to the adder 39 through the buffer amplifier circuit 103, and the adder 39 outputs the voltage. The structure is as shown in FIG.

That is, the output from the amplifying unit 31 in FIG. 5 is supplied to the inverting input terminals of the amplifying circuits 63 and 64 having the amplification factor of 1. However, the oscillation frequency is shifted due to a change over time or the like. In this case, the DC voltage from the control circuit 20 of the mobile phone shown in FIG.

As the DC voltage supplied to the Vc terminal 40, a DC voltage higher than a predetermined value is supplied when the oscillation frequency shifts to a lower side, and a DC voltage lower than a predetermined value when the oscillation frequency shifts to a higher side. Is supplied.

The comparator 65 checks whether or not a DC voltage lower or higher than the above-mentioned predetermined value is supplied from the control circuit 20. When the DC voltage is supplied to the inverting input terminal, the comparator 65 is turned off. Then, the switching element 66 is turned on, and 6
7 is turned off, and as a result, a DC voltage lower or higher than the predetermined value supplied to the Vc terminal 40 is supplied to the non-inverting input terminal of the amplifier circuit 64. If the low voltage is supplied thereto, the variation in FIG. The voltage supplied to the cathode of the collector diode 49 decreases, the capacitance increases, and the oscillation frequency decreases.

Conversely, if the DC voltage supplied to the Vc terminal 40 increases, the varactor diode
And the oscillation frequency increases. That is, the adder 39 prevents the oscillation frequency from being shifted due to a change over time.

Next, the output from the adder 39 is supplied to the sample hold circuit 41 as shown in FIG.

The sample-hold circuit 41 includes an amplifier circuit 68 and a capacitor 6 connected to its non-inverting input terminal.
9 and the switching element 70 and the like provided on the input side thereof.

That is, the switching element 70 is configured to be repeatedly opened and closed by the power supply control unit 44 shown in FIG. 1, and the closing time is 10 μsec and the opening time is 310 μsec as shown in FIG.

At the time of closing, the capacitor 69 is charged to the DC voltage level set according to the above conditions,
The DC voltage value supplied to the cathode of the varactor diode 49 is determined by this charge level.

However, after the switching element 70 is opened, the charging voltage of the capacitor 69 decreases due to self-discharge, so that the switching element 70 is closed again for charging after 310 μsec as described above.

When the switching element 70 is opened, all of the amplification section 31, the adder 39, and the first and second D / A conversion sections 3 are instructed by the power supply control section 44.
By stopping power supply to 8, 37, energy saving is achieved.

It is to be noted that the power supply to these is stopped without fail after the sample hold circuit 41 is opened as shown in FIG. 7, so that the capacitor 69 is reliably charged.

On the other hand, the memory 36 repeatedly executes a predetermined routine, and power is supplied to the memory 36 by the power supply control section 44 at intermittent intervals to save energy.

The energization time to the memory 36 is 2.56 msec, which is one cycle time of the routine. Therefore, the energization time is set to 1 sec.

The memory 36 is formed of an EEPROM and is capable of rewriting data.

Specifically, as shown in FIG.
Eight control voltage setting groups are provided, each group including a byte.

Temperature detection data is stored in the first byte of each control voltage setting group, slope setting data is stored in the second byte, slope setting data is stored in the third byte, and offset voltage data is stored in the fourth byte.

The first control voltage setting group is the first linear control voltage (polarity, slope,
The second control voltage setting group is higher than the second control voltage setting group, and the third control voltage setting group is higher than the third control voltage setting group. The group is the fourth higher temperature side,
The fifth control voltage setting group is higher than the fifth control voltage setting group, the sixth control voltage setting group is higher than the sixth control voltage setting group, and the seventh control voltage setting group is higher than the fifth control voltage setting group. The seventh and eighth control voltage setting groups on the high temperature side form the eighth linear control voltage on the higher temperature side. However, depending on the characteristics of the crystal resonator 24, the eighth control voltage setting group may be used. Some can perform temperature compensation from low to high temperatures without using up to a set group.

That is, the greatest feature of this embodiment is that the temperature compensation from low temperature to high temperature is linearly approximated by at most eight linear control voltages.

In this embodiment, first, the case 26 shown in FIG. 3 is mounted on the substrate 23, and the IC 25 and the crystal oscillator 24 are placed in a thermostatic chamber in a sealed state, and data is written in the memory 36. Start with that. At that time, the switching element 70 in FIG. 6 is held in the open state.

First, the temperature of the constant temperature bath is gradually raised from -30 ° C to 80 ° C, and a DC voltage is applied to the varactor diode 49 via the capacitor 69 and the amplifier circuit 68 of Fig. 6 every 10 ° C during that period. To do.

The oscillation frequency of the voltage controlled crystal oscillator 42 is, for example, a reference frequency of 12.8 M at each 10 ° C.
A control voltage that is constant at Hz is plotted, and this is connected to obtain the M line in FIG.

Similarly, the oscillation frequency of the voltage controlled crystal oscillator 42 is 12.8 MH, which is the reference frequency, every 10 ° C.
A control voltage at +1 ppm from z is plotted and connected to obtain the Y line.

Next, the oscillation frequency of the voltage-controlled crystal oscillator 42 is the reference frequency of 12.8 MHz for each 10 ° C.
Then, the control voltage at which -1 ppm is plotted is plotted, and this is connected to obtain the K line.

Then, if the temperature range of -30 ° C. to 80 ° C. is connected so as to be within the control voltage band sandwiched by the Y line and the K line, FIG.
The five linear control voltages (T lines) can be obtained.

Looking at this linear control voltage T line, the first line from a low temperature is from −30 ° C. to −12 ° C. and becomes a linear control voltage connecting 3.45V to 2.54V.

The second one is from -12 ° C to + 9 ° C.
It becomes a linear control voltage connecting 54V to 2.33V.

The third one is from 9 ° C. to 43 ° C. and 2.33
It is a linear control voltage connecting V to 2.55V.

The fourth one is from 43 ° C. to 63 ° C., 2.5
It becomes a linear control voltage connecting 5V to 2.35V.

The fifth one is from 63 ° C. to 80 ° C. and 2.3.
It is a linear control voltage connecting 5V to 1.65V.

The above-mentioned data for each of these five linear control voltages are stored in the first to fifth control voltage setting groups of the memory 36 as temperature detection data, slope setting data, and offset voltage data, respectively. It will be done.

When the data storage in the memory 36 is completed in this way, the switching element 70 in FIG. 6 is returned to the steady state, and the power supply control section 44 controls the opening / closing as described above.

In this state, when the temperature of the thermostat is gradually raised from −30 ° C. to 80 ° C. again, the anode of the varactor diode 49 has a memory 3 depending on the temperature.
Based on the data from 6, the control voltage (T
As a result, the oscillation frequency of the voltage-controlled crystal oscillator 42 is provided within ± 1 ppm as shown by the line H in FIG. 10, and an extremely high precision crystal oscillation device is provided.

The L line in FIG. 10 shows the oscillation frequency fluctuation when the control voltage as described above is not applied, and even if the L line and the H line of the present embodiment are compared, It will be understood that the accuracy of the linear approximation by the linear control voltage of the book is extremely high.

The temperature detection data of each control voltage setting group of the memory 36 is converted into a DC voltage by the first D / A converter 38 of FIG. 1 and transmitted to the temperature detector 32. Compared to the detected temperature at.
Since the temperature sensor 30 uses a semiconductor diode, the output voltage linearly decreases as the temperature increases.

Then, if the voltage from the first D / A converter 38 is higher than the temperature comparison, the sequence is executed to read the data of the next control voltage setting group of the memory 36.

When the DC voltage from the temperature sensor 30 becomes higher than the DC voltage of the first D / A converter 38 by repeating the above, the slope setting data and the offset voltage data of the control voltage setting group in the memory 36 are read out. Will be done. The inclination setting data is supplied to the polarity inverting circuit 33 and the variable attenuator 34 of the amplifying unit 31 shown in FIG. Also, the offset voltage data is supplied to the offset adjustment circuit 100 of FIG. 5 and the amplification circuit 53 in the amplification circuit 35 via the second D / A conversion section 37 as described above.

As described above, in the present embodiment, the linear approximation is performed by using the linear control voltage within 8 lines.
This is the case for the voltage-controlled crystal oscillator one by one.
In confirming that the shapes of the control voltage bands shown in Fig. 7 were different, if there were still eight linear control voltages, ±
This is based on the finding that a highly accurate control of 1 ppm can be realized.

This makes it possible to set eight groups of the actual operation control voltage setting of the memory 36, and achieves a drastic reduction in the memory size, and a reduction in the size and simplification of the control circuit due to the reduction in the memory size. Becoming
As a result, it was possible to expand the effects of achieving energy savings.

[0090]

As described above, the present invention provides a crystal oscillator,
A frequency adjustment element electrically connected to the crystal oscillator; and a control circuit for controlling a voltage applied to the frequency adjustment element.The control circuit is connected to a temperature sensor and the temperature sensor. A temperature detecting section, a memory electrically connected to the temperature detecting section, an amplifying section electrically connected to the memory and the temperature sensor, and an electrical section between the memory and the temperature detecting section. A first D / A conversion unit interposed therebetween, and a second D / A conversion unit electrically interposed between the memory and the amplification unit, wherein the amplification unit is connected to the temperature sensor. The memory includes a polarity inversion circuit connected thereto, a variable attenuator, an offset adjustment circuit, and an amplification circuit sequentially connected to the polarity inversion circuit. The memory has eight or less control voltage setting groups that are actually operated. The control voltage setting group It is obtained by a structure for storing the amplification degree setting data and offset voltage data and temperature detection data.

With the above structure, the memory has eight or less of the temperature detection data, the amplification degree setting data, and the offset voltage data as one control voltage setting group as the actual operation. Also, the memory capacity is small, and even a control circuit of a memory having actually operated control voltage setting groups of 8 or less has a simple structure and is easily miniaturized. It will be.

Further, if the memory capacity is small and the control circuit is simple, the power consumption can be easily reduced. Further, in the amplifying section, the polarity is set by the polarity inverting circuit, and then the control voltage, the slope of which is set by the variable attenuator, is adjusted by the offset adjusting circuit, then amplified by the amplifying circuit, and applied to the frequency adjusting element. Therefore, the frequency adjustment accuracy is high.

[Brief description of the drawings]

FIG. 1 is a block diagram of a crystal oscillation device according to an embodiment of the present invention.

FIG. 2 is a block diagram of a mobile phone using the crystal oscillation device of FIG. 1;

FIG. 3 is an exploded perspective view of a TCXO used in the crystal oscillation device of FIG. 1;

FIG. 4 is a block diagram of a voltage controlled crystal oscillator used in the crystal oscillation device of FIG.

FIG. 5 is a circuit diagram of an amplification unit used in the crystal oscillation device of FIG. 1;

6 is a circuit diagram of an adder and a sample hold circuit used in the crystal oscillator of FIG.

FIG. 7 is a time chart showing an operation state of a main part of the crystal oscillation device of FIG. 1;

8 is a memory map of a memory used in the crystal oscillator of FIG.

9 is a diagram showing a control voltage applied to a varactor diode of a voltage controlled crystal oscillator used in the crystal oscillator of FIG.

10 is a diagram showing a voltage applied to a varactor diode of a voltage controlled crystal oscillator used in the crystal oscillator of FIG. 1 and an oscillation frequency.

[Explanation of symbols]

 24 Crystal oscillator 30 Temperature sensor 31 Amplifying unit 32 Temperature detecting unit 33 Polarity inverting circuit 34 Variable attenuator 35 Amplifying circuit 36 Memory 37 Second D / A converting unit 38 First D / A converting unit 41 Sample and hold circuit 42 Voltage controlled crystal oscillator 100 Offset adjustment circuit

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Chikao Maeda 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (12)

[Claims] 1. A crystal oscillator, a frequency adjusting element electrically connected to the crystal oscillator, and a control circuit for controlling a voltage applied to the frequency adjusting element, wherein the control circuit includes a temperature sensor, A temperature detector electrically connected to the temperature sensor, a memory electrically connected to the temperature detector, an amplifier electrically connected to the memory and the temperature sensor; A first digital-to-analog converter (hereinafter referred to as a D / A converter) electrically interposed between the detector and a second digital-to-analog converter electrically interposed between the memory and the amplifier; A digital / analog converter (hereinafter, referred to as a D / A converter), wherein the amplifying unit includes: a polarity inverting circuit connected to the temperature sensor;
It is composed of a variable attenuator, an offset adjusting circuit and an amplifying circuit which are sequentially connected to the polarity reversing circuit, and the memory has eight or less control voltage setting groups which are actually operated, and each control voltage setting group is a temperature detection A crystal oscillator that stores data, amplification setting data, and offset voltage data. 2. The crystal oscillating device according to claim 1, wherein at least one of the amplifying section, the first and second D / A converting sections, the temperature detecting section and the memory performs an intermittent operation. 3. The pause time in the intermittent operation of at least one of the amplification section, the first and second D / A conversion sections, and the temperature detection section is shorter than the pause time in the intermittent operation of the memory. Crystal oscillator. 4. The crystal oscillation device according to claim 2, wherein a sample hold circuit is interposed between the frequency adjustment element and the amplification section. 5. The crystal oscillator according to claim 1, wherein the lower output level of the variable attenuator is set to a voltage higher than 0. 6. The crystal oscillation device according to claim 1, wherein the first and second D / A conversion units are variable attenuators. 7. The crystal oscillator according to claim 6, wherein the lower output level of the variable attenuator is set to a voltage higher than 0. 8. The crystal oscillating device according to claim 1, wherein the frequency adjusting element comprises a plurality of varactor diodes, and these varactor diodes are electrically connected to an input side and an output side of the crystal oscillator. 9. The crystal oscillator according to claim 8, wherein the capacitance of the varactor diode on the input side is equal to or larger than the capacitance of the varactor diode on the output side. 10. The crystal oscillation device according to claim 8, wherein the number of varactor diodes electrically connected to the input and output sides of the crystal oscillator is selected according to the oscillation frequency of the crystal oscillator. 11. The open circuit switch is provided between the amplifying section and the frequency adjusting element, and an external voltage input terminal is electrically connected between the open circuit switch and the frequency adjusting element. Crystal oscillator. 12. A crystal oscillator, a frequency adjusting element electrically connected to the crystal oscillator, and a control circuit for controlling a voltage applied to the frequency adjusting element, wherein the control circuit includes a temperature sensor, A temperature detection unit electrically connected to the temperature sensor, a memory electrically connected to the temperature detection unit, an amplification unit electrically connected to the memory and the temperature sensor, the memory and the temperature A first D / A converter electrically interposed between the detector and a second D / A electrically interposed between the memory and the amplifier.
A conversion unit, the amplification unit is composed of a polarity reversal circuit connected to the temperature sensor, a variable attenuator connected to the polarity reversal circuit in order, an offset adjustment circuit, and an amplification circuit, the memory In a crystal oscillation device having 8 or less control voltage setting groups that are actually operated, the amplifier section and the frequency adjusting element are opened, and in this open state, the crystal oscillation device is placed in a thermostatic chamber. By changing the temperature of the constant temperature bath from low temperature to high temperature, and applying a control voltage to the frequency adjusting element for each predetermined temperature within this variable temperature, the oscillation frequency of the crystal oscillator falls within a predetermined error range. The control voltage range of is detected, and the low temperature to the high temperature are connected by a straight line within 8 lines so that the temperature falls within the control voltage range from the low temperature to the high temperature obtained by this detection. Adjustment of the crystal oscillator in which data calculated from each straight line and the detection output from the same low temperature to the high temperature of the temperature sensor is stored in the memory as temperature detection data, amplification degree setting data, and offset voltage data corresponding to each straight line Method.