JP5178457B2 - Oscillator - Google Patents

Description

  The present invention relates to an oscillator.

  Conventionally, various oscillators have been developed. For example, there is a crystal oscillator that uses a crystal resonator as a piezoelectric element. Such a crystal oscillator is mounted on, for example, a mobile phone, and the mobile phone uses an output signal output from the crystal oscillator as a clock signal.

  FIG. 2 shows a configuration of the oscillator 10 as an example of such a crystal oscillator. The oscillator 10 includes a crystal resonator X10 as a piezoelectric element, and generates an output signal Fout having a desired oscillation frequency.

  One end of the crystal unit X10 is connected to one end of a resistor R10 as a feedback resistor and to the input terminal of the inverter INV10. A variable capacitor C10 is connected between one end of the crystal unit X10 and the ground GND.

  On the other hand, the other end of the crystal unit X10 is connected to the other end of the resistor R10 and to the output terminal of the inverter INV10. A variable capacitor C20 is connected between the other end of the crystal unit X10 and the ground GND.

  The output terminal of the inverter INV10 is connected to the input terminal of the inverter INV20 as a buffer, and an output signal Fout having a desired oscillation frequency is output from the output terminal of the inverter INV20.

  By the way, in the case of such an oscillator 10, various methods have been developed as a method for outputting an output signal Fout having a constant oscillation frequency from the oscillator 10 regardless of a change in temperature. There is a way to compensate.

  As a method for compensating the frequency temperature characteristic of the oscillator 10, a frequency temperature characteristic opposite to the frequency temperature characteristic of the crystal unit X10 (that is, the phase is shifted by 180 degrees with respect to the frequency temperature characteristic of the crystal unit X10). There is a method of performing temperature compensation by generating a compensation voltage having frequency temperature characteristics) and applying the compensation voltage to the variable capacitors C10 and C20.

  There is also a method of outputting an output signal Fout having a constant oscillation frequency by accommodating the oscillator 10 in a thermostatic chamber, regardless of an external temperature change.

The following is a list of literature names related to temperature compensated oscillators.
JP 2006-67079 A JP-A-10-303645

  By the way, in the method for compensating the frequency temperature characteristic of the oscillator 10, the frequency temperature characteristic of the crystal unit X10 and the frequency temperature characteristic of the compensation voltage are shifted (that is, fitting) due to variations in the frequency temperature characteristic of the crystal unit X10.・ There was a problem that the accuracy of temperature compensation was reduced.

  In addition, since the secular change of the characteristics of the crystal unit X10 depends on the manufacturing method and members of the crystal unit X10, the change of the oscillation frequency of the output signal Fout due to the secular change of the characteristics of the crystal unit X10 should be adjusted. There was a problem that was difficult.

  Further, in the method of accommodating the oscillator 10 in the thermostatic bath, there is a problem that the number of parts is increased and the oscillator 10 is enlarged.

  An object of the present invention is to provide an oscillator that can suppress a change in the oscillation frequency of an output signal due to a temperature change or a secular change with a simple configuration.

An oscillator according to one aspect of the present invention includes a piezoelectric element, a variable capacitance element connected between the piezoelectric element and a ground, and generates an output signal having a desired oscillation frequency; and the oscillation A frequency voltage conversion unit that is connected to the output side of the unit and generates a voltage signal by converting the oscillation frequency of the output signal output from the oscillation unit into a voltage, and a reference voltage corresponding to the desired oscillation frequency The storage unit for storing data, and connected to the output side of the frequency voltage conversion unit, and connected to the output side of the storage unit via a digital / analog conversion circuit, and output from the frequency voltage conversion unit By comparing the voltage signal with the reference voltage data given from the storage unit via a digital / analog conversion circuit and converted into an analog signal, the voltage signal and the voltage signal Calculates a difference between the reference voltage data, and a comparator unit to be applied to the variable capacitance element so as compensation voltage is connected to the output side of the frequency voltage converter, when manufacturing the oscillator, said frequency-voltage conversion When the oscillator is used, a switch is provided that switches between the frequency voltage conversion unit and the comparison unit when the oscillator is used .

  The oscillator according to an aspect of the present invention is connected to the output side of the frequency voltage converter, and when the oscillator is manufactured, the frequency voltage converter and the storage unit are in a conductive state, When the oscillator is used, it further includes a switch for bringing the frequency voltage conversion unit and the comparison unit into a conductive state.

  According to the oscillator of the present invention, it is possible to suppress a change in the oscillation frequency of the output signal due to a temperature change or a secular change with a simple configuration.

  Further, according to the oscillator of the present invention, it is possible to suppress variation in frequency characteristics of the oscillator.

  Further, according to the oscillator of the present invention, the oscillator can be operated in any one of a manufacturing mode for manufacturing an oscillator and a use mode for using the oscillator with a simple configuration in which a switch is provided only on the output side of the frequency voltage conversion unit. Can be operated.

  Further, according to the oscillator of the present invention, the oscillation frequency can be adjusted at a higher speed than the case where the oscillation frequency is adjusted using the output signal output from the second inverter.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a configuration of an oscillator 100 according to the embodiment of the present invention. The oscillator 100 is mounted on an electronic device such as a mobile phone, for example, and generates and outputs an output signal Fout having an oscillation frequency required for the mobile phone. Such a cellular phone uses the output signal Fout output from the oscillator 100 as a clock signal, thereby controlling the operation of various built-in circuits.

  The crystal oscillation circuit 200 includes a crystal resonator X100 as a piezoelectric element, and generates an output signal having a desired oscillation frequency. In the present embodiment, the crystal resonator X100 is used as the piezoelectric element, but various other piezoelectric elements such as a piezoelectric ceramic can be used.

  One end of the crystal unit X100 is connected to one end of a resistor R100 as a feedback resistor and to the input terminal of the inverter INV100. A variable capacitor C100 is connected between one end of the crystal unit X100 and the ground GND.

  On the other hand, the other end of the crystal unit X100 is connected to the other end of the resistor R100 and to the output terminal of the inverter INV100. Further, a variable capacitor C200 is connected between the other end of the crystal unit X100 and the ground GND.

  The variable capacitors C100 and C200 operate as a variable capacitance element for adjusting the oscillation frequency of the output signal Fout according to the applied voltage. In this case, a variable capacitance diode may be used instead of the variable capacitors C100 and C200.

  As described above, the crystal oscillation circuit 200 corresponding to the oscillation unit includes the piezoelectric element and the variable capacitance element connected between the piezoelectric element and the ground, and generates an output signal having a desired oscillation frequency. .

  The output terminal of the inverter INV100 is connected to the input terminal of the inverter INV200 as a buffer, and an output signal Fout having a desired oscillation frequency is output from the output terminal of the inverter INV200.

  By the way, in the case of the present embodiment, the operating mode of the oscillator 100 includes a manufacturing mode in a manufacturing state in which the oscillator 100 is manufactured and a usage mode in which the oscillator 100 is used after being manufactured and shipped. There is.

  When manufacturing the oscillator 100, data corresponding to the manufacturing mode is written and stored in the memory 300 via the data input / output terminal DIO. When the data corresponding to the manufacturing mode is stored in the memory 300, the control circuit 400 switches the connection state of the switch SW100 to the analog / digital (A / D) conversion circuit 600 side.

  At the same time, by applying a voltage input from the outside via a voltage input terminal (not shown) to the variable capacitors C100 and C200, the capacitances of the variable capacitors C100 and C200 are changed, and the oscillation frequency of the output signal Fout is increased. Adjust to the desired oscillation frequency. The desired oscillation frequency refers to an oscillation frequency required in an electronic device in which the oscillator 100 is mounted.

  In this state, the frequency / voltage (F / V) conversion circuit 500 corresponding to the frequency voltage conversion unit converts the oscillation frequency of the output signal output from the crystal oscillation circuit 200 and divided by the frequency dividing circuit 450 into a voltage. As a result, a voltage signal is generated and output to the gain adjustment circuit 550.

  The gain adjustment circuit 550 adjusts the gain based on the power supply voltage data of the oscillator 100 given from the control circuit 400, thereby converting the voltage signal output from the frequency / voltage (F / V) conversion circuit 500 into the power supply voltage. After being adjusted to a voltage signal corresponding to the signal, it is output to the analog / digital (A / D) conversion circuit 600 via the switch SW100.

  The analog / digital (A / D) conversion circuit 600 converts the input voltage signal into digital data, and writes and stores the obtained voltage data in the memory 300 as reference voltage data. That is, the memory 300 corresponding to the storage unit stores reference voltage data corresponding to a desired oscillation frequency.

  Note that, by analyzing the oscillation frequency of the output signal Fout output from the oscillator 100, correction data for suppressing variation in frequency characteristics of the oscillator 100 is generated, and this data is stored in the memory 300 via the data input / output terminal DIO. Write and memorize. That is, the memory 300 further stores correction data for correcting the frequency characteristics unique to the crystal oscillation circuit 200.

  In this way, the memory 300 stores reference voltage data corresponding to the oscillation frequency required in the electronic device in which the oscillator 100 is mounted, and correction data for suppressing variation in the frequency characteristics of the oscillator 100. The

  After that, when the manufacturing process of the oscillator 100 is completed and shipping is to be performed, data corresponding to the use mode is written and stored in the memory 300 via the data input / output terminal DIO, and corresponds to the manufacturing mode. To be erased from the memory 300. When the data corresponding to the use mode is read from the memory 300, the control circuit 400 switches the connection state of the switch SW100 to the comparator 700 side.

  Subsequently, the oscillator 100 is mounted on an electronic device such as a mobile phone, for example, and continuously generates and outputs an output signal Fout having a desired oscillation frequency. That is, in the case of the present embodiment, the frequency / voltage (F / V) conversion circuit 500 converts the oscillation frequency of the output signal output from the crystal oscillation circuit 200 and divided by the frequency dividing circuit 450 into a voltage. Thus, a voltage signal is generated and output to the gain adjustment circuit 550.

  The gain adjustment circuit 550 adjusts the gain based on the power supply voltage data of the oscillator 100 given from the control circuit 400, thereby converting the voltage signal output from the frequency / voltage (F / V) conversion circuit 500 into the power supply voltage. After being adjusted to a voltage signal according to, it is output to the comparator 700 via the switch SW100.

  On the other hand, the control circuit 400 reads the reference voltage data corresponding to the oscillation frequency required in the electronic device in which the oscillator 100 is mounted from the memory 300, and outputs this to the digital / analog (D / A) conversion circuit 800. The digital / analog (D / A) conversion circuit 800 converts the inputted reference voltage data into an analog signal, and outputs the obtained reference voltage data to the comparator 700.

The comparator 700 corresponding to the comparison unit receives the voltage signal supplied from the frequency / voltage (F / V) conversion circuit 500 through the gain adjustment circuit 550 and the switch SW100 in sequence , and the control circuit 400 and digital / analog ( D / A) The difference between the voltage signal and the reference voltage data is calculated by comparing with the reference voltage data sequentially given through the conversion circuit 800 and converted into an analog signal, and gain adjustment is performed using this difference as a compensation voltage. Output to the circuit 900.

  At that time, the control circuit 400 reads the correction data from the memory 300 and supplies it to the gain adjustment circuit 900. The gain adjustment circuit 900 adjusts the gain based on the correction data given from the control circuit 400, thereby adjusting the compensation voltage output from the comparator 700 and suppressing variations in the frequency characteristics of the oscillator 100.

  By applying the compensation voltage output from the gain adjustment circuit 900 to the variable capacitors C100 and C200, the capacitances of the variable capacitors C100 and C200 are changed. In this manner, the gain adjustment circuit 900 corresponding to the gain adjustment unit adjusts the compensation voltage output from the comparator 700 by adjusting the gain based on the correction data given from the memory 300 via the control circuit 400. And then applied to the variable capacitors C100 and C200.

  Thereby, the oscillator 100 adjusts the oscillation frequency of the output signal Fout so as to be an oscillation frequency required in the electronic device in which the oscillator 100 is mounted. Thereafter, the oscillator 100 continuously adjusts the oscillation frequency of the output signal Fout by repeating the above-described operation.

  As described above, according to the present embodiment, the oscillation frequency of the output signal output from the crystal oscillation circuit 200 is constantly monitored, and even if the oscillation frequency of the output signal changes due to temperature change or aging change, the oscillation is immediately performed. By adjusting the frequency, it is possible to suppress a change in the oscillation frequency of the output signal with a simple configuration.

  The above-described embodiment is an example and does not limit the present invention. For example, a resistor may be connected between the connection point of the crystal unit X100 and the variable capacitor C200 and the other end of the crystal unit X100. Of the connection lines for connecting the other end of the crystal unit X100, one end of the variable capacitor C200, the other end of the resistor R100, and the output terminal of the inverter INV100, the connection line and the connection point of the crystal unit X100, A resistor may be connected between the connection line and the connection point of the resistor R100.

  In the above-described embodiment, the case where the oscillator 100 is mounted on the mobile phone has been described. However, the oscillator 100 may be mounted on various other electronic devices such as a navigation device having a GPS function.

  In the above-described embodiment, the case where the compensation voltage output from the gain adjustment circuit 900 is applied to the variable capacitors C100 and C200 has been described. However, the compensation voltage output from the comparator 700 is directly applied to the variable capacitors C100 and C200. You may make it apply to.

  Further, switches are provided between the frequency / voltage (F / V) conversion circuit 500 and the analog / digital (A / D) conversion circuit 600 and between the frequency / voltage (F / V) conversion circuit 500 and the comparator 700, respectively. You may do it.

  At this time, if data corresponding to the manufacturing mode is stored in the memory 300, the switch connected to the analog / digital (A / D) conversion circuit 600 is turned on and the switch connected to the comparator 700 is turned on. Is turned off.

  Subsequently, when data corresponding to the use mode is stored in the memory 300, the switch connected to the analog / digital (A / D) conversion circuit 600 is turned off, and the switch connected to the comparator 700 is turned on. Turn on the.

  That is, the point is that it is connected to the output side of the frequency / voltage (F / V) conversion circuit 500, and when the oscillator 100 is manufactured, the frequency / voltage (F / V) conversion circuit 500 and the memory 300 are connected. When the oscillator 100 is used in the conductive state, a switch for connecting the frequency / voltage (F / V) conversion circuit 500 and the comparator 700 may be provided.

It is a circuit diagram which shows the structure of the oscillator by embodiment of this invention. It is a circuit diagram which shows the structure of the conventional oscillator.

Explanation of symbols

10, 100 Oscillator 200 Crystal oscillation circuit 300 Memory 400 Control circuit 500 Frequency / voltage (F / V) conversion circuit 700 Comparator 900 Gain adjustment circuit X10, X100 Crystal resonator R10, R100 Resistors C10, C20, C100, C200 Variable capacitor INV10 , INV20, INV100, INV200 Inverter SW100 switch

Claims (1)

An oscillation unit that includes a piezoelectric element and a variable capacitance element connected between the piezoelectric element and the ground, and generates an output signal having a desired oscillation frequency;
A frequency voltage conversion unit that is connected to an output side of the oscillation unit and generates a voltage signal by converting an oscillation frequency of the output signal output from the oscillation unit into a voltage;
A storage unit for storing reference voltage data corresponding to the desired oscillation frequency;
The voltage signal connected to the output side of the frequency voltage conversion unit and connected to the output side of the storage unit via a digital / analog conversion circuit, and the voltage signal output from the frequency voltage conversion unit is output from the storage unit. A difference between the voltage signal and the reference voltage data is calculated by comparing with the reference voltage data given through a digital / analog conversion circuit and converted into an analog signal, and the difference between the voltage signal and the reference voltage data is calculated as a compensation voltage. A comparison unit applied to the element ;
When manufacturing an oscillator connected to the output side of the frequency voltage conversion unit, the frequency voltage conversion unit and the storage unit are in a conductive state, and when using the oscillator, the frequency voltage conversion unit An oscillator comprising: a switch that makes a conductive state between a section and the comparison section .

Images