JP5291564B2 - Oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an oscillator device capable of suppressing variation in oscillation frequency of an output signal, even if an ambient temperature of the oscillator abruptly changes. <P>SOLUTION: The oscillator device includes a switch SW and a switch control circuit 1000 connected between a gain control unit 900 and an addition unit 600, the switch being turned ON in timing t20 wherein a control signal SI supplied from outside changes from a first potential to a second potential higher than the first potential to output a correction voltage VC generated by the gain control unit 900 to the addition unit 600 to add it, and then being turned OFF in timing t30 a time T, that correction time data stored in a memory 700 indicates, later to limit the output of the correction voltage VC to the addition unit 600. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to an oscillator.

  Conventionally, various oscillators have been developed, such as a temperature compensated crystal oscillator. This temperature-compensated crystal oscillator has a temperature compensation circuit for compensating the frequency temperature characteristics of a crystal resonator used as a piezoelectric element, and is mounted on an electronic device such as a mobile phone or a personal navigation device (PND). used.

  Here, FIG. 3 shows a configuration of an oscillator 10 as an example of such a temperature compensation crystal oscillator. The oscillator 10 includes a crystal resonator X10 as a piezoelectric element and an IC chip 20 electrically connected to the crystal resonator X10, and generates an output signal Fout having a desired oscillation frequency.

  Inside the IC chip 20, a crystal oscillation circuit 30 connected to the crystal resonator X10 and a temperature compensation circuit 40 for compensating the frequency temperature characteristics of the crystal resonator X10 are formed.

  More specifically, one end of the crystal unit X10 is connected to one end of a resistor R10 as a feedback resistor in the crystal oscillation circuit 30, and is also connected to an 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 in the crystal oscillation circuit 30 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.

  The temperature compensation circuit 40 is a circuit for compensating the frequency-temperature characteristics of the crystal unit X10 in order to output the output signal Fout having a constant oscillation frequency from the oscillator 10 regardless of a change in temperature.

  Specifically, the temperature compensation circuit 40 includes a temperature sensor for measuring the temperature around the crystal unit X10, and generates a desired compensation voltage based on the temperature obtained by the temperature sensor.

  The temperature compensation circuit 40 applies the compensation voltage to the variable capacitors C10 and C20, and changes the capacitance of the variable capacitors C10 and C20, thereby adjusting the oscillation frequency of the output signal Fout to perform temperature compensation.

  In this way, the oscillator 10 generates an output signal Fout having a desired oscillation frequency and outputs it to the outside.

JP 2008-271355 A

  By the way, electronic devices such as mobile phones and personal navigation devices (PND) on which such an oscillator 10 is mounted are becoming smaller. For this reason, the electronic component mounted in the said electronic device is also reduced in size, and the distance between each electronic component is shortened.

  As a result, the distance between the oscillator 10 and an electronic component that generates heat, such as a power amplifier, is shortened, and the oscillator 10 is easily affected by the heat generated by the power amplifier during operation.

  That is, when the oscillator 10 is outputting the output signal Fout having a desired oscillation frequency and heat is generated by starting a power amplifier disposed in the vicinity of the oscillator 10, the ambient temperature of the oscillator 10 is increased. , Change rapidly and rise.

  Incidentally, the oscillator 10 includes a crystal resonator X10 and an IC chip 20 on which a temperature compensation circuit 40 having a temperature sensor is formed. The crystal resonator X10 and the IC chip 20 are provided on a substrate or a container on which these are mounted. According to the shape, they are arranged so as to be separated by a predetermined distance.

  For this reason, the heat generated from the power amplifier reaches the crystal unit X10 and the IC chip 20 at different timings. Thus, the rapid temperature change that occurs immediately after the power amplifier is started causes a temperature difference to occur between the periphery of the crystal unit X10 and the periphery of the IC chip 20. After that, a certain time is required until the temperature difference generated between the periphery of the crystal unit X10 and the periphery of the IC chip 20 disappears.

  Therefore, immediately after the power amplifier is started up and while a temperature difference is generated between the periphery of the crystal unit X10 and the periphery of the IC chip 20, the temperature compensation formed in the IC chip 20 is compensated. The circuit 40 cannot correctly measure the temperature around the crystal unit X10.

  As a result, the temperature compensation circuit 40 cannot compensate the frequency temperature characteristic of the crystal unit X10, and there is a problem that a so-called frequency drift occurs in which the oscillation frequency of the output signal Fout output from the oscillator 10 fluctuates. .

  An object of the present invention is to provide an oscillator that can suppress fluctuations in the oscillation frequency of an output signal even when the ambient temperature of the oscillator changes rapidly.

An oscillator according to one embodiment of the present invention includes a piezoelectric element and a variable capacitance element connected to the piezoelectric element and connected between the piezoelectric element and a ground, and generates an output signal having a desired oscillation frequency. An oscillation unit that outputs, a temperature compensation unit that generates a compensation voltage for changing the capacitance of the variable capacitance element, gain data that is used to generate a correction voltage for correcting the compensation voltage, and correction A storage unit that preliminarily stores correction time data indicating the time of frequency drift occurring in the previous output signal, and a desired adjustment while adjusting the gain based on the gain data stored in the storage unit The correction voltage generated by the gain adjustment unit is added to the gain adjustment unit that generates the correction voltage having a voltage level of: and the compensation voltage generated by the temperature compensation unit. An addition unit that corrects the compensation voltage by adding as necessary and applies the corrected compensation voltage to the variable capacitance element, and is connected between the gain adjustment unit and the addition unit, The correction voltage generated by the gain adjustment unit is added to the addition signal by switching to an ON state at a timing when an externally applied control signal changes from a first potential to a second potential that is higher than the first potential. Outputting the correction voltage to the adding unit by switching to an off state at a timing when the time indicated by the correction time data stored in the storage unit has elapsed. and a limit switch unit, the control signal, in response to the electronic device the oscillator is mounted is shifted to the operating state, from said first potential first Changes of potential.

  Further, in the oscillator according to one aspect of the present invention, the gain data and the correction time data are obtained from a timing at which the control signal changes from the first potential to the second potential. The correction voltage is selected so as to maintain a constant oscillation frequency of the output signal until the time has elapsed.

  According to the oscillator of the present invention, it is possible to suppress fluctuations in the oscillation frequency of the output signal even if the temperature around the oscillator changes rapidly.

  Further, according to the oscillator of the present invention, it is possible to accurately detect the timing at which an electronic device in which the oscillator is mounted transitions to an operating state.

  Further, according to the oscillator of the present invention, it is possible to continue outputting an output signal having a constant oscillation frequency.

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

  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 an embodiment of the present invention, and FIG. 2 shows an example of a timing chart in the oscillator 100. 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 oscillator 100 includes a crystal resonator X100 as a piezoelectric element and an IC chip 200 electrically connected to the crystal resonator X100, and generates an output signal Fout 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.

  The IC chip 200 is generated by a crystal oscillation circuit 300 connected to the crystal resonator X100, a temperature compensation circuit 400 that generates a compensation voltage for compensating the frequency temperature characteristics of the crystal resonator X100, and the temperature compensation circuit 400. A correction voltage generation circuit 500 that generates a correction voltage for correcting the compensation voltage, and an addition circuit 600 that adds the compensation voltage and the correction voltage.

  More specifically, one end of the crystal unit X100 is connected to one end of a resistor R100 as a feedback resistor in the crystal oscillation circuit 300, and is also connected to an 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 in the crystal oscillation circuit 300 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.

  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.

  As described above, the crystal oscillation circuit 300 corresponds to the oscillation unit, is connected to the crystal resonator X100, has the variable capacitors C100 and C200 connected between the crystal resonator X100 and the ground, and has a desired oscillation. An output signal Fout having a frequency is generated and output.

  The temperature compensation circuit 400 is a circuit for compensating the frequency temperature characteristic of the crystal unit X100 in order to output the output signal Fout having a constant oscillation frequency from the oscillator 100 regardless of the change in temperature.

  Specifically, the temperature compensation circuit 400 includes a temperature sensor for measuring the temperature around the crystal unit X100, and generates a desired compensation voltage based on the temperature obtained by the temperature sensor.

  The temperature compensation circuit 400 normally applies this compensation voltage to the variable capacitors C100 and C200 via the adder circuit 600, and changes the capacitance of the variable capacitors C100 and C200, thereby changing the oscillation frequency of the output signal Fout. Adjust to compensate for temperature.

  That is, the temperature compensation circuit 400 corresponds to the temperature compensation unit, and generates a compensation voltage for changing the capacitances of the variable capacitors C100 and C200.

  In this way, the oscillator 100 generates an output signal Fout having a desired oscillation frequency and outputs it to the outside.

  By the way, the mobile phone is configured to calculate the current position of the mobile phone by receiving radio waves transmitted from GPS satellites and acquiring positioning information at regular time intervals. It operates (FIG. 2 (a)).

  That is, the mobile phone alternately repeats an operation state (time t20 to t40) in which the positioning information is acquired and the current position is calculated, and a standby state (time t40 to t60) in which the positioning information acquisition is stopped.

  In order to reduce current consumption, the oscillator 100 mounted on the cellular phone corresponds to the intermittent operation of the cellular phone, and outputs an output signal Fout () having a desired oscillation frequency at regular time intervals. FIG. 2 (c)) is output.

  That is, the oscillator 100 alternates between an on state (time t10 to t40) in which the output signal Fout having a desired oscillation frequency is output and an off state (time t40 to t50) in which the output signal Fout is stopped. Repeat in order.

  It should be noted that a certain time is required from the timing when the oscillator 100 is switched to the ON state until the oscillation frequency of the output signal Fout (FIG. 2C) transitions to the stable state. Therefore, the oscillator 100 is switched to the on state at a timing (time t10) earlier than the timing (time t20) at which the mobile phone transitions to the operation state.

  In the case of the present embodiment, among electronic components mounted on a mobile phone, an electronic component that generates heat, such as a power amplifier, used when performing positioning, is a timing at which the mobile phone transitions to an operating state. At (time t20), the mobile phone is turned on and activated, and then turned off at the timing (time t40) when the mobile phone transitions to the standby state.

  That is, when the oscillator 100 outputs an output signal Fout having a desired oscillation frequency (FIG. 2C), heat is generated by starting a power amplifier disposed in the vicinity of the oscillator 100. The temperature around the oscillator 100 rapidly changes and rises.

  By the way, the oscillator 100 includes a crystal resonator X100 and an IC chip 200 on which a temperature compensation circuit 400 having a temperature sensor is formed. The crystal resonator X100 and the IC chip 200 are provided on a substrate or a container on which these are mounted. According to the shape, they are arranged so as to be separated by a predetermined distance.

  For this reason, the heat generated from the power amplifier reaches the crystal unit X100 and the IC chip 200 at different timings. Thus, the rapid temperature change that occurs immediately after the power amplifier is started causes a temperature difference to occur between the periphery of the crystal unit X100 and the periphery of the IC chip 200. After that, a certain time is required until the temperature difference generated between the periphery of the crystal unit X100 and the periphery of the IC chip 200 disappears.

  Therefore, immediately after the activation of the power amplifier, while the temperature difference is generated between the periphery of the crystal unit X100 and the periphery of the IC chip 200 (time t20 to t30), the inside of the IC chip 200 The temperature compensation circuit 400 formed in (1) cannot correctly measure the temperature around the crystal unit X100.

  As a result, the temperature compensation circuit 400 cannot compensate the frequency temperature characteristic of the crystal unit X100, and the so-called frequency drift in which the oscillation frequency of the output signal Fout (FIG. 2C) output from the oscillator 100 fluctuates. D is generated.

  In the case of the present embodiment, in the manufacturing process for manufacturing the oscillator 100, the oscillator 100 is actually mounted on the mobile phone and operated, whereby the oscillation of the output signal Fout (FIG. 2 (c)) output from the oscillator 100 is performed. Run a test to check the frequency.

  As a result, the time T (time t20 to t30) during which the frequency drift D is generated is measured, and the temperature compensation is performed so that the oscillation frequency of the output signal Fout (FIG. 2C) remains constant without fluctuation. A gain G used to generate a correction voltage for correcting the compensation voltage generated by the circuit 400 is calculated.

  The time T thus obtained is stored as correction time data in the memory 700 of the correction voltage generation circuit 500, and the gain G is stored in the memory 700 as gain data.

  That is, the memory 700 corresponds to the storage unit, and stores in advance gain data used when generating a correction voltage for correcting the compensation voltage and correction time data indicating a time for correcting the compensation voltage.

  Thereafter, the oscillator 100 is mounted and used in a mobile phone when the manufacturing process is completed and shipped.

  That is, when the oscillator 100 is turned on at a predetermined timing (time point t10), the crystal oscillation circuit 300 and the temperature compensation circuit 400 are activated, and the output signal Fout having a desired oscillation frequency (FIG. 2 (c) )) Is output.

  On the other hand, the voltage generation circuit 800 of the correction voltage generation circuit 500 generates a predetermined voltage and outputs it to the gain adjustment circuit 900. The gain adjustment circuit 900 is composed of, for example, an operational amplifier, and generates a correction voltage by adjusting the voltage supplied from the voltage generation circuit 800 based on the gain data stored in the memory 700. Output to.

  That is, the gain adjustment circuit 900 corresponds to the gain adjustment unit, and generates a correction voltage having a desired voltage level while adjusting the gain based on the gain data stored in the memory 700.

  By the way, the oscillator 100 receives an intermittent signal SI (FIG. 2 (a)) whose signal level changes corresponding to the intermittent operation of the mobile phone. The intermittent signal SI is input to the switch control circuit 1000 of the correction voltage generation circuit 500.

  The switch control circuit 1000 includes, for example, a flip-flop, and switches the connection state of the switch SW based on the given intermittent signal SI (FIG. 2A) and the correction time data stored in the memory 700. It is a circuit for.

  When the intermittent signal SI (FIG. 2A) is maintained at the “L” level (time t10 to t20), the switch control circuit 1000 turns off the switch SW, thereby correcting the correction voltage VC ( 2B is limited to the addition circuit 600.

  In this state, when the intermittent signal SI (FIG. 2A) changes from the “L” level to the “H” level (time t20), the switch control circuit 1000 turns on the switch SW, and then the correction time data. The switch SW is maintained in the ON state for the time T indicated by (time t20 to t30).

  In this case, the gain adjustment circuit 900 generates the correction voltage VC (FIG. 2B) while adjusting the voltage applied from the voltage generation circuit 800 based on the gain data stored in the memory 700, This is output to the adder circuit 600 via the switch SW (time t20 to t30).

  The adder circuit 600 corrects the compensation voltage by adding the compensation voltage generated by the temperature compensation circuit 400 and the correction voltage generated by the correction voltage generation circuit 500. Then, the adding circuit 600 applies the obtained compensation voltage to the variable capacitors C100 and C200 during the time T (time t20 to t30), and changes the capacitance of these variable capacitors C100 and C200, thereby making the constant voltage constant. The output signal Fout having the oscillation frequency (FIG. 2C) is maintained to be output.

  As described above, from the timing when the intermittent signal SI (FIG. 2A) changes from the “L” level to the “H” level (time t20), that is, from the timing when the mobile phone transitions to the operating state and the power amplifier is activated. During the time T (time point t20 to t30) in which a temperature difference is generated between the periphery of the crystal unit X100 and the periphery of the IC chip 200, the corrected compensation voltage is changed to the variable capacitors C100 and C200. To be applied.

  That is, the adder circuit 600 corresponds to the adder, and corrects the compensation voltage by adding the compensation voltage generated by the gain adjustment circuit 900 to the compensation voltage generated by the temperature compensation circuit 400 as necessary. Then, the corrected compensation voltage is applied to the variable capacitors C100 and C200.

  Thereafter, at a timing (time t30) when the time T elapses and the temperature difference generated between the periphery of the crystal unit X100 and the periphery of the IC chip 200 disappears, the switch control circuit 1000 turns off the switch SW. By doing so, it is limited that the correction voltage VC (FIG. 2B) is supplied to the adder circuit 600. As a result, the compensation voltage generated by the temperature compensation circuit 400 is applied to the variable capacitors C100 and C200.

  In this state, the oscillator 100 is switched to the off state at a timing (time t40) when the mobile phone transitions to the standby state, and thereafter, the above-described operation is sequentially repeated.

  In this way, the switch SW that forms a switch unit together with the switch control circuit 1000 is connected between the gain adjustment circuit 900 and the addition circuit 600, and is an intermittent signal SI (FIG. 2A) as a control signal given from the outside. ) Is switched to the ON state at a timing (time t20) when the first potential corresponding to the “L” level changes from the first potential corresponding to the “L” level to the second potential corresponding to the “H” level higher than the first potential. The correction voltage VC (FIG. 2B) generated by the circuit 900 is output to the addition circuit 600 for addition, and then the timing at which the time T indicated by the correction time data stored in the memory 700 has elapsed (time point t30). ), The output of the correction voltage VC (FIG. 2B) to the adder circuit 600 is restricted by switching to the OFF state.

  Note that the intermittent signal SI (FIG. 2A) as the control signal changes from the “L” level to the “H” level in response to the transition of the mobile phone on which the oscillator 100 is mounted to the operating state. (Time t20).

  Further, the gain data and the correction time data keep the oscillation frequency of the output signal Fout constant from the timing when the intermittent signal changes from the “L” level to the “H” level until the time T indicated by the correction time data elapses. The correction voltage VC is selected so as to generate the correction voltage VC (FIG. 2B).

  As described above, according to the present embodiment, even when the ambient temperature of the oscillator 100 changes rapidly, it is possible to suppress the fluctuation of the oscillation frequency of the output signal Fout, and accordingly, an output having a constant oscillation frequency. The signal Fout can be continuously output.

  As a result, if such an oscillator 100 is mounted on a mobile phone, it is possible to prevent positioning errors and positioning time delays from occurring, and therefore accurate positioning can be performed.

  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.

10, 100 Oscillator 20, 200 IC chip 30, 300 Crystal oscillation circuit 40, 400 Temperature compensation circuit 500 Correction voltage generation circuit 600 Addition circuit 700 Memory 800 Voltage generation circuit 900 Gain adjustment circuit 1000 Switch control circuit X10, X100 Crystal resonator R10 , R100 Resistors C10, C20, C100, C200 Variable capacitors INV10, INV20, INV100, INV200 Inverter SW switch

Claims (2)

A piezoelectric element;
An oscillation unit connected to the piezoelectric element, having a variable capacitance element connected between the piezoelectric element and a ground, and generating and outputting an output signal having a desired oscillation frequency;
A temperature compensation unit for generating a compensation voltage for changing the capacitance of the variable capacitance element;
A storage unit for preliminarily storing gain data used when generating a correction voltage for correcting the compensation voltage, and correction time data indicating a time of frequency drift occurring in the output signal before correction; ,
A gain adjusting unit that generates the correction voltage having a desired voltage level while adjusting the gain based on the gain data stored in the storage unit;
The correction voltage generated by the gain adjustment unit is added to the compensation voltage generated by the temperature compensation unit as necessary to correct the compensation voltage, and the corrected compensation voltage is An adding unit applied to the variable capacitance element;
By switching to an ON state at a timing when a control signal supplied from outside is connected between the gain adjustment unit and the addition unit and changes from a first potential to a second potential higher than the first potential. The correction voltage generated by the gain adjustment unit is output to the addition unit for addition, and then switched to the off state at the timing when the time indicated by the correction time data stored in the storage unit has elapsed. And a switch unit that restricts output of the correction voltage to the adder unit, and
The control signal is
The oscillator that changes from the first potential to the second potential in response to a transition of an electronic device in which the oscillator is mounted to an operating state . The gain data and the correction time data are
The correction voltage is such that the oscillation frequency of the output signal is kept constant until the time indicated by the correction time data elapses from the timing when the control signal changes from the first potential to the second potential. The oscillator according to claim 1, wherein the oscillator is selected to generate .

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