JP2009065419A - Temperature compensation piezoelectric oscillator - Google Patents

Temperature compensation piezoelectric oscillator Download PDF

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JP2009065419A
JP2009065419A JP2007231116A JP2007231116A JP2009065419A JP 2009065419 A JP2009065419 A JP 2009065419A JP 2007231116 A JP2007231116 A JP 2007231116A JP 2007231116 A JP2007231116 A JP 2007231116A JP 2009065419 A JP2009065419 A JP 2009065419A
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temperature
compensation
circuit
voltage
piezoelectric oscillator
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Masayuki Ishikawa
匡亨 石川
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Miyazaki Epson Corp
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Abstract

<P>PROBLEM TO BE SOLVED: To obtain a temperature compensation piezoelectric oscillator which satisfies a temperature compensation accuracy of a piezoelectric oscillator, downsizing, low power consumption current, and the like, and improves a phase noise characteristic. <P>SOLUTION: The temperature compensation piezoelectric oscillator has a temperature sensor 6 detecting a temperature, a compensation voltage generation circuit 7 generating a plurality of compensation voltages according to the temperature detection result of the temperature sensor 6, a piezoelectric oscillator 5 having at least a piezoelectric vibrator X and a MOS capacitive element, and oscillating with a predetermined oscillation frequency by applying a compensation voltage from the compensation voltage generation circuit 7 to the MOS capacitive element, and a noise removal circuit 8 selecting any of the compensation voltages outputted from the compensation voltage generation circuit 7 based on the output of the temperature sensor 6 and removing a noise superimposed on the selected compensation voltage. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

本発明は、各種の通信機器に用いられる温度補償型圧電発振器に関し、特に電子回路で発生したベースバンドノイズを抑圧した低位相雑音化を図るのに好適なものである。   The present invention relates to a temperature-compensated piezoelectric oscillator used in various communication devices, and is particularly suitable for reducing the phase noise by suppressing baseband noise generated in an electronic circuit.

近年、圧電発振器は周波数安定度、小型軽量、低価格等により携帯電話等の通信機器から水晶時計のような民生機器まで、多くの分野で用いられている。中でも圧電振動子の周波数温度特性を補償した温度補償型圧電発振器（ＴＣＸＯ）は、周波数安定度を必要とする携帯電話等に広く用いられている。
このうち、サーミスタの抵抗温度特性を利用したデスクリートタイプの温度補償型圧電発振器（以下、直接型ＴＣＸＯと称する）は、一般的な間接型ＴＣＸＯのように温度補償電圧を必要としないため、ベースバンドノイズが発振回路に重畳せず、位相雑音特性に優れている。しかし、直接型ＴＣＸＯはデスクリート部品で回路を構成することから、小型化に限界があり、今日では圧電振動子以外をＩＣ化した間接型ＴＣＸＯが主流となっている。 In recent years, piezoelectric oscillators are used in many fields from communication devices such as mobile phones to consumer devices such as quartz watches because of their frequency stability, small size and light weight, and low price. In particular, a temperature compensated piezoelectric oscillator (TCXO) that compensates for the frequency temperature characteristics of a piezoelectric vibrator is widely used in mobile phones and the like that require frequency stability.
Among these, a discrete type temperature compensated piezoelectric oscillator (hereinafter referred to as a direct type TCXO) using the resistance temperature characteristic of a thermistor does not require a temperature compensated voltage unlike a general indirect type TCXO. Band noise is not superimposed on the oscillation circuit, and phase noise characteristics are excellent. However, since the direct type TCXO constitutes a circuit with discrete components, there is a limit to miniaturization, and today, the indirect type TCXO in which ICs other than the piezoelectric vibrator are integrated is mainly used.

また、間接型ＴＣＸＯは、補償電圧発生回路で生成した電圧を可変容量素子に印加して、その容量を変化させ、圧電振動子の周波数温度特性を補償する圧電発振器である。圧電振動子にＡＴカット水晶振動子を用いる場合は、その周波数温度特性が３次曲線を呈することから、補償電圧も３次曲線となる電圧を生成する必要がある。しかし、この補償方法は、位相雑音特性の面からみると補償電圧から発生するベースバンドノイズが発振回路に重畳するため、ＴＣＸＯの位相雑音特性が劣化するという問題があった。   The indirect TCXO is a piezoelectric oscillator that compensates the frequency temperature characteristics of the piezoelectric vibrator by applying a voltage generated by a compensation voltage generation circuit to a variable capacitance element and changing its capacitance. When an AT-cut crystal resonator is used as the piezoelectric resonator, the frequency-temperature characteristic exhibits a cubic curve, and therefore it is necessary to generate a voltage that also has a cubic curve as a compensation voltage. However, this compensation method has a problem in that the phase noise characteristic of the TCXO deteriorates because the baseband noise generated from the compensation voltage is superimposed on the oscillation circuit in terms of the phase noise characteristic.

特許文献１には、補償方式を変えて位相雑音の低減化を図ったＴＣＸＯが開示されている。この補償方式では可変容量素子の非線形な領域を使用することで、補償電圧には線形の電圧を用いることが可能となり、位相雑音の低減化が実現できる。つまり、可変容量素子が線形、補償電圧が非線形という従来の方式と逆の補償方式である。
図４は、特許文献１に開示された温度補償型圧電発振器の回路構成であり、温度補償発振器３０は、圧電振動子Ｘ、ＭＯＳ型容量素子及び増幅回路を有するコルピッツ型水晶発振器３１と、温度センサ３２と、補償電圧発生回路３３と、を備えている。コルピッツ型水晶発振器３１の圧電振動子Ｘと接地間に接続される可変容量回路は、低温補償用のＭＯＳ型容量素子ＭＬと高温補償用のＭＯＳ型容量素子ＭＨとが、共に同一極性方向に直列に接続され、更に直流阻止用の容量Ｃ３を介して接地されている。そして、低温補償用容量素子ＭＬ、高温補償用容量素子ＭＨには夫々抵抗Ｒ４、Ｒ５を介して低温用補償電圧ＶＬ、高温用補償電圧ＶＨが供給され、容量素子ＭＬ、ＭＨの接点には抵抗Ｒ３を介して基準電圧Ｖｒｅｆが印加されるように構成されている。ＭＯＳ容量素子のゲート電圧と容量との関係の一例は、周知のように図５に示すようなゲート電圧−容量特性を呈する。 Patent Document 1 discloses a TCXO in which phase noise is reduced by changing a compensation method. In this compensation method, by using a non-linear region of the variable capacitance element, a linear voltage can be used as the compensation voltage, and phase noise can be reduced. That is, this is a compensation method opposite to the conventional method in which the variable capacitance element is linear and the compensation voltage is non-linear.
FIG. 4 shows a circuit configuration of the temperature compensated piezoelectric oscillator disclosed in Patent Document 1. The temperature compensated oscillator 30 includes a Colpitts crystal oscillator 31 having a piezoelectric vibrator X, a MOS capacitor, and an amplifier circuit, and a temperature. A sensor 32 and a compensation voltage generation circuit 33 are provided. In the variable capacitance circuit connected between the piezoelectric vibrator X of the Colpitts-type crystal oscillator 31 and the ground, the MOS capacitor element ML for low temperature compensation and the MOS capacitor element MH for high temperature compensation are both in series in the same polarity direction. And is grounded via a DC blocking capacitor C3. The low-temperature compensation capacitive element ML and the high-temperature compensation capacitive element MH are supplied with the low-temperature compensation voltage VL and the high-temperature compensation voltage VH via the resistors R4 and R5, respectively, and a resistor is connected to the contact between the capacitive elements ML and MH. The reference voltage Vref is applied via R3. An example of the relationship between the gate voltage and the capacitance of the MOS capacitor element exhibits a gate voltage-capacitance characteristic as shown in FIG.

例えば、低温用補償電圧ＶＬは、２５℃以下の範囲では０．５Ｖ〜３Ｖの範囲で一次的に変化し、且つ２５℃以上ではほぼ一定の０．５Ｖとなるような電圧とする。また高温度補償電圧ＶＨは、２５℃以上の範囲では０．５Ｖ〜３Ｖの範囲で一次的に変化し、且つ２５℃以下ではほぼ一定の０．５Ｖとなるような電圧とする。この補償方式の補償電圧は、低温用補償電圧、高温用補償電圧と２つの補償電圧を必要とするが、温度に対して直線的に変化する線形電圧を生成すればよく、回路構成が簡素化され、ベースバンドノイズを低減することができる。
特開２００１−６０８２８公報 For example, the low-temperature compensation voltage VL is set to a voltage that temporarily changes in the range of 0.5 V to 3 V in the range of 25 ° C. or lower and becomes substantially constant 0.5 V in the range of 25 ° C. or higher. Further, the high temperature compensation voltage VH is a voltage that changes temporarily in the range of 0.5 V to 3 V in the range of 25 ° C. or higher and becomes substantially constant 0.5 V in the range of 25 ° C. or lower. The compensation voltage of this compensation method requires a compensation voltage for low temperature, a compensation voltage for high temperature, and two compensation voltages, but it is only necessary to generate a linear voltage that changes linearly with respect to temperature, thus simplifying the circuit configuration. Baseband noise can be reduced.
JP 2001-60828 A

しかしながら、近年、温度補償型圧電発振器の位相雑音に関する客先要求は一段と厳しくなり、特許文献１で開示されている温度補償型圧電発振器の補償方式でも、位相雑音特性に関する要求仕様を満たさないという問題があった。これは温度補償型圧電発振器の発振周波数の高周波化の要求もあり、周知のように周波数が２倍になると理論的には位相雑音は６ｄＢ劣化するからである。
位相雑音を低減するには、補償電圧発生回路から生じる補償電圧ノイズを低減するか、発振回路の周波数可変感度を下げる方法がある。しかし、補償電圧ノイズを低減するには、補償電圧発生回路の電流を増やすことが必要であったり、ＩＣを構成する素子のサイズを大きくする必要があるなど、ＴＣＸＯの小型化、低消費電流化の要求に逆行することになる。また、発振回路の周波数可変感度を下げる方法では、周波数の温度補償量に影響を及ぼし、使用できる振動子が制限されるなど、位相雑音特性以外の問題が生じる虞がある。
本発明は、上記問題を解決するためになされたものであり、周波数の温度補償精度、小型化、低消費電流等を満たしながら、位相雑音特性を改善した温度補償型圧電発振器を提供することにある。 However, in recent years, customer requirements regarding the phase noise of the temperature compensated piezoelectric oscillator have become more severe, and even the compensation method of the temperature compensated piezoelectric oscillator disclosed in Patent Document 1 does not satisfy the required specifications regarding the phase noise characteristics. was there. This is because the oscillation frequency of the temperature compensated piezoelectric oscillator is also required to be increased. As is well known, when the frequency is doubled, the phase noise is theoretically degraded by 6 dB.
In order to reduce the phase noise, there are methods of reducing the compensation voltage noise generated from the compensation voltage generation circuit or reducing the frequency variable sensitivity of the oscillation circuit. However, in order to reduce the compensation voltage noise, it is necessary to increase the current of the compensation voltage generation circuit or to increase the size of the elements constituting the IC. Will go against the request. Further, in the method of reducing the frequency variable sensitivity of the oscillation circuit, there is a possibility that problems other than the phase noise characteristic may occur, such as affecting the temperature compensation amount of the frequency and limiting the usable vibrator.
The present invention has been made to solve the above problems, and provides a temperature compensated piezoelectric oscillator having improved phase noise characteristics while satisfying frequency temperature compensation accuracy, miniaturization, low current consumption, and the like. is there.

本発明の温度補償型圧電発振器は、温度を検出する温度センサと、前記温度センサの温度検出結果に基づいて複数の補償電圧を発生する補償電圧発生回路と、少なくとも、圧電振動子とＭＯＳ容量素子を備え、前記補償電圧発生回路からの補償電圧を前記ＭＯＳ容量素子に印加することにより所定の発振周波数で発振する圧電発振回路と、前記補償電圧発生回路から出力される複数の補償電圧のうち、前記温度センサの温度検出結果に基づいて何れかの補償電圧を少なくとも一つ選択し、前記選択した補償電圧に重畳するノイズを除去するノイズ除去回路と、を備えることを特徴とする。
このような本発明によれば、ノイズ除去回路によりベースバンドノイズの少ない温度補償型圧電発振器を実現することができる。 A temperature-compensated piezoelectric oscillator according to the present invention includes a temperature sensor that detects temperature, a compensation voltage generation circuit that generates a plurality of compensation voltages based on a temperature detection result of the temperature sensor, and at least a piezoelectric vibrator and a MOS capacitor element A piezoelectric oscillation circuit that oscillates at a predetermined oscillation frequency by applying a compensation voltage from the compensation voltage generation circuit to the MOS capacitor, and among a plurality of compensation voltages output from the compensation voltage generation circuit, And a noise removing circuit that selects at least one compensation voltage based on a temperature detection result of the temperature sensor and removes noise superimposed on the selected compensation voltage.
According to the present invention as described above, a temperature compensated piezoelectric oscillator with less baseband noise can be realized by a noise removal circuit.

本発明の温度補償型圧電発振器は、前記ノイズ除去回路は、前記温度センサの温度検出結果に基づき前記複数の補償電圧の中から何れか一つを選択して出力する選択回路と、前記選択回路から出力された補償電圧に重畳するノイズを除去する容量素子と、を備えることを特徴とする。
このような本発明によれば、ノイズ除去回路によりベースバンドノイズの少ない温度補償型圧電発振器を実現することができる。 In the temperature compensated piezoelectric oscillator according to the present invention, the noise removal circuit selects and outputs any one of the plurality of compensation voltages based on a temperature detection result of the temperature sensor, and the selection circuit And a capacitive element that removes noise superimposed on the compensation voltage output from.
According to the present invention as described above, a temperature compensated piezoelectric oscillator with less baseband noise can be realized by a noise removal circuit.

また本発明の温度補償型圧電発振器は、前記補償電圧発生回路は二つの補償電圧を発生するものであって、前記ノイズ除去回路は、前記温度センサの信号を２値化した信号に基づいて前記選択回路により選択を行うことを特徴とする。
このような本発明によれば、温度に連動して選択回路を確実に動作させることが可能となる。 In the temperature-compensated piezoelectric oscillator of the present invention, the compensation voltage generation circuit generates two compensation voltages, and the noise removal circuit is based on a signal obtained by binarizing the signal of the temperature sensor. The selection is performed by a selection circuit.
According to the present invention as described above, the selection circuit can be reliably operated in conjunction with the temperature.

本発明の温度補償型圧電発振器は、選択回路が、ヒステリシス特性を有することを特徴とする。
このような本発明によれば、選択回路の切替温度付近における温度変化に対し、切替スイッチのばたつきを防止することが可能となり、スイッチ動作を安定にすることができる。 The temperature compensated piezoelectric oscillator of the present invention is characterized in that the selection circuit has a hysteresis characteristic.
According to the present invention, it is possible to prevent the changeover switch from fluttering with respect to a temperature change in the vicinity of the changeover temperature of the selection circuit, and the switch operation can be stabilized.

本発明の温度補償型圧電発振器は、圧電振動子以外の回路がＩＣ化されていることを特徴とする。
このような本発明によれば、温度補償型圧電発振器は大幅に小型化されると共に、良好な周波数温度特性を有し、ベースバンドノイズの少ない温度補償型圧電発振器を実現することができる。 The temperature-compensated piezoelectric oscillator of the present invention is characterized in that a circuit other than the piezoelectric vibrator is integrated into an IC.
According to the present invention as described above, the temperature compensated piezoelectric oscillator can be significantly reduced in size, and can be realized with a temperature compensated piezoelectric oscillator having good frequency temperature characteristics and low baseband noise.

以下、本発明の実施の形態を図面に基づいて詳細に説明する。
図１は本発明の実施の形態に係る温度補償型圧電発振器の構成を示した図である。
この図１に示すように、本実施の形態に係る温度補償型圧電発振器１は、圧電発振回路５、温度センサ６、補償電圧発生回路７、及びノイズ除去回路８を備える。
圧電発振器５は、圧電振動子Ｘ、ＭＯＳ容量素子、増幅回路を有するコルピッツ型水晶発振器である。圧電発振回路５では、抵抗Ｒ１を介してトランジスタＴｒのコレクタを電源Ｖｃｃに接続し、抵抗Ｒｅを介してトランジスタＴｒのエミッタを接地し、トランジスタＴｒのベース−接地間に容量Ｃ１、Ｃ２の直列接続回路を接続する。更に、容量Ｃ１、Ｃ２の直列接続回路の中点とトランジスタＴｒのエミッタとを接続し、コレクタとベース間を抵抗Ｒ２で接続する。
そして、低温補償用ＭＯＳ型容量素子ＭＬと高温補償用ＭＯＳ型容量素子ＭＨとは、共に同一極性方向に直列に接続し、さらにその直列回路の一方の端子は一端が接地された直流阻止用の容量Ｃ３の他端に接続し、他方の端子は圧電振動子Ｘを介してトランジスタＴｒのベースに接続する。更に、低温補償用ＭＯＳ型容量素子ＭＬと高温補償用ＭＯＳ型容量素子ＭＨとの接点に、抵抗Ｒ３を介して基準電圧Ｖｒｅｆを印加するようにしている。なお、圧電発振器５の出力はトランジスタのエミッタから容量Ｃｏを介して出力する。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing a configuration of a temperature compensated piezoelectric oscillator according to an embodiment of the present invention.
As shown in FIG. 1, the temperature compensated piezoelectric oscillator 1 according to the present embodiment includes a piezoelectric oscillation circuit 5, a temperature sensor 6, a compensation voltage generation circuit 7, and a noise removal circuit 8.
The piezoelectric oscillator 5 is a Colpitts crystal oscillator having a piezoelectric vibrator X, a MOS capacitor, and an amplifier circuit. In the piezoelectric oscillation circuit 5, the collector of the transistor Tr is connected to the power source Vcc via the resistor R1, the emitter of the transistor Tr is grounded via the resistor Re, and the capacitors C1 and C2 are connected in series between the base and ground of the transistor Tr. Connect the circuit. Further, the midpoint of the series connection circuit of the capacitors C1 and C2 is connected to the emitter of the transistor Tr, and the collector and base are connected by a resistor R2.
The low-temperature compensation MOS capacitive element ML and the high-temperature compensation MOS capacitive element MH are both connected in series in the same polarity direction, and one terminal of the series circuit is for DC blocking with one end grounded. The other end of the capacitor C3 is connected, and the other terminal is connected to the base of the transistor Tr via the piezoelectric vibrator X. Further, the reference voltage Vref is applied to the contact point between the low-temperature compensation MOS capacitive element ML and the high-temperature compensation MOS capacitive element MH via a resistor R3. The output of the piezoelectric oscillator 5 is output from the emitter of the transistor through the capacitor Co.

低温補償用ＭＯＳ型容量素子ＭＬと圧電振動子Ｘとの接点には、抵抗Ｒ４を介して低温補償電圧ＶＬが、高温補償用ＭＯＳ型容量素子ＭＨと容量Ｃ３の接点には抵抗Ｒ５を介して高温補償電圧ＶＨが、補償電圧発生回路７から供給される。
温度センサ６は、例えばサーミスタやダイオードセンサーなどにより構成され、当該温度補償型圧電発振器１の周囲温度を検出する。
補償電圧発生回路７は温度センサ６の温度検出結果に基づいて低温補償電圧ＶＬと高温補償電圧ＶＨとを出力するが、例えば常温以下の低温部では低温補償電圧ＶＬが支配的であり、該電圧ＶＬと基準電圧Ｖｒｅｆとの差がＭＯＳ型容量素子ＭＬに印加されて、その容量を変化させて圧電振動子Ｘの周波数を補償する。一方、常温以上の高温部では高温補償電圧ＶＨが支配的となり、基準電圧Ｖｒｅｆと高温補償電圧ＶＨとの差がＭＯＳ型容量素子ＭＨに印加され、その容量を変化させて圧電振動子Ｘの周波数を補償する。 The low temperature compensation voltage VL is connected to the contact point between the low temperature compensation MOS capacitor element ML and the piezoelectric vibrator X via the resistor R4, and the contact point between the high temperature compensation MOS capacitor element MH and the capacitor C3 is connected via the resistor R5. A high temperature compensation voltage VH is supplied from the compensation voltage generation circuit 7.
The temperature sensor 6 is composed of, for example, a thermistor or a diode sensor, and detects the ambient temperature of the temperature compensated piezoelectric oscillator 1.
The compensation voltage generation circuit 7 outputs the low temperature compensation voltage VL and the high temperature compensation voltage VH based on the temperature detection result of the temperature sensor 6. For example, the low temperature compensation voltage VL is dominant in the low temperature portion below room temperature. The difference between VL and the reference voltage Vref is applied to the MOS capacitor ML, and the capacitance is changed to compensate the frequency of the piezoelectric vibrator X. On the other hand, the high temperature compensation voltage VH becomes dominant in the high temperature portion above room temperature, and the difference between the reference voltage Vref and the high temperature compensation voltage VH is applied to the MOS capacitor MH, and the capacitance is changed to change the frequency of the piezoelectric vibrator X. To compensate.

本実施の形態の温度補償型圧電発振器１は、補償電圧発生回路７の出力部に、ノイズ除去回路８を設けた点に特徴がある。ノイズ除去回路８は、選択回路を構成する制御回路９及び切替スイッチ（ＳＷ）１０と、フィルタ回路を構成する容量素子Ｃ５及び抵抗Ｒ６、Ｒ７により構成される。
抵抗Ｒ６は補償電圧発生回路７の低温補償電圧を出力する出力ラインに挿入され、抵抗Ｒ７は補償電圧発生回路７の高温補償電圧を出力する出力ラインに挿入される。
Ａ／Ｄ回路９は、温度センサ６の出力電圧に基づき切替スイッチ１０に切替信号を出力する。切替スイッチ１０は、接点Ａが抵抗Ｒ７の一端に接続され、接点Ｂが抵抗Ｒ６の一端に接続される。また接点Ｃは一方が接地された容量素子Ｃ５に接続される。 The temperature-compensated piezoelectric oscillator 1 of the present embodiment is characterized in that a noise removing circuit 8 is provided at the output portion of the compensation voltage generating circuit 7. The noise removal circuit 8 includes a control circuit 9 and a changeover switch (SW) 10 that constitute a selection circuit, a capacitive element C5 that constitutes a filter circuit, and resistors R6 and R7.
The resistor R6 is inserted into the output line for outputting the low temperature compensation voltage of the compensation voltage generation circuit 7, and the resistor R7 is inserted into the output line for outputting the high temperature compensation voltage of the compensation voltage generation circuit 7.
The A / D circuit 9 outputs a switching signal to the changeover switch 10 based on the output voltage of the temperature sensor 6. In the changeover switch 10, the contact A is connected to one end of the resistor R7, and the contact B is connected to one end of the resistor R6. The contact C is connected to the capacitive element C5, one of which is grounded.

このように構成されるノイズ除去回路８では、温度センサ６の出力電圧に基づき制御回路９より切替信号が出力され、この切替信号により切替スイッチ１０が容量素子Ｃ５の接続先を抵抗Ｒ６、Ｒ７の何れか一方に選択するように動作する。例えば、常温以下の温度では、切替スイッチ１０が接点Ｂに接続され、容量素子Ｃ５は補償電圧発生回路７の低温補償電圧を出力する出力ラインに接続される。また、常温以上の温度では切替スイッチ１０は、接点Ａに接続され、容量素子Ｃ５は補償電圧発生回路７の高温補償電圧を出力する出力ラインに接続される。   In the noise removal circuit 8 configured in this way, a switching signal is output from the control circuit 9 based on the output voltage of the temperature sensor 6, and the changeover switch 10 connects the capacitive element C5 to the resistors R6 and R7 by this switching signal. It operates to select either one. For example, at a temperature below room temperature, the changeover switch 10 is connected to the contact B, and the capacitive element C5 is connected to the output line that outputs the low-temperature compensation voltage of the compensation voltage generation circuit 7. Further, at a temperature equal to or higher than normal temperature, the changeover switch 10 is connected to the contact A, and the capacitive element C5 is connected to an output line that outputs the high temperature compensation voltage of the compensation voltage generation circuit 7.

図２（ａ）は、上記した制御回路の構成例を示した図である。
この図に示す制御回路９は、コンパレータ１１と、３つの抵抗Ｒ１０、Ｒ１１及びＲ１２により構成され、コンパレータ１１の出力端子と＋入力端子との間に抵抗Ｒ１２が接続されている。コンパレータ１１の−入力端子には、温度センサ６の出力電圧Ｖｓが抵抗Ｒ１０を介して入力され、コンパレータ１１の＋入力端子には、基準電圧Ｖｒｅｆ１が抵抗Ｒ１１を介して入力される。ここで、温度センサ６が常温のときに呈する出力電圧Ｖｓと同じ電圧を基準電圧Ｖｒｅｆ１する。 FIG. 2A is a diagram illustrating a configuration example of the control circuit described above.
The control circuit 9 shown in this figure includes a comparator 11 and three resistors R10, R11, and R12, and a resistor R12 is connected between the output terminal and the + input terminal of the comparator 11. The output voltage Vs of the temperature sensor 6 is input to the negative input terminal of the comparator 11 via the resistor R10, and the reference voltage Vref1 is input to the positive input terminal of the comparator 11 via the resistor R11. Here, the same voltage as the output voltage Vs exhibited when the temperature sensor 6 is at room temperature is used as the reference voltage Vref1.

図２（ｂ）は、温度センサ６の温度−出力電圧特性を示した図、図２（ｃ）は、図２（ａ）に示す制御回路９の入力電圧−出力電圧特性を示した図である。
制御回路９の出力電圧レベル（ハイ電圧又はロー電圧）は、コンパレータの種類、電源電圧等で決まるが、そのハイ電圧をＶHI、ロー電圧をＶLOとすると、制御回路９から出力される出力電圧Ｖｃｎｔは、図２（ｃ）に示すヒステリシス特性を有し、その切替電圧Ｖ１、Ｖ２は、周知のように、基準電圧Ｖｒｅｆ１、ハイ電圧をＶHI、抵抗Ｒ１１、Ｒ１２を用いて、
Ｖ１＝Ｖｒｅｆ１−（ＶHI＋Ｖｒｅｆ１）×Ｒ１１／（Ｒ１１＋Ｒ１２）・・（１）
Ｖ２＝Ｖｒｅｆ１−（ＶHI−Ｖｒｅｆ１）×Ｒ１１／（Ｒ１１＋Ｒ１２）・・（２）
と表すことができる。 2B is a diagram showing the temperature-output voltage characteristics of the temperature sensor 6, and FIG. 2C is a diagram showing the input voltage-output voltage characteristics of the control circuit 9 shown in FIG. 2A. is there.
The output voltage level (high voltage or low voltage) of the control circuit 9 is determined by the type of the comparator, the power supply voltage, and the like. If the high voltage is V HI and the low voltage is V LO , the output output from the control circuit 9 The voltage Vcnt has a hysteresis characteristic shown in FIG. 2C. The switching voltages V1 and V2 are, as is well known, using a reference voltage Vref1, a high voltage V HI , and resistors R11 and R12,
V1 = Vref1− ( VHI + Vref1) × R11 / (R11 + R12) (1)
V2 = Vref1- (V HI -Vref1) × R11 / (R11 + R12) ·· (2)
It can be expressed as.

いま、温度センサ６の周囲の温度が低温度範囲（常温、例えば２５℃から−３０℃の範囲）である場合には、温度センサ６の出力電圧Ｖｓは基準電圧Ｖｒｅｆ１より高いので、制御回路９の出力電圧Ｖｃｎｔはロー電圧ＶLOになる。一方、温度センサ６が高温度範囲（常温から８０℃の範囲）では、温度センサ６の出力電圧Ｖｓは基準電圧Ｖｒｅｆ１より低くなるので、制御回路９の出力電圧Ｖｃｎｔはハイ電圧ＶHIになる。
更に詳しく説明すれば、制御回路９の出力電圧Ｖｃｎｔは、温度センサ６の温度が低温度範囲（−３０℃〜常温）にある場合、つまり、温度センサ６の出力電圧Ｖｓが、温度センサ６が常温のときに呈する基準電圧Ｖｒｅｆ１より高い場合には、出力電圧Ｖｃｎｔはロー電圧ＶLOの状態である。温度が上昇して常温より高くなり、温度センサ６の出力電圧Ｖｓは基準電圧Ｖｒｅｆ１より下がるが、温度センサ６の出力電圧Ｖｓが式（１）で示す切替電圧Ｖ１に達するまで、制御回路９の出力電圧Ｖｃｎｔはロー電圧ＶLOの状態を継続する。温度センサ６の出力電圧Ｖｓが切替電圧Ｖ１より低く成る際に、出力電圧Ｖｃｎｔはロー電圧ＶLOからハイ電圧ＶHIに急激に変化する。 Now, when the temperature around the temperature sensor 6 is in a low temperature range (normal temperature, for example, a range from 25 ° C. to −30 ° C.), the output voltage Vs of the temperature sensor 6 is higher than the reference voltage Vref1, so that the control circuit 9 the output voltage Vcnt to the low voltage V LO. On the other hand, when the temperature sensor 6 is in a high temperature range (range from room temperature to 80 ° C.), the output voltage Vs of the temperature sensor 6 is lower than the reference voltage Vref1, so that the output voltage Vcnt of the control circuit 9 becomes the high voltage V HI .
More specifically, the output voltage Vcnt of the control circuit 9 is equal to the output voltage Vs of the temperature sensor 6 when the temperature of the temperature sensor 6 is in the low temperature range (−30 ° C. to normal temperature). If higher than the reference voltage Vref1 that exhibits at room temperature, the output voltage Vcnt is a state of low voltage V LO. The temperature rises and becomes higher than normal temperature, and the output voltage Vs of the temperature sensor 6 falls below the reference voltage Vref1, but until the output voltage Vs of the temperature sensor 6 reaches the switching voltage V1 shown by the equation (1), the output voltage Vcnt continues the state of the low voltage V LO. When the output voltage Vs of the temperature sensor 6 becomes lower than the switching voltage V1, the output voltage Vcnt is abruptly changed from the low voltage V LO to high voltage V HI.

逆に、温度センサ６の温度が高温度範囲（常温〜８０℃）ある場合には、温度センサ６の出力電圧Ｖｓは基準電圧Ｖｒｅｆ１より低いため、制御回路９の出力電圧Ｖｃｎｔはハイ電圧ＶHIとなる。温度センサ６の温度が下降し、常温より低くなると、温度センサ６の出力電圧Ｖｓは基準電圧Ｖｒｅｆ１より高くなるが、出力電圧Ｖｓが式（２）で示す切替電圧Ｖ２に達するまで、Ａ／Ｄ回路９の出力電圧Ｖｃｎｔはハイ電圧ＶHIの状態を継続する。
温度センサ６の出力電圧Ｖｓが切替電圧Ｖ２より高くなる際にＡ／Ｄ回路９の出力電圧Ｖｃｎｔはハイ電圧ＶHIからロー電圧ＶLOに急激に変化する。つまり、Ａ／Ｄ回路９の出力電圧Ｖｃｎｔは、温度センサ６の出力Ｖｓに対してヒステリシス曲線を呈することになる。 Conversely, when the temperature of the temperature sensor 6 is in the high temperature range (room temperature to 80 ° C.), the output voltage Vs of the temperature sensor 6 is lower than the reference voltage Vref1, and therefore the output voltage Vcnt of the control circuit 9 is the high voltage V HI. It becomes. When the temperature of the temperature sensor 6 decreases and becomes lower than the normal temperature, the output voltage Vs of the temperature sensor 6 becomes higher than the reference voltage Vref1, but the A / D until the output voltage Vs reaches the switching voltage V2 expressed by the equation (2). the output voltage Vcnt of the circuit 9 continues the state of the high voltage V HI.
The output voltage Vs of the temperature sensor 6 and the output voltage Vcnt of the A / D circuit 9 when higher than the switching voltage V2 is rapidly changed from the high voltage V HI to the low voltage V LO. That is, the output voltage Vcnt of the A / D circuit 9 exhibits a hysteresis curve with respect to the output Vs of the temperature sensor 6.

以上のように、制御回路９の入力電圧Ｖｓ−出力電圧Ｖｃｎｔ特性に、温度センサ６の電圧Ｖｓに対して常温を中心としたヒステリシス特性を持たせる理由は次の通りである。本実施形態の温度補償型圧電発振器は、ＭＯＳ容量素子の特性と関連して、常温近傍を境として、常温より低い場合には低温補償電圧ＶＬがＭＯＳ容量素子ＭＬの容量変化が大きくなるような電圧値となるため、温度補償の支配的となり、常温より高い場合には高温部補償電圧ＶＨがＭＯＳ容量素子ＭＨの容量変化が大きくなるような電圧値となるため、温度補償の支配的となる。ここで支配的とは、温度変化に対し補償電圧特性は１次関数であるが、電圧に対して容量変化が非線形であるＭＯＳ容量素子の、容量変化が急峻になる電圧が印加される状態になるため、発振周波数が大きく変化するいわゆる感度が高い状態であることを意味する。発振器の位相雑音はＭＯＳ容量素子の容量変化による周波数可変感度と、ＭＯＳ容量素子に印加される電圧のベースバンドノイズで決まる。よって、支配的となる方の補償電圧に接続する抵抗の方に、容量素子Ｃ５を接続して、周知のＲＣローパスフィルタを構成し、ベースバンドノイズの除去を図ったのである。   As described above, the reason why the input voltage Vs-output voltage Vcnt characteristic of the control circuit 9 has the hysteresis characteristic centered on the normal temperature with respect to the voltage Vs of the temperature sensor 6 is as follows. In the temperature compensated piezoelectric oscillator according to the present embodiment, the low temperature compensation voltage VL has a large capacitance change of the MOS capacitor element ML when the temperature is lower than the room temperature with a boundary around the room temperature as a boundary in relation to the characteristics of the MOS capacitor element. Since it becomes a voltage value, it becomes dominant in temperature compensation, and when it is higher than normal temperature, the high-temperature portion compensation voltage VH becomes a voltage value at which the capacitance change of the MOS capacitor element MH becomes large, and thus becomes dominant in temperature compensation. . Dominant means that the compensation voltage characteristic with respect to the temperature change is a linear function, but the MOS capacitor element whose capacitance change is non-linear with respect to the voltage is applied with a voltage at which the capacitance change becomes steep. Therefore, this means that the so-called sensitivity where the oscillation frequency changes greatly is high. The phase noise of the oscillator is determined by the frequency variable sensitivity due to the capacitance change of the MOS capacitor and the baseband noise of the voltage applied to the MOS capacitor. Therefore, a capacitor element C5 is connected to the resistor connected to the dominant compensation voltage to configure a known RC low-pass filter to eliminate baseband noise.

図３（ａ）は制御回路９の他の構成例を示した図である。
この図に示す制御回路９は、インバータ回路１２を２段縦続接続し、一段目の入力に抵抗Ｒ１５接続し、一段目の入力と２段目の出力とを抵抗Ｒ１６で接続して構成するようにしている。この場合も、入力電圧Ｖｓ−出力電圧Ｖｃｎｔ特性が、図３（ｃ）に示すようにヒステリシス特性を有する。但し、図３（ｃ）に示す切替電圧Ｖ’１、Ｖ’２が、図２（ｃ）に示した切替電圧Ｖ１、Ｖ２と異なる。
この場合、ヒステリシス電圧ＶＨ（切替電圧の差）は電源電圧ＶＤＤ、抵抗Ｒ１５、Ｒ１６を用いて、式（３）のように表すことができる。
ＶＨ＝（Ｒ１５／Ｒ１６）×ＶＤＤ・・・（３）
そして、切替電圧Ｖ’１、Ｖ’２は、インバータ１２のしきい値電圧Ｖｔｈと、電源電圧ＶＤＤ、抵抗Ｒ１５、Ｒ１６を用いて、
Ｖ’１＝（Ｖｔｈ−（Ｒ１５×ＶＤＤ）／（Ｒ１５＋Ｒ１６））×（Ｒ１５＋Ｒ１６）／Ｒ１６・・・（４）
Ｖ’２＝Ｖｔｈ×（Ｒ１５＋Ｒ１６）／Ｒ１６・・・（５）
のように表すことができる。 FIG. 3A is a diagram showing another configuration example of the control circuit 9.
The control circuit 9 shown in this figure is configured by cascading two stages of inverter circuits 12, connecting a resistor R15 to a first-stage input, and connecting a first-stage input and a second-stage output by a resistor R16. I have to. Also in this case, the input voltage Vs-output voltage Vcnt characteristic has a hysteresis characteristic as shown in FIG. However, the switching voltages V′1 and V′2 shown in FIG. 3C are different from the switching voltages V1 and V2 shown in FIG.
In this case, the hysteresis voltage VH (difference in switching voltage) can be expressed as in Expression (3) using the power supply voltage VDD and the resistors R15 and R16.
VH = (R15 / R16) × VDD (3)
The switching voltages V′1 and V′2 are obtained by using the threshold voltage Vth of the inverter 12, the power supply voltage VDD, and the resistors R15 and R16.
V′1 = (Vth− (R15 × VDD) / (R15 + R16)) × (R15 + R16) / R16 (4)
V′2 = Vth × (R15 + R16) / R16 (5)
It can be expressed as

このように本実施の形態の温度補償型圧電発振器１は、補償電圧発生回路７の出力部にノイズ除去回路８を付加したことで、ベースバンドノイズの少ない圧電発振器を実現することができる。
またノイズ除去回路８は、制御回路９により温度センサ６の出力電圧を２値化し、２値化した信号に基づいて切替スイッチ１０を切り替えるように構成しているので、切替スイッチ１０の温度に対する切り替え動作の精度を大幅に向上することができる。 Thus, the temperature compensated piezoelectric oscillator 1 according to the present embodiment can realize a piezoelectric oscillator with less baseband noise by adding the noise removing circuit 8 to the output portion of the compensation voltage generating circuit 7.
Further, the noise removal circuit 8 is configured to binarize the output voltage of the temperature sensor 6 by the control circuit 9 and to switch the changeover switch 10 based on the binarized signal. The accuracy of operation can be greatly improved.

なお、本実施例においては、補償電圧発生回路７が低温補償電圧と高温補償電圧の二つの補償電圧出力を備えた構成としたが、複数の補償電圧出力を備えるようにしても良い。例えば、低温補償領域と高温補償領域とをそれぞれ２分割し（温度領域を４分割し）、これらに対応した４つの補償電圧を補償電圧発生回路７から出力し、これら４つの補償電圧を加算或いは切り替えて圧電発振回路５へ供給するようにする。このとき、４つの補償電圧のうち何れか一つの補償電圧を４入力のスイッチ１０で選択し、容量素子Ｃ５にてノイズ除去を行うようにしても良い。或いは、補償電圧発生回路７が複数の補償電圧を出力する構成とし、更にスイッチ１０と容量素子Ｃ５とをもう一つ追加してもよい。このとき、複数の補償電圧のうち何れか二つの補償電圧を選択して、同時に二つの補償電圧のノイズ除去を行うようにする。このようにすれば、複数の補償電圧に対してはノイズ除去回路の数を極力抑えることができる。勿論、選択スイッチ１０と容量素子Ｃ５の数は極力少ないほうが好ましい。   In the present embodiment, the compensation voltage generation circuit 7 is configured to include two compensation voltage outputs, ie, a low temperature compensation voltage and a high temperature compensation voltage. However, a plurality of compensation voltage outputs may be provided. For example, the low-temperature compensation region and the high-temperature compensation region are each divided into two (the temperature region is divided into four), and four compensation voltages corresponding to these are output from the compensation voltage generation circuit 7 and these four compensation voltages are added or It is switched and supplied to the piezoelectric oscillation circuit 5. At this time, any one of the four compensation voltages may be selected by the four-input switch 10 and noise may be removed by the capacitive element C5. Alternatively, the compensation voltage generation circuit 7 may output a plurality of compensation voltages, and another switch 10 and a capacitive element C5 may be added. At this time, any two compensation voltages are selected from the plurality of compensation voltages, and noise removal of the two compensation voltages is performed simultaneously. In this way, the number of noise removal circuits can be suppressed as much as possible for a plurality of compensation voltages. Of course, it is preferable that the number of selection switches 10 and capacitive elements C5 be as small as possible.

また、これまで説明した本実施の形態の温度補償型圧電発振器は、圧電振動子Ｘ以外の回路を半導体上に集積化（ＩＣ化）することが可能であり、ＩＣ化した場合は、周波数温度特性が優れ、小型で且つ、ベースバンドノイズの少ない温度補償型圧電発振器を実現することができる。また２つの補償電圧に対し、１つのコンデンサで対応できるために、ＩＣの小型化を実現できる。なお、ノイズ除去回路８の容量素子Ｃ５は、要求されるローパス特性から大きな容量となる場合には、外付けの容量を用いてもよい。なお、容量素子Ｃ５としてＭＯＳ容量でも良い   In addition, the temperature compensated piezoelectric oscillator according to the present embodiment described so far can integrate circuits (ICs) other than the piezoelectric vibrator X on a semiconductor. A temperature compensated piezoelectric oscillator having excellent characteristics, small size, and low baseband noise can be realized. Further, since one capacitor can handle two compensation voltages, it is possible to reduce the size of the IC. Note that the capacitor C5 of the noise removal circuit 8 may be an external capacitor when the capacitance is large due to the required low-pass characteristics. The capacitor C5 may be a MOS capacitor.

本発明に係る温度補償型圧電発振器の構成を示す回路図。1 is a circuit diagram showing a configuration of a temperature compensated piezoelectric oscillator according to the present invention. （ａ）はＡ／Ｄ回路９を示す回路図、（ｂ）は温度センサの温度Ｔｅｍｐ−出力電圧Ｖｓ特性図、（ｃ）はヒシテリシス特性を示す図。(A) is a circuit diagram showing the A / D circuit 9, (b) is a temperature Temp-output voltage Vs characteristic diagram of the temperature sensor, (c) is a diagram showing hysteresis characteristics. （ａ）は他のＡ／Ｄ回路９を示す回路図、（ｂ）は温度センサの温度Ｔｅｍｐ−出力電圧Ｖｓ特性図、（ｃ）はヒシテリシス特性を示す図。(A) is a circuit diagram showing another A / D circuit 9, (b) is a temperature Temp-output voltage Vs characteristic diagram of the temperature sensor, (c) is a diagram showing hysteresis characteristics. 従来の温度補償型圧電発振器の構成を示す回路図。The circuit diagram which shows the structure of the conventional temperature compensation type | mold piezoelectric oscillator. ＭＯＳ型容量素子のゲート電圧−容量特性を示す図。The figure which shows the gate voltage-capacitance characteristic of a MOS type capacitive element.

符号の説明Explanation of symbols

１…温度補償型圧電発振器、５…圧電発振回路、６…温度センサ、７補償電圧発生回路、８…ノイズ除去回路、９…制御回路、１０…切替スイッチ、１１…コンパレータ、１２…インバータ、Ｔｒ…トランジスタ、Ｃ…容量、Ｒ…抵抗   DESCRIPTION OF SYMBOLS 1 ... Temperature compensation type piezoelectric oscillator, 5 ... Piezo oscillation circuit, 6 ... Temperature sensor, 7 Compensation voltage generation circuit, 8 ... Noise removal circuit, 9 ... Control circuit, 10 ... Changeover switch, 11 ... Comparator, 12 ... Inverter, Tr ... transistor, C ... capacitance, R ... resistance

Claims (5)

温度を検出する温度センサと、
前記温度センサの温度検出結果に基づいて複数の補償電圧を発生する補償電圧発生回路と、
少なくとも、圧電振動子とＭＯＳ容量素子を備え、前記補償電圧発生回路からの補償電圧を前記ＭＯＳ容量素子に印加することにより所定の発振周波数で発振する圧電発振回路と、
前記補償電圧発生回路から出力される複数の補償電圧のうち、前記温度センサの温度検出結果に基づいて何れかの補償電圧を少なくとも一つ選択し、前記選択した補償電圧に重畳するノイズを除去するノイズ除去回路と、
を備えることを特徴とする温度補償型圧電発振器。 A temperature sensor for detecting the temperature;
A compensation voltage generating circuit for generating a plurality of compensation voltages based on a temperature detection result of the temperature sensor;
A piezoelectric oscillation circuit including at least a piezoelectric vibrator and a MOS capacitance element, and oscillating at a predetermined oscillation frequency by applying a compensation voltage from the compensation voltage generation circuit to the MOS capacitance element;
At least one of the plurality of compensation voltages output from the compensation voltage generation circuit is selected based on the temperature detection result of the temperature sensor, and noise superimposed on the selected compensation voltage is removed. A noise removal circuit;
A temperature-compensated piezoelectric oscillator comprising: 前記ノイズ除去回路は、前記温度センサの温度検出結果に基づき前記複数の補償電圧の中から何れか一つを選択して出力する選択回路と、前記選択回路から出力された補償電圧に重畳するノイズを除去する容量素子と、を備えることを特徴とする請求項１に記載の温度補償型圧電発振器。   The noise removal circuit includes a selection circuit that selects and outputs any one of the plurality of compensation voltages based on a temperature detection result of the temperature sensor, and noise that is superimposed on the compensation voltage output from the selection circuit. The temperature-compensated piezoelectric oscillator according to claim 1, further comprising: 前記補償電圧発生回路は二つの補償電圧を発生するものであって、前記ノイズ除去回路は、前記温度センサの信号を２値化した信号に基づいて前記選択回路により選択を行うことを特徴とする請求項２に記載の温度補償型圧電発振器。   The compensation voltage generation circuit generates two compensation voltages, and the noise removal circuit performs selection by the selection circuit based on a binarized signal of the temperature sensor signal. The temperature compensated piezoelectric oscillator according to claim 2. 前記選択回路は、ヒステリシス特性を有することを特徴とする請求項１乃至３の何れかに記載の温度補償型圧電発振器。   4. The temperature compensated piezoelectric oscillator according to claim 1, wherein the selection circuit has a hysteresis characteristic. 前記圧電振動子以外の回路がＩＣ化されていることを特徴とする請求項１乃至４の何れかに記載の温度補償型圧電発振器。   5. The temperature compensated piezoelectric oscillator according to claim 1, wherein a circuit other than the piezoelectric vibrator is formed as an IC.
JP2007231116A 2007-09-06 2007-09-06 Temperature compensation piezoelectric oscillator Withdrawn JP2009065419A (en)

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