JP2006222645A - Temperature-compensated oscillator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a temperature-compensated oscillator which is simple in circuit configuration, adapted for a reduction in size easily adjusted, and has a higher temperature compensating performance. <P>SOLUTION: A temperature detecting circuit 15 detects the temperature of a crystal oscillation circuit 131, and outputs a temperature-dependent voltage to the input terminal 32 of a first gate voltage generating circuit 31 and the input terminal 34 of the second gate voltage generating circuit 33. The output terminal 38 of the first gate voltage generating circuit 31 is connected to the gate 37 of a p-channel MOS transistor 41, so that a voltage difference between the gate 37 of the p-channel MOS transistor 41 and the source 47 of the p-channel MOS transistor 41 connected to a power line 23 increases with a rise in temperature. When the above temperature difference reaches to a temperature T1 above the threshold voltage of the p-channel MOS transistor 41, a current starts to flow through a resistor element 45 via the drain 43 of the p-channel MOS transistor 41. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a temperature compensated oscillator that compensates for the temperature characteristics of a crystal oscillator using a crystal resonator.

  An oscillator using a crystal resonator (a so-called crystal oscillator) has a feature of high frequency stability as compared with other oscillators. However, when a crystal oscillator is used as a reference oscillator for a mobile radio in recent years, the phenomenon that the oscillation frequency varies depending on the temperature of the usage environment becomes a problem. This frequency variation due to temperature is a phenomenon caused by temperature characteristics of a crystal resonator provided in the crystal oscillator.

  In order to solve this problem, so-called temperature compensated oscillators that compensate for the temperature characteristics of crystal resonators are widely used (see, for example, Patent Document 1), and in particular, the temperature of a method called “indirect method” A temperature compensated oscillator employing the compensation method has the advantage that it can be integrated.

  FIG. 6 is a diagram for explaining the temperature compensation principle of the temperature-compensated oscillator by the indirect method. In this figure, the temperature detection circuit 201 is a circuit that outputs a temperature detection voltage depending on the temperature. The temperature detection voltage output from the temperature detection circuit 201 is supplied to each of the high-temperature part third-order voltage generation circuit 203, the low-temperature part third-order voltage generation circuit 205, and the first-order voltage generation circuit 207 that constitute the control voltage generation circuit 213. Input after sorting.

  The control voltage generation circuit 213 includes a zero-order term voltage generation circuit 209 in addition to the high-temperature portion third-order voltage generation circuit 203, the low-temperature portion third-order voltage generation circuit 205, and the first-order voltage generation circuit 207. The control voltage output from each of the voltage generation circuits (203, 205, 207, and 209) is input to the addition circuit 211.

  The adder circuit 211 synthesizes these four control voltages to compensate for the third-order temperature characteristic and the first-order temperature characteristic of the AT-cut crystal, and adjusts the oscillation frequency at a specific temperature by the zero-order term voltage generation circuit 209. A control voltage is generated and input to the frequency adjustment circuit 215. In this way, fluctuations due to temperature in the oscillation frequency of the crystal oscillation circuit 217 are compensated.

  Here, the generation of the third-order term voltage is performed by the operational amplifier circuit, but the operational amplifier circuit can only generate the third-order term voltage in the first quadrant in the two-dimensional plane of the input voltage and the output voltage. Originally, the third-order term voltage expressed by a cubic curve can take a value in a region corresponding to the first quadrant and the third quadrant in the two-dimensional plane of the input voltage and the output voltage, but only the third-order voltage in the first quadrant. In order to generate the third-order voltage in the third quadrant, which is the remaining region, a procedure is necessary in which the third-order voltage in the first quadrant is generated and then inverted. . For this reason, in order for the adder circuit 211 to generate a continuous third-order voltage, two circuits of the high-temperature part third-order voltage generation circuit 203 and the low-temperature part third-order voltage generation circuit 205 are required.

  For this reason, there is known a temperature compensated oscillator that employs a system that can generate a continuous third-order voltage with a simpler circuit.

  FIG. 7 is a diagram for explaining the temperature compensation principle of this system. The temperature detection circuit 201 in this figure outputs a temperature detection voltage depending on the temperature, and inputs this to the control voltage generation circuit 213. The control voltage generation circuit 213 includes three voltage generation circuits including a third-order term voltage generation circuit 221, a first-order term voltage generation circuit 207, and a zero-order term voltage generation circuit 209, and the temperature detection voltage input from the temperature detection circuit 201. Are distributed and input to the third-order term voltage generation circuit 221 and the first-order term voltage generation circuit 207 that can generate a series of third-order term voltages.

The control voltage output from each of the three voltage generation circuits (221, 207, 209) included in the control voltage generation circuit 213 is different from the configuration shown in FIG. An input to the adjustment circuit 215 compensates for fluctuations in the oscillation frequency of the crystal oscillation circuit 217 due to temperature.
JP 2004-029746 A

  As described above, the conventional circuit configuration as shown in FIG. 6 requires two third-order voltage generation circuits using operational amplifier circuits to compensate for the temperature characteristics of the AT-cut crystal, An adder circuit is also required, resulting in an increase in circuit scale, and in addition, there is a problem that complicated adjustment is required for each circuit in order to correct variations in manufacturing of these increased circuits.

  Further, in the method using one third-order term voltage generating circuit invented to reduce the circuit scale as shown in FIG. 7, the third-order term voltage generating circuit for generating the third-order term voltage has a single output. Therefore, in order to perform high-temperature part compensation and low-temperature part compensation by a single voltage variable capacitive element constituting a frequency adjustment circuit provided to change the oscillation frequency of the crystal oscillation circuit, the voltage variable capacitive element There is a problem that the linear portion of the voltage vs. capacitance change is insufficient, and depending on the temperature characteristics of the crystal resonator, the compensation capability reaches the limit, and the temperature cannot be sufficiently compensated at the maximum temperature or the minimum temperature in the operating temperature range.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a temperature-compensated oscillator having a simple circuit configuration, suitable for miniaturization, easy adjustment, and greater temperature compensation capability. There is to do.

  In order to solve such a problem, the present invention provides a temperature-compensated oscillator that detects a temperature of a power source, a crystal oscillation circuit, and the vicinity of the crystal oscillation circuit. A temperature detection circuit that generates an output voltage, a control voltage generation circuit that generates a third-order voltage as a control voltage when the output voltage from the temperature detection circuit is input, and a control voltage that is input from the control voltage generation circuit A frequency adjustment circuit for adjusting an oscillation frequency of the crystal oscillation circuit, wherein the control voltage generation circuit outputs a non-linear voltage based on an output voltage output from the temperature detection circuit. The first and second active elements are both inserted through a resistance element between first and second power supply lines for supplying power from the power supply, and The output end of one active element is the front Is the first output of the control voltage, the output terminal of said second active device is characterized in that there is a second output of the control voltage.

  According to a second aspect of the present invention, in the temperature compensated oscillator according to the first aspect, each of the first and second active elements is a MOS transistor, and each of the MOS transistors is connected to the temperature detection circuit. The output voltage is input to the gate, and the drain is connected to at least one of the two power supply lines via the resistance element.

  According to a third aspect of the present invention, in the temperature compensated oscillator according to the first or second aspect, the frequency adjustment circuit includes a plurality of voltage variable capacitance elements constituting a load capacitance of the crystal oscillation circuit, A control voltage output from the first output terminal and a control voltage output from the second output terminal are distributed and applied to the plurality of voltage variable capacitance elements.

  According to a fourth aspect of the present invention, in the temperature-compensated oscillator according to any one of the first to third aspects, the control voltage generation circuit includes first and second third-order voltage generation circuits and variable voltage generation. And a control voltage generation circuit including a first control voltage of a third-order voltage generated by the first third-order voltage generation circuit and a third-order voltage generated by the second third-order voltage generation circuit. The third control voltage of the first-order voltage generated based on the output voltage of the temperature detection circuit, and the fourth of the zero-order voltage generated based on the output voltage of the variable voltage generation circuit. And a fifth control voltage of the external input voltage are output to the frequency adjustment circuit, and the frequency adjustment circuit oscillates the crystal oscillation circuit based on the first to fifth control voltages. It is characterized by controlling the frequency.

  According to a fifth aspect of the present invention, in the temperature compensated oscillator according to the fourth aspect, the frequency adjustment circuit is a voltage variable capacitance element that constitutes a load capacitance of the crystal oscillation circuit, and The first and second voltage variable capacitance elements whose capacitance values are changed by a control voltage of 5, and the first control voltage is applied to one electrode of the first voltage variable capacitance element, 2 control voltage is applied to one electrode of the second voltage variable capacitance element, the fourth control voltage and the fifth control voltage are separated from each other, and the other of the first voltage variable capacitance elements And is applied to the other electrode of the second voltage variable capacitance element.

  According to the temperature compensated oscillator of the present invention, since a complicated circuit such as a plurality of third-order term generating circuits and an adding circuit using an operational amplifier circuit is not required, the number of active elements used in the semiconductor integrated circuit is reduced. It can be reduced. As a result, the area of the semiconductor integrated circuit chip can be greatly reduced, and the temperature compensation capability can be improved as compared with the conventional method in which the temperature compensation is performed in the high temperature part and the low temperature part with a single voltage variable capacitance element. Improvement can be achieved, and the effect of improving the yield and reducing the price is achieved.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram for explaining a circuit configuration example of a temperature compensated oscillator according to the present invention. The temperature compensated oscillator includes a power supply 11, a control voltage generation circuit 71, a temperature detection circuit 15, and a frequency adjustment. A circuit 121 and a crystal oscillation circuit 131 are provided.

  Among these, the control voltage generation circuit 71 has two power supply lines, one of which is illustrated as a first power supply line 23 and the other as a second power supply line 35. The variable voltage generation circuit 13, the first gate voltage generation circuit 31, the second gate voltage generation circuit 33, the P-channel MOS transistor 41 which is the first MOS transistor, and the second MOS transistor. N channel MOS transistor 53, resistance elements 45, 49, 59 and 63, and external voltage input terminal 17 are arranged as shown in the block diagram of FIG. In this example, the P-channel MOS transistor 41 and the N-channel MOS transistor 53 are used, but other active elements may be used.

  Here, the first gate voltage generation circuit 31 and the P channel MOS transistor 41 as the first MOS transistor, the second gate voltage generation circuit 33 and the N channel MOS transistor 53 as the second MOS transistor, and The resistance elements 45, 49, 59, and 63 constitute a third-order voltage generation circuit.

  The variable voltage generating circuit 13 is not particularly limited in its configuration as long as it can generate an arbitrary voltage, but is preferably a circuit that generates an arbitrary voltage by memory control. The external voltage input terminal 17 has a function of directly applying a voltage from the outside to the frequency adjusting circuit 121, and a voltage conversion circuit (for example, converting the external voltage into an appropriate value as necessary) A memory-controlled voltage conversion circuit is added.

  The frequency adjustment circuit 121 includes MIS type variable capacitors 83, 89, 103, 109, capacitive elements 81, 87, 101, 107 and capacitive elements 85, 91, 105, 111, and resistive elements 73, 75, 77, 79. And the resistance elements 93, 95, 97, and 99.

  The crystal oscillation circuit 131 includes a crystal resonator 123 that is a piezoelectric resonator, an inverter 125, and a feedback resistance element 127.

  Capacitance elements 81, 87, 101, 107 and capacitance elements 85, 91, 105, 111 and MIS variable capacitance capacitors 83, 89, 103, 109 provided in the frequency adjustment circuit 121 are respectively connected to the crystal oscillation circuit 131. MIS variable capacitors 83, 89, 103, and 109 are capacitive elements that constitute a load capacitor, and the capacitance values of the MIS variable capacitors 83, 89, 103, and 109 vary depending on the control voltage.

  The temperature detection circuit 15 is not limited in configuration as long as the output voltage linearly changes depending on the temperature, but when configured on a semiconductor integrated circuit, as shown in FIG. The circuit utilizing the temperature characteristics of the drain current of the MOS transistor is most preferable.

  In the control voltage generation circuit 71 shown in FIG. 1, the first gate voltage generation circuit 31 and the second gate voltage generation circuit 33 convert the output voltage from the temperature detection circuit 15 into an appropriate value, This is a circuit for inputting to the gate 37 of the P-channel MOS transistor 41 as the first MOS transistor and the gate 39 of the N-channel MOS transistor 53 as the second MOS transistor. Such a gate voltage generating circuit preferably has a digital voltage dividing circuit configuration in which the voltage division ratio can be changed by memory control as shown in FIG.

  In the control voltage generation circuit 71 shown in FIG. 1, the positive power supply line 14 of the power supply 11 is connected to the first power supply line 23 and the input terminal 30 of the first gate voltage generation circuit 31, and the negative power supply line of the power supply 11. Reference numeral 12 is connected to the second power supply line 35 and the input terminal 36 of the second gate voltage generation circuit 33, and serves as a ground power supply. The output 25 from the temperature detection circuit 15 is connected to the input terminal 32 of the first gate voltage generation circuit 31 and the input terminal 34 of the second gate voltage generation circuit 33 to generate the first gate voltage. The output terminal 38 of the circuit 31 is connected to the gate 37 of the P-channel MOS transistor 41 which is the first MOS transistor, and the output terminal 40 of the second gate voltage generating circuit 33 is connected to the N-channel MOS transistor 53 which is the second MOS transistor. Each is connected to the gate 39. The source 47 of the P-channel MOS transistor 41, which is the first MOS transistor, is connected to the first power supply line 23, and the source 55 of the N-channel MOS transistor 53 is connected to the second power supply line 35, respectively.

  The temperature detection circuit 15 shown in FIG. 1 is inserted into the power supply line 23 and the power supply line 35 and is supplied with power from the power supply 11, but the temperature detection circuit 15 is not necessarily inserted into the power supply line 23 and the power supply line 35. There is no need to supply power to the temperature detection circuit 15 from another power source such as a voltage regulator.

  Further, the drain 43 of the P-channel MOS transistor 41 which is the first MOS transistor is connected to the first power supply line 23 through the resistance element 49 and is connected to the second power supply line 35 through the resistance element 45. is doing. Further, the drain 57 of the N-channel MOS transistor 53 is connected to the first power supply line 23 through the resistance element 59 and is connected to the second power supply line 35 through the resistance element 63. The connection point between the drain 43 of the P-channel MOS transistor 41, the resistance element 49, and the resistance element 45 forms the first output terminal 51 of the control voltage of the control voltage generation circuit 71, and the drain 57 of the N-channel MOS transistor 53. A connection point between the resistance element 59 and the resistance element 63 forms a second output terminal 61 of the control voltage of the control voltage generation circuit 71.

  In the frequency adjustment circuit 121 shown in FIG. 1, the capacitive element 81, the MIS variable capacitor 83, and the capacitive element 85 are connected in series, and the terminals of the capacitive element 81 that are not connected to the MIS variable capacitor 83 are The crystal oscillator 123 of the crystal oscillation circuit 131 and the inverter 125 are connected. The terminal of the capacitive element 85 that is not connected to the MIS variable capacitor 83 is connected to the ground power supply. Further, the capacitive element 87, the MIS variable capacitor 89 and the capacitive element 91, the capacitive element 101, the MIS variable capacitive capacitor 103 and the capacitive element 105, and the capacitive element 107, the MIS variable capacitive capacitor 109 and the capacitive element 111, The connection is made in the same manner as described above.

  The resistance elements 73, 75, 77, 79, 93, 95, 97, 99 of the frequency adjustment circuit 121 are for preventing high frequency current from the crystal oscillation circuit 131 from leaking to the control voltage generation circuit 71. . The capacitive elements 81, 85, 87, 91, 101, 105, 107, 111 have a control voltage applied to the MIS type variable capacitance capacitors 83, 89, 103, 109 from the control voltage generation circuit 71. Or to prevent leakage to the ground power source.

  The first output terminal 51 of the control voltage of the control voltage generation circuit 71 is connected to the connection point between the capacitive element 81 and the MIS variable capacitor 83 and the capacitive element 101 and the MIS variable capacitor via the resistance elements 75 and 95. 103 are connected to connection points, respectively. Similarly, the second output terminal 61 of the control voltage of the control voltage generation circuit 71 is connected to the connection point between the capacitive element 87 and the MIS variable capacitor 89 via the resistance elements 73 and 93, and the capacitive element 107 and the MIS type. Each is connected to a connection point of the variable capacitor 109.

  The output 29 of the variable voltage generation circuit 13 is connected to a connection point between the MIS variable capacitor 89 and the capacitor element 91 and a connection point between the MIS variable capacitor 109 and the capacitor element 111 via the resistance elements 77 and 97, respectively. Connected. The output 18 of the external voltage input terminal 17 is connected to the connection point between the MIS variable capacitor 83 and the capacitor element 85 and the connection point between the MIS variable capacitor 103 and the capacitor element 105 via the resistor elements 79 and 99, Is connected to each. In the crystal oscillation circuit 131 shown in FIG. 1, the feedback resistance element 127 and the crystal resonator 123 are both connected by being inserted between the input and output of the inverter 125.

  In the temperature detection circuit 15 shown in FIG. 1, as shown in FIG. 2, an N-channel MOS transistor 167 is inserted between the power supply line 23 and the power supply line 35, and the drain 169 is connected to the power supply line 23 via the resistance element 171. Is connected to the output 25 of the temperature detection circuit 15 at the same time. The resistance elements 161 and 163 are connected in series and are inserted between the power supply line 23 and the power supply line 35. The connection point 162 between the resistance elements 161 and 163 is connected to the gate 165 of the MOS transistor 167.

  In the control voltage generating circuit 71 shown in FIG. 1, the first gate voltage generating circuit 31 and the second gate voltage generating circuit 33 are connected to input terminals 30 and 34 and input terminals 32 and 36 as shown in FIG. N−1 resistance elements 135 (referred to as R1, R2,..., Rn−1 in FIG. 3) are connected in series, and a MOS transistor 137 as a switch element is connected to each of the connection points. Are connected to each other (referred to as MOST1, MOST2,..., MOSTn in FIG. 3), and a digital signal from the memory circuit 139 is applied to the gates of the MOS transistors to selectively turn on the MOS transistors. As a result, the voltage applied between the input terminals 30 and 34 and the input terminals 32 and 36 is arbitrarily divided and output to the output terminals 38 and 40.

  Hereinafter, the operation of the above-described temperature compensated oscillator will be described with reference to FIGS. 3, 4, and 5 in addition to FIGS. 1 and 2. The temperature detection circuit 15 detects the temperature of the crystal oscillation circuit 131 and outputs a temperature-dependent voltage to the input terminal 32 of the first gate voltage generation circuit 31 and the input terminal 34 of the second gate voltage generation circuit 33. To do. In the temperature detection circuit 15, the resistance elements 161 and 163 apply a voltage obtained by dividing the voltage applied between the power supply line 23 and the power supply line 35 to the gate 165 of the N-channel MOS transistor 167 as a gate voltage. The ratio of the resistance values of the resistance elements 161 and 163 is selected so that the gate voltage exceeds the threshold voltage of the N-channel MOS transistor 167.

  A drain current flows through the resistance element 171, and a voltage is output to the output 25 of the temperature detection circuit 15. Due to the temperature characteristics of N-channel MOS transistor 167, the drain current increases as the temperature increases, the voltage across resistance element 171 increases, and the voltage output to output 25 decreases as the temperature increases. That is, the output voltage of the temperature detection circuit 15 decreases in inverse proportion to the temperature. At this time, if the temperature gradient of the output voltage is insufficient, it may be amplified by an operational amplifier circuit.

  In the above-described example, the temperature detection circuit 15 has a single configuration example. However, the temperature detection circuit 15 includes a plurality of temperature detection circuits, and outputs thereof are the first gate voltage generation circuit 31 and the second gate. It may be distributed and input to the voltage generation circuit 33. Further, the first gate voltage generation circuit 31 and the second gate voltage generation circuit 33 are not essential, and the output voltage from the temperature detection circuit 15 is supplied to the gate 37 of the P-channel MOS transistor 41 as the first MOS transistor, You may input directly into the gate 39 of the N channel MOS transistor 53 which is a 2nd MOS transistor.

  As described above, the output voltage of the temperature detection circuit 15 decreases as the temperature rises, and the voltage at the output terminal 38 of the first gate voltage generation circuit 31 also depends on the voltage division ratio. It goes down with the rise. Since the output terminal 38 of the first gate voltage generation circuit 31 is connected to the gate 37 of the P-channel MOS transistor 41, the gate 37 of the P-channel MOS transistor 41 and the P-channel MOS transistor connected to the power supply line 23. The voltage difference between the source 47 of the transistor 41 and the source 47 increases as the temperature rises. When the voltage difference reaches a temperature T1 that exceeds the threshold voltage of the P-channel MOS transistor 41, the voltage difference passes through the drain 43 of the P-channel MOS transistor 41. Current begins to flow through the resistance element 45.

  As a result, when the temperature rises exceeding the temperature T1, the drain 43 of the P-channel MOS transistor 41 outputs a non-linear voltage to the first output terminal 51 of the control voltage of the control voltage generation circuit 71. When the temperature is equal to or lower than the T1 temperature, the P-channel MOS transistor 41 enters a cut-off state in which no current flows through its drain 43, and the voltage at the first output terminal 51 of the control voltage of the control voltage generation circuit 71 is A voltage obtained by dividing the voltage applied between the first power supply line 23 and the second power supply line 35 by the resistance element 45 becomes a constant value and does not depend on the temperature.

  On the other hand, since the output terminal 40 of the second gate voltage generation circuit 33 also has the same effect on the temperature, the gate 39 of the N-channel MOS transistor 53 and the source of the N-channel MOS transistor 53 connected to the ground power supply. The voltage difference from 55 decreases with increasing temperature (in other words, increases with decreasing temperature). When the temperature decreases and the voltage difference reaches the temperature T2 that exceeds the threshold voltage of the N-channel MOS transistor 53, current begins to flow to the resistance element 59 through the drain 57 of the N-channel MOS transistor 53.

  As a result, when the temperature decreases beyond the temperature T 2, the drain 57 of the N-channel MOS transistor 53 outputs a non-linear voltage to the second output terminal 61 of the control voltage of the control voltage generation circuit 71. When the temperature is equal to or higher than T2, the current does not flow to the drain 57 of the N-channel MOS transistor 53, and the voltage at the second output terminal 61 of the control voltage of the control voltage generating circuit 71 is the resistance element 59 and the resistance element. In 63, the voltage applied between the first power supply line 23 and the second power supply line 35 is a divided value, which is constant regardless of the temperature.

  FIG. 4 is a diagram showing the relationship between the output voltage of the first output terminal 51 and the output voltage of the second output terminal 61 and the temperature of the control voltage of the control voltage generation circuit 71 described above. In FIG. 4, a curve 141 indicates an output voltage with respect to the temperature of the first output terminal 51 of the control voltage of the control voltage generation circuit 71, and a curve 143 indicates the temperature of the second output terminal 61 of the control voltage of the control voltage generation circuit 71. The output voltage with respect to is shown. A point 145 on the curve 141 is the temperature T1, and in a temperature range lower than this temperature, the curve 141 is a portion 147 parallel to the temperature axis, and the output voltage is constant with respect to the temperature. This constant value is determined by the ratio of the resistance values of the resistance element 49 and the resistance element 45.

  A point 149 on the curve 143 is the temperature T2. In a temperature range higher than this temperature, the curve 143 is a portion 151 parallel to the temperature axis, and the output voltage is constant with respect to the temperature. This constant value is determined by the ratio of the resistance values of the resistance element 59 and the resistance element 63. As is clear from what has already been described, the output voltages in the range where the output voltage is constant with respect to temperature on the curves 141 and 143 can be selected independently of each other.

  The temperature T1 and the temperature T2 are determined by the output voltage of the first gate voltage generation circuit 31 and the output voltage of the second gate voltage generation circuit 33. Since these output voltages can be arbitrarily determined as described above, These output voltages are determined so that T1 is around 40 ° C. and T2 is around 10 ° C. Between the temperature T1 and the temperature T2, the output voltage of the first output terminal 51 of the control voltage of the control voltage generation circuit 71 and the output voltage of the second output terminal 61 of the control voltage of the control voltage generation circuit 71 are constant. It becomes the value of. In this way, the control voltage generation circuit 71 adds the output of the first output terminal 51 of the control voltage and the output voltage of the second output terminal 61 of the control voltage in a manner from the low temperature to the high temperature. A continuous third-order voltage is output as a control voltage in the temperature range.

  In the above description, the source 47 of the P-channel MOS transistor 41 is directly connected to the first power supply line 23. However, in order to limit the current flowing through the drain, the source 47 and the power supply line 23 are connected. A resistance element may be inserted between them. For the same purpose, a resistance element may be inserted between the source 55 of the N-channel MOS transistor 53 and the second power supply line 35.

  In the above-described embodiment, the first MOS transistor is a P-channel MOS transistor, but both the first MOS transistor and the second MOS transistor can be N-channel MOS transistors. However, in this case, the gradient of the output voltage with respect to the temperature of the first gate voltage generation circuit 31 is reversed (that is, the output voltage of the gate voltage generation circuit 31 increases with the temperature rise), and control is performed. The output voltage of the first output terminal 51 of the control voltage of the voltage generation circuit 71 is input to the electrodes on the opposite side of the MIS variable capacitors 83 and 103 of the frequency adjustment circuit 121. Further, both the first MOS transistor and the second MOS transistor can be constituted by P-channel MOS transistors.

  In this case, the output voltage of the second gate voltage generation circuit 33 is increased as the temperature rises, and the output voltage of the second output terminal 61 of the control voltage of the control voltage generation circuit 71 is the frequency adjustment circuit 121. The MIS type variable capacitors 89 and 107 are input to the opposite electrodes.

  In other words, when the first MOS transistor and the second MOS transistor are composed of the same conductivity type MOS transistor, the output voltage of the first gate voltage generation circuit 31 and the output of the second gate voltage generation circuit 33 The point that the gradient of the voltage with respect to the temperature is opposite to each other, and the point that the input of the control voltage is the electrode on the opposite side of the MIS type variable capacitor constituting the frequency adjustment circuit 121 is the same as in the above embodiment. Is different. In addition, since the effect | action itself acquired also with such a structure is the same, detailed description is abbreviate | omitted.

  On the other hand, the primary term voltage simply needs to change linearly with respect to temperature. There are several means to realize this, and an example will be described. The first means selects the temperature coefficient of the resistance element 49 and the resistance element 45 or the temperature coefficient of the resistance element 59 and the resistance element 63 to be different, and the ratio of the resistance values of the resistance element 49 and the resistance element 45; This is means for changing the ratio of the resistance values of the resistance element 59 and the resistance element 63 depending on the temperature.

  At this time, the sum of the degree of difference in temperature coefficient between the resistive element 49 and the resistive element 45 and the degree of difference in temperature coefficient between the resistive element 59 and the resistive element 63 determines the temperature gradient of the primary term voltage. And the temperature coefficient difference between the resistance element 45 and the temperature coefficient difference between the resistance element 59 and the resistance element 63 do not necessarily coincide with each other so that the primary term voltage has a desired temperature gradient. Select the degree of difference. By selecting in this way, the primary term voltage is automatically added to the voltage at the first output terminal 51 of the control voltage and the voltage at the second output terminal 61 of the control voltage.

  The second means is a means for configuring the power supply 11 with a voltage regulator having temperature characteristics, and giving the output voltage of the power supply 11 temperature characteristics. The temperature characteristics of this voltage regulator are determined by the temperature characteristics of the active elements and passive elements constituting the voltage regulator, and the circuit configuration, and these are appropriately selected so that the output voltage of the power source 11 has a desired temperature gradient. To be. Also in this case, as described above, the first-order voltage is automatically added to the voltage at the first output terminal 51 of the control voltage and the voltage at the second output terminal 61 of the control voltage.

  In addition to the above, various means for generating a first-order voltage can be considered. In short, as long as a voltage that changes linearly with respect to temperature can be added to the control voltage, the first and second means described above can be used. Obviously, the present invention is not limited to these. In this way, the control voltage generation circuit 71 uses the control voltage including not only the third-order voltage but also the first-order voltage as the control voltage, and the first output terminal 51 of the control voltage and the second output terminal 61 of the control voltage. Occurs.

  Next, the operation of the frequency adjustment circuit 121 to which the above-described control voltage is input will be described. FIG. 5 is a diagram showing the relationship between the applied voltage and the capacitance value of the MIS variable capacitors 83, 89, 103, and 109, which are voltage variable capacitors, constituting the frequency adjustment circuit 121. As shown in FIG. In the linear portion 153 of the curve 151 shown in FIG. 5, the applied voltage and the capacitance value of the voltage variable capacitance element change linearly. Further, the oscillation frequency of the crystal oscillation circuit 131 changes linearly with respect to the change in the capacitance value of the capacitive element constituting the load capacitance.

  Therefore, the voltage input to the frequency adjustment circuit 121, that is, the voltage applied to the MIS variable capacitors 83, 89, 103, and 109 is within the voltage range of the linear portion 153 of the curve 151 shown in FIG. A change in the voltage applied to the MIS variable capacitors 83, 89, 103, and 109 and a change in the oscillation frequency of the crystal oscillation circuit 131 are in a linear relationship. As long as this is the case, a control voltage including a third-order term voltage and a first-order term voltage with respect to the temperature is input to the frequency adjustment circuit 121 so that changes in the third-order term and the first-order term with respect to the temperature of the oscillation frequency of the crystal oscillation circuit 131 are eliminated. Thus, temperature compensation of the oscillation frequency of the crystal oscillation circuit 131 is performed.

  More specifically, the output voltage of the first output terminal 51 of the control voltage of the control voltage generation circuit 71 is applied to the MIS variable capacitors 89 and 109. When the temperature is equal to or higher than the T1 temperature, the frequency adjustment circuit 121 changes the oscillation frequency of the crystal oscillation circuit 131 so as to cancel the temperature change of the third-order term and the first-order term of the high-temperature portion of the oscillation frequency of the crystal oscillation circuit 131. When the temperature is equal to or lower than the temperature T1, the oscillation of the crystal oscillation circuit 131 The oscillation frequency of the crystal oscillation circuit 131 is changed so as to cancel only the temperature change of the first-order frequency.

  On the other hand, the output voltage at the second output terminal 61 of the control voltage of the control voltage generation circuit 71 is applied to the MIS variable capacitors 83 and 103. When the temperature is equal to or lower than T2, the frequency adjustment circuit 121 is the crystal oscillation circuit 131. The oscillation frequency of the crystal oscillation circuit 131 is changed so as to cancel the temperature change of the third-order term and the first-order term of the low-temperature portion of the oscillation frequency of the oscillation frequency. The oscillation frequency of the crystal oscillation circuit 131 is changed so as to cancel only the change.

  In this way, the output voltage of the first output terminal 51 of the control voltage of the control voltage generation circuit 71 is applied to the MIS variable capacitors 89 and 109 to compensate the temperature of the high temperature part, and the control voltage generation circuit 71 Since the output voltage of the second output terminal 61 of the control voltage is applied to the MIS variable capacitors 83 and 103 to perform temperature compensation in the low temperature portion, the voltage and capacitance value of each MIS variable capacitor are linearly related. Can be used independently for temperature compensation in the high temperature and low temperature regions.

  This will be described in more detail. Since the output voltage of the first output terminal 51 of the control voltage of the control voltage generation circuit 71 is applied to the MIS type variable capacitors 89 and 109 and only temperature compensation of the high temperature part is performed, the compensation action is the crystal oscillation circuit. The output voltage of the first output terminal 51 of the control voltage of the control voltage generation circuit 71 changes only in the direction of decreasing the oscillation frequency of 131 (that is, the direction of increasing the capacitance values of the MIS variable capacitors 89 and 109). Therefore, the resistance element 49 and the resistance element 45 are set so that the output voltage of the first output terminal 51 of the control voltage of the control voltage generation circuit 71 at the temperature T2 is in the vicinity of the point 157 below the curve 151 shown in FIG. Select the ratio of resistance values.

  On the other hand, since the output voltage of the second output terminal 61 of the control voltage of the control voltage generation circuit 71 is applied to the MIS variable capacitors 83 and 103 and only temperature compensation of the low temperature part is performed, the compensation action is quartz. The output voltage of the second output terminal 61 of the control voltage of the control voltage generation circuit 71 is only in the direction of increasing the oscillation frequency of the oscillation circuit 131 (that is, the direction of decreasing the capacitance values of the MIS variable capacitors 89 and 109). Therefore, the resistance element 59 and the resistance are set so that the output power of the second output terminal 61 of the control voltage of the control voltage generation circuit 71 at the temperature T1 is near the point 155 which is the upper part of the curve 151 shown in FIG. The ratio of the resistance values of the element 63 is selected.

  By selecting in this way, the linear portion 153 of the curve 151 shown in FIG. 5 that can be used for temperature compensation is effectively doubled and the temperature compensation capability is improved.

  Next, the operation of the 0th-order term voltage will be described. As the zero-order term voltage, an arbitrary constant voltage that does not depend on temperature is input to the frequency adjustment circuit 121. This voltage is output from the variable voltage generation circuit 13 to the output 29 and applied to the MIS variable capacitors 89 and 109 of the frequency adjustment circuit 121. However, at this time, the zero-order term voltage is applied to the electrodes of the MIS variable capacitors 89 and 109 to which the output voltage of the first output terminal 51 of the control voltage of the control voltage generation circuit 71 is not applied. . Since the voltage applied to the MIS variable capacitors 89 and 109 is the difference between the voltages applied to both electrodes of the MIS variable capacitors 89 and 109, the change in the zero-order term voltage is caused by the crystal oscillation circuit 131. Change the oscillation frequency.

  The description of the action of the external input voltage input from the external voltage input terminal 17 is the same as the 0th-order term voltage, and is therefore omitted.

  The temperature compensated oscillator according to the present invention has been described with reference to the embodiments. However, the above embodiments are merely examples for carrying out the present invention, and the present invention is not limited thereto. It is apparent from the above description that various modifications of these embodiments are within the scope of the present invention, and that various other embodiments are possible within the scope of the present invention.

  The present invention provides a temperature compensated oscillator having a simple circuit configuration, suitable for miniaturization, easy adjustment, and greater temperature compensation capability.

1 is a block circuit diagram showing an embodiment of a temperature compensated oscillator according to the present invention. FIG. 2 is a block circuit diagram illustrating a specific configuration example of a temperature detection circuit 15 in FIG. 1. FIG. 3 is a block circuit diagram illustrating a specific configuration example of a first gate voltage generation circuit 31 and a second gate voltage generation circuit 33 in FIG. 1. FIG. 6 is a curve diagram showing the relationship between the output voltage of the first output terminal 51 and the output voltage of the second output terminal 61 and the temperature of the control voltage of the control voltage generation circuit 71 in FIG. 1. FIG. 2 is a curve diagram showing the relationship between the applied voltage and the capacitance value of MIS variable capacitors 83, 89, 103, and 109 constituting the frequency adjustment circuit 121 in FIG. It is a block diagram which shows the 1st structural example of the conventional temperature compensation type | mold oscillator. It is a block diagram which shows the 2nd structural example of the conventional temperature compensation type | mold oscillator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Power supply 13 Variable voltage generation | occurrence | production circuit 15 Temperature detection circuit 23 1st power supply line 31 1st gate voltage generation circuit 33 2nd gate voltage generation circuit 35 2nd power supply line 41 P channel MOS transistors 45, 49, 59, 63 Resistance element 51, 61 Output terminal 53 N-channel MOS transistor 71 Control voltage generation circuit 83, 89, 103, 109 MIS type variable capacitor 121 Frequency adjustment circuit 123 Crystal oscillator 131 Crystal oscillation circuit

Claims (5)

A power source, a crystal oscillation circuit, a temperature detection circuit that detects a temperature in the vicinity of the crystal oscillation circuit and generates an output voltage, and an output voltage from the temperature detection circuit is input to obtain a third-order voltage as a control voltage. A control voltage generation circuit that generates, and a frequency adjustment circuit that receives the control voltage from the control voltage generation circuit and adjusts the oscillation frequency of the crystal oscillation circuit,
The control voltage generation circuit includes first and second active elements that output a non-linear voltage based on the output voltage output from the temperature detection circuit,
Each of the first and second active elements is inserted through a resistance element between first and second power supply lines for supplying power from the power supply,
The output terminal of the first active element is a first output terminal of the control voltage, and the output terminal of the second active element is a second output terminal of the control voltage. Temperature compensated oscillator. The first and second active elements are both MOS transistors,
2. The MOS transistor according to claim 1, wherein an output voltage from the temperature detection circuit is input to a gate, and a drain is connected to at least one of the two power supply lines via the resistance element. 2. The temperature compensated oscillator according to 1. The frequency adjustment circuit has a plurality of voltage variable capacitance elements constituting a load capacitance of the crystal oscillation circuit,
A control voltage output from the first output terminal and a control voltage output from the second output terminal are distributed and applied to the plurality of voltage variable capacitance elements. The temperature compensated oscillator according to claim 1 or 2. The control voltage generation circuit includes first and second third-order voltage generation circuits and a variable voltage generation circuit,
The control voltage generation circuit includes a first control voltage of a third-order voltage generated by the first third-order voltage generation circuit and a second control of a third-order voltage generated by the second third-order voltage generation circuit. A third control voltage of a first-order voltage generated based on the voltage, an output voltage of the temperature detection circuit, and a fourth control voltage of a zero-order term voltage generated based on the output voltage of the variable voltage generation circuit; Outputting a fifth control voltage of the external input voltage to the frequency adjustment circuit;
The temperature compensation type according to any one of claims 1 to 3, wherein the frequency adjustment circuit controls an oscillation frequency of the crystal oscillation circuit based on the first to fifth control voltages. Oscillator. The frequency adjustment circuit is a voltage variable capacitance element that constitutes a load capacitance of the crystal oscillation circuit, and includes first and second voltage variable capacitance elements whose capacitance values are changed by the first to fifth control voltages. Prepared,
The first control voltage is applied to one electrode of the first voltage variable capacitor, while the second control voltage is applied to one electrode of the second voltage variable capacitor;
The fourth control voltage and the fifth control voltage are separated and applied to the other electrode of the first voltage variable capacitance element and the other electrode of the second voltage variable capacitance element. The temperature compensated oscillator according to claim 4, wherein the temperature compensated oscillator is provided.

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