JP5321715B2 - Oscillator, semiconductor device, electronic device, and watch - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress power consumption of an oscillator including a crystal oscillating circuit, a semiconductor device, an electronic apparatus, or the like as a whole. <P>SOLUTION: An oscillator comprises: a constant voltage generating circuit that includes a first constant current source for generating a first constant current and a constant voltage controlling transistor energized with the first constant current for generating a constant voltage; a crystal oscillating circuit that is oscillated and driven by the constant voltage supplied from the constant voltage generating circuit. The constant voltage has a first slope that varies in response to the first constant current in an operation guaranteed temperature range. In the crystal oscillating circuit, an oscillation stop voltage in the operation guaranteed temperature range has a second slope. The first slope is set so as to minimize a sum of current consumption of the crystal oscillating circuit that has a correlation with a difference between the first slope and the second slope and current consumption of the constant voltage generating circuit that has a correlation with a magnitude of the first constant current. The first constant current is set to a value that causes the constant voltage controlling transistor to be operated in a sub-threshold region. <P>COPYRIGHT: (C)2013,JPO&amp;INPIT

Description

  The present invention relates to an oscillation device, a semiconductor device, an electronic device, and a timepiece.

  There is known an oscillation device including a constant voltage generation circuit that generates a constant voltage and a crystal oscillation circuit that oscillates a crystal resonator using the generated constant voltage. Such an oscillating device is widely used in watches, mobile phones, computer terminals, and the like. Such an oscillating device is required to suppress power consumption particularly when mounted in a mobile device such as a mobile phone.

  Since the power consumption of the crystal oscillation circuit increases as the constant voltage for driving the crystal oscillation circuit increases, it is desirable to reduce the constant voltage as much as possible from the viewpoint of power consumption. On the other hand, the crystal oscillation circuit has an oscillation stop voltage determined by an inverter used in the crystal oscillation circuit, characteristics of the crystal resonator to be oscillated, a load capacity, and the like. It is known that the oscillation stop voltage linearly decreases with a predetermined slope as the temperature rises in a general guaranteed operating temperature range (for example, −40 ° C. to 80 ° C.). Since the oscillation operation of the crystal oscillation circuit stops when the supplied constant voltage falls below the oscillation stop voltage, the constant voltage must always be set to be equal to or higher than the oscillation stop voltage in the operation guarantee temperature range.

  Here, in the guaranteed operating temperature range, the constant voltage temperature change is the same as the oscillation stop voltage temperature change, that is, the slope of the constant voltage with respect to the temperature change is the same as the slope of the oscillation stop voltage with respect to the temperature change. A technique is known (for example, Patent Document 1). In this way, the constant voltage can be reduced as much as possible above the oscillation stop voltage over the entire guaranteed operating temperature range, and the power consumption of the crystal oscillation circuit can be reduced.

Japanese Patent Laid-Open No. 10-538358

  However, in the above technique, current consumption in the constant voltage generation circuit is not taken into consideration. For this reason, even if the power consumption of the crystal oscillation circuit can be reduced, the power consumption in the constant voltage generation circuit increases, and as a result, the power consumption of the entire electronic circuit may increase. For example, in the above technique, in the constant voltage generation circuit, a relatively high current is passed through the constant voltage control transistor so that the constant voltage control transistor operates in a region that greatly exceeds the threshold value Vth.

  The present invention has been made in view of the above problems, and an object of the present invention is to reduce the power consumption of an oscillation device, a semiconductor device, an electronic device, and the like including a constant voltage generation circuit and a crystal oscillation circuit as a whole.

  In order to solve the above problems, a first aspect of the present invention provides an oscillation device. The oscillation device according to the first aspect includes a constant voltage generation circuit and a crystal oscillation circuit. The constant voltage generation circuit includes: a first constant current source that generates a first constant current; and a constant voltage control transistor that generates a constant voltage when the first constant current is supplied. , Having a first slope with respect to a temperature change, and the first slope varies in accordance with the first constant current. The crystal oscillation circuit is a crystal oscillation circuit that is oscillated and driven by a constant voltage supplied from the constant voltage generation circuit, and an oscillation stop voltage that is a lower limit value of the constant voltage that can be oscillated is 2 slopes. In the stop circuit, the first slope is correlated with the consumption current of the crystal oscillation circuit having a correlation with the difference between the first slope and the second slope, and the magnitude of the first constant current. The sum of the constant voltage generation circuit and the current consumption is determined to be a minimum. According to the oscillation device according to the first aspect, the power consumption of the entire oscillation device can be suppressed.

  In the oscillation device according to the first aspect, the first constant current may be set to a value that causes the constant voltage control transistor to operate in a subthreshold region. By doing so, the current consumption of the constant voltage generation circuit can be made extremely small, so that the power consumption of the entire oscillation device can be suppressed.

  The oscillation device according to the first aspect further includes an intermittent control unit that intermittently operates the first inclination, and the first constant current is a current consumption of the crystal oscillation circuit, and during the intermittent operation. It may be determined so that the sum of the current consumption of the constant voltage generation circuit is minimized. By doing so, the current consumption of the constant voltage generation circuit can be suppressed by the intermittent operation, and therefore the first slope can be set to make the current consumption of the crystal oscillation circuit smaller. As a result, the power consumption of the entire oscillation device can be further suppressed.

  In the oscillation device according to the first aspect, the constant voltage generation circuit may include a plurality of transistors, and at least one transistor selected from the plurality of transistors may be used as the constant voltage control transistor. .

  A second aspect of the present invention provides an oscillation device. The oscillation device according to the first aspect includes a constant voltage generation circuit, a crystal oscillation circuit, and a constant current circuit. The constant voltage generation circuit includes: a first constant current source that generates a first constant current with reference to a reference voltage; and a constant voltage control transistor that generates a constant voltage when the first constant current is energized. In addition, the constant voltage has a first slope with respect to a temperature change, and fluctuates according to the first constant current. The crystal oscillation circuit is a crystal oscillation circuit that is oscillated and driven by a constant voltage supplied from the constant voltage generation circuit, and an oscillation stop voltage that is a lower limit value of the constant voltage that can be oscillated is 2 slopes. The constant current circuit generates a second constant current using a constant current control transistor, and generates the reference voltage using the second constant current. In the oscillation device, the first inclination is correlated with a consumption current of the crystal oscillation circuit having a correlation with a difference between the first inclination and the second inclination, and a magnitude of the first constant current. It is determined that the sum of the current consumption of the constant voltage generation circuit and the current consumption of the constant current circuit having a correlation with the magnitude of the second constant current is minimized. According to the oscillation device according to the second aspect, the power consumption of the entire oscillation device can be suppressed.

  In the oscillation device according to the second aspect, the first constant current is set to a value that causes the constant voltage control transistor to operate in a subthreshold region, and the first slope is the subthreshold value of the constant current control transistor. It may be set to a value that operates in the area. By doing so, the current consumption of the constant voltage generation circuit and the constant current circuit can be made extremely small, so that the power consumption of the entire oscillation device can be suppressed.

  The oscillation device according to the second aspect further includes an intermittent control unit that intermittently operates the first constant current source and the constant current circuit, and the first inclination is a current consumption of the crystal oscillation circuit. And the sum of the current consumption of the constant voltage generation circuit during the intermittent operation and the current consumption of the constant current circuit during the intermittent operation may be set to a minimum. In this way, since the current consumption of the constant voltage generation circuit and the constant current circuit can be suppressed by the intermittent operation, the first slope can be set to make the current consumption of the crystal oscillation circuit smaller. As a result, the power consumption of the entire oscillation device can be further suppressed.

  In the oscillation device according to the above aspect, the constant voltage at the upper limit temperature of the guaranteed operating temperature range may be set to an oscillation start voltage of the crystal oscillation circuit at the upper limit temperature, and the upper limit temperature of the guaranteed operating temperature range may be set. The constant voltage may be set to a value obtained by adding a noise margin to the oscillation start voltage of the crystal oscillation circuit at the upper limit temperature. In addition, the constant voltage includes a first value obtained by adding a noise margin to the oscillation start voltage of the crystal oscillation circuit at all temperatures in the guaranteed operating temperature range, the constant voltage at the upper limit temperature of the guaranteed operating temperature range, It may be set between a second value obtained by adding the first value to the constant voltage difference at the lower limit temperature of the guaranteed operating temperature range. In this way, the current consumption of the crystal oscillation circuit can be minimized within a range where the operation of the crystal oscillation circuit does not stop.

  In the oscillation device according to the above aspect, the difference between the constant voltage at the lower limit temperature of the guaranteed operating temperature range and the oscillation stop voltage at the lower limit temperature may be 0.4 volts or less, and the lower limit of the guaranteed operating temperature range The difference between the constant voltage at the temperature and the oscillation stop voltage at the lower limit temperature is less than or equal to twice the difference between the constant voltage at the upper limit temperature of the operation guaranteed temperature range and the oscillation stop voltage at the upper limit temperature. good.

  The present invention can be realized in various aspects in addition to the above aspect. For example, the present invention is realized as a semiconductor device including the oscillation device according to the above aspect. The present invention also includes an electronic device that includes the oscillation device according to the above aspect or the semiconductor device and generates an operation reference signal using the oscillation output of the oscillation device, or the oscillation device according to the above aspect or the semiconductor device. And a clock that generates a time reference signal using the oscillation output of the oscillation device.

Explanatory drawing which shows schematic structure of an oscillation apparatus. Explanatory drawing which shows the internal structure of a constant current circuit. Explanatory drawing which shows the internal structure of a regulator. Explanatory drawing which shows the internal structure of a crystal oscillation circuit. The figure which shows the temperature characteristic of an oscillation apparatus. The figure explaining the characteristic of a constant voltage control transistor. FIG. 5 is a first diagram illustrating optimization of temperature characteristics of the oscillation device according to the first embodiment. FIG. 6 is a second diagram for explaining optimization of temperature characteristics of the oscillation device according to the first embodiment. FIG. 6 is a third diagram for explaining optimization of temperature characteristics of the oscillation device according to the first embodiment. The figure which shows the structure of the regulator in 2nd Example. The figure which shows the structure of the regulator in 3rd Example. The timing chart which shows an intermittent operation signal. The figure explaining optimization of the temperature characteristic of the oscillation apparatus in 3rd Example. The figure which shows an example of the constant current circuit which can be intermittently operated.

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

A. First embodiment:
・ Configuration of oscillator:
The oscillator according to the first embodiment will be described with reference to FIGS. FIG. 1 is an explanatory diagram showing a schematic configuration of the oscillation device. FIG. 2 is an explanatory diagram showing the internal configuration of the constant current circuit. FIG. 3 is an explanatory diagram showing the internal configuration of the regulator. FIG. 4 is an explanatory diagram showing the internal configuration of the crystal oscillation circuit. As shown in FIG. 1, the oscillation device 100 includes a constant current circuit 230, a regulator 210, a crystal oscillation circuit 110, and a control circuit 220.

  The constant current circuit 230 generates constant currents Iref1 and Iref2 as described later, and generates a reference voltage Vref using the generated constant current. As shown in FIG. 2, the constant current circuit 230 is supplied with a high potential side power source VD and a low potential side power source VS. The constant current circuit 230 includes a depletion type N-channel field effect transistor M11 whose source and gate are connected to the low potential side power source VS. The transistor M11 functions as a constant current source that generates the constant current Iref1. The constant current Iref1 is set to about 5 nA to 12 nA (nanoampere), for example. An enhancement type P-channel field effect transistor M12 is disposed between the drain of the transistor M11 and the high potential side power source VD. In the following, an N-channel field effect transistor will be referred to as an n-transistor, a P-channel field effect transistor will be referred to as a p-transistor, and unless otherwise specified, it is an enhancement type transistor.

  The constant current circuit 230 further includes a p-transistor M13 and an n-transistor M14. The source of the p-transistor M13 is connected to the high potential side power source VD. The n transistor M14 is disposed between the drain of the p transistor M13 and the low potential power source VS. The p-transistor M13 forms a current mirror with the p-transistor M12 described above. As a result, the constant current Iref2 is passed through the p transistor M13 and the n transistor M14 connected in series. The constant current Iref2 is, for example, a value that is approximately three times that of Iref1. The n-transistor M14 is diode-connected, and the drain-source voltage of the n-transistor M14 is kept constant. As a result, a potential obtained by adding the drain-source voltage of the n-transistor M14 to the potential of the low potential side power supply VS is output as the reference voltage Vref. A capacitor C1 is disposed as a stabilizing capacitor between the output node of Vref and the low potential side power supply VS.

  The regulator 210 is a constant voltage generation circuit that generates the constant voltage VR with reference to the reference voltage Vref supplied from the constant current circuit 230. The regulator 210 includes a differential amplifier circuit 2101 and an output circuit 2102.

  The differential amplifier circuit 2101 includes an n-transistor M21 that functions as a constant current source, two n-transistors M22 and M23 that form a differential pair, and two p-transistors M24 and M25 that form a current mirror. . The reference voltage Vref described above is input to the gate of the n-transistor M21, and as a result, a constant current I1 is generated. In this embodiment, the constant current I1 is the same as the constant current Iref1 described above.

  The output circuit 2102 includes an n-transistor M31 that functions as a constant current source, a p-transistor M32 that is diode-connected, and a p-transistor M33 that functions as an output transistor. The three transistors M31 to M33 are arranged in series in the order of the signs from the low potential side power supply VS side between the low potential side power supply VS and the high potential side power supply VD. The reference voltage Vref described above is input to the gate of the n-transistor M31, and as a result, a constant current I2 is generated. The constant current I2 is set to 50 nA in this embodiment. The value of the constant current I2 has an important meaning for suppressing the power consumption of the oscillation device 100, and will be described in detail later.

  The differential amplifier circuit 2101 is a circuit that amplifies and outputs the difference between the voltage input to the first input terminal and the voltage input to the second input terminal. The reference voltage Vref is input to the gate of the n-transistor M22 that is the first input terminal of the differential amplifier circuit 2101. The drain voltage FB of the n-transistor M31 is input to the gate of the n-transistor M23 that is the second input terminal of the differential amplifier circuit 2101. The drain voltage of the p-transistor M24 that is the output of the differential amplifier circuit 2101 is input to the gate of the p-transistor M33 of the output circuit 2102. As a result, the drain current of the p-transistor M33 is controlled so that the reference voltage Vref and the drain voltage FB of the n-transistor M31 in the output circuit 2102 are the same (Vref = FB). As a result, the constant voltage VR output from the output node of the output circuit 2102 (the source of the p transistor M33) is set to a value obtained by adding the source-drain voltage Vds of the p transistor M32 to the reference voltage Vref (VR = Vref + Vds). ). Thus, since the value of the constant voltage VR depends on the characteristics of the p-transistor M32, the p-transistor M32 is also referred to as a constant-voltage control transistor in this specification.

  The regulator 210 includes capacitors C2, C3, and C4. The capacitor C2 is disposed between the reference voltage input node and the low-potential side power supply VS as a stabilization capacitor for the reference voltage Vref. The capacitor C3 has a phase compensation capacitance between the output node of the differential amplifier circuit 2101 (the drain of the p transistor M24 and the gate of the p transistor M33) and the output node of the output transistor (the source of the p transistor M33). Is arranged. The capacitor C4 is disposed between the output node of the constant voltage VR and the low-potential side power supply VS as a stabilization capacitor of the constant voltage VR.

  The crystal oscillation circuit 110 is a circuit that oscillates the crystal resonator 500. The crystal oscillation circuit 110 is supplied with a constant voltage VR and a low-potential-side power source VS, and is driven to oscillate using the constant voltage VR. The crystal oscillation circuit 110 includes an inverter 1101 and a feedback circuit 1102. The feedback circuit 1102 includes a gate terminal 111 connected to one end of the crystal resonator 500, a drain terminal 112 connected to the other end of the crystal resonator 500, a feedback resistor Rf, an output resistor Rd, and a phase compensation capacitor. Contains Cac. The feedback circuit 1102 inverts the phase of the drain output of the inverter 1101 by 180 degrees and inputs the feedback to the gate of the inverter 1101. The inverter 1101 includes a pair of p-transistor M41 and n-transistor M42 whose drains are connected to each other. The inverter 1101 is disposed between the low-potential side power source VS and the constant voltage VR, and is driven by being supplied with electric power due to the potential difference between the two. In the crystal oscillation circuit 110 having the above configuration, when a constant voltage VR is applied to the inverter 1101, the transistor pairs constituting the inverter 1101 are alternately turned on and off, and finally the crystal resonator 500 performs a stable oscillation operation. To do. As a result, an oscillation signal FS having a predetermined frequency is output from the output node of the crystal oscillation circuit 110 (the drain of the inverter 1101). In the crystal oscillation circuit 110, capacitors CG and CD are arranged as oscillation stabilization capacitors between the gate terminal 111 and the low potential power source VS and between the drain terminal 112 and the low potential power source VS, respectively. Has been.

  The control circuit 220 receives the oscillation signal FS and divides or multiplies the oscillation signal FS to generate a clock signal having a desired frequency. The clock signal generated by the oscillation device 100 is supplied to, for example, the central processing unit 600 of an electronic device in which the oscillation device 100 is mounted. For example, the central processing unit 600 uses the supplied clock signal as an operation reference signal for the central processing unit 600 itself or other circuits or semiconductor devices controlled by the central processing unit 600. Alternatively, the central processing unit 600 implements a clock function and a time measurement function, for example, using the supplied clock signal as a time reference signal. Examples of electronic devices on which the oscillation device 100 is mounted include mobile devices such as mobile phones and laptop computers, and home appliances such as videos, DVDs, game devices, and personal computers. In this embodiment, the oscillation device 100 is formed as a semiconductor device using a semiconductor manufacturing technique. The oscillation device 100 may be formed as the same semiconductor device as the central processing unit 600, or may be formed as a semiconductor device separate from the central processing unit 600 and connected to the central processing unit 600 via an interface. good.

・ Temperature characteristics of the oscillator:
Next, temperature characteristics of the oscillation device 100 will be described with reference to FIGS. FIG. 5 is a diagram illustrating temperature characteristics of the oscillation device 100. FIG. 6 is a diagram for explaining the characteristics of the constant voltage control transistor. In the crystal oscillation circuit 110, there is an oscillation stop voltage VI determined by the characteristics of the crystal resonator 500 used, the characteristics of the inverter 1101, the capacitors CG, CD, and the like. The oscillation stop voltage VI is a lower limit value of the constant voltage VR that can be oscillated by the crystal oscillation circuit 110. When the constant voltage VR is lower than the oscillation stop voltage VI, the oscillation operation of the crystal oscillation circuit 110 is stopped. On the other hand, the power consumption of the crystal oscillation circuit 110 depends on the constant voltage VR, and increases as the constant voltage VR increases. In order to drive the crystal oscillation circuit 110 with low power consumption, it is desirable to set the value of the supplied constant voltage VR as small as possible. Therefore, it is desirable that the constant voltage VR supplied from the regulator 210 to the crystal oscillation circuit 110 is set to a value that is larger than the oscillation stop voltage VI and as small as possible.

  As shown in FIG. 5, it is known that the oscillation stop voltage VI of the crystal oscillation circuit 110 decreases linearly with respect to a temperature change. The oscillation stop voltage VI at the lower limit temperature T0 (−40 ° C. in this embodiment) of the predetermined guaranteed operating temperature is VI (T0), and the oscillation stop voltage VI at the upper limit temperature T1 (85 ° C. in this embodiment) is VI ( T1). A variation amount of the oscillation stop voltage VI with respect to a temperature change is represented by ΔVI = VI (T1) −VI (T0). ΔVI corresponds to the magnitude of the slope of the straight line representing the temperature characteristics of the oscillation stop voltage VI.

  In this embodiment, the temperature characteristic of the constant voltage VR is adjusted as shown in FIG. The constant voltage VR decreases linearly with respect to the temperature change as shown in FIG. The constant voltage VR at the lower limit temperature T0 of the predetermined guaranteed operating temperature is expressed as VR (T0), and the constant voltage VR at the upper limit temperature T1 is expressed as VR (T1). A variation amount of the constant voltage VR with respect to a temperature change is ΔVR = VR (T1) −VR (T0). ΔVR corresponds to the magnitude of the slope of the straight line representing the temperature characteristic of the constant voltage VR.

  Here, the main factor that determines the fluctuation amount ΔVR corresponding to the slope of the constant voltage VR will be described. FIG. 6 shows the relationship between the absolute value | Vgs | of the gate-source voltage in the constant voltage control transistor M32 described above included in the output circuit 2102 of the regulator 210 and the constant current I2 energized between the drain and source. It is shown. FIG. 6 shows a | Vgs | -I2 curve at the lower limit temperature T0 and a | Vgs | -I2 curve at the upper limit temperature T1.

  Here, when the constant current I2 is constant at Ib, the absolute value | ΔVgs (Ib) | of the fluctuation amount of the gate-source voltage between the lower limit temperature T0 and the upper limit temperature T1 is shown in FIG. It is expressed by the width. On the other hand, when the constant current I2 is Ia lower than Ib, the absolute value | ΔVgs (Ia) | of the fluctuation amount of the gate-source voltage between the limit temperature T0 and the upper limit temperature T1 is shown in FIG. Expressed in width. As can be seen, the absolute value | ΔVgs | of the fluctuation amount of the gate-source voltage with respect to the temperature change increases as the constant current I2 to be applied decreases, and decreases as it increases.

  Since the constant voltage control transistor M32 is diode-connected as shown in FIG. 3, the gate-source voltage and the drain-source voltage are equal (Vgs = Vds). Since VR = Vref + Vds as described above, assuming that Vref is constant, ΔVR = ΔVds = ΔVgs. Therefore, the absolute value | ΔVR | of the fluctuation amount with respect to the temperature change of the constant voltage VR and the absolute value of the slope of the straight line representing the temperature change of the constant voltage VR become larger as the energizing constant current I2 becomes smaller and becomes smaller as it becomes larger. I understand that

Optimization of Temperature Characteristics of Oscillation Device A method for optimally setting the temperature characteristics of the oscillation device 100 as described above will be described with reference to FIGS. Here, the purpose of optimizing the temperature characteristics of the oscillation device 100 is to operate the oscillation device without stopping at all temperatures within the guaranteed operating temperature range, and to reduce the current consumption of the oscillation device 100 as much as possible. is there. The policy for this is as follows.
1. The constant voltage VR (T1) at the upper limit temperature T1 is set to the oscillation start voltage Vs (T1) + the noise margin voltage Vn at the upper limit temperature T1.
2. In order to suppress the current consumption of the crystal oscillation circuit 110, the inclination of the constant voltage VR with respect to the temperature change (corresponding to ΔVR) is made as close as possible to the inclination of the oscillation stop voltage VI with respect to the temperature change (corresponding to ΔVI).
3. In order to suppress the current consumption of the regulator 210, the constant current I2 is made as small as possible.

  Here, the oscillation stop voltage VI is a voltage at which the oscillating crystal oscillation circuit 110 stops oscillating, whereas the oscillation start voltage Vs is a voltage at which the stopped crystal oscillation circuit 110 starts oscillating. It is. The oscillation start voltage Vs is about the oscillation stop voltage VI + 0.1V. The noise margin voltage Vn is a margin provided in consideration of fluctuation of the constant voltage VR due to noise, and is about 0.1 V in this embodiment. Therefore, in this embodiment, VR (T1) is set to VI (T1) + 0.4V. This setting can be realized by selecting a transistor having an appropriate threshold voltage Vth as the constant voltage control transistor M32 in accordance with the magnitude of the constant current I2. Thus, when VR (T1) is set, the constant voltage VR is a value VRmin obtained by adding the noise margin Vn to the oscillation start voltage Vs of the crystal oscillation circuit 110 and the upper limit temperature T1 at all temperatures in the guaranteed operating temperature range. It is set between the constant voltage VR (T1) and a value VRmax obtained by adding VRmin to the difference between the constant voltage VR (T0) at the lower limit temperature T0 (Vs + Vn ≦ VR ≦ Vs + Vn + (VR (T0) −VR (T1)). .

  Further, the second policy and the third policy are in conflict with each other as can be understood from the temperature characteristics described above. That is, if ΔVR is reduced to approach ΔVI, the consumption current of regulator 210 increases. For this reason, selection of the constant voltage control transistor M32 and setting of the constant current I2 are important in optimizing the temperature characteristics of the oscillation device 100.

  FIG. 7 shows the relationship between the constant current I2 and the constant voltage VR when one p-transistor is used as the constant voltage control transistor M32, and the absolute value of the fluctuation amount with respect to the temperature change of the constant current I2 and the constant voltage VR. The relationship with ΔVR | is shown. FIG. 7 shows the constant voltage VR (T0) at the lower limit temperature T0 and the constant voltage VR (T1) at the upper limit temperature T1 as the relationship between the constant current I2 and the constant voltage VR. When the constant voltage control transistor M32 is used, the constant current I2 can be set in the constant current setting range shown in the figure, but the constant current I2 with VR (T1) as Vs (T1) + noise margin voltage is shown in FIG. Ix shown in FIG.

  FIG. 8 shows | ΔVR | and crystal oscillation circuit 110 when VR (T1) is set to Vs (T1) + noise margin voltage while appropriately changing the transistor used for constant voltage control transistor M32 and constant current I2. The relationship between the consumption current Iosc and the relationship between | ΔVR | and the consumption current Ireg of the regulator 210 are shown. The consumption current Iosc and the consumption current Ireg used the consumption current at the median value t (25 ° C. = normal temperature in this embodiment) of the guaranteed operating temperature range.

  In FIG. 8, as shown by the wavy line on the right side, when the constant current I2 is made too small, | ΔVR | becomes larger than | ΔVI |, and as shown in FIG. 9A, the slope of the constant voltage VR However, it becomes larger than the slope of the oscillation stop voltage VI. The consumption current Iosc at the temperature t of the crystal oscillation circuit 110 has a correlation with the difference between | ΔVR | and | ΔVI |, and the consumption current Iosc increases as the difference increases. That is, if the difference between | ΔVR | and | ΔVI | is large, the constant voltage VR becomes larger than necessary at the temperature t. Therefore, although the current consumption Ireg of the regulator 210 is small, the current consumption Iosc of the crystal oscillation circuit 110 is large, and the current consumption of the entire oscillation device 100 is large.

  On the other hand, in FIG. 8, if the constant current I2 is set large as shown by the left wavy line, | ΔVR | and | ΔVI | can be made equal as shown in FIG. 9B. In this way, the constant voltage VR can be minimized at the temperature t. However, the consumption current Ireg of the regulator 210 is naturally correlated with the magnitude of the constant current I2, and the consumption current Ireg increases as the constant current I2 increases. Although the current consumption Iosc of the crystal oscillation circuit 110 can be minimized, the current consumption Ireg of the regulator 210 increases, and the current consumption of the entire oscillation device 100 increases.

  In the present embodiment, as shown by the middle wavy line in FIG. 8, by optimizing the constant voltage control transistor M32 and the constant current I2, the sum of the current consumption Iosc of the crystal oscillation circuit 110 and the current consumption Ireg of the regulator 210 is obtained. | ΔVR | aim is set so that is minimized.

  According to the present embodiment described above, the sum of the consumption current Iosc of the crystal oscillation circuit 110 and the consumption current Ireg of the regulator 210 can be minimized, and as a result, the consumption current of the entire oscillation device 100 can be suppressed. Specifically, in this embodiment, the constant current I2 of the regulator 210 is suppressed to a level of several tens of nA. When the constant voltage control transistor M32 is energized, the low current of this low level causes the constant voltage control transistor M32 to operate in a region near the threshold voltage Vth or in a region below the threshold voltage Vth, a so-called subthreshold region.

B. Second embodiment:
A second embodiment will be described with reference to FIG. In the oscillation device in the second embodiment, the difference from the first embodiment is the configuration of the regulator. The other configuration is the same as that of the first embodiment, and a description thereof will be omitted. FIG. 10 is a diagram showing the configuration of the regulator in the second embodiment. The regulator 210a in the second embodiment is different from the regulator 210 in the first embodiment in that a plurality of constant voltage control transistors M32a to M32d can be selected instead of one constant voltage control transistor M32 in the output circuit 2102a. It is a point provided.

  Specifically, the plurality of constant voltage control transistors M32a to M32d are connected in series with p transistors SWa to SWd that function as switches, respectively. Each set of the constant voltage control transistor and the switching transistor is connected in parallel. Selection signals XTa to XTd are input from the control circuit 220 to the gates of the switching transistors SWa to SWd, and are switched on and off. The plurality of constant voltage control transistors M32a to M32d include a plurality of types of transistors having different current amplification factors β. The current amplification factor β can be set to an arbitrary value by changing the gate width W and the gate length L of the transistor. Of the plurality of constant voltage control transistors M32a to M32d, a transistor connected in series with the turned-on switching transistor is used to control the value of the constant voltage VR. Since the other structure of the regulator 210a is the same as that of the regulator 210 in the first embodiment, the same components are denoted by the same reference numerals in FIG. 10 as those in FIG.

  According to the oscillation device in the second embodiment, the value of the constant voltage VR can be finely adjusted by selectively using one or a plurality of transistors from the plurality of constant voltage control transistors M32a to M32d. . That is, the constant voltage VR that is output increases as the transistor having a small current amplification factor β is selected, and the constant voltage VR that is output decreases as the transistor having a large current amplification factor β is selected.

  As a result, for example, the constant voltage VR can be finely adjusted to minimize power consumption as the oscillation stop voltage VI of the crystal oscillation circuit 110 varies slightly depending on the type of the crystal resonator 500. it can.

C. Third embodiment:
With reference to FIG. 11 to FIG. 13, the oscillation device in the third embodiment will be described. FIG. 11 is a diagram showing the configuration of the regulator in the third embodiment. FIG. 12 is a timing chart showing the intermittent operation signal. FIG. 13 is a diagram for explaining optimization of temperature characteristics of the oscillation device according to the third embodiment.

  In the oscillation device according to the third embodiment, the difference from the first embodiment is the configuration of the regulator. The other configuration is the same as that of the first embodiment, and a description thereof will be omitted. The regulator 210b in the third embodiment is different from the regulator 210 in the first embodiment in that two transistors M01 and M02 that function as switches for intermittent operation are provided. The first intermittent operation transistor M01 is a p-transistor, and is arranged in series between the two p-transistors M24 and M25 constituting the differential pair of the differential amplifier circuit 2101 and the high-potential-side power supply VD. . The second intermittent operation transistor M02 is arranged in series between the n transistors M21 and M35 serving as two constant current sources and the low potential side power source VS.

  The first intermittent operation signal LPV is input from the control circuit 220 to the gate of the first intermittent operation transistor M01, and is switched on and off. The second intermittent operation signal XLPV is input from the control circuit 220 to the gate of the second intermittent operation transistor M02 and switched on and off. In addition, a capacitor C5 is disposed between the output node of the differential amplifier circuit 2101 and the high-potential-side power supply VD as a stabilization capacitor for the output node of the differential amplifier circuit 2101 during intermittent operation. Since the other configuration of the regulator 210b is the same as that of the regulator 210 in the first embodiment, the same components are denoted by the same reference numerals in FIG. 11 as those in FIG.

  When the first intermittent operation signal LPV is high, the first intermittent operation transistor M01 is turned off, and the supply of current to the differential amplifier circuit 2101 is cut off. When the first intermittent operation signal LPV is low, the first intermittent operation transistor M01 is turned on, and a current is supplied to the differential amplifier circuit 2101. The second intermittent operation signal XLPV is an inverted signal of the first intermittent operation signal LPV. When the second intermittent operation signal XLPV is low, the second intermittent operation transistor M02 is turned off, and the current supply to the differential amplifier circuit 2101 and the output circuit 2102 is cut off. When the second intermittent operation signal XLPV is high, the second intermittent operation transistor M02 is turned on, and current is supplied to the differential amplifier circuit 2101 and the output circuit 2102. Therefore, when the first intermittent operation signal LPV is high and the second intermittent operation signal XLPV is low, the regulator 210b stops operating, and the first intermittent operation signal LPV is low and the second intermittent operation signal XLPV is low. When high, regulator 210 operates. As shown in FIG. 12, the first intermittent operation signal LPV and the second intermittent operation signal XLPV repeat high and low at a predetermined timing. As a result, the constant voltage VR output from the regulator 210 is kept constant. By such an intermittent operation, the regulator 210 outputs a constant voltage VR that can be practically used, and its current consumption is kept low.

  In the vibration circuit in the third embodiment, | ΔVR | aim can be made smaller than that in the vibration circuit in the first embodiment, and the slope of the constant voltage VR with respect to the temperature change can be made closer to the slope of the oscillation stop voltage VI with respect to the temperature change. . That is, in the regulator 210b, even if the constant current I2 that flows when the second intermittent operation signal XLPV is high is higher than the first embodiment, the constant current I2 that flows when the second intermittent operation signal XLPV is low is 0. This is because the current consumption can be kept low on a time average basis.

  Further description will be given with reference to FIG. The consumption current Ireg of the time-average regulator during the intermittent operation is lower than the consumption current Ireg when there is no intermittent operation. Therefore, the line indicating the relationship between | ΔVR | and the consumption current Ireg of the regulator 210 in the third embodiment is lower than the line indicating the relationship between | ΔVR | and the consumption current Ireg of the regulator 210 in the first embodiment. Shift to the current side. As a result, the sum of the consumption current Ireg of the regulator 210a and the consumption current Iosc of the crystal oscillation circuit 110 is minimized | ΔVR | aim is smaller than that in the case where there is no intermittent operation (first embodiment). . That is, by setting the constant current I2 and selecting the constant voltage control transistor M32 so as to realize such | ΔVR | aim, the inclination with respect to the temperature change of the constant voltage VR is changed to the inclination with respect to the temperature change of the oscillation stop voltage VI. Can be closer. Specifically, according to the experiment conducted by the applicant, the difference between the constant voltage VR (T0) at the lower limit temperature T0 and the oscillation stop voltage VI (TO) at the lower limit temperature T0 can be close to 0.4 volts or less. . The difference between the constant voltage VR (T0) at the lower limit temperature T0 and the oscillation stop voltage VI (T0) at the lower limit temperature T0 is the difference between the constant voltage VR (T1) at the upper limit temperature T1 and the oscillation stop voltage VI (T1) at the upper limit temperature T1. ) And the difference can be close to twice or less.

  As a result, the current consumption Iosc itself of the crystal oscillation circuit 110 can be suppressed. As a result, the current consumption of the entire oscillating device in the third embodiment can be significantly reduced as compared with the first embodiment.

D. Variations:
・ First modification:
In the above embodiment, the constant currents Iref1 and Iref2 in the constant current circuit 230 are fixed to a small value of the nA level, and the temperature characteristics of the constant voltage VR are adjusted by adjusting the constant current I2 and the constant voltage control transistor M32 in the regulator 210. It is done by. The temperature characteristic of Vref, which is the output of the constant current circuit 230, is the same as that of the constant voltage VR in the regulator 210, as is the case with the constant current I2 and the constant voltage control transistor M32. It may vary depending on the size and the characteristics of the transistors M11, M12, and M14 in the constant current circuit 230. As a result, the change in the reference voltage Vref causes a change in the constant current I2 in the regulator 210, and thus slightly affects the temperature characteristics of the constant voltage VR. Therefore, if the constant currents Iref1 and Iref2 are increased, the slope | ΔVR | with respect to the temperature change of the constant voltage VR can be reduced. Therefore, in addition to the adjustment of the constant current I2 and the constant voltage control transistor M32 in the regulator 210, the adjustment of the constant currents Iref1 and Iref2 and the transistors M11, M12, and M14 of the constant current circuit 230 may be performed. In such a case, the gradient | ΔVR | with respect to the temperature change may be set so that the sum of the consumption currents of the regulator 210, the constant current circuit 230, and the crystal oscillation circuit 110 is minimized. When such adjustment is performed, the constant currents Iref1, Iref2, and I2 are suppressed to a level of several nA to several tens of nA. When a low current of this level is applied to the transistors M12 and M14 and the constant voltage control transistor M32, these transistors operate in a region near the threshold voltage Vth or below the threshold voltage Vth, a so-called subthreshold region. Let

・ Second modification:
In the third embodiment, the regulator 210b is intermittently operated, but the constant current circuit 230 may also be intermittently operated. FIG. 14 is a diagram illustrating an example of a constant current circuit capable of intermittent operation. The constant current circuit 230b shown in FIG. 14 includes a third intermittent operation transistor M03 and a fourth intermittent transistor M04. The third intermittent operation transistor M03 is disposed between the n-transistor M14 (constant current source) and the low potential side power source VS. The fourth intermittent transistor M04 is disposed between the p-transistor M13 and the high potential side power supply VD. Similar to the second intermittent operation transistor M02, the third intermittent operation transistor M03 functions as a switch that is switched on and off by the second intermittent operation signal XLPV from the control circuit 220. Similar to the first intermittent operation transistor M01, the fourth intermittent transistor M04 functions as a switch that is turned on and off by the first intermittent operation signal LPV from the control circuit 220. Since the other configuration of the constant current circuit 230b is the same as that of the constant current circuit 230 shown in FIG. 2, the same components are denoted by the same reference numerals as those of FIG. 2 in FIG.

  According to this modification, the current consumption of the entire oscillation device can be further suppressed. Further, when the slope | ΔVR | with respect to the temperature change is set so as to minimize the total current consumption of the regulator 210, the constant current circuit 230, and the crystal oscillation circuit 110 as in the first modification example, The current consumption of the constant current circuit 230 during intermittent operation may be taken into consideration.

・ Third modification:
In the above embodiment, as shown in FIG. 1, the clock signal that is the output of the oscillation device 100 is output to the central processing unit 600, but is not limited thereto. For example, when the oscillation device 100 is mounted on a watch such as a wristwatch, the second hand, the minute hand, and the hour hand of the clock are rotated using a 1 Hz clock signal obtained by dividing the oscillation signal FS as a time reference signal. It is good also as outputting to the drive coil of the step motor to drive.

  As mentioned above, although the Example and modification of this invention were demonstrated, this invention is not limited to these Example and modification at all, and implementation in a various aspect is possible within the range which does not deviate from the summary. It is.

DESCRIPTION OF SYMBOLS 100 ... Oscillator 110 ... Crystal oscillation circuit 111 ... Gate terminal 112 ... Drain terminal 210, 210a, 210b ... Regulator 220 ... Control circuit 230, 230b ... Constant current circuit 500 ... Crystal oscillator 600 ... Central processing unit 1101 ... Inverter 1102 ... Feedback circuit 2101 ... Differential amplifier circuit 2102, 2102a ... Output circuit

Claims (13)

An oscillation device,
A first constant current source for generating a first constant current; and a constant voltage control transistor for generating a constant voltage that is energized with the first constant current. A constant voltage generating circuit having a slope of 1 and the first slope fluctuates according to the first constant current;
A crystal oscillation circuit driven to oscillate by a constant voltage supplied from the constant voltage generation circuit, wherein an oscillation stop voltage, which is a lower limit value of the constant voltage capable of oscillation, has a second gradient with respect to a temperature change; A crystal oscillation circuit;
With
The first slope has a correlation with a consumption current of the crystal oscillation circuit correlated with a difference between the first slope and the second slope, and the constant voltage generation correlated with the magnitude of the first constant current. It is determined to minimize the sum of the current consumption of the circuit,
The oscillation device according to claim 1, wherein the first constant current is set to a value for operating the constant voltage control transistor in a subthreshold region. The oscillation device according to claim 1 further includes:
An intermittent control unit for intermittently operating the first constant current source;
The first inclination is determined such that the sum of the current consumption of the crystal oscillation circuit and the current consumption of the constant voltage generation circuit during the intermittent operation is minimized. The oscillation device according to claim 1 or 2,
The constant voltage generation circuit includes a plurality of transistors,
An oscillation device in which at least one transistor selected from the plurality of transistors is used as the constant voltage control transistor. An oscillation device,
A first constant current source that generates a first constant current with reference to a reference voltage; and a constant voltage control transistor that is energized with the first constant current and generates a constant voltage. A constant voltage generation circuit having a first slope with respect to a temperature change and fluctuating according to the first constant current;
A crystal oscillation circuit driven to oscillate by a constant voltage supplied from the constant voltage generation circuit, wherein an oscillation stop voltage, which is a lower limit value of the constant voltage capable of oscillation, has a second gradient with respect to a temperature change; A crystal oscillation circuit;
A constant current circuit that generates a second constant current using a constant current control transistor, and generates the reference voltage using the second constant current;
With
The first slope has a correlation with a consumption current of the crystal oscillation circuit correlated with a difference between the first slope and the second slope, and the constant voltage generation correlated with the magnitude of the first constant current. The sum of the current consumption of the circuit and the current consumption of the constant current circuit having a correlation with the magnitude of the second constant current is determined to be a minimum,
The first constant current is set to a value for operating the constant voltage control transistor in a subthreshold region;
The oscillation device according to claim 2, wherein the second constant current is set to a value for operating the constant current control transistor in a subthreshold region. The oscillation device according to claim 4 further includes:
An intermittent control section for intermittently operating the first constant current source and the constant current circuit;
The first slope minimizes the sum of the current consumption of the crystal oscillation circuit, the current consumption of the constant voltage generation circuit during the intermittent operation, and the current consumption of the constant current circuit during the intermittent operation. Oscillator as defined in The oscillation device according to any one of claims 1 to 5,
The oscillation device, wherein the constant voltage at the upper limit temperature of the guaranteed operating temperature range is set to an oscillation start voltage of the crystal oscillation circuit at the upper limit temperature. The oscillation device according to any one of claims 1 to 5,
The oscillation device, wherein the constant voltage at the upper limit temperature of the guaranteed operating temperature range is set to a value obtained by adding a noise margin to the oscillation start voltage of the crystal oscillation circuit at the upper limit temperature. The oscillation device according to any one of claims 1 to 5,
The constant voltage includes a first value obtained by adding a noise margin to the oscillation start voltage of the crystal oscillation circuit, the constant voltage at the upper limit temperature of the operation guarantee temperature range, and the operation guarantee at all temperatures in the operation guarantee temperature range. An oscillation device that is set between a second value obtained by adding the first value to a difference between the constant voltages at a lower limit temperature of a temperature range. The oscillation device according to any one of claims 1 to 8,
The oscillation device, wherein a difference between the constant voltage at the lower limit temperature of the guaranteed operating temperature range and the oscillation stop voltage at the lower limit temperature is 0.4 volts or less. The oscillation device according to any one of claims 1 to 9,
The difference between the constant voltage at the lower limit temperature of the guaranteed operating temperature range and the oscillation stop voltage at the lower limit temperature is 2 of the difference between the constant voltage at the upper limit temperature of the guaranteed operating temperature range and the oscillation stop voltage at the upper limit temperature. Oscillator that is less than double.   A semiconductor device comprising the oscillation device according to claim 1.   An electronic device that includes the oscillation device according to claim 1 or the semiconductor device according to claim 11 and generates an operation reference signal using an oscillation output of the oscillation device.   A timepiece including the oscillation device according to claim 1 or the semiconductor device according to claim 11 and generating a time reference signal using an oscillation output of the oscillation device.

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