JP7263041B2 - Oscillator control circuit and integrated circuit - Google Patents

Description

The present invention relates to an oscillator control circuit for controlling an oscillator and an integrated circuit comprising the oscillator control circuit.

In addition to the primary vibration exhibiting high stability, the crystal oscillator sometimes generates a secondary vibration at a frequency higher than the resonance frequency of the primary vibration. Therefore, a crystal oscillator that suppresses the secondary vibration has been proposed.

For example, Patent Literature 1 discloses an oscillation resonance circuit including a crystal oscillator and first and second capacitors, an oscillation transistor, a crystal oscillator between a base and a collector, and a crystal oscillator between an emitter and a collector. In a crystal oscillator of Colpitts type in which the first capacitor is connected to the second capacitor between the emitter and the base, the reactance between the emitter and the collector or between the emitter and the base is obtained by connecting an LC series circuit to the first or second capacitor in parallel. It is disclosed that the reactance parallel circuit is composed of a parallel circuit and has a resonance characteristic that becomes capacitive at the oscillation frequency of the main vibration, and the resonance frequency of the LC series circuit is configured to match the oscillation frequency of the secondary vibration. According to this configuration, the impedance of the LC series circuit becomes zero at the oscillation frequency of the secondary vibration, and the oscillation gain becomes zero, so that the oscillation due to the secondary vibration can be suppressed.

JP 2010-41346 A

However, using an LC filter for a crystal oscillator causes the following problems. First, when the LC series resonance characteristic is steep (high Q value), tolerance for variations in the LC element value becomes strict in order to match the oscillation frequency of the secondary vibration and the LC resonance frequency. In other words, since elements with little variation are required, the cost of parts increases. Secondly, when the LC series resonance characteristic is moderated (low Q value), for example, the oscillation frequency of the main oscillation of an SС cut crystal oscillator is only about 10% away from the oscillation frequency of the secondary oscillation. The oscillation gain of is also reduced. Thirdly, the LC series circuit that constitutes the LC filter cannot be integrated due to its element value and becomes an external component. As a result, the number of parts increases, which hinders cost reduction and miniaturization.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an oscillator control circuit and an integrated circuit capable of controlling an oscillator having no LC filter and causing a resonator to oscillate with main oscillation.

In order to solve the above problems, an oscillator control circuit according to the present invention is an oscillator control circuit that controls an oscillator that oscillates a resonator to generate an oscillation signal, wherein the frequency of the oscillation signal is set to a predetermined threshold value. By comparing with the frequency determination circuit that detects the secondary vibration of the resonator, the comparison is performed every time a predetermined time elapses, and when the secondary vibration is detected by the frequency determination circuit and performing damping control of the oscillator so as to reduce energy supply to the resonator, and performing the damping control without performing the damping control when the secondary vibration is not detected by the frequency determination circuit. and a control circuit for releasing when it is closed .

Further, in order to solve the above problems, an integrated circuit according to the present invention includes the oscillator control circuit and the oscillator.

According to the present invention, it is possible to control an oscillator that does not have an LC filter and cause the resonator to oscillate with the main oscillation.

1 is a block diagram showing a configuration example of an oscillator control circuit and an integrated circuit according to a first embodiment of the present invention; FIG. 3 is a circuit diagram showing an example of a frequency determination circuit in the oscillator control circuit according to the first embodiment of the present invention; FIG. 3 is a circuit diagram showing an example of a frequency determination circuit in the oscillator control circuit according to the first embodiment of the present invention; FIG. 4 is a circuit diagram showing an example of a timer circuit in the oscillator control circuit according to the first embodiment of the invention; FIG. 4 is a circuit diagram showing an example of an attenuation control circuit in the oscillator control circuit according to the first embodiment of the present invention; FIG. 4 is a circuit diagram showing an example of an attenuation control circuit in the oscillator control circuit according to the first embodiment of the present invention; FIG. 4 is a flow chart showing an operation example of the oscillator control circuit according to the first embodiment of the present invention; FIG. 4 is a diagram showing an example of a timing chart of the oscillator control circuit according to the first embodiment of the present invention; FIG. FIG. 5 is a block diagram showing a configuration example of an oscillator control circuit and an integrated circuit according to a second embodiment of the present invention; FIG. 9 is a block diagram showing a configuration example of an oscillator control circuit and an integrated circuit according to a third embodiment of the present invention; FIG. 11 is a block diagram showing a configuration example of an oscillator control circuit and an integrated circuit according to a fourth embodiment of the present invention; It is a figure which shows the example of the timing chart of the oscillator control circuit based on the 4th Embodiment of this invention. 10 is a flow chart showing an operation example of the oscillator control circuit according to the fourth embodiment of the present invention; FIG. 11 is a block diagram showing a configuration example of an oscillator control circuit and an integrated circuit according to a fifth embodiment of the present invention; FIG. 11 is a block diagram showing a configuration example of an oscillator control circuit and an integrated circuit according to a sixth embodiment of the present invention;

An embodiment of the present invention will be described in detail below with reference to the drawings.

(First embodiment)
First, an oscillator control circuit and an integrated circuit according to the first embodiment of the present invention will be described. FIG. 1 is a block diagram showing a configuration example of an oscillator control circuit and an integrated circuit according to the first embodiment. The integrated circuit 1 shown in FIG. 1 comprises an oscillator control circuit 10 and an oscillator 20 .

The resonator 30 is a resonator having a secondary vibration, such as an SC-cut crystal resonator or an AT-cut crystal resonator.

The oscillator 20 shapes the waveform of the signal obtained by oscillating the resonator 30 from a sine wave to a square wave to generate an oscillation signal. The oscillator 20 then outputs an oscillation signal to the outside of the integrated circuit 1 and to the oscillator control circuit 10 .

The oscillator control circuit 10 is a circuit that controls the oscillator 20 and includes a frequency determination circuit 11 , a control circuit 12 and a timer circuit 13 .

The frequency determination circuit 11 detects the secondary vibration of the resonator 30 by comparing the frequency of the oscillation signal generated by the oscillator 20 with a predetermined threshold value. In this embodiment, a binary signal indicating whether or not the secondary vibration is oscillating is output as the determination result. The frequency determination circuit 11 then outputs the determination result to the control circuit 12 and the timer circuit 13 . The frequency determination circuit 11 may compare the frequency of the oscillation signal with the frequency threshold, or convert the frequency of the oscillation signal into voltage and then compare it with the voltage threshold.

2A and 2B are circuit diagrams showing an example of the frequency determination circuit 11 of the FV conversion (frequency-voltage conversion) circuit system. The example shown in FIG. 2A shows a peak hold circuit system, and the frequency determination circuit 11 has a frequency-voltage conversion circuit 111 and a comparator 112 .

The switch of the frequency-voltage conversion circuit 111 is short-circuited when the level of the oscillation signal generated by the oscillator 20 is high, and opened when it is low. The frequency-voltage conversion circuit 111 holds the peak value of the capacitor voltage, which changes according to the frequency of the oscillation signal, and outputs it to the comparator 112 . When the resonator 30 is oscillating, the output voltage of the frequency-voltage conversion circuit 111 is lower in the secondary vibration with the higher frequency of the oscillation signal than in the primary vibration with the lower frequency of the oscillation signal.

The comparator 112 compares the voltage input from the frequency-voltage conversion circuit 111 with a voltage threshold (Vref), and determines that the resonator 30 is oscillating due to secondary vibration when the voltage is equal to or less than the voltage threshold. Further, when the voltage input from the frequency-voltage conversion circuit 111 exceeds the voltage threshold, the comparator 112 determines that the resonator 30 is not oscillating due to the secondary vibration. In this embodiment, the comparator 112 outputs a high-level signal when it is determined that the secondary vibration is oscillating, and determines that the secondary vibration is not oscillating (oscillating with the primary vibration or non-oscillating). If so, it outputs a low level signal.

Thus, the frequency determination circuit 11 converts the frequency of the oscillation signal into a DC voltage and then compares it with the voltage threshold. Since the DC voltage is easier to measure than the dynamic AC operation, the frequency determination circuit 11 can improve the resolution of the frequency threshold adjustment and set the frequency threshold with high accuracy.

Further, in the example shown in FIG. 2B, the frequency determination circuit 11 has an N-th order high-pass filter 113 and a holding circuit 114 . Note that FIG. 2B shows the first-order high-pass filter 113 .

High pass filter 113 extracts the high frequency component of the oscillation signal generated by oscillator 20 and outputs the extracted high frequency component signal to comparator 112 . Comparator 112 compares the high frequency component signal with a voltage threshold (Vref) and outputs the comparison result to holding circuit 114 . Since the oscillation signal is blocked when the frequency of the oscillation signal is equal to or lower than the cutoff frequency of the high-pass filter 113, the high-frequency component signal becomes smaller than the voltage threshold, and the frequency of the oscillation signal exceeds the cutoff frequency of the high-pass filter 113. In this case, the oscillating signal passes through, so the high frequency component signal is greater than the voltage threshold. A holding circuit 114 is a latch circuit, a flip-flop circuit, or the like, and temporarily holds the comparison result of the comparator 112 .

If the frequency determination circuit 11 is a peak hold circuit as shown in FIG. 2A, it is necessary to capture the peak value at high speed. In this regard, since the frequency determination circuit 11 shown in FIG. 2B includes the high-pass filter 113, the operation of capturing the peak value at high speed becomes unnecessary. Therefore, even if the band of the comparator 112 is low, it is possible to perform frequency determination.

The timer circuit 13 is a circuit that manages the timer time, and notifies the control circuit 12 that the timer time has elapsed when a predetermined timer time has elapsed after the timer is reset. In this embodiment, a pulse signal is output when the timer time elapses. The timer time should be longer than the time required for the frequency of the oscillation signal to become zero (for example, several hundred milliseconds) when the oscillator 20 is under attenuation control.

FIG. 3 is a circuit diagram showing an example of the timer circuit 13. As shown in FIG. In the example shown in FIG. 3 , timer circuit 13 has delay circuit 131 , XOR circuit 132 , OR circuit 133 , constant current source 134 , switch 135 , capacitor 136 and comparator 137 .

The timer circuit 13 will be described assuming that the level of the output signal of the frequency-voltage conversion circuit 111 becomes high when the resonator 30 oscillates due to the secondary vibration. When the level of the output signal of the frequency-voltage conversion circuit 111 becomes high, the delay circuit 131 and the XOR circuit 132 generate a pulse signal whose level is high only during the delay time of the delay circuit 131 . The level of the output signal of the OR circuit 133 is also high during the period when the level of the pulse signal is high.

The switch 135 short-circuits when the level of the output signal of the OR circuit 133 is high, and opens when it is low. Shorting switch 135 resets the timer.

Capacitor 136 accumulates the charge input from constant current source 134 while switch 135 is open, during which the voltage of capacitor 136 rises.

Comparator 137 compares the voltage of capacitor 136 with a predetermined threshold (Vref). In this embodiment, the comparator 137 generates a signal that becomes low level when the voltage of the capacitor 136 is equal to or less than the threshold and becomes high level when the voltage of the capacitor 136 exceeds the threshold. Output to the OR circuit 133 . When the level of the output signal of the comparator 137 becomes high, the level of one input signal of the OR circuit 133 becomes high, so the timer circuit 13 generates a pulse for resetting the timer each time the output toggles. becomes.

When the frequency determination circuit 11 detects the secondary vibration and the timer circuit 13 notifies that the timer time has elapsed, the control circuit 12 instructs the oscillator 20 to reduce the energy supply to the resonator 30. to control. This control over the oscillator 20 is hereinafter referred to as "attenuation control". The damping control may power down the oscillator 20 to stop supplying energy to the resonator 20 , may reduce the bias current of the oscillator 20 , or may reduce the feedback resistance of the oscillator 20 .

Although the oscillator control circuit 10 includes the timer circuit 13 in this embodiment, the timer circuit 13 is not an essential component. In the oscillator control circuit 10 without the timer circuit 13, the control circuit 12 controls the oscillator 20 to reduce the energy supply to the resonator 30 when the secondary vibration is detected by the frequency determination circuit 11. conduct.

FIG. 4 is a circuit diagram showing an example of a circuit for performing attenuation control. FIG. 4A is a circuit diagram when attenuation control is performed by reducing the bias current of the oscillator 20. FIG. A circuit surrounded by a dotted line in FIG. 4A constitutes a bias current source with a current value switching function. FIG. 4B is a circuit diagram when attenuation control is performed by reducing the feedback resistance of oscillator 20. In FIG. A circuit surrounded by a dotted line in FIG. 4B constitutes a feedback resistor with a resistance value switching function. In this specification, "attenuation" includes "stop". Therefore, in the circuit diagram shown in FIG. 4A, the bias current may be zero during attenuation control. Further, in the circuit diagram shown in FIG. 4B, the feedback resistance may be set to zero during attenuation control.

Next, the operation of oscillator control circuit 10 will be described with reference to FIG. FIG. 5 is a flow chart showing an operation example of the oscillator control circuit 10. As shown in FIG.

In step S101, the oscillator control circuit 10 activates the oscillator 20 and causes the resonator 30 to oscillate. In step S102, the timer circuit 13 determines whether or not the timer time has elapsed. If the timer time has elapsed (step S102-Yes), the process proceeds to step S103.

In step S103, the oscillator control circuit 10 uses the frequency determination circuit 11 to determine whether or not the frequency of the oscillation signal exceeds the threshold. Here, the threshold is the frequency threshold. If the frequency of the oscillation signal exceeds the threshold (step S103-Yes), the process proceeds to step S104, and if the frequency of the oscillation signal is equal to or less than the threshold (step S103-No), the process proceeds to step S105. Specifically, when the oscillator 20 is started, the resonator 30 may oscillate not as the primary vibration but as the secondary vibration. If it is not oscillating due to vibration, the process proceeds to step S105.

In step S104, the oscillator control circuit 10 performs attenuation control on the oscillator 20 so that the frequency of the oscillation signal becomes zero. After that, the process returns to step S102.

In step S105, the oscillator control circuit 10 does not perform attenuation control, and cancels the attenuation control if the attenuation control for the oscillator 20 has been performed. After that, the process returns to step S102. That is, when the resonator 30 oscillates due to the secondary vibration, the oscillator control circuit 10 repeats the damping control in step S104 until the secondary vibration is released.

FIG. 6 is a diagram showing an example of a timing chart of the oscillator control circuit 10. As shown in FIG. Here, an example is shown in which the resonator 30 oscillates in the secondary vibration when the oscillator 20 is started, cannot escape from the secondary vibration in the first damping control, and escapes from the secondary vibration in the second damping control and oscillates in the primary vibration. there is

The first stage of FIG. 6 shows the frequency Fosc of the oscillation signal and the frequency threshold Fth. below the frequency threshold.

The second row in FIG. 6 shows the waveform of the output signal of the frequency determination circuit 11. FIG. When the frequency of the oscillation signal exceeds the frequency threshold, the frequency determination circuit 11 determines that it is a secondary vibration, and sets the level of the output signal to high. It determines that there is no output signal, and sets the level of the output signal to low.

The third row in FIG. 6 shows the waveform of the output signal of the timer circuit 13 . The timer circuit 13 manages the timer time, and repeats the operation of resetting the timer after setting the level of the output signal to high when the timer time elapses.

The fourth row in FIG. 6 shows whether or not the control circuit 12 performs attenuation control on the oscillator 20 . The control circuit 12 determines whether or not to perform attenuation control at the timing when the output signal of the timer circuit 13 of the third stage becomes high level. At the timing when the output signal of the timer circuit 13 of the third stage becomes high level, if the output signal of the frequency determination circuit 11 of the first stage is high level, attenuation control is performed, and the frequency determination circuit 11 of the first stage is controlled. Attenuation control is not performed when the output signal of is at low level.

In this manner, the oscillator control circuit 10 detects the secondary vibration of the resonator 30 by the frequency determination circuit 11, and when the resonator 30 oscillates due to the secondary vibration, the oscillator control circuit 10 controls the oscillator so as to reduce the energy supply to the resonator 30. 20 damping control. Therefore, according to the present embodiment, it is possible to control the oscillator 20 having no LC filter and cause the resonator 30 to oscillate with the main vibration.

In addition, the oscillator control circuit 10 further includes the timer circuit 13, so that it is possible to accurately define the timing of performing attenuation control of the oscillator 20 and the timing of canceling the attenuation control.

(Second embodiment)
Next, an oscillator control circuit and an integrated circuit according to a second embodiment of the invention will be described. FIG. 7 is a block diagram showing a configuration example of an oscillator control circuit and an integrated circuit according to the second embodiment. The integrated circuit 1 shown in FIG. 7 is the same as in the first embodiment. However, it differs from the first embodiment in that the temperature of the resonator 30 is controlled by a constant temperature control circuit 40 . Differences from the first embodiment will be described below.

A constant temperature control circuit 40 controls the temperature of the resonator 30 to be constant. Constant temperature control circuit 40 is known and generally comprises temperature sensor 41 , temperature control circuit 42 and heater 43 . The temperature control circuit 42 controls the heater 43 so that the temperature obtained by the temperature sensor 41 is constant. The constant temperature control circuit 40 and the resonator 30 may be packaged as an OCXO (Oven Controlled X'tal Oscillator).

When the temperature of the resonator 30 changes, the oscillation frequency may also change. For example, when an SC-cut crystal is used as the resonator 30, the characteristic of the oscillation frequency with respect to temperature generally has a downwardly convex parabolic shape. In this regard, by controlling the resonator 30 with the constant temperature control circuit 40 like the OCXO, the oscillation frequency can be kept constant even if the environmental temperature changes. Furthermore, the temperature of the frequency determination circuit 11 provided in the adjacent integrated circuit 1 can be kept substantially constant, and the temperature fluctuation of the frequency determination circuit 11 can be reduced. Therefore, according to the present embodiment, the secondary vibration can be detected with high precision in the frequency determination circuit 11 .

(Third Embodiment)
Next, an oscillator control circuit and an integrated circuit according to a third embodiment of the invention will be described. FIG. 8 is a block diagram showing a configuration example of an oscillator control circuit and an integrated circuit according to the third embodiment. An integrated circuit 1A shown in FIG. This embodiment differs from the first embodiment in that the oscillator control circuit 10A includes a memory 14. FIG. Differences from the first embodiment will be described below.

The memory 14 is, for example, a non-volatile memory or a one-time memory, and stores parameters for determining the threshold value used in the frequency determination circuit 11 and the timer time of the timer circuit 13 . The memory 14 may also store parameters for adjusting the offset of the oscillation frequency and the negative resistance value used in the oscillator 20 . The values stored in the memory 14 are adjusted for each integrated circuit 1A.

The memory 14 may also store an oscillation damping time from when the control circuit 12 performs damping control to reduce energy supply to the resonator 30 until the oscillation of the resonator 30 stops. When the resonator 30 oscillates due to the secondary vibration, it is necessary to control the attenuation of the oscillation, wait until the oscillation stops, and then oscillate the resonator 30 again. That is, an oscillation damping time is required to completely eliminate the secondary vibration component (B-mode oscillation component) from the resonator 30 .

The oscillation damping time is determined by the oscillation period and Q value of the resonator 30 . It is known that the damping constant .zeta. representing the time constant for damping the oscillation amplitude and the Q value are in the following relational expression (1). The damping constant ζ represents the damping degree of the waveform damping envelope.

Q=1/(2ζ) (1)

Further, it is known that the logarithmic attenuation rate δ, which is the natural logarithm of the amplitude ratio of adjacent periods, is expressed by the following equation (2).

δ=2πζ/√(1−ζ ² ) (2)

Calculating using the above formula, for example, when the Q value of the resonator 30 is 1,000,000 and the oscillation frequency is 50 MHz, resetting the oscillator 20 requires a decay time of about 100 ms until oscillation stops. . Here, it is assumed that the oscillation stops when the oscillation amplitude becomes about 10 ⁻⁹ times that before resetting.

Thus, the oscillator control circuit 10A stores various parameters, setting values, etc. in the memory 14. FIG. Therefore, according to the present embodiment, manufacturing variations can be corrected, and the oscillator 20 can be controlled with high accuracy. For example, it is possible to set the threshold value used in the frequency determination circuit 11 exactly at the center between the oscillation frequency of the primary vibration and the oscillation frequency of the secondary vibration.

Further, the oscillator control circuit 10A stores a different oscillation damping time for each resonator 30 in the memory 14, thereby restarting the oscillator 20 after the oscillation damping time set according to the characteristics of the resonator 30 has passed. Therefore, it is possible to reliably oscillate with the main vibration.

(Fourth embodiment)
Next, an oscillator control circuit and an integrated circuit according to a fourth embodiment of the invention will be described. FIG. 9 is a block diagram showing a configuration example of an oscillator control circuit and an integrated circuit according to the fourth embodiment. The integrated circuit 1B shown in FIG. 9 includes an oscillator control circuit 10B and an oscillator 20. As shown in FIG. This embodiment differs from the first embodiment in that the oscillator control circuit 10B includes a stop circuit 15. FIG. Differences from the first embodiment will be described below.

In this embodiment, the frequency determination circuit 11 outputs the detection result of the secondary vibration (the determination result of whether or not the secondary vibration is oscillating) to the control circuit 12 and the timer circuit 13, and further outputs it to the stop circuit 15. do. The timer circuit 13 also notifies the control circuit 12 and the stop circuit 15 that the timer time has elapsed. Further, the oscillator 20 outputs the oscillation signal to the outside of the integrated circuit 1B and the frequency determination circuit 11, and also to the stop circuit 15. FIG.

The stop circuit 15 detects when the frequency determination circuit 11 does not detect the secondary vibration, when the timer circuit 13 notifies that the timer time has elapsed, and when the resonator 30 is oscillating (when the frequency of the oscillation signal is not zero). ), the operation of the frequency determination circuit 11 and the timer circuit 13 is stopped.

The operation of oscillator control circuit 10B will be described with reference to FIG. FIG. 10 is a flow chart showing an operation example of the oscillator control circuit 10B. Since steps S201 to S204 are the same as steps S101 to S104 in FIG. 5 described above, description thereof will be omitted.

At step S205, the oscillator control circuit 10B determines whether or not the frequency of the oscillation signal is zero. If the frequency of the oscillation signal is not zero (step S205-No), the process proceeds to step S206, and if the frequency of the oscillation signal is zero (step S205-Yes), the process proceeds to step S207.

In step S206, the oscillator control circuit 10B causes the stop circuit 15 to stop the operations of the frequency determination circuit 11 and the timer circuit 13. FIG. In this case, since the resonator 30 is oscillating with the main vibration, the oscillator 20 is continuously operated.

In step S207, the oscillator control circuit 10B does not perform attenuation control, and if attenuation control for the oscillator 20 has been performed, cancels the attenuation control. After that, the process returns to step S202. That is, when the resonator 30 oscillates due to the secondary vibration, the oscillator control circuit 10B repeats the damping control in step S204 until the secondary vibration is released.

FIG. 11 is a diagram showing an example of a timing chart of the oscillator control circuit 10B. Here, as in FIG. 6 described above, the resonator 30 oscillates due to the secondary vibration when the oscillator 20 is started, the secondary vibration cannot be escaped by the first damping control, and the secondary vibration is generated by the second damping control. It shows an example of oscillating with the main vibration after getting out. The first, second, and fourth stages of FIG. 11 are the same as the first, second, and fourth stages of FIG. 6, and thus description thereof is omitted.

The fifth row in FIG. 11 indicates whether or not the stop circuit 15 performs stop control. The stop circuit 15 determines whether or not to perform stop control at the timing when the output signal of the third-stage timer circuit 13 becomes high level. When the output signal of the timer circuit 13 of the third stage becomes high level, the output signal of the frequency determination circuit 11 of the first stage is low level and the resonator 30 is oscillating, stop control is performed. and the operation of the frequency determination circuit 11 and the timer circuit 13 is stopped.

The third stage of FIG. 11 shows the waveform of the output signal of the timer circuit 13. When the stop circuit 15 performs stop control, the operation is stopped, so the level of the output signal remains low. Further, when stop control is performed by the stop circuit 15, the level of the output signal of the frequency determination circuit 11 shown in the second stage of FIG. 11 also maintains low.

Once the resonator 30 oscillates with the main vibration, it maintains the main vibration until the oscillator 20 is reset. Therefore, the oscillator control circuit 10B includes a stop circuit 15, which stops the operations of the frequency determination circuit 11 and the timer circuit 13 when the resonator 30 oscillates due to the main vibration. Therefore, according to this embodiment, it is possible to reduce power consumption. Moreover, it is possible to suppress the occurrence of spurious components of frequency components other than the frequency of the oscillation signal.

(Fifth embodiment)
Next, an oscillator control circuit and an integrated circuit according to a fifth embodiment of the invention will be described. FIG. 12 is a block diagram showing a configuration example of an oscillator control circuit and an integrated circuit according to the fifth embodiment. The present embodiment differs from the first embodiment in that the integrated circuit 1C has a reset terminal 31. FIG. Differences from the first embodiment will be described below.

A reset terminal 31 is a terminal for individually resetting only the oscillator 20 . When the input signal of reset terminal 31 is activated, only oscillator 20 is reset. As described with reference to FIG. 7, when the constant temperature control circuit 40 controls the constant temperature of the resonator 30, the constant temperature control circuit 40 is not reset.

If the frequency is stuck due to the application of a surge that exceeds the IC standard after the power is turned on, the IC will not operate normally. If a means of dropping the power supply voltage is taken for recovery, the temperature of the resonator 30 will drop, and it will take time to return to the original temperature state, resulting in a longer frequency settling time. In this regard, according to the present embodiment, when a system such as a base station detects a communication error, only the oscillator 20 can be reset individually, and the frequency settling time can be shortened by suppressing the temperature drop of the resonator 30. can be shortened.

(Sixth embodiment)
Next, an oscillator control circuit and integrated circuit according to a sixth embodiment of the present invention will be described. FIG. 13 is a block diagram showing a configuration example of an oscillator control circuit and an integrated circuit according to the sixth embodiment. An integrated circuit 1D shown in FIG. 13 includes an oscillator control circuit 10C and an oscillator 20. An oscillator 20 is provided. This embodiment differs from the first embodiment in that an oscillator control circuit 10C includes a frequency dividing circuit 16. FIG. Differences from the first embodiment will be described below.

The frequency divider circuit 16 divides the frequency of the oscillation signal generated by the oscillator 20 by a frequency division ratio greater than 1 to generate a frequency-divided signal. Then, the frequency division circuit 16 outputs the frequency division signal to the frequency determination circuit 11 .

The frequency determination circuit 11 detects the secondary vibration of the resonator 30 by comparing the frequency of the frequency-divided signal generated by the frequency division circuit 16 with a predetermined threshold value.

Since the oscillator control circuit 10C includes the frequency dividing circuit 16, the operation of the frequency determination circuit 11 is slowed down. Therefore, according to this embodiment, it is possible to improve the determination accuracy of the frequency determination circuit 11 .

The configuration of each embodiment described above can be combined as appropriate. For example, the oscillator control circuit 10C may include the stop circuit 15 described in the fourth embodiment. In that case, the stop circuit 15 may stop the frequency dividing circuit 16 . This makes it possible to prevent the frequency-divided signal from being output as a spurious signal.

Although the above embodiments have been described as representative examples, it will be apparent to those skilled in the art that many modifications and substitutions may be made within the spirit and scope of the invention. Therefore, the present invention should not be construed as limited by the embodiments described above, and various modifications and changes are possible without departing from the scope of the appended claims. For example, it is possible to combine a plurality of configuration blocks described in the configuration diagrams of the embodiments into one, or divide one configuration block.

Reference Signs List 1, 1A, 1B, 1C, 1D integrated circuit 10, 10A, 10B, 10C oscillator control circuit 11 frequency determination circuit 12 control circuit 13 timer circuit 14 memory 15 stop circuit 16 frequency dividing circuit 20 oscillator 30 resonator 31 reset terminal 40 constant temperature Control circuit 41 Temperature sensor 42 Temperature control circuit 43 Heater 111 Frequency voltage conversion circuit 112 Comparator 113 High pass filter 114 Holding circuit 131 Delay circuit 132 XOR circuit 133 OR circuit 134 Constant current source 135 Switch 136 Capacitor 137 Comparator

Claims (13)

An oscillator control circuit that controls an oscillator that oscillates a resonator to generate an oscillation signal,
a frequency determination circuit that detects the secondary vibration of the resonator by comparing the frequency of the oscillation signal with a predetermined threshold;
performing the comparison each time a predetermined time elapses;
performing damping control of the oscillator so as to reduce energy supply to the resonator when the secondary vibration is detected by the frequency determination circuit ;
a control circuit that does not perform the damping control when the secondary vibration is not detected by the frequency determination circuit, and cancels the damping control when the damping control is performed;
an oscillator control circuit comprising: 2. The oscillator control circuit according to claim 1, wherein said control circuit controls said oscillator so as to stop supplying energy to said resonator when said secondary vibration is detected by said frequency determination circuit. Further comprising a timer circuit that notifies that the timer time has elapsed,
The control circuit reduces the supply of energy to the resonator when the secondary vibration is detected by the frequency determination circuit and the timer circuit notifies that the timer time has elapsed. 2. The oscillator control circuit according to claim 1, wherein the control of When the secondary vibration is detected by the frequency determination circuit and the timer circuit notifies that the timer time has elapsed, the control circuit stops supplying energy to the resonator. 4. The oscillator control circuit of claim 3, for controlling an oscillator. When the secondary vibration is not detected by the frequency determination circuit, the timer circuit notifies that the timer time has elapsed, and the resonator is oscillating, the frequency determination circuit and the timer circuit 5. The oscillator control circuit according to claim 3, comprising a stop circuit for stopping operation. 6. An oscillator control circuit as claimed in any one of claims 3 to 5, comprising a memory for storing parameters for determining the threshold value and the timer period. 7. The oscillator control circuit according to claim 6, wherein said memory stores the time from when said control circuit performs control to reduce energy supply to said resonator until when said resonator stops oscillating. 8. The oscillator control circuit according to claim 1, wherein said frequency determination circuit converts the frequency of said oscillation signal into a voltage and then compares it with said threshold. The frequency determination circuit includes a high-pass filter that extracts a high-frequency component of the oscillation signal;
a comparator that compares the high frequency component with the threshold;
a holding circuit that temporarily holds the comparison result of the comparator;
9. The oscillator control circuit of claim 8, comprising: a frequency dividing circuit that divides the frequency of the oscillation signal to generate a frequency-divided signal;
The frequency determination circuit detects the secondary vibration of the resonator by comparing the frequency-divided signal instead of the oscillation signal with the threshold.
10. An oscillator control circuit as claimed in any one of claims 1 to 9. 11. The oscillator control circuit according to claim 1, wherein said resonator is controlled by a constant temperature control circuit so that the temperature thereof is constant. an oscillator control circuit according to any one of claims 1 to 11;
the oscillator;
An integrated circuit comprising: 13. The integrated circuit of claim 12, comprising a reset terminal for individually resetting only said oscillators.

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