JP2013192109A - Oscillator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve an oscillator operable with a low power consumption without causing any area increase and deteriorated accuracy.SOLUTION: A bias generating circuit 21 generates a bias signal for driving a voltage control oscillation section 41 on the basis of an output of a reference signal generating circuit 11 that generates a reference signal. A holding circuit 31 depends on an inputted signal during normal operation and inputs the bias signal to the oscillation section, but does not depend on the inputted signal during holding operation and inputs the bias signal during the normal operation to the voltage control oscillation section 41. A timing signal generating circuit 61 brings at least one of the reference signal generating circuit 11 and the bias generating circuit 21 into a low power consumption state in a prescribed time at a prescribed cycle, and also switches the holding circuit between the normal operation and the holding operation.

Description

  The present invention relates to an oscillator.

The Real Time Clock (RTC) used for timing applications is required to continue to operate even when the installed system is powered down or when the main power is not supplied. The That is, since an auxiliary battery or the like is required to operate for a long time, there has been a demand for low voltage driving and low power consumption.
Furthermore, in recent years, high timing accuracy has been demanded in the construction of a more accurate system, and the demand for an oscillator that generates a more stable clock has increased.

In general, a highly stable oscillator has a reference voltage generation circuit having a small power supply voltage dependency, and is driven by a bias signal generated based on the reference voltage generation circuit. There may be a temperature compensation circuit for reducing the frequency change of the oscillator due to temperature.
As an example of a highly stable oscillator using temperature compensation, there is an oscillator described in Patent Document 1. FIG. 7 is a diagram showing the configuration of the oscillator described in Patent Document 1. In FIG. In FIG. 7, the oscillator includes a crystal piezoelectric element 50, a voltage-controlled oscillator 40 that can change the frequency depending on the voltage, and a bias generator that generates a bias signal necessary for driving the voltage-controlled oscillator 40. The circuit 20 includes a reference signal generation circuit 10 that drives the bias generation circuit 20.

Here, the bias generation circuit 20 includes all bias voltage and bias current circuits for driving the voltage-controlled oscillation unit 40 in addition to the approximate cubic function generator.
The reference signal generation circuit 10 is a constant level generation circuit. The reference signal generation circuit 10 is composed of, for example, a bandgap reference circuit using a silicon bandgap, and is a voltage source or current source that is highly stable with respect to external changes such as a power supply voltage.

Japanese Patent No. 3233946

  Incidentally, for example, an oscillator used for an RTC product may be required to have a total current consumption of 1 μA or less. In order to configure a highly stable oscillator, a bias generation circuit such as the above-described reference signal generation circuit and temperature compensation circuit is required. However, it is very difficult to configure these circuits with low current consumption. In order to drive with low current consumption, for example, a large resistance is required, so there is a concern about an increase in chip area. In addition, MOS (Metal-Oxide-Semiconductor) transistors driven by minute currents are highly sensitive to device mismatches, resulting in not only large manufacturing variations but also degradation of power supply voltage fluctuation characteristics.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an oscillator that can operate with low power consumption without increasing the area or degrading accuracy.

  In order to solve the above-described problem, an oscillator according to one embodiment of the present invention generates an oscillation unit (for example, corresponding to the voltage-controlled oscillation unit 41 in FIG. 1) driven by an input bias signal and a reference signal. A reference signal generation circuit (for example, corresponding to the reference signal generation circuit 11 in FIG. 1) and a bias generation circuit for generating the bias signal for driving the oscillation unit based on the output of the reference signal generation circuit (for example, FIG. 1) and the bias signal is input to the oscillating unit depending on the input signal during normal operation, and during normal operation without depending on the input signal during holding operation. A holding circuit (for example, corresponding to the holding circuit 31 in FIG. 1), and at least one of the reference signal generation circuit and the bias generation circuit for a predetermined period of time. And a timing signal generation circuit (for example, corresponding to the timing signal generation circuit 61 in FIG. 1) for generating a signal for setting a power consumption state and a signal for switching the holding circuit between a normal operation and a holding operation. It is characterized by that.

  According to this configuration, at least one of the reference signal generation circuit and the bias generation circuit that generates the reference signal is set in the low power consumption state for a predetermined time at a predetermined cycle, and the holding circuit is switched between the normal operation and the holding operation. Therefore, even when the circuit is in a low power consumption state, a bias signal during normal operation is output to the oscillation unit, so that each circuit has a low area without increasing the area and reducing accuracy to achieve low power consumption. An oscillator that can operate with power consumption can be realized.

The low power consumption state of the reference signal generation circuit and the bias generation circuit is preferably, for example, a power down state. By setting the power down state, power consumption can be suppressed.
Preferably, the holding circuit is disposed between the bias generation circuit and the oscillation unit, and a signal input to the holding circuit is a signal output from the bias generation circuit. For example, corresponding to the case of the first, second, or fourth embodiment, the normal operation and the holding operation are realized by the holding circuit, so that the bias depends on the signal input to the holding circuit during the normal operation. Outputs a signal to the oscillation unit and outputs a bias signal during normal operation to the oscillation unit during the holding operation without depending on the signal input to the holding circuit. An oscillator that can be operated with low power consumption without increasing the area or degrading accuracy can be realized.

The low power consumption state of the reference signal generation circuit and the bias generation circuit is preferably, for example, a power down state. By setting the power down state, power consumption can be suppressed.
Another holding circuit may be further arranged between the reference signal generation circuit and the bias generation circuit, and the signal input to the other holding circuit may be a signal output from the reference signal generation circuit. For example, corresponding to the case of the fourth embodiment, by realizing the normal operation and the holding operation by the holding circuit, the holding circuit outputs the reference signal depending on the input signal during the normal operation, Since the reference signal during normal operation is output without depending on the input signal during the holding operation, the reference signal equivalent to the normal state can be used even when the reference signal generation circuit is in a low power consumption state. .

  The holding circuit may be disposed between the reference signal generation circuit and the bias generation circuit, and a signal input to the holding circuit may be a signal output from the reference signal generation circuit. For example, corresponding to the case of the third embodiment, by realizing the normal operation and the holding operation by the holding circuit, the holding circuit outputs the reference signal depending on the input signal during the normal operation, Since the reference signal during normal operation is output to the oscillation unit without depending on the input signal during the holding operation, the reference signal equivalent to the normal state is used even when the reference signal generation circuit is in a low power consumption state. Therefore, it is possible to realize an oscillator that can operate with low power consumption without increasing the area or reducing accuracy due to the low current consumption of the reference signal generation circuit.

A booster circuit for boosting the reference signal (for example, corresponding to the booster circuit 12 in FIG. 3) may be included. For example, corresponding to the case of the second, third, or fourth embodiment, a stable reference signal that is a voltage that exceeds the power supply voltage by inputting and boosting the reference signal directly or as an output of the holding circuit to the booster circuit Can be generated.
The booster circuit preferably performs a boosting operation according to the output of the oscillation unit. By operating the booster circuit with the output of the oscillation unit, an oscillator that can operate with low power consumption can be realized.

  Further, another booster circuit for boosting the bias signal (for example, corresponding to the booster circuit 12 in FIG. 6) and an output from the other booster circuit are used as a power source, and based on the output of the reference signal generation circuit. It may further include another bias generation circuit (for example, corresponding to the bias generation circuit 22 in FIG. 6) that generates another bias signal for driving the oscillation unit. For example, corresponding to the case of the fifth embodiment, a signal having a voltage exceeding the power supply voltage obtained by boosting the signal held by the holding circuit is used in another bias circuit, so that it is higher than the power supply voltage even during the holding operation. A signal can be supplied to the oscillator, and an oscillator that can operate with low power consumption can be realized.

The timing signal generation circuit preferably receives the output of the oscillation unit as an input. With this configuration, each part of the oscillator can be operated at an appropriate timing.
In addition, it is preferable that the oscillating portion uses a quartz piezoelectric element. With this configuration, a stable oscillation output can be obtained.

  According to the present invention, at least one of the reference signal generation circuit and the bias generation circuit that generates the reference signal is set in a low power consumption state for a predetermined time in a predetermined cycle, and depends on an input signal during normal operation. The bias signal is output to the oscillation unit, and during the holding operation, the area is increased by switching the holding circuit that outputs the bias signal during normal operation to the oscillation unit, regardless of the input signal, between normal operation and holding operation. It is possible to realize an oscillator that can operate with low power consumption without causing deterioration of accuracy.

It is a figure which shows the structure of the oscillator by the 1st Embodiment of this invention. It is a wave form diagram which shows the operation example of the oscillator by the 1st Embodiment of this invention. It is a figure which shows the structure of the oscillator by the 2nd Embodiment of this invention. It is a figure which shows the structure of the oscillator by the 3rd Embodiment of this invention. It is a figure which shows the structure of the oscillator by the 4th Embodiment of this invention. It is a figure which shows the structure of the oscillator by the 5th Embodiment of this invention. It is a figure which shows the structure of the conventional oscillator.

Next, embodiments of the present invention will be described in detail with reference to the drawings. In each figure referred to below, the same parts as those in the other figures will be described with the same reference numerals.
(First embodiment)
FIG. 1 shows a block diagram of an oscillator as the first embodiment of the present invention. In FIG. 1, the oscillator according to the first embodiment of the present invention includes a reference signal generation circuit 11, a bias generation circuit 21, a holding circuit 31, a voltage control oscillation unit 41, a crystal piezoelectric element 51, and a timing signal generation. And an oscillation signal is output from the output terminal FOUT.

Here, the bias generation circuit 21 includes all bias voltage circuits and bias current circuits for driving the voltage controlled oscillation unit 41.
The reference signal generation circuit 11 and the bias generation circuit 21 can switch between the normal operation state and the power-down state according to the voltage value of the signal INT_PD output from the timing signal generation circuit 61.

  The holding circuit 31 performs an operation of switching between a normal state and a hold state (holding state) according to the signal INT_HD output from the timing signal generation circuit 61. The normal state of the holding circuit 31 is a state in which the signal V_HOLD output from the holding circuit 31 changes depending on the input signal to the holding circuit 31 (the signal BIAS_O output from the bias generation circuit 21). On the other hand, the hold state of the holding circuit 31 is that the input signal (signal BIAS_O) to the holding circuit 31 and the signal V_HOLD output from the holding circuit 31 are disconnected, and the voltage value of the signal V_HOLD output from the holding circuit 31 is In this state, the normal voltage value of the signal V_HOLD is output regardless of the state of the input signal (signal BIAS_O).

Here, FIG. 2 is a timing chart showing an example of the operation of each part of the oscillator of FIG. As shown in FIG. 2, the reference signal generation circuit 11 and the bias generation circuit 21 normally operate in a section where the signal INT_PD output from the timing signal generation circuit 61 is at the HI level. The voltage value of BIAS_O is a normal operating voltage.
On the other hand, in the interval in which the signal INT_PD output from the timing signal generation circuit 61 is at the LO level, both the reference signal generation circuit 11 and the bias generation circuit 21 are in the power-down state, so that the voltage of the output signal BIAS_O of the bias generation circuit 21 The value is a power down voltage (for example, 0 V).

  The holding circuit 31 is in a normal state only during a period in which the voltage value of the output signal BIAS_O of the bias generation circuit 21 is stable. For this reason, the signal INT_HD output from the timing signal generation circuit 61 changes from the LO level to the HI level later (at a later timing) than the signal INT_PD, and changes from the HI level to the LO level earlier (at an earlier timing) than the signal INT_PD. A changing signal.

Since the current consumption of the reference signal generation circuit 11 and the bias generation circuit 21 in the power-down state is only a leakage current, it can be regarded as almost 0 (zero). Therefore, if the time of the HI level section of the signal INT_PD output from the timing signal generation circuit 61 is T1, and the period of the signal INT_PD is T2, the current consumption during the intermittent operation is expressed by the following equation (1).
(Current consumption during intermittent operation) = (Current consumption during normal operation) × (T1 / T2) (1)
Therefore, if the time of the period T2 can be made sufficiently longer than the time T1, the current consumption of each circuit can be made sufficiently smaller than the current consumption of the voltage controlled oscillator 41, and therefore only the minimum current consumption required for oscillation is required. It is possible to configure a highly stable oscillator.

Signals for controlling the timing operation, such as the signal INT_HD and the signal INT_PD, are generated in the timing signal generation circuit 61 based on the output of the voltage controlled oscillator 41 in order to suppress current consumption.
According to the configuration of FIG. 1, a highly stable crystal oscillator that can operate with low current consumption can be realized.
The above description has been made using the voltage controlled oscillator 41 that can control the frequency by the input bias signal. However, the present invention is not limited to the voltage controlled oscillator, and all oscillations driven by the input bias signal. Part is included.

(Second Embodiment)
A block diagram of an oscillator as a second embodiment of the present invention is shown in FIG. 3, the oscillator according to the second embodiment of the present invention has a configuration in which a booster circuit 12 is added between the reference signal generation circuit 11 and the bias generation circuit 21 in the oscillator of FIG.
The output signal VREF of the reference signal generation circuit according to the first embodiment is boosted by the boosting circuit and input to the bias generation circuit 21. In the reference signal generation circuit, it is difficult to generate a voltage higher than the power supply voltage. By boosting this voltage, it is possible to generate a signal HVREF that is a stable reference signal that is a voltage exceeding the power supply voltage.

The booster circuit 12 normally requires a clock. As this clock, the output of its own voltage controlled oscillator 41 may be used as shown in FIG.
According to the configuration of FIG. 3, a highly stable crystal oscillator that can operate with low current consumption and low power consumption can be realized.

(Third embodiment)
A block diagram of an oscillator as a third embodiment of the present invention is shown in FIG. 4, the oscillator according to the third embodiment of the present invention has a configuration in which a holding circuit 32 is added between the reference signal generation circuit 11 and the booster circuit 12 instead of the holding circuit 31 in the oscillator of FIG. 3. is there.

  In this embodiment, the holding circuit 32 receives the output signal VREF of the reference signal generation circuit 11 and the output of the holding circuit 32 is input to the booster circuit 12 to generate the signal HVREF. At this time, when the bias generation circuit 21 is configured only by a digital circuit, for example, if there is no portion where a DC current flows except for the leak path, it is not necessary to enter the power-down state. Absent.

The output signal VREF_HOLD of the holding circuit 32 always outputs the same voltage as the VREF voltage during normal operation during intermittent operation. Further, if the booster circuit 12 is operated using the output of its own voltage controlled oscillator 41 as a clock, the signal HVREF, which is an output signal of the booster circuit 12, can maintain the voltage even during the intermittent operation. In other words, it is possible to generate a stable reference signal having a voltage higher than the supplied power supply voltage even during intermittent operation, and at the same time, it is possible to configure a highly stable oscillator with only the minimum current consumption necessary for oscillation. it can.
According to the configuration of FIG. 4, it is possible to realize a highly stable crystal oscillator that can operate with low current consumption and low voltage.

(Fourth embodiment)
FIG. 5 shows a block diagram of an oscillator as the fourth embodiment of the present invention. In FIG. 5, the oscillator according to the fourth embodiment of the present invention has a holding circuit 32 added between the reference signal generation circuit 11 and the booster circuit 12 in addition to providing the holding circuit 31 in the oscillator of FIG. 3. It is a configuration.

When the bias generation circuit 21 of the third embodiment shown in FIG. 4 consumes DC current, the bias generation circuit 21 must be operated intermittently in order to reduce current consumption. At this time, a holding circuit 31 that holds the output signal of the bias generation circuit 21 during the power-down state is required.
According to the configuration of FIG. 5, it is possible to realize a highly stable crystal oscillator that can operate with low current consumption and low power consumption.

(Fifth embodiment)
A block diagram of an oscillator as a fifth embodiment of the present invention is shown in FIG. In FIG. 6, the oscillator according to the fifth embodiment of the present invention is the same as the oscillator shown in FIG. And a bias generation circuit 22 mainly composed of a digital circuit that can be ignored in comparison with the above.

  In FIG. 6, the reference signal generation circuit 11 and the bias generation circuit 21 operate intermittently, but the output signal at the time of the normal operation of the bias generation circuit 21 is always maintained at substantially the same voltage by the holding circuit 31 during the intermittent operation. By boosting the signal BIAS1_HOLD held by the holding circuit 31 as an input to the booster circuit 12, it is possible to hold a highly stable reference signal higher than the power supply voltage even during intermittent operation. By using this highly stable reference signal as an input of the bias generation circuit 22, for example, as a power supply, the highly stable signal BIAS2_O can be supplied to the voltage controlled oscillator 41 even during intermittent operation. As shown in FIG. 6, all the blocks with large current consumption other than the voltage-controlled oscillation unit 41 operate intermittently, so that a highly stable oscillator can be configured with only the minimum current consumption necessary for oscillation.

According to the configuration of FIG. 6, it is possible to realize a highly stable crystal oscillator that can operate with low current consumption and low power consumption.
In the above description, the bias generation circuit 21 and the bias generation circuit 22 are added to the oscillator shown in FIG. 1. However, the bias generation circuit 21 described above is added to any of the oscillators shown in FIGS. In addition, the bias generation circuit 22 may be added.

By the way, the above-mentioned example of the high stability oscillator is a temperature-compensated crystal oscillator, but the present invention is also applicable to a crystal oscillator without temperature compensation.
The present invention is not limited to a crystal oscillator, but can be applied to an oscillator that requires a bias signal from the outside, such as a SAW (Surface Acoustic Wave) oscillator and a MEMS (Micro Electro Mechanical Systems) oscillator.

10, 11 Reference signal generation circuit 12 Booster circuit 20, 21, 22 Bias generation circuit 31, 32 Holding circuit 40, 41 Voltage-controlled oscillation unit 50, 51 Crystal piezoelectric element 61 Timing signal generation circuit

Claims (10)

An oscillation unit driven by an input bias signal;
A reference signal generation circuit for generating a reference signal;
A bias generation circuit for generating the bias signal for driving the oscillation unit based on an output of the reference signal generation circuit;
A holding circuit that inputs the bias signal to the oscillation unit depending on a signal input during normal operation, and outputs a bias signal during normal operation without depending on the input signal during holding operation;
Timing for generating a signal for causing at least one of the reference signal generation circuit and the bias generation circuit to be in a low power consumption state for a predetermined time in a predetermined cycle, and a signal for switching the holding circuit between a normal operation and a holding operation A signal generation circuit;
An oscillator comprising:   The oscillator according to claim 1, wherein a low power consumption state of the reference signal generation circuit and the bias generation circuit is a power-down state.   3. The holding circuit is disposed between the bias generation circuit and the oscillating unit, and a signal input to the holding circuit is a signal output from the bias generation circuit. The oscillator described.   Another holding circuit is further disposed between the reference signal generation circuit and the bias generation circuit, and a signal input to the another holding circuit is a signal output from the reference signal generation circuit. The oscillator according to claim 3.   2. The holding circuit is disposed between the reference signal generation circuit and the bias generation circuit, and a signal input to the holding circuit is a signal output from the reference signal generation circuit. Or the oscillator of 2.   The oscillator according to any one of claims 1 to 5, further comprising a boosting circuit that boosts the reference signal.   The oscillator according to claim 6, wherein the booster circuit performs a boosting operation according to an output of the oscillation unit. Another booster circuit for boosting the bias signal;
Another bias generation circuit that uses the output from the other booster circuit as a power source and generates another bias signal that drives the oscillation unit based on the output of the reference signal generation circuit;
The oscillator according to any one of claims 1 to 7, further comprising:   The oscillator according to any one of claims 1 to 8, wherein the timing signal generation circuit receives an output of the oscillating unit as an input.   The oscillator according to any one of claims 1 to 9, wherein the oscillating unit uses a crystal piezoelectric element.

Images