JP2006270161A - Oscillator and oscillation method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the matter of a conventional oscillator that a CR oscillation circuit cannot assist actuation of oscillation of a crystal oscillation circuit sufficiently. <P>SOLUTION: The oscillator comprises a crystal oscillation circuit oscillating a first signal having a frequency defined by a crystal oscillator, and a CR oscillation circuit creating a second signal having a second frequency substantially identical to the above-mentioned frequency in a transient period until the crystal oscillation circuit oscillates the first signal steadily and supplying the second signal to the crystal oscillation circuit. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an oscillation apparatus and an oscillation method including a crystal oscillation circuit that oscillates a signal having a frequency defined by a crystal oscillator.

  In the conventional oscillation device described above, for example, as described in Patent Document 1 below, in order to oscillate accurately even under oscillation conditions having different specifications, the oscillation start by the crystal oscillation circuit is CR. The oscillation circuit supports it.

JP 2004-140817 A

  However, since the CR oscillation circuit is intended to induce the activation of the oscillation of the crystal oscillation circuit, it merely gives a disturbance to the crystal oscillation circuit, so that the oscillation activation of the crystal oscillation circuit is supported. For example, there is a problem that the time required to oscillate the signal steadily cannot be shortened sufficiently.

  In order to solve the above problem, an oscillation device according to the present invention includes a crystal oscillation circuit that oscillates a first signal having a frequency defined by a crystal oscillator, and the crystal oscillation circuit makes the first signal steady. A CR oscillation circuit that generates a second signal having a second frequency substantially the same as the frequency and supplies the second signal to the crystal oscillation circuit in a transition period until the oscillation starts. Including.

  According to the oscillation device of the present invention, in the transition period until the crystal oscillation circuit oscillates the first signal having the first frequency steadily, the CR oscillation circuit includes the crystal oscillation circuit. The second signal having a second frequency substantially the same as the first frequency is supplied to the first signal generated by the crystal oscillation circuit by the second signal having the second frequency. Since the oscillation of the first signal having the frequency is promoted, the oscillation of the first signal is supported by giving a simple disturbance having no relationship with the first frequency to the crystal oscillation circuit. Compared to the conventional oscillation device, the oscillation of the first signal by the crystal oscillation circuit can be supported more appropriately.

  In the oscillation device according to the present invention described above, the CR oscillation circuit includes a capacitance, a resistor, and a plurality of cascaded inverters, and receives the first current by receiving the first current. By receiving a first inverter for generating a voltage and a second voltage for supplying a second current having a value substantially the same as the value of the first current to the plurality of inverters; A second inverter that generates a third voltage that should be substantially the same as the value of the first voltage; and the second inverter based on the difference between the first voltage and the third voltage. And a ballast circuit having an operational amplifier for adjusting the value of the voltage.

  In the oscillation device according to the present invention, the first switch provided between the output terminal of the CR oscillation circuit and the connection point between the crystal oscillator and the crystal oscillation circuit, By switching the second switch connected to the output end and the first switch from the initial connection state to the cut-off state, the second signal from the output end of the CR oscillation circuit becomes the crystal oscillator. And a first step for prohibiting output to a connection point between the crystal oscillation circuits, and, following the first step, by switching the second switch from the initial cutoff state to the connection state, A second step for allowing the first signal from the output terminal of the crystal oscillation circuit to be output to the outside of the oscillation device, and the second step by the CR oscillation circuit following the second step. The raw signal Further comprising a control circuit for performing the third step of prohibiting.

  In the oscillation device according to the present invention, the first switch provided between the output terminal of the CR oscillation circuit and the connection point between the crystal oscillator and the crystal oscillation circuit, By switching the second switch connected to the output end and the first switch from the initial connection state to the cut-off state, the second signal from the output end of the CR oscillation circuit becomes the crystal oscillator. And a first step of prohibiting output to a connection point between the crystal oscillation circuits, and a second step of prohibiting generation of the second signal by the CR oscillation circuit following the first step. Then, following the second step, the first signal from the output terminal of the crystal oscillation circuit is transferred to the outside of the oscillation device by switching the second switch from the initial cutoff state to the connection state. Output Further comprising a control circuit for performing the third step of allowing.

  In the above-described oscillation device according to the present invention, at least one length between the first step and the second step and between the second step and the third step is the first step. More than two clocks defined by the signal.

  In order to solve the above-described problem, the oscillation method according to the present invention performs an operation of oscillating while increasing the frequency of an oscillating signal from a frequency lower than the first frequency to be oscillated constantly toward the first frequency. In the process, the oscillation operation is accelerated by supplying the oscillation operation with a second signal having a second frequency substantially the same as the first frequency.

  An embodiment of an oscillation device using an oscillation method according to the present invention will be described with reference to the drawings.

"Constitution"
FIG. 1 shows the configuration of the oscillator according to the embodiment. As shown in FIG. 1, the oscillation device OD of the embodiment outputs a crystal oscillation signal OS_X having a crystal oscillation frequency F_X that is a frequency defined by the crystal oscillator 1. The circuit 2 includes a CR oscillation circuit 3, a stabilization circuit 4, a first switch SW 1, a second switch SW 2, and a control circuit 5.

  The crystal oscillator 1 has the same structure and function as conventionally known.

  In the crystal oscillation circuit 2, the crystal oscillator 1 is connected between the gate terminal G and the drain terminal D, and the output terminal out is connected to the switch SW 2 and the control circuit 5. The crystal oscillation circuit 2 constitutes a conventionally known Colpitts oscillation circuit in cooperation with the crystal oscillator 1 and outputs a crystal oscillation signal OS_X from its output terminal out.

  The CR oscillation circuit 3 steadily outputs the crystal oscillation signal OS_X after starting the oscillation device OD, that is, after starting the power supply device (not shown) for supplying power to the oscillation device. In the transition period until oscillation occurs, the crystal oscillator 1 and the crystal oscillation circuit 2 are supplied with a CR oscillation signal OS_CR having a CR oscillation frequency F_CR that is substantially the same as the crystal oscillation frequency F_X. And a connection point between the crystal oscillation circuit 2 and an output terminal out which can be connected.

  In order to stabilize the CR oscillation frequency F_CR of the CR oscillation signal OS_CR generated by the CR oscillation circuit 3, the stabilization circuit 4 controls the oscillation operation of the CR oscillation circuit 3 from its output terminal out to the input terminal of the CR oscillation circuit 3. A signal for the control is output to in.

  FIG. 2 shows a configuration of the CR oscillation circuit and the stabilization circuit of the embodiment. The CR oscillation circuit 3 has the same configuration as that conventionally known. Specifically, as shown in FIG. 2, three cascaded first inverter IN1, second inverter IN2, third Inverter IN3, resistor R connected between the input terminal of first inverter IN1 and the output terminal of third inverter IN3, and between the input terminal of first inverter IN1 and the output terminal of second inverter IN2 And a capacitance C connected to the.

  The three inverters IN1, IN2, and IN3 have a power supply voltage terminal connected to an output terminal out of an operational amplifier OP (described later) in the stabilization circuit 4, and a ground voltage terminal connected to the ground voltage (GND). Yes.

  As illustrated in FIG. 2, the stabilization circuit 4 includes a constant current generation circuit CI, a first inverter INV1, a second inverter INV2, and an operational amplifier OP. Here, the inverters IN1, IN2, and IN3 in the CR oscillation circuit 3 and the inverters INV1 and INV2 in the stabilization circuit 4 have inherent transistor structures such as transistor size, that is, channel width, channel length, and drain capacitance. Should be identical.

  The constant current generation circuit CI causes the first inverter INV1 to generate a fixed first voltage V1 such as a threshold voltage Vth (for example, 1.5V when the power supply voltage Vdd is 3V). A constant current I is supplied to the power supply voltage terminal of one inverter INV1.

  The input terminal and the output terminal of the first inverter INV1 are connected to each other, the connection point is connected to the + input terminal of the operational amplifier OP, and the first input terminal of the operational amplifier OP is connected to the first input terminal described above. The voltage V1 is given. The ground voltage terminal of the first inverter INV1 is connected to the ground voltage.

  The operational amplifier OP is applied with a third voltage V3 (described later) from the second inverter INV2 at the negative input terminal, and in the CR oscillation circuit 3 according to the difference between the first voltage V1 and the second voltage V3. The second voltage V2, which is a voltage that allows the constant current I (the same value as the constant current I supplied to the first inverter INV1 in the stabilization circuit 4) to flow through the three inverters IN1, IN2, and IN3, is adjusted. While generating.

  The input terminal and the output of the second inverter INV2 are connected, the second voltage V2 from the operational amplifier OP is applied to the power supply voltage terminal, and the ground voltage terminal is connected to the ground potential. The second inverter INV2 is a third voltage V3 that is essentially the same value as the first voltage V1, and actually uses the third voltage V3 that varies depending on the magnitude of the second voltage V2 as an operational amplifier OP. To the negative side input terminal.

  The ballast circuit 4 having the above-described configuration supplies (1) temperature fluctuations and fluctuations in the power supply voltage Vdd by supplying constant current I to the three inverters IN1, IN2, and IN3 in the CR oscillation circuit 3. The influence of the two inverters IN1, IN2, and IN3 can be suppressed, and thereby the CR oscillation frequency F_CR can be stabilized. (2) The influence on the CR oscillation frequency F_CR given by the variation in characteristics can be suppressed, and thus the CR oscillation frequency F_CR can be stabilized similarly.

  Returning to FIG. 1, the first switch SW 1 is connected between the connection point between the crystal oscillator 1 and the crystal oscillation circuit 2, in other words, between the gate terminal G of the crystal oscillation circuit 2 and the output terminal out of the CR oscillation circuit 3. It is provided and is initially connected. The second switch SW2 is composed of an AND element (AND element), one input terminal of which is connected to the output terminal out of the crystal oscillation circuit 2, and the crystal oscillation signal OS_X is output from the output terminal. The second switch SW2 is in the cut-off state at the initial stage.

  The control circuit 5 has an input terminal in connected to the output terminal out of the crystal oscillation circuit 2, a third control output terminal cout3 connected to the input terminal of the second switch SW2, and a second control output. The terminal cout2 is connected to the controlled terminal cnt of the CR oscillation circuit 3, and the first control output terminal cout1 is connected to the controlled terminal of the first switch SW1.

  FIG. 3 shows the configuration of the control circuit of the embodiment. As shown in FIG. 3, the control circuit 5 includes a counter CTR, a first flip-flop DFF1, a second flip-flop DFF2, and a third flip-flop DFF3. The counter CTR has the same configuration and function as a conventionally known counter circuit, and the first, second, and third flip-flops DFF1, DFF2, and DFF3 have the same configuration and function as a conventionally known D flip-flop. It has a function. The counter CTR has first, second, and third output terminals out1, out2, and out3 connected to clock terminals C of the first, second, and third flip-flops DFF1, DFF2, and DFF3. The data terminals D of the flip-flops DFF1, DFF2, and DFF3 are connected to the ground voltage Vss, the ground voltage Vss, and the power supply voltage Vdd.

  In the control circuit 5, the counter CTR is based on the CR oscillation signal OS_CR input to the input terminal “in” according to three predetermined count numbers (periods t 1 to t 2 in the time chart of FIG. 4, time t 1 to t The first, second, and third count-up signals CU1, CU2, and CU3 indicating that the count-up has been performed are counted as the first, second, and third count-up signals after counting the period of time t4 and the period of time t1 to time t3, respectively. Output from the output terminals out1, out2, and out3 to the clock terminals C of the first, second, and third flip-flops DFF1, DFF2, and DFF3.

  Upon receiving the first count-up signal CU1, the first flip-flop DFF1 outputs the ground voltage Vss applied to the data terminal D from the output terminal Q to the first switch SW1, thereby the first switch SW1 is turned off. Upon receiving the second count-up signal CU2, the second flip-flop DFF2 outputs the ground voltage Vss applied to the data terminal D from the output terminal Q to the CR oscillation circuit 3, thereby causing the CR oscillation circuit 3 to The generation of the CR oscillation signal OS_CR is stopped. When the third flip-flop DFF3 receives the third count-up signal CU3, the third flip-flop DFF3 outputs the power supply voltage Vdd applied to the data terminal D from the output terminal Q to the second switch SW2, whereby the second switch SW2 is switched from the initial cut-off state to the connected state, thereby allowing the crystal oscillation signal OS_X from the crystal oscillation circuit 2 to be output to the outside.

<Operation>
FIG. 4 is a time chart illustrating the operation of the oscillation device according to the embodiment. Hereinafter, the operation of the oscillation device OD will be described with reference to the time chart of FIG.

  Time t0: The user of the OD of the oscillation device turns on a power supply device (not shown) that supplies power to the oscillation device OD.

  Time t1: The CR oscillation circuit 3 starts generating the CR oscillation signal OS_CR having the CR oscillation frequency F_CR as soon as the switch of the power supply circuit is turned on. Since the first switch SW1 is in the connected state at the initial stage, the CR oscillation signal OS_CR is supplied to the crystal oscillator 1 and the crystal oscillation circuit 2 through the first switch SW1. The CR oscillation signal OS_CR is received by the control circuit 5 via the crystal oscillation circuit 2, and the counter CTR in the control circuit 5 starts counting the clock of the CR oscillation signal OS_CR.

  Time t2: The control circuit 5 outputs the first control signal CNT1 indicating that the count has been increased to the first switch SW1, thereby setting the first switch SW1 to the cut-off state, and the CR oscillation from the CR oscillation circuit 3 The supply of the signal OS_CR toward the crystal oscillator 1 and the crystal oscillation circuit 2 is stopped.

  Time t3: At time t3, which is a time that is two clocks or more away from the CR oscillation signal OS_CR from the time t2, the control circuit 5 sends the third control signal CNT3 indicating that the count has been increased to the second switch In this way, the second switch SW2 is connected to allow the crystal oscillation signal OS_X from the crystal oscillation circuit 2 to be output to the outside.

  Time t4: At time t4, which is a time that is two clocks or more away from the CR oscillation signal OS_CR from the time t3, the control circuit 5 sends the second control signal CNT2 indicating that the count is up to the CR oscillation circuit 3 This causes the CR oscillation circuit 3 to stop generating the CR oscillation signal OS_CR.

"effect"
As described above, in the oscillation device OD of the embodiment, the crystal oscillation circuit 2 is based on the crystal oscillator 1 and the crystal oscillation signal OS_X from the time t1 that is not shortly after the time t0 when the oscillation device OD is started up by turning on the power supply device. In a transient period up to time t2 at which the crystal oscillation frequency F_X of the crystal oscillation signal OS_X and the crystal oscillation circuit OS_X Since the CR oscillation signal OS_CR having the CR oscillation frequency F_CR that is substantially the same is supplied, the crystal oscillation circuit 2 is more stable than the conventional oscillation device that merely gives a disturbance. It is possible to reduce the time required until OS_X can be generated.

  In addition, since the length between time t2 and time t3 and between time t3 and time t4 is equal to or longer than two clocks of the CR oscillation signal OS_CR, the control circuit 5 switches, for example, the first switch SW1 from the connected state. It is possible to avoid a situation in which the operation of the oscillation device OD is controlled in an order opposite to the original order, in which the second switch SW2 is switched from the cutoff state to the connected state before switching to the cutoff state. .

<Modification>
FIG. 5 is a time chart showing another operation of the oscillation device. The oscillation device OD described above may operate along the time chart shown in FIG. 5 in addition to the time chart shown in FIG. Hereinafter, the operation of the oscillation device OD will be described with reference to another time chart shown in FIG.

  Time t3: After the same operation as described above is performed at time t0, t1, and t2, when time t3 is reached, which is a time that is two clocks or more away from the CR oscillation signal OS_CR from time t2. In the same manner as the operation at time t4 in the embodiment, the control circuit 5 outputs the second control signal CNT2 indicating that the count has been increased to the CR oscillation circuit 3, thereby causing the CR oscillation circuit 3 to transmit the CR oscillation signal. The generation of OS_CR is stopped.

  Time t4: At time t4, which is a time that is two clocks or more away from the CR oscillation signal OS_CR from time t3, the control circuit 5 counts up in the same manner as the operation at time t3 in the above-described embodiment. The third control signal CNT3 indicating the effect is output to the second switch SW2, thereby bringing the second switch SW2 into a connected state and allowing the crystal oscillation signal OS_X from the crystal oscillation circuit 2 to be output to the outside. To do.

  As described above, in contrast to the order in which the oscillation of the CR oscillation circuit 3 is stopped after the second switch SW2 is connected by the oscillation device OD in the embodiment, the oscillation device OD in the modification example The same effect as that of the above-described embodiment can be obtained also by the procedure of setting the second switch SW2 in the connected state after stopping the oscillation of the CR oscillation circuit 3.

The figure which shows the structure of the oscillation apparatus of an Example. The figure which shows the structure of CR oscillation circuit of an Example, and a stable circuit. The figure which shows the structure of the control circuit of an Example. The time chart which shows operation | movement of the oscillation apparatus of an Example. The time chart which shows operation | movement of the oscillation apparatus of a modification.

Explanation of symbols

OD Oscillator 1 Crystal oscillator 2 Crystal oscillator circuit 3 CR oscillator circuit 4 Stabilizer circuit 5 Control circuit SW1 First switch SW2 Second switch.

Claims (6)

A crystal oscillation circuit for oscillating a first signal having a frequency defined by the crystal oscillator;
In a transition period until the crystal oscillation circuit oscillates the first signal steadily, a second signal having a second frequency substantially the same as the frequency is generated, and the second signal is An oscillation device comprising: a CR oscillation circuit that supplies the crystal oscillation circuit. The CR oscillation circuit has a capacitance, a resistor, and a plurality of inverters connected in cascade,
A first inverter that generates a first voltage by receiving a supply of a first current;
By receiving a second voltage for supplying a second current having a value substantially the same as the value of the first current to the plurality of inverters, a value substantially equal to the value of the first voltage is obtained. A second inverter that generates a third voltage that should be the same value as
The oscillation device according to claim 1, further comprising a stabilization circuit including an operational amplifier that adjusts a value of the second voltage based on a difference between the first voltage and the third voltage. A first switch provided between an output end of the CR oscillation circuit and a connection point between the crystal oscillator and the crystal oscillation circuit;
A second switch connected to the output terminal of the crystal oscillation circuit;
By switching the first switch from the initial connection state to the cutoff state, the second signal from the output terminal of the CR oscillation circuit is output to the connection point between the crystal oscillator and the crystal oscillation circuit. A first step that prohibits
Subsequent to the first step, the first signal from the output terminal of the crystal oscillation circuit is output to the outside of the oscillation device by switching the second switch from the initial cutoff state to the connection state. A second step of allowing
2. The oscillation device according to claim 1, further comprising a control circuit that performs a third step of prohibiting generation of the second signal by the CR oscillation circuit subsequent to the second step. A first switch provided between an output end of the CR oscillation circuit and a connection point between the crystal oscillator and the crystal oscillation circuit;
A second switch connected to the output terminal of the crystal oscillation circuit;
By switching the first switch from the initial connection state to the cutoff state, the second signal from the output terminal of the CR oscillation circuit is output to the connection point between the crystal oscillator and the crystal oscillation circuit. A first step that prohibits
Subsequent to the first step, a second step of prohibiting the generation of the second signal by the CR oscillation circuit;
Subsequent to the second step, the first signal from the output terminal of the crystal oscillation circuit is output to the outside of the oscillation device by switching the second switch from the initial cutoff state to the connection state. The oscillation device according to claim 1, further comprising a control circuit that performs a third step of permitting the operation.   At least one length between the first step and the second step and between the second step and the third step is equal to or longer than two clocks defined by the first signal. The oscillation device according to claim 3 or 4, wherein In the process of oscillating while increasing the frequency of the oscillating signal from the lower frequency than the first frequency to be oscillated steadily toward the first frequency, the second frequency substantially the same as the first frequency. An oscillation method characterized in that the oscillation operation is promoted by supplying a second signal having a frequency of 1 to the oscillation operation.

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