JP5034763B2 - Oscillator - Google Patents

Description

  The present invention relates to an oscillator using a vibrator.

  An oscillator 1 using a crystal resonator 110 such as a SAW (Surface Acoustic Wave) resonator, a tuning fork resonator, or an AT resonator is configured by a circuit as shown in FIG. 5A, for example. (See FIG. 2 of Non-Patent Document 1). Further, an equivalent circuit 111 of the crystal unit 110 includes an equivalent series inductor L1, an equivalent series capacitor C1, an equivalent series resistance R1, and an equivalent series connected in parallel thereto, as shown in FIG. 5B. It is expressed by a circuit including a parallel capacitor C0 (see FIG. 1 of Non-Patent Document 1). The Q characteristic Q1, which is the quality factor of the crystal unit, is calculated as Q1 = ω × L1 / R1 when the angular frequency is ω, and the oscillation start time td1 is as td1 = (2 × Q1) / ω. Is calculated.

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  However, although the crystal resonator 110 can increase the frequency purity of oscillation when the Q characteristic is set high, there is a problem that the startup time of oscillation is delayed.

  The present invention has been made to solve the above-described problems, and can be realized as the following forms or application examples.

[Application Example 1]
A first element, a second terminal, a resistance element and an inductor connected in series between the first terminal and the second terminal, and a vibrator connected in parallel with the resistance element And a capacitor connected between the first terminal and the second terminal, and an oscillation circuit unit connected between the first terminal and the second terminal to vibrate the vibrator The value of the inductor, the resistance value of the resistance element, the value of the equivalent series inductor of the vibrator, and the resistance value of the equivalent series resistance of the vibrator are (the value of the inductor / the resistance element) Resistance value) <(value of equivalent series inductor of the vibrator / resistance value of equivalent series resistance of the vibrator).

  According to this configuration, since the LC parallel oscillation circuit composed of the inductor and the capacitor first oscillates until the vibrator starts oscillating, the vibrator can be started in a shorter time than the vibrator alone. If oscillation starts, an oscillator with high frequency purity can be realized.

[Application Example 2]
A first element, a second terminal, a resistance element and a capacitor connected in series between the first terminal and the second terminal, and a vibrator connected in parallel with the resistance element An inductor connected between the first terminal and the second terminal, and an oscillation circuit unit connected between the first terminal and the second terminal to vibrate the vibrator The value of the inductor, the resistance value of the resistance element, the value of the equivalent series inductor of the vibrator, and the resistance value of the equivalent series resistance of the vibrator are (the value of the inductor / the resistance element) Resistance value) <(value of equivalent series inductor of the vibrator / resistance value of equivalent series resistance of the vibrator).

  According to this configuration, since the LC parallel oscillation circuit composed of the inductor and the capacitor first oscillates until the vibrator starts oscillating, the vibrator can be started in a shorter time than the vibrator alone. If oscillation starts, an oscillator with high frequency purity can be realized.

[Application Example 3]
The oscillator according to the above, wherein a resistance value of an equivalent series resistance of the vibrator is smaller than a resistance value of the resistance element.

  According to this configuration, since the LC parallel oscillation circuit composed of the inductor and the capacitor first oscillates until the vibrator starts oscillating, the vibrator can be started in a shorter time than the vibrator alone. If oscillation starts, an oscillator with high frequency purity can be realized.

[Application Example 4]
The oscillator according to the above, wherein the value of the inductor is smaller than the value of the equivalent series inductor of the vibrator.

  According to this configuration, since the LC parallel oscillation circuit composed of the inductor and the capacitor first oscillates until the vibrator starts oscillating, the vibrator can be started in a shorter time than the vibrator alone. If oscillation starts, an oscillator with high frequency purity can be realized.

[Application Example 5]
In the oscillator described above, the oscillation circuit section includes a pair of first active elements and second active elements that are differentially connected between the first terminal and the second terminal. An oscillator characterized by being a type circuit.

  According to this configuration, since the LC parallel oscillation circuit composed of the inductor and the capacitor first oscillates until the vibrator starts oscillating, the vibrator can be started in a shorter time than the vibrator alone. If oscillation starts, an oscillator with high frequency purity can be realized.

  Hereinafter, embodiments of an oscillator will be described with reference to the drawings.

(First embodiment)
<Configuration of oscillator>
First, the configuration of the oscillator according to the first embodiment will be described with reference to FIG. FIG. 1 is a circuit diagram showing a configuration of an oscillator according to the first embodiment. As shown in FIG. 1, the oscillator 1 includes a terminal OUT1 that is a first terminal, a terminal OUT2 that is a second terminal, and a resistor R2 and an inductor connected in series between the terminal OUT1 and the terminal OUT2. L2, a vibrator 110 connected in parallel with the resistor element R2, a capacitor C2 connected between the terminal OUT1 and the terminal OUT2, and a terminal C1 connected between the terminal OUT1 and the terminal OUT2 to vibrate the vibrator 110. And an oscillation circuit unit 100 composed of a cross-coupled circuit.

  The oscillation circuit unit 100 includes an Nch transistor N1 that is a first active element and an Nch transistor N2 that is a second active element. The gate terminal of the Nch transistor N1 is connected to the source terminal of the Nch transistor N2. The gate terminal of the Nch transistor N2 is connected to the source terminal of the Nch transistor N1, thereby forming a cross-coupled circuit. The source terminal of the Nch transistor N1 is connected to the power supply potential VDD via the current source 121, and the source terminal of the Nch transistor N2 is connected to the power supply potential VDD via the current source 122. Further, a capacitor Ca is connected between the source terminal of the Nch transistor N1 and the source terminal of the Nch transistor N2.

  The terminals OUT1 and OUT2 are connected to the ground potential GND through the current source 120.

  The vibrator 110 is composed of a SAW vibrator, and an equivalent circuit 111 of the vibrator 110 is equivalent to an equivalent series inductor L1 and an equivalent series capacitor C1 connected in series as shown in FIG. It is expressed by a circuit composed of a resistor R1 and an equivalent parallel capacitor C0 connected in parallel therewith.

<Oscillator operation>
Next, the operation of the oscillator will be described with reference to FIG. FIG. 2 is a timing diagram showing the operation of the oscillator.

  FIG. 2A is a timing chart showing an oscillation time of an LC parallel resonance circuit composed of a resistance element R2, an inductor L2, and a capacitor C2 connected between the terminal OUT1 and the terminal OUT2. The resistance element R2 is set to a value larger than the resistance value of the equivalent series resistance R1 of the equivalent circuit 111, and the inductor L2 is set to a value smaller than the equivalent series inductor L1 of the equivalent circuit 111. The Q characteristic Q2 of the LC parallel resonance circuit composed of the resistor element R2, the inductor L2, and the capacitor C2 is Q2 = ω × L2 / R2 when the angular frequency is ω, and the oscillation start time td2 is td2 = (2 × Q2) / ω = 2 × L2 / R2. As shown in FIG. 2A, the LC parallel resonant circuit composed of the resistor element R2, the inductor L2, and the capacitor C2 is configured so that the oscillation frequency reaches 24 MHz at about 6 μs. To do.

  On the other hand, FIG. 2B is a timing diagram showing an oscillation time of an LC parallel resonance circuit composed of the vibrator 110, the inductor L2, and the capacitor C2 connected between the terminal OUT1 and the terminal OUT2. The Q characteristic Q1 of the LC parallel resonance circuit composed of the vibrator 110, the inductor L2, and the capacitor C2 is Q1 = ω × (L1 + L2) / R1, and the oscillation start time td1 is td1 = (2 × Q1) / ω. = 2 × (L1 + L2) / R1. Since the value of the inductor L2 is much smaller than the value of the inductor L1, the oscillation start time td1 is td1≈2 × L1 / R1. As shown in FIG. 2B, the LC parallel resonance circuit composed of the vibrator 110, the inductor L2, and the capacitor C2 has an oscillation frequency that gradually increases from 0 seconds, and the oscillation frequency is about 100 μsec. Assume that it is configured to reach 10 MHz.

  Here, the reason why the oscillation start time td2 is considerably shorter than the oscillation start time td1 is that the Q characteristic Q2 of the LC parallel resonant circuit is orders of magnitude smaller than the Q characteristic Q1.

  As described above, the oscillation start time td2 is td2 = 2 × L2 / R2, and the oscillation start time td1 is td1 = L1 / R1, so if L2 / R2 <L1 / R1, then td2 <td1 Become.

  Here, even if the resistance value of the resistance element R2 is set to a value larger than the resistance value of the equivalent series resistance R1 of the equivalent circuit 111, the oscillation starting time td2 can be made shorter than the oscillation starting time td1. Even if the inductor L2 is set to a value smaller than the equivalent series inductor L1 of the equivalent circuit 111, the oscillation start time td2 can be made shorter than the oscillation start time td1.

  FIG. 2C is a timing chart showing the oscillation time of the oscillator 1. The oscillator 1 immediately after reaching the oscillation frequency = 24 MHz by the LC parallel resonance circuit composed of the resistance element R2, the inductor L2, and the capacitor C2 at the time of (td2 =) about 6 μsec, the oscillator 110, the inductor L2, and the capacitor The oscillation frequency of the parallel resonance circuit configured with C2 is 10 MHz.

  According to the present embodiment described above, the following effects can be obtained.

  In this embodiment, since the LC parallel oscillation circuit composed of the inductor and the capacitor oscillates first in the period until the vibrator starts oscillating, the vibrator can be activated in a shorter time than the vibrator alone. If oscillation is started, an oscillator with high frequency purity can be realized.

  Although the embodiments of the oscillator have been described above, the present invention is not limited to these embodiments, and can be implemented in various forms without departing from the spirit. Hereinafter, a modification will be described.

  (Modification 1) Modification 1 of the oscillator will be described. In the first embodiment, the case where the oscillation circuit unit 100 is configured by the Nch transistors N1 and N2 has been described, but may be configured by a Pch transistor.

  (Modification 2) Modification 2 of the oscillator will be described. The capacitor C2 and the inductor L2 of the oscillator 1 of the first embodiment may be reversely arranged as shown in FIG.

  (Modification 3) Modification 3 of the oscillator will be described. The resistance element R2 included in the oscillator 1 of the first embodiment may be a variable resistance element VR2 as shown in FIG. The startup time can be controlled by the variable resistance element VR2.

  (Modification 4) Modification 4 of the oscillator will be described. In the first embodiment, the case where the vibrator 110 is configured by a SAW vibrator has been described, but a tuning fork vibrator, an AT vibrator, an FBAR (Film Bulk Acoustic Resonator), a MEMS vibrator, and an SMR (Solid Mounted Resonator). It may be configured with such as.

1 is a circuit diagram showing a configuration of an oscillator according to a first embodiment. The timing diagram which shows operation | movement of an oscillator. The circuit diagram which shows the structure of the oscillator of the modification 2. FIG. FIG. 9 is a circuit diagram showing a configuration of an oscillator according to modification 3; The circuit diagram which shows the structure of the conventional oscillator.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Oscillator, 100 ... Oscillator circuit part, 110 ... Vibrator, 111 ... Equivalent circuit, 120, 121, 122 ... Current source.

Claims (5)

A first terminal;
A second terminal;
A resistance element and an inductor connected in series between the first terminal and the second terminal;
A vibrator connected in parallel with the resistance element;
A capacitor connected between the first terminal and the second terminal;
An oscillation circuit unit that is connected between the first terminal and the second terminal and vibrates the vibrator;
Including
The value of the inductor, the resistance value of the resistance element, the value of the equivalent series inductor of the vibrator, and the resistance value of the equivalent series resistance of the vibrator are:
Satisfying the relationship (value of the inductor / resistance value of the resistive element) <(value of equivalent series inductor of the vibrator / resistance value of equivalent series resistance of the vibrator).
An oscillator characterized by that. A first terminal;
A second terminal;
A resistance element and a capacitor connected in series between the first terminal and the second terminal;
A vibrator connected in parallel with the resistance element;
An inductor connected between the first terminal and the second terminal;
An oscillation circuit unit that is connected between the first terminal and the second terminal and vibrates the vibrator;
Including
The value of the inductor, the resistance value of the resistance element, the value of the equivalent series inductor of the vibrator, and the resistance value of the equivalent series resistance of the vibrator are:
Satisfying the relationship (value of the inductor / resistance value of the resistive element) <(value of equivalent series inductor of the vibrator / resistance value of equivalent series resistance of the vibrator).
An oscillator characterized by that.   3. The oscillator according to claim 1, wherein a resistance value of an equivalent series resistance of the vibrator is smaller than a resistance value of the resistance element.   3. The oscillator according to claim 1, wherein the value of the inductor is smaller than the value of an equivalent series inductor of the vibrator. 5. The oscillator according to claim 1, wherein the oscillation circuit unit includes a first active element differentially connected between the first terminal and the second terminal, and a second active element. An oscillator characterized by being a cross-coupled circuit including any active element .

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