JP3004817B2 - Crystal oscillation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal oscillation circuit, and more particularly to a crystal oscillation circuit capable of outputting a high _VPP voltage with low current consumption.

[0002]

2. Description of the Related Art Oscillation circuits having a quartz oscillator have been widely used as basic oscillation sources in standard signal generators, frequency counters, frequency synthesizers, etc. because of their extremely good frequency stability.

FIG. 7 is a circuit diagram showing the configuration of a conventional crystal oscillation circuit. The output of the oscillator 1 comprising a quartz oscillator via a coupling capacitor C ₁ connected to the gate electrode of the output transistor 2. Coupling by connecting a resistor R ₁ between the capacitor C ₁ and the gate electrode, grounds the other end. The drain of the output transistor 2 via the resistor R ₂ is connected to the power supply terminal 3, the source is grounded through the resistor R _S, a capacitor C ₂ in parallel with the resistor R _S. Further, the drain of the output transistor 2 is output capacitor C ₃ via connected to the output terminal 4, an oscillation signal of a predetermined frequency from the output terminal is output. On the other hand, the output level of the output oscillation signal generally needs to be 1 V _PP or more, and a current consumption of about 1 to 1.2 mA is required to secure this output level.

[0004]

Various circuit devices driven by a battery such as a mobile phone have been put into practical use. When a crystal oscillation circuit is used as an oscillation source of a circuit device driven by a battery, current consumption is reduced as much as possible. It is strongly requested.

As a method of reducing the current consumption, a resistor R _S connected between the source of the output transistor and the ground is used.
May be increased. However, when the resistance value of the resistor R _S is increased, the V
_{Since the PP} voltage is too small, an output level of 1 V _PP or more cannot be obtained. In this case, if the power supply voltage is set high, a large V _PP output can be obtained, but there is a disadvantage that power consumption increases.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to realize a crystal oscillation circuit capable of obtaining a large _VPP output level with a smaller current consumption.

[0007]

SUMMARY OF THE INVENTION A crystal oscillation circuit according to the present invention includes an oscillation section including a crystal oscillator, an output transistor having a control electrode coupled to an output of the oscillation section, and a first main electrode of the output transistor. And a power supply terminal and an output terminal coupled to each other, wherein the second main electrode of the output transistor is grounded via a resistor, and the first main electrode of the output transistor is connected to the oscillation frequency of the crystal resonator. Connected to a power supply terminal via a parallel resonance circuit and a constant voltage circuit having substantially equal resonance frequencies, and the resistance value of a resistor connected to the second main electrode of the output transistor is increased to obtain an output _Vpp larger than the power supply voltage value. It is characterized in that it is set to a value to be set.

[0008]

The current consumption can be reduced by grounding the output transistor via a resistor having a large resistance value. However, grounding via a high resistance reduces the current consumption, but also lowers the V _PP voltage of the output signal. Therefore, in the present invention, a parallel resonance circuit having a resonance frequency equal to the oscillation frequency of the crystal unit is connected between the power supply terminal and the output transistor. Since the impedance of the parallel resonance circuit at resonance is extremely large, the current flowing through the branch passing through the power supply terminal, the parallel resonance circuit, the output transistor and the resistor is greatly reduced, and the voltage between both ends of the parallel resonance circuit is also increased. The power consumption is reduced, and the V _PP voltage of the output signal can be extremely increased. As a result, a high V _PP voltage can be obtained even if the output transistor is grounded via a high resistance, and a large V _PP can be obtained with low current consumption.
_{A PP} output signal can be generated. It is most effective to use this crystal oscillation circuit in a region where the output voltage changes greatly with respect to the power supply voltage. For this purpose, it is necessary to keep the fluctuation of the power supply voltage as small as possible. However, since a battery that causes voltage fluctuations is used in a mobile phone or the like, if this crystal oscillation circuit is used as it is, an undesired situation occurs in which the output voltage fluctuates due to fluctuations in the power supply voltage. I will. For this reason,
In the present invention, a constant voltage circuit is connected between the parallel resonance circuit and the power supply terminal. By connecting a constant voltage circuit, a stable output voltage can be obtained, and as a result, a low power consumption and a large output V _PP can be obtained.

[0009]

FIG. 1 is a circuit diagram showing the configuration of an example of a crystal oscillation circuit according to the present invention. Oscillator section 10 has, for example, a crystal oscillator 11 the oscillation frequency of 12.8 MHz, connecting a resistor R ₁₀ and the inverter 12 of 1M ohm in parallel with the crystal oscillator. To one electrode of the crystal oscillator is connected a parallel circuit of a capacitor C ₁₀ and the variable capacitor C _11, grounding the other ends of the capacitors. Further, the other electrode of the crystal oscillator 11 is connected a capacitor C _12, and grounding the other end. The output terminal 13 of the oscillator 10 the oscillation signal is generated in 12.8 MHz, connects the output terminal 13 to the gate of the output transistor 14 through a coupling capacitor C ₁₃ of 5 pF. Bound coupling resistor R ₁₁ of 470K ohms between the capacitor C ₁₃ and the gate, grounding the other end. The source of the output transistor 14 is grounded via a resistor R _S, is connected to the resistor R _S capacitor C ₁₄ in parallel. The drain of the output transistor 14, a capacitor C ₁₅ and the inductor L ₁ Metropolitan constant voltage circuit 16 for generating a constant voltage of 2V via the parallel resonant circuit 15 consisting of
, And this constant voltage circuit is connected to the power supply terminal 17. The resonance frequency of the parallel resonance circuit 15 is set to be substantially equal to the oscillation frequency of the crystal resonator 11. The output of the constant voltage circuit 16 is also connected to the control input of the inverter 12 as well as connected to 0.01μF of the smoothing capacitor C _16. The drain of the output transistor 14 is connected to the output terminal 18 via a 0.01μF output capacitor C _17.

Next, a performance comparison between the crystal oscillation circuit according to the present invention and a conventional crystal oscillation circuit will be described. In a comparative experiment, a circuit having the configuration shown in FIG. 1 was used as the crystal oscillation circuit according to the present invention, and a resistor was connected as a conventional crystal oscillation circuit instead of the parallel resonance circuit 15 provided in the output stage of the circuit shown in FIG. And the resistance R _S having various resistance values was used. Then, the performance was compared by measuring the output level V _PP and the current consumption while changing the power supply voltage. FIG.
6, the horizontal axis indicates the power supply voltage, and the vertical axis indicates the output V _PP
(Solid line) and current consumption (dashed line).

FIG. 2 shows a conventional crystal oscillator in which R _S = 1.
The performance when set to 8 kΩ is shown. As the power supply voltage increased, the output V _PP and the current consumption also increased. At a power supply voltage of 2 V, the output V _PP is 0.6 V and the current consumption is 0.6 mA. At a power supply voltage of 3 V, the output V _PP is
1.0 V and the current consumption was 1.1 mA.

FIG. 3 shows a conventional crystal oscillation circuit in which R _S =
The performance when set to 3.9 kΩ is shown. Increasing the resistance value of the resistor R _S reduces the current consumption. However, the output V _PP also dropped, and it was not possible to obtain an output V _{PP of} 1 V or more even if the power supply voltage was set to 5 V or more.

FIG. 4 shows a crystal oscillator according to the present invention.
The performance when _S = 1.8 kΩ is shown. As shown in FIG. 4, the output V _PP sharply increases as the power supply voltage increases. Moreover the output V _PP of 2.7 V is obtained at the power supply voltage is 2.0 V, about 4.5 times or more the output V _PP is obtained in comparison with the performance of conventional crystal oscillation circuit shown in FIG. The current consumption was almost the same as the performance result shown in FIG. From these experimental results, it can be understood that providing a parallel resonance circuit in the output stage is a very effective method for increasing the output V _PP .

FIGS. 5 and 6 show performance results when the resistance value of the resistor R _S is increased to 3.9 kΩ and 8.2 kΩ, respectively. As the resistance value of the resistor R _S increases, the output V _PP gradually decreases. On the other hand, the current consumption is greatly reduced with the increase of the resistance R _S. When comparing the performance results shown in performance results and 2 shown in FIG. 6, when the power supply voltage 2V, the output level of the present invention is 2.2 V _PP, the V _PP conventional apparatus
It is 0.6 V, and the output V _PP has improved the performance by about 3.7 times or more. The current consumption is from 0.6mA to 0.4
It is greatly reduced to mA.

The present invention is not limited to the above-described embodiment, and various changes and modifications are possible. For example, although a field-effect transistor is used as an output transistor in the above-described embodiment, a bipolar transistor can of course be used. Further, in the above-described embodiment, the Colpitts oscillator is used as the oscillator, but the present invention can be applied to a Hartley oscillator and a non-adjustment oscillator.

[0016]

According to the present invention as described in the foregoing, since there is provided a parallel resonance circuit of approximately the same resonance frequency as the oscillation frequency of the quartz resonator at the output stage, a very large V _PP with very small power consumption Can be generated. Further, in the present invention, since the constant voltage circuit is connected between the power supply terminal and the parallel resonance circuit, it can be used in a region where the output V _PP changes greatly with respect to the power supply voltage. The effect of obtaining a large output V _PP with electric power can be effectively achieved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an example of a crystal oscillation circuit according to the present invention.

FIG. 2 is a graph showing the performance of a conventional crystal oscillator.

FIG. 3 is a graph showing the performance of a conventional crystal oscillation circuit.

FIG. 4 is a graph showing the performance of the crystal oscillation circuit according to the present invention.

FIG. 5 is a graph showing the performance of the crystal oscillation circuit according to the present invention.

FIG. 6 is a graph showing the performance of the crystal oscillation circuit of the present invention.

FIG. 7 is a circuit diagram showing a configuration of a conventional crystal oscillation circuit.

[Explanation of symbols]

 10 Oscillator 11 Crystal oscillator 14 Output transistor 15 Parallel resonance circuit 16 Constant voltage circuit 17 Power supply terminal 18 Output terminal

Claims (1)

(57) [Claims] An oscillator including a crystal oscillator; an output transistor having a control electrode coupled to an output of the oscillator; a power supply terminal and an output terminal coupled to a first main electrode of the output transistor; In a crystal oscillation circuit in which a second main electrode of the output transistor is grounded via a resistor, a first resonance electrode of the output transistor is connected to a parallel resonance circuit having a resonance frequency substantially equal to the oscillation frequency of the crystal resonator, and a constant voltage. And a resistor connected to a power supply terminal via a circuit, and a resistance value of a resistor connected to the second main electrode of the output transistor is set to a value at which an output _Vpp larger than a power supply voltage value is obtained. circuit.