JP2000286637A - Oscillation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the oscillation start time of a crystal oscillation circuit while the center potential of the output of the circuit is fixed and, at the same time, to reduce the power consumption of the circuit. SOLUTION: A crystal oscillation circuit is provided with a three-state inverter buffer 12 and an ON/OFF control circuit 11. At the time of starting the oscillation circuit to oscillate, the buffer 12 is turned on and the circuit is started with the total gain of the buffer 12 and a logic inverter 13. Since the power supply to a logic element is fixed, the center potential of the output to the succeeding stage does not vary, but is fixed. The oscillation of the oscillation circuit is continued by only using the gain of the logic inverter 13 by turning off the three-state inverter buffer 12 by means of the ON/OFF control circuit 11 after the time required for stabilizing the oscillation circuit has elapsed. Since the oscillation circuit is made to make oscillating operations by only using the gain of the logic inverter 13 of a CMOS, the power consumption of the oscillation circuit can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an oscillation circuit,
In particular, it relates to a crystal oscillation circuit with low power consumption and a short oscillation start-up time.

[0002]

2. Description of the Related Art A conventional crystal oscillation circuit has a CM shown in FIG.
It was configured like an OS oscillation circuit. In FIG.
18 is a CMOS inverter, 19 is a feedback resistor, 20 is a crystal oscillator, 21 is a gate-side capacitor, and 22 is a source-side capacitor. In this oscillation circuit, the CMOS inverter 18
Operates as an amplifying element, and outputs the output of the CMOS inverter 18 to the feedback resistor 19, the crystal oscillator 20, the gate-side capacitor 21,
Oscillation is caused by feedback through the source-side capacitor 22. In the crystal oscillation circuit, since the Q of the crystal oscillator is large, it takes a longer time from startup until the oscillation is stabilized as compared with the CR oscillation circuit.

As a conventional example of shortening the oscillation start time of the crystal oscillation circuit, there is a crystal oscillation circuit disclosed in Japanese Utility Model Laid-Open No. 6-77318. In this crystal oscillation circuit, as shown in FIG. 4, a parallel circuit of a switch element and a resistor is provided between a current control type crystal oscillation circuit and a power supply. When the power is turned on, the switch element is turned on to increase the voltage applied to the oscillation circuit. After a certain period of time when the oscillation stabilizes, the switching element is turned off to lower the applied voltage.

[0004]

However, in the configuration of the conventional example shown in FIG. 3, if the capacity of the CMOS inverter is reduced in order to reduce power consumption, the amplifying action of the CMOS inverter is reduced and the oscillation start time is reduced. become longer. Further, when the capacity of the CMOS inverter is increased to shorten the oscillation start time, the amplifying action of the CMOS inverter is improved, but there is a problem that the power consumption is increased.

In the conventional configuration shown in FIG. 4, the power consumption is reduced and the oscillation operation time is shortened. However, in order to change the voltage applied to the logic inverter, the output signal to the next stage is changed. The center potential changes. Since the threshold value of the next gate is constant, there is a problem that the phase of the oscillation signal changes due to a change in the center potential.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems, and to reduce the power consumption and shorten the oscillation operation time of an oscillation circuit without changing the voltage applied to a logic inverter used as an amplification element. I do.

[0007]

In order to solve the above-mentioned problems, according to the present invention, an oscillation circuit includes a logic inverter as an amplifying element, a crystal oscillator, a feedback resistor, a gate-side capacitor, and a source-side. A configuration is provided that includes a capacitor and a three-state inverter buffer that is connected in parallel and forward direction to the logic inverter, and that is turned on only for a certain period of time when the oscillation is started.

[0008] With this configuration, when the three-state inverter buffer is in the on state, the gain applied to the logic inverter can be increased to a larger value than the normal one without changing the voltage applied to the logic inverter, and the oscillation operation can be performed. Time until stabilization can be shortened, and power consumption can be reduced.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to a first aspect of the present invention is directed to a logic inverter as an amplifying element, a crystal oscillator, a feedback resistor, a gate-side capacitor, a source-side capacitor, and a logic inverter. In addition, the oscillation circuit is equipped with a three-state inverter buffer that is arranged in the forward direction and is turned on only for a certain period of time at the time of oscillation startup. It has the effect of shortening the time until stabilization.

According to a second aspect of the present invention, there is provided a crystal oscillator, a feedback resistor connected in parallel with the crystal oscillator, a logic inverter connected in parallel with the feedback resistor, and the logic inverter. A capacitor provided on the gate side and the source side of the logic inverter, a three-state inverter buffer connected in parallel and forward with the logic inverter, and a control circuit for turning off the three-state inverter buffer after a lapse of a predetermined time from the start of oscillation. The oscillation circuit has a function of turning off the three-state inverter buffer and continuing the oscillation operation with low power consumption.

Hereinafter, an embodiment of the present invention will be described with reference to FIG.
This will be described in detail with reference to FIG.

(Embodiment) An embodiment of the present invention is a crystal oscillation circuit in which a three-state inverter buffer is connected to a logic inverter in parallel and in a forward direction, and is turned on only for a certain period of time when oscillation is started.

FIG. 1 is a circuit diagram of a crystal oscillation circuit according to an embodiment of the present invention. In FIG. 1, an on / off control circuit
Reference numeral 11 denotes a circuit for controlling on / off of the three-state inverter buffer. 12 is a three-state inverter buffer. 13 is a CMOS logic inverter, 14
Is a feedback resistor, 15 is a crystal oscillator, 16 is a gate-side capacitor, and 17 is a source-side capacitor. FIG. 2 is an operation flowchart of the oscillation circuit according to the embodiment of the present invention.

The operation of the thus-configured crystal oscillation circuit according to the embodiment of the present invention will be described with reference to FIG.
When the power is turned on, the crystal oscillation circuit starts oscillating.
At the time of starting the oscillation, the three-state inverter buffer 12 is turned on for a certain period of time determined by the resistor and the capacitor by the signal of the on / off control circuit 11 composed of a resistor, a capacitor, an operational amplifier and the like. The crystal oscillation circuit is started with a gain larger than usual, in accordance with the gain of the three-state inverter buffer 12 and the gain of the logic inverter 13.
Therefore, the rise time of the oscillation is shortened. Since the voltage applied to the logic inverter 13 is not changed, the center potential of the output signal to the next stage does not change. Therefore, the phase of the oscillation signal does not change.

After a certain period of time when the oscillation is stabilized, the three-state inverter buffer 12 is turned off by a signal from the on / off control circuit 11. A logic inverter with the lowest gain at which the crystal oscillation circuit is stable and can oscillate
Oscillation continues with a gain of only 13. In addition, ON / OFF
The control circuit 11 may be a timer, a delay element, or the like.

Rather than changing the voltage applied to the inverter, the three-state inverter buffer 12 is turned on at the time of oscillation startup, and a large gain is obtained in accordance with the gain of the CMOS logic inverter 13, so that the oscillation startup time can be reduced. . In addition, by turning off the three-state inverter buffer 12 after a certain period of time when the oscillation is in a steady state, the oscillation is performed with the gain of only the CMOS logic inverter 13, so that the oscillation operation can be continued with low power consumption. Furthermore, since the power supply of the logic element is constant, the center potential of the output to the next stage does not change and remains constant.

As described above, in the embodiment of the present invention,
The oscillation circuit is arranged in parallel and forward direction with the logic inverter as the amplifying element, the crystal oscillator, the feedback resistor, the gate-side capacitor, the source-side capacitor, and the logic inverter. When the three-state inverter buffer is in the ON state, it is possible to obtain a larger gain than usual without changing the applied voltage to the logical inverter, together with the gain of the logical inverter. ,
The time until the oscillation operation stabilizes can be reduced, and the power consumption can be reduced.

[0018]

As is apparent from the above description, according to the present invention, the oscillation circuit comprises a logic inverter as an amplifying element, a crystal oscillator, a feedback resistor, a gate-side capacitor, a source-side capacitor, A three-state inverter buffer that is arranged in parallel with the logic inverter in the forward direction and that is turned on only at certain times when the oscillation starts is provided, so that the oscillation start time is reduced without changing the output center potential. Thus, an effect that the oscillation operation can be performed with low power consumption can be obtained.

[Brief description of the drawings]

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

FIG. 2 is an operation flowchart of the crystal oscillation circuit according to the embodiment of the present invention;

FIG. 3 is a configuration diagram of a conventional crystal oscillation circuit,

FIG. 4 is a configuration diagram of another conventional crystal oscillation circuit.

[Explanation of symbols]

 11 ON / OFF control circuit 12 Three-state inverter buffer 13 Logical inverter 14, 19 Feedback resistor 15, 20 Crystal oscillator 16, 21 Gate side capacitor 17, 22 Source side capacitor 18 Logical inverter

Claims (2)

[Claims] 1. A logic inverter as an amplifying element, a crystal oscillator, a feedback resistor, a gate-side capacitor, a source-side capacitor, are connected in parallel and forward to the logic inverter, and are provided for a certain period of time when oscillation is started. An oscillation circuit comprising: a three-state inverter buffer that is turned on only. 2. A crystal oscillator, a feedback resistor connected in parallel with the crystal oscillator, a logic inverter connected in parallel with the feedback resistor, and capacitors provided on a gate side and a source side of the logic inverter. An oscillation circuit comprising: a three-state inverter buffer connected in parallel with the logic inverter in a forward direction; and a control circuit for turning off the three-state inverter buffer after a lapse of a predetermined time from the start of oscillation.