JPH1093347A - Clock oscillation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the clock oscillating circuit with high accuracy in which a duty ratio is constant even on the occurrence of a temperature drift or dispersion in circuit components with a simple configuration. SOLUTION: The clock oscillating circuit is made up of an oscillator 6 comprising a parallel circuit consisting of a quartz oscillator 1, of a 1st resistor 2 connected in parallel with the quartz oscillator 1, and of a 1st inverter amplifier 5 and comprising a 1st capacitor 3 and a 2nd capacitor 4 connected between input and output terminals of the parallel circuit and a reference potential point and made up of a clock compensation circuit 19 consisting of a 2nd inverter amplifier 17 and a 2nd resistor 18 connecting to the oscillator 6. Even when a threshold voltage of the 1st inverter amplifier 5 is varied by temperature drift or the like, the input DC component of the 2nd inverter amplifier 17 of the same configuration is similarly varied, resulting that the DC component of a waveform of a signal received by the 1st inverter amplifier 5 is reduced and the duty ratio of the output waveform is always kept constant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a clock oscillation circuit required for a digital circuit.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a conventional clock oscillation circuit. A conventional clock oscillation circuit includes a crystal unit 1, a resistor 2, a first capacitor 3, a second capacitor 4, and an amplifier 5.
The output waveform of the oscillator 6 is input to the converter 7 and a rectangular wave is output. The output waveform of the converter 7 is LPF
10 is input. The power supply voltage Vcc is changed to the resistance 11 and the resistance 1
2, a constant voltage Vc between the Hi level and the Lo level of the output waveform of the converter 7 is generated. The output of the LPF 10 and the constant voltage Vc are
5 is input to an amplifier 14 having a feedback resistance. The output of the amplifier 14 is fed back to the input of the amplifier 5 through the resistor 16 so that the output voltage of the LPF 10 and the constant voltage Vc are controlled.

In this circuit configuration, a highly accurate clock waveform with a constant duty ratio can be always obtained even if a temperature drift or a variation due to a circuit element occurs.

[0004]

However, the conventional clock oscillation circuit requires an LPF for integrating an output clock waveform, a circuit for comparing the integrated output clock with a reference signal, and the like. Has the disadvantage that the circuit configuration becomes large and complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned drawbacks, and provides a high-precision clock oscillation circuit having a fixed duty ratio and a high accuracy even if a temperature drift or variation in circuit elements occurs with a simple configuration. is there.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a clock oscillation circuit for outputting a clock waveform having a constant frequency.
A clock oscillation circuit composed of an oscillator composed of a parallel circuit of an oscillator and a first amplifier, and a clock compensation circuit composed of a series circuit of a second amplifier and a resistor connected to the oscillator and having input and output directly connected, is there.

According to the present invention, there is provided a clock oscillation circuit for outputting a clock waveform having a constant frequency, wherein the oscillator and the first
An oscillator comprising a parallel circuit of an amplifier and a first resistor, and a first and second capacitor connected between the parallel circuit and a reference potential; a second amplifier connected to the oscillator and directly connected to the input and output; And a clock compensating circuit comprising a series circuit of two resistors.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A clock oscillation circuit according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit configuration of a clock oscillation circuit.

Referring to FIG. 1, a clock oscillation circuit according to the present invention includes a parallel circuit including a crystal unit 1, a first resistor 2 and a first inverter amplifier 5 connected in parallel to the crystal unit 1, and An oscillator 6 comprising a first capacitor 3 and a second capacitor 4 connected between the input and output of the circuit and a reference potential point; a second inverter amplifier 17 and a second resistor connected to the oscillator 6 And a clock compensating circuit 19 composed of the clock compensating circuit 18.

Here, the input and output of the second inverter amplifier 17 constituting the clock compensation circuit 19 are directly connected, and a second resistor 18 is connected to the second inverter amplifier 17 in series.

Further, the first inverter amplifier 5 and the second inverter amplifier 17 are formed in the same integrated circuit 19, and the temperature drift and the variation of circuit elements are almost the same.

Next, the operation of the clock oscillation circuit of the present invention will be described with reference to FIG.

It is now assumed that the signal waveform at the point a is A, and the threshold voltage of the first inverter amplifier 5 is TH1, which is intermediate between the Hi level and the Lo level. In this state, the duty ratio of the output signal waveform is 50%
It has become.

Here, when the threshold voltage changes from TH1 to TH2 due to a temperature drift or the like, the Hi period of the output signal waveform becomes shorter as shown by c, and the duty ratio becomes smaller than in the normal state.

Therefore, by connecting the clock compensating circuit 19, the first inverter amplifier 5
Of the first inverter amplifier 5 and the second inverter amplifier 17 are configured in the same integrated circuit when the threshold voltage of
The DC component at the input of the inverter amplifier 5 also decreases by the same amount,
The signal waveform at point a also drops from A to B.

Therefore, even if the threshold voltage drops to TH2, the signal waveform at point a also drops to B, and an output waveform having a duty ratio of 50% as shown in signal waveform D can be obtained.

[0018]

As described above, according to the present invention, the duty ratio can be kept constant even if a temperature drift or a variation of circuit elements occurs without using the conventionally required LPF and comparison circuit. Thus, a highly accurate clock waveform can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a clock oscillation circuit of the present invention.

FIG. 2 is a diagram for explaining a change in a duty ratio due to a temperature drift.

FIG. 3 is a diagram illustrating a conventional clock oscillation circuit.

[Explanation of symbols]

 Reference Signs List 1 crystal oscillator 2 first resistor 3 first capacitor 4 second capacitor 5 first inverter amplifier 6 oscillator 17 second inverter amplifier 18 second resistor 19 clock compensation circuit

Claims (3)

[Claims] 1. A clock oscillation circuit for outputting a clock waveform of a constant frequency, comprising: an oscillator comprising a parallel circuit of a vibrator and a first amplifier; and a second amplifier connected to the oscillator and having an input / output directly connected. A clock oscillation circuit comprising a clock compensation circuit comprising a series circuit with a resistor. 2. A clock oscillation circuit for outputting a clock waveform having a constant frequency, comprising: an oscillator; a first amplifier;
An oscillator including a parallel circuit of resistors and a first and second capacitor connected between the parallel circuit and a reference potential; a second amplifier connected to the oscillator and having an input / output directly connected to the second resistor; A clock oscillation circuit including a clock compensation circuit including a series circuit. 3. The clock oscillation circuit according to claim 1, wherein said first amplifier and said second amplifier are in the same integrated circuit.