# US 9,520,830 B2 · Crystal oscillator

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- Number: US 9,520,830 B2
- Document ID: US9520830B2
- Status: Granted
- Kind: B2
- Application number: 14/973,819
- Filed: 2015-12-18
- Published: 2016-06-23
- Granted: 2016-12-13
- Earliest claimed: 2014-12-19
- Assignees: Fanuc Corporation
- Applicants: FANUC Corporation
- Inventors: Junichi Sato; Katsuhiko Watanabe
- Web page: https://patentgrep.com/patent/US9520830B2

## CPC

- H03B 5/30: with frequency-determining element being electromechanical resonator
- H03B 5/36: active element in amplifier being semiconductor device ({H03B5/323, H03B5/326} , H03B5/38 take precedence)
- H03B: GENERATION OF OSCILLATIONS, DIRECTLY OR BY FREQUENCY-CHANGING, BY CIRCUITS EMPLOYING ACTIVE ELEMENTS WHICH OPERATE IN A NON-SWITCHING MANNER; GENERATION OF NOISE BY SUCH CIRCUITS (generators adapted for electrophonic musical instruments G10H; masers or lasers H01S; generation of oscillations in plasma H05H)

## Abstract

A crystal oscillator has characteristics in that reduction in oscillation margin makes the crystal oscillator less likely to oscillate, with the result that an amplitude of a voltage waveform at an input terminal of a CMOS inverter is reduced. A crystal oscillator of the invention has a detection circuit that outputs an alarm signal when the amplitude of the voltage waveform at the input terminal of the CMOS inverter becomes equal to or less than a predetermined specified value. As a result, it is possible to detect a change in the oscillation margin of the crystal oscillator without switching between circuits even after the crystal oscillator is incorporated in a device.

## Claims

### Claim 1

A crystal oscillator, comprising:
a quartz resonator;
an oscillation circuit including a CMOS inverter, a capacitor, and a resistor, the oscillation circuit configured to oscillate the quartz resonator;
a CMOS buffer configured as an output circuit, and having an input coupled to an output of the CMOS inverter; and
a detection circuit having an input coupled to an input of the CMOS inverter, the detection circuit configured to output an alarm signal when an amplitude of a voltage waveform at the input of the CMOS inverter becomes equal to or less than at least one predetermined specified value.

### Claim 2 (depends on 1)

The crystal oscillator according to claim 1, wherein a plurality of different values are set as the specified value, and the alarm signals to be output when the amplitude of the voltage waveform becomes equal to or less than the set respective specified values are made different for every specified value.

### Claim 3 (depends on 1)

The crystal oscillator according to claim 1, wherein the detection circuit is a full-wave rectifier.

### Claim 4 (depends on 1)

The crystal oscillator according to claim 1, wherein the detection circuit is a peak hold circuit.

### Claim 5 (depends on 1)

The crystal oscillator according to claim 1, wherein the detection circuit is a sample hold circuit.

### Claim 6 (depends on 1)

The crystal oscillator according to claim 1, wherein the alarm signal includes light.

### Claim 7 (depends on 1)

The crystal oscillator according to claim 1, wherein the alarm signal includes sound.

### Claim 8 (depends on 1)

The crystal oscillator according to claim 1, wherein the alarm signal includes an error display on a display unit.

### Claim 9 (depends on 2)

The crystal oscillator according to claim 2, wherein different alarm signals include light of different colors.

### Claim 10 (depends on 2)

The crystal oscillator according to claim 2, wherein different alarm signals include light of different brightness.

### Claim 11 (depends on 2)

The crystal oscillator according to claim 2, wherein different alarm signals include sound of different pitches.

### Claim 12 (depends on 2)

The crystal oscillator according to claim 2, wherein different alarm signals include sound of different volumes.

### Claim 13 (depends on 2)

The crystal oscillator according to claim 2, wherein different alarm signals include different display modes on a display unit.