JPH0575446A - Voltage controlled crystal oscillator - Google Patents

Abstract

PURPOSE:To correct a secular change at all times by providing a voltage controlled frequency correction circuit in the crystal oscillator circuit. CONSTITUTION:Two voltage control circuits 2, 3 are provided in the inside of the crystal oscillator circuit 1, a temperature sensor 8 and an A/D converter 9 designate an allowable temperature range for frequency correction, a CPU 7 sends data for frequency correction, which are stored in a memory 6 and either a D/A converter 4 or 5 is operated to correct the frequency.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voltage control type crystal oscillating device used for a car phone, a mobile phone and the like.

[0002]

2. Description of the Related Art FIG. 2 shows the configuration of a conventional voltage controlled crystal oscillator. In FIG. 2, reference numeral 1 is a crystal oscillating circuit, which incorporates a voltage control circuit 2. Reference numeral 7 is a CPU that generates voltage data that controls the oscillation frequency of the crystal oscillation circuit 1, and 4 is a D / A converter that converts the digital signal data from the CPU 7 into an analog signal and supplies the analog signal to the crystal oscillation circuit 1. .

Next, the operation of the above conventional example will be described. In FIG. 2, correction data for controlling the oscillation frequency is issued from the CPU 7, and is supplied to the voltage control circuit 1 via the D / A converter 4. With this correction data, a desired oscillation frequency can be obtained.

[0004]

However, the above-mentioned conventional voltage-controlled crystal oscillation device has a problem that when the temperature inside or around the device changes, the fluctuation of the oscillation frequency due to the temperature change cannot be corrected. It was

The present invention solves such a conventional problem, and an object of the present invention is to provide an excellent voltage control type crystal oscillating device capable of correcting the frequency fluctuation with respect to the temperature change with time.

[0006]

In order to achieve the above object, the present invention provides two frequency control voltage correction circuits inside a crystal oscillation device, a temperature sensor and a memory, and changes with time. The frequency is corrected with respect to.

[0007]

Therefore, according to the present invention, by the two frequency control circuits for changing the frequency, the temperature sensor and the memory,
The configuration is such that frequency correction is performed with respect to changes over time.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows the configuration of an embodiment of the present invention. Reference numeral 1 is a crystal oscillating circuit, which has two voltage control circuits 2 and 3 incorporated therein as voltage control means.
Reference numeral 7 is a CPU that generates correction data for controlling the oscillation frequency of the crystal oscillation circuit 1, and 4 and 5 are D / A converters that convert the correction data of a digital signal from the CPU 7 into an analog signal and supply the analog signal to the crystal oscillation circuit 1. , 6 is a memory that is a storage unit that stores the correction data from the CPU 7 and stores it as holding data, 8 is a temperature sensor, and 9 is an analog signal obtained from the temperature sensor that is converted into digital signal data and supplied to the CPU A / D converter. That is, the temperature sensor 8 and the A / D converter 9 form a temperature detection unit that detects temperature and generates temperature data. Although not shown in the figure, from a PLL circuit or the like,
Error data for AFC (automatic frequency control), that is, correction data is supplied.

Next, the operation of the above embodiment will be described. In FIG. 1, a temperature sensor 8 is used to specify an allowable temperature range for frequency correction. For example, the voltage control circuit 2 is used for AFC by the two voltage control circuits 2 and 3 for frequency variation, and the voltage control circuit 3 is used. If the temperature detected by the temperature sensor 8 is within the allowable temperature range, the memory 6 holds the frequency information corrected by the AFC, and the D / A converter 4 causes the voltage control circuit 2 to control the AFC. Apply correction for. At this point of time, the voltage control circuit 2 comes to perform correction for aging, and the voltage control circuit 3 comes to carry out correction for AFC. Thus, if the temperature is within the allowable temperature range for frequency correction, the roles of the voltage control circuits 2 and 3 are alternately reversed,
By holding the correction data in the memory, stable frequency accuracy can always be obtained.

[0010]

According to the present invention, as is apparent from the above-mentioned embodiment, when the AFC is operated in the allowable temperature range for frequency correction, the correction data becomes the correction data for aging, This has the effect of always obtaining stable frequency accuracy.

[Brief description of drawings]

FIG. 1 is a block diagram of a voltage controlled crystal oscillator according to an embodiment of the present invention.

FIG. 2 is a block diagram of a conventional voltage controlled crystal oscillator device.

[Explanation of symbols]

 1 Crystal oscillator circuit 2, 3 Voltage control circuit 4, 5 D / A converter 6 Memory 7 CPU 8 Temperature sensor 9 A / D converter

Claims (1)

[Claims] 1. Two voltage control means for changing frequency,
A temperature detecting unit that generates temperature data and a storage unit that stores the correction data for frequency correction and stores the temperature data as a holding data are provided, and an allowable range of the temperature data is designated, and the holding data is stored in one of the voltage control units. To the voltage control means for supplying the temperature data to the voltage control means for aging, and to supply the correction data to the other voltage control means to be the voltage control means for frequency correction. .