JPS63269811A - Digital temperature compensated crystal oscillator - Google Patents

Abstract

PURPOSE:To perform a wide range of temperature compensation even with the same number of bits as in a conventional device and to obtain compensation accuracy with a high level, by providing first and second storage parts and an arithmetic part, and performing the temperature compensation by computing the temperature compensation data of both storage parts by the arithmetic part. CONSTITUTION:Temperature information from a temperature sensor part 1 is inputted to the first storage part 3 and the second storage part 4 of the storage part 10 via an A/D conversion part 2, and the output of the storage part 3 is inputted to the arithmetic part 5, then, addition is performed. Added temperature compensation data is converted to a voltage at a D/A conversion part 6, and is inputted to a voltage controlled crystal oscillator 7. In such a case, the temperature compensation data obtained from the temperature characteristic of a representative quartz oscillator is stored in the storage part 3, and in the storage part 4, the temperature compensation information of respective quartz oscillator is stored. In such a way, by performing the temperature compensation by computing the temperature compensation data of the storage parts 3 and 4, the wide range of temperature compensation can be realized and the accuracy can be heightened even with the same number of bits as in the conventional device.

Description

DETAILED DESCRIPTION OF THE INVENTION OBJECTS OF THE INVENTION [Field of Industrial Application] The present invention relates to a temperature compensated crystal oscillator using a digital circuit.

[Prior Art J] In recent years, many oscillators using digital technology have been announced using crystal resonators. This is to improve the temperature characteristics of the oscillator, but conventional oscillators placed in a constant temperature bath require a large amount of power and cannot be miniaturized. Therefore, in many cases, temperature compensation data of the crystal resonator is stored in a ROM-IC in advance, and temperature compensation is performed based on this stored data.

FIG. 4 is a block diagram of a conventional digital temperature compensated crystal oscillator. The temperature sensor section consists of a temperature sensing element such as a thermistor, and this temperature information is stored in a ROM which is a storage section.
and outputs the compensation data at the address corresponding to the temperature. This signal is converted into a voltage by a D/A converter, and then entered into a voltage controlled crystal oscillator in which a variable capacitance diode is connected to a crystal resonator for temperature compensation.

[Problems to be Solved by the Invention] However, the conventional digital temperature compensated crystal oscillator requires a large capacity ROM to compensate for a wide temperature range. Therefore, there has been a demand for effective use of the information stored in the ROM.

The temperature compensable range of the digital temperature compensated crystal oscillator is determined by the number of bits of the A/D converter and D/A converter.

For example, the characteristic shown in FIG. 2 is the frequency-temperature characteristic of an AT-cut crystal resonator, which is widely used among crystal resonators, and has a characteristic of a cubic function. With this characteristic, the temperature range in which the frequency control on the vertical axis can be controlled by N bits is Tn in the figure. That is, in order to widen the compensation temperature range, it is necessary to make the number of bits larger than N.

EObject of the present invention] An object of the present invention is to provide a highly accurate digital temperature compensated crystal oscillator without increasing the number of control bits.

Configuration of the present invention> [Means for solving the problem 1 In the present invention, temperature compensation data is stored in the first ROM which is a storage unit.
Temperature compensation is performed by storing the data in the 2nd R○M in addition to the 1st ROM.
Temperature compensation data of the ROM and the second RO to 1 is calculated by an arithmetic circuit to perform temperature compensation.

[Operations and Examples] (First Example) FIG. 1 is a block diagram showing the configuration of the present invention. Temperature sensor section l consisting of a temperature sensing element such as a thermistor
The temperature information is transmitted to an A/D converter 2 that converts this temperature information into digital data and a first storage section 3.The first storage section 3 obtains temperature information from the temperature characteristics of a typical crystal resonator. The obtained temperature compensation data is stored in the mask ROM.
Mass production is possible. Since there is an error between the first storage section 3 and the actual crystal resonator due to a difference in cut angle, etc., temperature compensation data corresponding to this error is stored in the second storage section 4 during the manufacturing process.

That is, the second storage unit 4 stores temperature compensation information for each crystal resonator. The outputs of the first storage section 3 and the second storage section 11 are input to the calculation section 5. The arithmetic unit 5 adds the data in the first storage unit 3 and the second storage unit 4 using an adder. This added temperature compensation data is converted into a voltage by a D/A converter 6 and input to a voltage controlled crystal oscillator 7.

(Second Embodiment) The first storage unit 3 measures the temperature characteristics of each crystal resonator and creates data to compensate for the temperature characteristics, as in the conventional case. and the second
Errors occur in the storage unit 4 in temperature ranges that cannot be covered by the first storage unit 3, for example, in temperature ranges where the temperature characteristics have large rises and falls, unlike near room temperature, on the high temperature side or low temperature side. This error is stored as temperature compensation information in the second storage section 4, and the temperature is compensated in the first storage section 3 and the second storage section 4.

FIG. 3 shows the frequency-temperature characteristics of the oscillator when temperature compensation is performed only in the first storage section. Temperature compensation data for canceling errors that cannot be compensated for by the first storage unit alone is stored in the second storage unit.

In order to achieve good temperature characteristics over a wide range with the conventional configuration, a large-capacity ROM was required, but in the present invention, the first storage section and the first storage section alone are sufficient. By compensating for the temperature that cannot be compensated for in the second storage section, temperature compensation information can be efficiently written and temperature compensation can be performed. first storage section,
Although it is referred to as a second storage section, it is not necessary to use two ROM-ICs; it is sufficient to allocate the first storage section and the second storage section within one ROIVI-IC. High accuracy can be achieved simply by adding a section.

Effects of the Present Invention> According to the present invention, a wide range of temperature compensation is possible even with the same number of bits as in the prior art, and a highly accurate digital temperature compensated crystal oscillator has been created.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of the present invention, Fig. 2 is a graph showing the relationship between frequency over temperature range, and Fig. 3 is a graph showing frequency 1 quality characteristics when compensated only with 1 ROI = 1. , FIG. 4 is a block diagram showing a conventional configuration. ■・・・・・・Temperature sensor part, 2・・・・・・
...A/D converter, 3...First memory section, 4...Second memory section, 5......Calculation part, 6......D/A conversion part, 7......voltage controlled crystal oscillator, 10...
・・・・・・Memory Department Patent Executor Kinseki Co., Ltd. Figure 2

Claims (1)

[Claims] A temperature sensor unit that measures temperature with a temperature sensing element or the like, an A/D converter unit that converts temperature information from the temperature sensor unit into a digital quantity, a storage unit that stores temperature compensation data of a crystal oscillator in advance, and In a digital temperature-compensated crystal oscillator comprising a D/A conversion section that converts data from a storage section into an analog quantity and a voltage-controlled crystal oscillator whose frequency changes depending on a voltage, the storage section has a first storage section and a second storage section. A digital temperature-compensated crystal oscillator comprising: a digital temperature-compensated crystal oscillator, comprising: a calculating portion for calculating the outputs of the first storage portion and the second storage portion;