JP2001094347A - Crystal oscillator and drive characteristic measuring method for quartz oscillator in the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably and precisely measure a drive characteristic even after a quartz oscillator is loaded on an oscillator. SOLUTION: An oscillation circuit part 12 is constituted of the DLD characteristic measuring circuit part 13 of a quartz oscillator, which is surrounded by an illustrated broken line, an active oscillator 14 formed of a transistor, which is for driving a quartz oscillator 11, and a function circuit 15 (burr cap capacitor in the case of VCXO and temperature compensation circuit in the case of TCXO) for adjusting and controlling a frequency. The DLD characteristic measuring circuit part 13 is constituted of a crystal current control circuit 13a controlling crystal current and varying the drive level of the crystal oscillator 11 and a variable resistor 13b connected in series to the quartz oscillator 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal oscillator and a method for measuring drive characteristics of a crystal oscillator in the crystal oscillator.

[0002]

2. Description of the Related Art In recent years, performance evaluation based on drive characteristics (hereinafter referred to as DLD characteristics) of a quartz oscillator has been performed. This performance evaluation is performed by changing the power for driving the crystal resonator (or the current flowing through the crystal, hereinafter referred to as crystal current) and measuring the frequency and the loss at that time. In the DLD characteristics, if there is a phenomenon in which the frequency changes greatly or the loss changes suddenly, there is a possibility that a frequency abnormality or non-oscillation (oscillation failure) may occur when a crystal oscillator is configured. Will be higher.

However, the DLD characteristic is not reproducible because it depends on the surface properties of the crystal wafer used for the crystal unit and the attached foreign matter. May change.

[0004] The performance and reliability of a crystal oscillator are required due to the DLD characteristics of a crystal oscillator. However, a DLD characteristic test of a single crystal unit is insufficient. Because
This is because, in many cases, heat treatment is applied when the semiconductor device is mounted on a crystal oscillator, and the characteristics may change after the crystal oscillator is assembled. However, the current crystal oscillator cannot perform the DLD characteristic test after mounting. For this reason, after heat treatment of the quartz oscillator, DLD
Measures are taken by performing characteristic tests.

[0005]

It is extremely difficult to detect a defect in the DLD characteristic of a crystal oscillator based on the characteristics of a crystal oscillator. This is because, for example, even if the oscillation circuit has a DLD characteristic such that the oscillation frequency near 40 μW changes suddenly, no abnormality occurs in the frequency in an oscillation circuit having an oscillator drive power of 20 to 30 μW. Although no abnormality occurred at the time of the test, the frequency sudden change point was 25μ due to the change in DLD characteristics.
There is also a possibility that it will be near W, and the test will pass with the defective element included.

Therefore, a DLD characteristic test of a single crystal unit may be performed, but it is not perfect in any case due to a problem of characteristic change due to a subsequent heat treatment or the like.
Further, it is impossible to measure the DLD characteristics after mounting the crystal oscillator, and no decisive measures have been taken.

As a form of the crystal oscillator, there is a type in which a crystal resonator and an oscillation circuit are mounted on the same package (integrated crystal oscillator), and thus, the size of the crystal oscillator can be further reduced. However, due to its structure, the characteristics of a single crystal unit cannot be measured, so that the DLD characteristic test itself cannot be performed, and there is a problem that it cannot be used in the field of a crystal oscillator that requires high stability and high accuracy.

The present invention has been made in view of the above circumstances, and provides a crystal oscillator which can obtain high stability and high accuracy and can measure drive characteristics even after a crystal resonator is mounted on the oscillator. It is an object of the present invention to provide a method for measuring the drive characteristics of a crystal unit in the oscillator.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, a first aspect of the present invention is to provide a quartz oscillator and an electronically connected quartz oscillator for driving the quartz oscillator. , A function circuit for adjusting and controlling the frequency of the crystal unit, and an oscillation circuit unit having a drive level characteristic measurement circuit unit for the crystal unit.

[0010] A second invention is a crystal current control circuit for controlling the current flowing through the crystal unit by the drive level characteristic measurement circuit unit to make the drive level of the crystal unit variable,
And a variable resistor connected in series to the crystal unit.

According to a third aspect of the present invention, the drive level characteristic measuring circuit section has first and second registers, and an interface for reading set values of these registers and enabling external rewriting. The amount of control by the crystal current control circuit is adjusted by rewriting the register of
The variable resistance value is adjusted by rewriting the second register.

According to a fourth aspect of the invention, after setting a drive level to a certain value in a crystal current control circuit, the oscillation frequency of the crystal oscillator is measured, and the resistance value of the variable resistor is gradually increased from 0Ω. Monitoring the oscillator output and measuring the resistance value of the variable resistor when the oscillation stops, changing the drive level, and grasping the drive level characteristics of the crystal unit from the oscillation frequency and the variation of the variable resistance value. It is characterized by the following.

The fifth invention is characterized in that the setting of the drive level is rewritten from the outside through an interface, and the resistance value of the variable resistor is rewritten from the outside through the interface so as to gradually increase from 0Ω. It is.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a first embodiment of the present invention. In FIG. 1, reference numeral 11 denotes a crystal oscillator, and reference numeral 12 denotes an oscillation circuit unit. The oscillation circuit section 12 is a DLD characteristic measurement circuit section 1 of the crystal unit surrounded by a broken line in the figure.
3. From an active element 14 composed of a transistor or the like for driving the crystal oscillator 11 and a functional circuit 15 for frequency adjustment and control (for example, a varicap capacitor for VCXO, a temperature compensation circuit for TCXO) Be composed.

The DLD characteristic measuring circuit section 13 controls the crystal current (power for driving the crystal oscillator) to vary the drive level of the crystal oscillator 11.
3a and a variable resistor 1 connected in series to the crystal unit 11
3b.

In the first embodiment configured as described above, to perform a DLD characteristic test, first, the drive level is set to a certain value by the crystal current control circuit 13a. After the setting, the oscillation frequency of the crystal unit 11 is measured. At the time of this measurement, the resistance value of the variable resistor 13b is gradually increased from 0Ω. Simultaneously with the variable resistance value, the oscillation output is monitored to measure the resistance value of the variable resistor 13b when the oscillation is stopped. Then, the procedure of changing the drive level is performed, and the DLD characteristic of the crystal resonator is grasped from the crystal oscillator based on the fluctuation of the oscillation frequency and the variable resistance value.

FIG. 2 is a block diagram showing a second embodiment of the present invention. The same parts as those in the first embodiment are denoted by the same reference numerals, and detailed description is omitted. In FIG. 2, the DLD characteristic measuring circuit section 13 is configured such that registers 13c and 13d and an interface 13e are additionally provided in addition to the crystal current control circuit 13a and the variable resistor 13b.

The crystal current control circuit 13a has a function of controlling the crystal current to vary the drive level of the crystal oscillator 11, and of adjusting the control amount by rewriting the register 13c. . The variable resistor 13b is connected in series to the crystal unit 11, and has a function of adjusting the resistance value by rewriting the register 13d. Registers 13c and 13d
Reading and rewriting of the setting value of the interface 13
e.

In the second embodiment configured as described above, in order to perform the DLD characteristic test, first, in order to set the drive level to a certain value, the value of the register 13c is rewritten externally through the interface 13e, and the crystal current It controls and adjusts the control circuit 13a. After this control and adjustment, the oscillation frequency is measured. Thereafter, the value of the register 13d is rewritten through the interface 13e, and the resistance of the variable resistor 13b is gradually increased from 0Ω. Simultaneously with the variable resistance value, the oscillation output is monitored to measure the resistance value of the variable resistor 13b when the oscillation is stopped. afterwards,
The drive level is changed to the following value, and the DLD characteristic of the crystal resonator is grasped from the crystal oscillator based on the fluctuation of the oscillation frequency and the variable resistance value.

If the interface of the second embodiment is also used as an external interface, such as a temperature-compensated crystal oscillator, which can adjust the temperature compensation circuit constant by inputting / outputting data via an external interface, an inspection apparatus and a jig can be used. The DLD characteristic test of the crystal unit can be performed only by changing the test program without changing the test program. Thus, investment in inspection equipment can be significantly reduced.

[0021]

As described above, according to the present invention,
By adding the DLD characteristic measuring circuit of the crystal unit to the crystal oscillator, the DLD characteristic of the crystal unit can be measured even after the crystal unit is mounted on the crystal oscillator. As a result, DLD characteristic defective products which may be generated by heat treatment at the time of mounting the quartz oscillator are removed from the DLD.
It can be detected by the LD characteristic measuring circuit.

Further, since it becomes possible to inspect the DLD characteristic of a crystal unit, which was impossible with an integrated crystal oscillator,
It can also be used in the field of highly stable and high precision oscillators.

Further, as in the case of a temperature-compensated crystal oscillator, the temperature compensation circuit constant can be changed and the DLD characteristics test of the crystal unit can be performed at one time, and the characteristics can be automatically measured by a computer, so that the tact time can be reduced. And contribute to labor saving.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a block diagram showing a second embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Crystal oscillator 12 ... Oscillation circuit part 13 ... DLD characteristic measurement circuit part 13a ... Crystal current control circuit 13b ... Variable resistance 13c, 13d ... Register 13e ... Interface 14 ... Active element 15 ... Functional circuit

Claims (5)

[Claims] 1. A quartz oscillator, an active element electrically connected to the quartz oscillator, for driving the quartz oscillator, a functional circuit for adjusting and controlling the frequency of the quartz oscillator, and a quartz oscillator. And a oscillation circuit section having a drive level characteristic measurement circuit section. 2. The drive level characteristic measurement circuit section,
2. A crystal current control circuit for controlling a current flowing through a crystal unit to vary a drive level of the crystal unit, and a variable resistor connected in series to the crystal unit. Crystal oscillator. 3. The drive level characteristic measurement circuit section has first and second registers, and an interface that reads set values of these registers and enables external rewriting. The amount of control by the crystal current control circuit is adjusted by rewriting the register.
3. The crystal oscillator according to claim 1, wherein the variable resistance value is adjusted by rewriting the register. 4. After setting the drive level to a certain value in the crystal current control circuit, measure the oscillation frequency of the crystal oscillator,
At the same time as gradually increasing the resistance value of the variable resistor from 0Ω, monitoring the oscillation output and measuring the resistance value of the variable resistor when oscillation stops, changing the drive level, changing the oscillation frequency, 3. A drive level characteristic of the crystal unit is grasped from a change in resistance value.
A method for measuring a drive level characteristic of a crystal resonator in the crystal oscillator described in the above. 5. The method according to claim 4, wherein the setting of the drive level is rewritten from the outside through an interface, and the resistance value of the variable resistor is rewritten from the outside through the interface so as to gradually increase from 0Ω. Method for measuring drive level characteristics of crystal unit in crystal oscillators.