JPH02184103A - crystal oscillation circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a crystal oscillation circuit, and particularly to a crystal oscillation circuit suitable for use in electronic equipment requiring high reliability.

[Conventional technology]

An example of a conventional crystal oscillation circuit is an unadjusted crystal oscillation circuit shown in FIGS. 10 and 17 on page 186 of "Introduction to Transistor Circuits" by Yanagisawa.

[Problem to be solved by the invention]

In the above conventional technology, the active elements such as resistors, capacitors, and transistors that make up the oscillation circuit are connected as shown in the diagram, and no consideration has been given to the means for knowing the characteristics of the crystal resonator incorporated in the oscillation circuit. However, there were the following problems.

(1) Even if a crystal resonator has abnormal characteristics, once it is incorporated into an oscillation circuit, the active elements such as resistors, capacitors, and transistors that make up the oscillation circuit will be affected, and the crystal resonator will It is not possible to measure the characteristics of a single unit, and it is not known until the crystal oscillation circuit stops oscillating.

(2) In a crystal oscillation module in which a bare crystal resonator and an oscillation circuit are housed in a single case, even if foreign matter adheres to the crystal resonator during the manufacturing process and the characteristics deteriorate, it will not be noticeable after the case is sealed.

A crystal resonator used in a crystal oscillation circuit can be represented by an equivalent circuit shown in FIG. In this equivalent circuit, Lo is an inductance component, C0 is a capacitance component, and C is an inter-terminal capacitance component. The resonant frequencies of the crystal resonator are r, o,
It is determined by the series resonant frequency of c, and the pure resistance platform of the crystal resonator at the resonant frequency is represented by R. Below, this R
is called crystal impedance.

The problem mentioned in (2) above is that when foreign matter adheres to the electrodes of the crystal piece of a crystal resonator, the above-mentioned crystal impedance increases as shown in Figure 6 due to changes over time, and the operating conditions deteriorate. The operating condition of a certain 0 oscillator is that the loop gain of the feedback circuit is 0 dB at phase 0° (or -360°).
(1 times) or more is sufficient, but this condition is satisfied when oscillation continues. From the start of oscillation to the stable state, the gain of the amplifier is required to be large within the above conditions in order for the oscillation to grow. However, the gain of the amplifier is proportional to the voltage /JJX voltage. Therefore, it will be reduced by 4% in areas where the power supply voltage is low. Therefore, as shown in Figure 6, when the crystal impedance changes high, the impedance of the feedback circuit becomes high, and during the power supply startup transition period, the loop gain of the feedback circuit becomes less than 0 dB (1x), resulting in one oscillation. There is a probability that the condition will not hold.

The above-mentioned crystal impedance cannot be measured if the crystal resonator is connected to an oscillation circuit as in the past due to the influence of the single oscillation circuit.

The present invention has been made in view of the above circumstances, and its purpose is to solve the above-mentioned problems in the conventional technology, to enable the terminals of the crystal resonator to be arbitrarily disconnected from the oscillation circuit, and to It is an object of the present invention to provide a crystal oscillation circuit in which the characteristics of a single crystal resonator can be measured even after the crystal resonator is incorporated into an oscillation circuit, and defective products can be easily removed and failure analysis performed.

[Means to solve the problem]

The above-mentioned object of the present invention is to provide a crystal oscillation circuit comprising a crystal resonator and active elements such as a resistor, a capacitor, and a transistor, and to provide a means for separating the crystal resonator and the oscillation circuit comprising the active element. This is achieved by a crystal oscillation circuit characterized in that both terminals of the vibrator can be contacted from the outside.

[Effect]

In the crystal oscillator circuit according to the present invention, the crystal resonator is
Optionally disconnected from the oscillator circuit by a field effect transistor, relay or mechanical switch. This makes it possible to measure the crystal impedance of the crystal resonator.

〔Example〕

Embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 1 shows a crystal oscillation circuit which is an embodiment of the present invention. In FIG. 1, 1 is a crystal oscillator, 2 is an oscillation circuit, and is, for example, a circuit obtained by removing the crystal oscillator 1 from the known non-adjustable crystal oscillation circuit shown in FIG.
1 is a power supply terminal, 4 is an oscillation output terminal, 6 is a field effect transistor, 7 is a crystal resonator measurement terminal, and 17 is a GND terminal.

In FIG. 5, 1, 3.4, and 17 are the above-mentioned components, 11-13 are resistors, 14.15 are capacitors, and 16 is a transistor.

The operation of the embodiment shown in FIG. 1 is as follows. That is, when a power supply voltage is applied between the 'W1 source terminal 3 and the GND terminal 17, a voltage is applied between the gate (G) and source (S) of the first oscillation circuit 2 and the field effect transistor 6. Drain (D), Source (
S) is turned on, the crystal resonator 1 is connected to the oscillation circuit 2, and an oscillation operation is performed. Next, if no power supply voltage is applied.

Since the gate + - (a) + source (S) of the field effect transistor 6 is not biased, the drain (D) and source (S) of the field effect transistor 6 are in an off state, and the crystal resonator 1 is turned into an oscillation circuit. separated from 2. Therefore, if no power supply voltage is applied.

Crystal impedance can be measured between the crystal resonator measurement terminal 7 and the power supply terminal 3.

The embodiment shown in FIG. 2 is an example in which a field effect transistor is used for switching the connection of the crystal resonator 1 in the embodiment shown in FIG. 1, whereas a relay is used.

When a power supply voltage is applied between the power supply terminal 3 and the GND terminal 17, voltage is applied to the oscillation circuit and relay coil 8, the relay contact 9 is closed, the crystal resonator 1 is connected to the oscillation circuit 2, and oscillation operation is performed. be exposed. Next, when the power supply voltage is not applied, the relay contact 9 is in an open state, so that the crystal impedance can be measured between the crystal resonator measurement terminal 7 and the power supply terminal 3.

The embodiment shown in FIG. 3 is the same as the embodiment shown in FIG. 2, in which the relay is replaced from the make contact to the transfer contact.
Since it is not connected to the external noise, it has the feature of reducing the influence of external noise.

The embodiment shown in FIG. 4 shows an example in which the crystal resonator measurement terminal 7 and the crystal resonator connection terminal 1O are provided as independent terminals, and these two terminals are opened and closed by a mechanical switch. During oscillation operation, crystal resonator measurement terminal 7
and the crystal resonator connection terminal lO are connected by a mechanical switch, and the mechanical switch is opened when measuring the crystal impedance.

In each of the embodiments described above, the entire crystal oscillation circuit is housed in one case, and the power terminals 3. An example can be considered in which the GND terminal 17, the crystal resonator measurement terminal 79, the oscillation output terminal 4, and the crystal resonator measurement terminal 10 (FIG. 4 only) are provided as external connection terminals. In this case, when modularizing the crystal oscillator circuit of the embodiment shown in FIG. This can be done by patterning the substrate.

According to each of the embodiments described above, the crystal impedance of the crystal resonator can be arbitrarily measured even after the crystal resonator is mounted in the oscillation circuit, so that abnormalities in the crystal resonator can be easily detected. In particular, with the module in which the crystal resonator and oscillation circuit are housed in one case, the above measurements can be performed even after the case is sealed, so harmful foreign substances attached to the crystal piece can be checked before the case is sealed. This has the advantage that it can be done electrically in the post-process.

The modules currently mainly used are 4.
One of the pins is not used, so if this is used, the modules shown in each of the above embodiments can be housed in the same case as the present case.

〔Effect of the invention〕

As described above, according to the present invention, in the crystal oscillation circuit, a means for separating the crystal resonator and the oscillation circuit is provided, and both terminals of the crystal resonator are configured to be accessible from the outside, so that the crystal oscillation This has the remarkable effect that it is possible to realize a crystal oscillation circuit in which the characteristics of a single crystal resonator can be measured even after the crystal resonator is incorporated into the oscillation circuit.

[Brief explanation of the drawing]

1 to 4 are circuit diagrams showing embodiments of the present invention, FIG. 5 is a diagram showing an example of a known non-adjustable oscillation circuit, and FIG.
The figure shows the excitation current and crystal impedance characteristics of a crystal resonator, and FIG. 7 is an equivalent circuit diagram of the crystal resonator. 1: Crystal resonator, 2: Oscillation circuit, 3: lt power supply terminal 4
: Oscillation output terminal, 6: Field effect transistor, 7: Crystal resonator measurement terminal, 9: Relay contact, 5.11 to 13 are resistors, 14, 15: Capacitor, 16: Transistor, 1
7: GND terminal.

Claims (1)

[Scope of Claims] 1. In a crystal oscillation circuit comprising a crystal resonator and active elements such as resistors, capacitors, and transistors, means is provided for separating the crystal resonator and the oscillation circuit comprising the active elements; A crystal oscillation circuit characterized in that both terminals of a crystal resonator are configured to be accessible from the outside. 2. The crystal oscillation circuit according to claim 1, wherein a field effect transistor is used as the separation means. 3. The crystal excavation circuit according to claim 1, wherein a relay is used as the separation means. 4. The crystal oscillation circuit according to claim 1, wherein a mechanical switch is used as the separation means. 5. The crystal oscillation circuit according to claim 1, wherein a pattern of a substrate on which the crystal oscillation circuit is modularized and mounted is used as the mechanical switch.