JPH05114820A - Crystal oscillation circuit - Google Patents

Abstract

PURPOSE:To fit a crystal oscillator externally with only one IC pin when the circuit part of the crystal oscillation circuit except the crystal oscillator is made into IC. CONSTITUTION:First and second resistance elements 2 and 3 are connected between the input terminal of an inverter 1 for constituting a NOT circuit and a ground point and its input and output terminals and then made into IC. Only one IC pin 6 for fitting the crystal oscillator 4, which is grounded at one end, externally is provided at this integrated part 5 and the IC pin 6 is internally connected to the output terminal of the inverter 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crystal oscillator circuit.

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram of a conventional crystal oscillator circuit. In the figure, 1 is an inverter for forming a NOT circuit, 8 is a first capacitive element connected between an input terminal of the inverter 1 and ground, and 7 is an output terminal of the inverter 1 and an input of the inverter 1. A resistor element 4 connected between the terminals and 4 is a crystal oscillator similarly connected between the output terminal of the inverter 1 and the input terminal of the inverter 1, 9
Is a second capacitive element connected between the output terminal of the inverter 1 and the ground.

A circuit portion including the inverter 1, the resistance element 7, and the first and second capacitance elements 8 and 9 is integrated into an integrated circuit (hereinafter referred to as an IC), and the crystal oscillator 4 is externally attached to the IC portion 5. To be done. That is, two IC pins 6a, 6 are provided on the IC portion 5 for attaching the crystal oscillator 4 to the outside.
b is provided.

[0004]

As described above, the conventional crystal oscillator circuit has a structure in which the crystal oscillator 4 is connected between the input and output terminals of the inverter 1. Therefore, the circuit portion 5 excluding the crystal oscillator 4 is omitted. It was necessary to provide two IC pins 6a and 6b for externally attaching the crystal oscillator 4 when integrated into an IC.

An object of the present invention is to provide a crystal oscillator circuit to which a crystal oscillator can be externally attached with only one IC pin when the circuit portion excluding the crystal oscillator is integrated into an IC.

[0006]

In order to achieve the above object, the present invention provides an inverter 1 for constructing a NOT circuit as shown in FIG. 1 and an input terminal of the inverter 1 and a ground. The first resistance element 2 connected, the second resistance element 3 connected between the output terminal of the inverter 1 and the input terminal of the inverter 1, and the inverter 1
In this configuration, a crystal oscillator 4 connected between the output terminal and the ground is adopted.

[0007]

According to the present invention, as will be shown later by analysis results,
Crystal oscillation of a specific frequency is performed. Moreover, FIG.
As shown in, when the circuit portion 5 excluding the crystal oscillator 4 is integrated into an IC, the crystal oscillator 4 can be externally attached by using only one IC pin 6.

[0008]

1 is a circuit diagram of a crystal oscillator circuit according to an embodiment of the present invention. In the figure, 1 is an inverter for forming a NOT circuit, 2 is a first resistance element having a resistance value R1 connected between an input terminal of the inverter 1 and ground, and 3 is an output terminal of the inverter 1. The second resistance element 4 having a resistance value Rf connected to the input terminal of the inverter 1 for feedback is a crystal oscillator connected between the output terminal of the inverter 1 and the ground.

A circuit portion having the inverter 1 and the first and second resistance elements 2 and 3 is integrated into an IC, and a crystal oscillator 4 is externally attached to the IC portion 5. That is, this I
In the C-shaped portion 5, as shown as a substantial wiring diagram in FIG.
It is only necessary to provide one IC pin 6 for externally attaching the crystal oscillator 4.

The oscillating frequency of the crystal oscillating circuit of this embodiment having the above-mentioned structure is obtained as follows.

First, the crystal oscillator 4 can be represented by the equivalent circuit shown in FIG. Using this equivalent circuit,
The admittance Y of the crystal oscillator 4 is expressed by the following mathematical formula 1. However, the condition of Formula 2 was used.

[0012]

[Equation 1]

[0013]

[Equation 2]

Next, the input / output characteristics of the inverter 1 in FIG. 1 will be obtained. When the input voltage of the inverter 1 is V1 and the output voltage thereof is V0, when the output impedance of the inverter 1 is sufficiently small, Formula 3 is established, and Formula 4 is derived from Formula 3.

[0015]

[Equation 3]

[0016]

[Equation 4]

When the gain of the inverter 1 is A, the oscillation condition is given by equation 5.

[0018]

[Equation 5]

When Equation 4 is solved under the condition of Equation 5, the oscillation angular frequency ω is expressed by Equation 6.

[0020]

[Equation 6]

That is, the crystal oscillating circuit of the present embodiment having the above-mentioned structure causes the oscillation of the angular frequency determined by the characteristics of the crystal oscillator 4 expressed by the equation (6).

[0022]

As described above, according to the present invention, an inverter for forming a NOT circuit, a first inverter connected to an input terminal of the inverter and a ground connected to the input terminal of the inverter, and a second wiring connected to the input / output terminal of the inverter. Since the configuration including the first and second resistance elements and the crystal oscillator connected between the output terminal of the inverter and the ground is adopted, when the circuit portion excluding the crystal oscillator is integrated into an IC, The crystal oscillator can be externally attached only with the IC pin of the book, which is extremely useful.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a crystal oscillation circuit according to an embodiment of the present invention.

FIG. 2 is an equivalent circuit diagram of a crystal oscillator.

FIG. 3 is a substance wiring diagram in the case where a circuit portion of the crystal oscillation circuit of FIG. 1 excluding a crystal oscillator is integrated into an IC.

FIG. 4 is a circuit diagram of a conventional crystal oscillation circuit.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Inverter 2 1st resistance element 3 2nd resistance element 4 Crystal oscillator 5 IC part 6 IC pin

Claims (1)

[Claims] 1. An inverter for forming a NOT circuit, a first resistance element connected between an input terminal of the inverter and a ground, and an output terminal of the inverter and an input terminal of the inverter. A crystal oscillating circuit comprising: a second resistance element connected to the above; and a crystal oscillator connected between the output terminal of the inverter and the ground.