JPH02207603A - Crystal oscillation circuit - Google Patents

Abstract

PURPOSE:To execute oscillation as well even at a higher harmonic of a crystal resonator by changing a feedback resistance value and a capacity value between the input of an inverter and a ground and between an output and the ground by the change over of a switch in addition to the oscillation by the fundamental wave of the crystal resonator. CONSTITUTION:Three resistors Rf1-Rf3, to which switches S1-S3 to be controlled by a decoder 3 are serially connected, are parallelly connected to an inverter 1 to which a crystal resonator 2 is parallelly connected. Then, between the input of the inverter 1 and the ground and between the output and ground, capacitors Cg1, Cg2, Cd1 and Cd2, to which switches S4-S7 to be controlled by a decoder 4 are serially connected, are parallelly connected respectively. When only the switch S1 is turned on among the switches S1-S3 and only the resistor Rf1 is parallelly connected to the inverter 1, this circuit is oscillated by the fundamental wave of the crystal resonator 2. Then, when the switches S1 and S2 are turned on, the feedback resistance value is smaller than the resistor Rf1 and a maximum value is obtained with the frequency of high negative resistance. Thus, the oscillation can be executed as well even at a higher harmonic in addition to the fundamental wave of the crystal resonator.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a crystal oscillation circuit configured by connecting an inverter and a crystal resonator in parallel.

[Conventional technology]

FIG. 2 shows an example of a conventional crystal oscillation circuit of this type.

A crystal resonator 2 is connected in parallel to an inverter 1, and further,
One feedback resistor Rr is connected in parallel, one capacitor Cg is connected between the human power of the inverter 1 and the ground, and one capacitor C4 is connected between the output and the ground.

[Problem to be solved by the invention]

In the conventional crystal oscillator circuit as described above, the third order of the crystal resonator,
In order to oscillate with fifth-order harmonics, there is a problem in that it is necessary to increase the transistor size of the inverter or to attach external resistors and coils.

The present invention was made to solve the above problems.
It is an object of the present invention to provide a device that can not only oscillate with the fundamental wave of a crystal oscillator but also oscillate with harmonics of the crystal oscillator by turning on and off a switch.

[Means to solve the problem]

The crystal oscillation circuit of the present invention has a plurality of resistors connected in parallel to an inverter, each having a switch connected in series whose on/off is controlled by a decoder, and a decoder connected between the input and the ground of the inverter and between the output and the ground. Multiple capacitors connected in series with switches that are controlled to turn on and off are connected in parallel, and the feedback resistance value and the capacitance between the inverter input and ground and between the output and ground are changed by switching on and off of the switches. It is configured so that it can be used.

〔Example〕

FIG. 1 shows an embodiment of the invention.

The crystal oscillation circuit is the part surrounded by a broken line, and the whole shows a circuit of a crystal oscillation module IC that can obtain outputs at multiple frequencies.

Switches S, , S, , S whose on/off is controlled by a decoder 3 are connected to an inverter l in which crystal vibration number 2 is connected in parallel.
, three resistors R, , connected in series.

Rf! l R1M are connected in parallel, and switches S L+Ss, S are connected between the input and the ground of the inverter l, and between the output and the ground, and whose on/off is controlled by the decoder 4, respectively.
s, S, connected in series I C'll+ C9!
+ and Cdl+ Cd! are connected in parallel.

The output of inverter l is connected to switches 6, . . . controlled by decoder 5. 6t+, 6c and toggle flip-flop 7,
．． 7. The signal passes through one of the circuits constituted by the buffer 8 and is output.

In this oscillation circuit, only SI of the switches St, St, 33 is turned on, and only the resistor Rfl is connected to the inverter.
When the fundamental wave of crystal oscillator 2 oscillates and SI and 32 are turned on, the feedback resistance value becomes R.
fl (becomes), the negative resistance has a maximum value at a high frequency, and the harmonic components of the crystal resonator 2 tend to oscillate.

When St, Sz, and Ss are turned on, the feedback resistance value becomes even smaller than in the above case, and the negative resistance has its maximum value at a higher frequency, making it easier to oscillate with higher harmonic components ( Become.

On the other hand, when switches s, s, , S&, and St are all on, the capacitance between the input and ground of inverter 1 and between the output and ground is the largest, and the oscillation stability is good, but the gain of the oscillation circuit is overtone oscillation is less likely to occur.

Therefore, in order to cause overtone oscillation, Ss
, Sb is turned on, Ss and St are turned off, and the inverter l
Reduce the capacitance between the input and ground and between the output and ground.

The output of the inverter 1 is connected to the switches 6, . Depending on whether 6b and 6c are turned on or off, the output is output directly through Bacher 8 or through toggle flip-flop 7.
Either the frequency is changed once by □ and outputted through the backer 8, or the frequency is changed twice by toggle flip-flops 7a and 7b and then outputted through the backer 8.

With the above configuration, outputs of various frequencies can be obtained with one module IC.

〔Effect of the invention〕

As explained above, according to the present invention, the basics of crystal oscillators can be easily changed by simply switching a switch via a decoder without increasing the transistor size of the inverter or adding external resistors or coils. Besides waves 3
It is possible to oscillate even harmonics of the next, fifth, etc., and there is an effect that outputs of many frequencies can be obtained with one oscillation circuit.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing an example of a conventional crystal oscillation circuit of this type. 1... Inverter, 2... Crystal resonator, 3, 4.5
...Decoder, 6a, 6b, 6c...Switch 1-
．． 1b...Toggle flip-flop, 8...Buffer 1-1Rfl+ Rfl+ Rls...Resistance,
C@I+ C1l Cab, Caz...Capacity, S
++ Sz+ S3+S4+ Ss, Ss, St
···switch. Note that the same reference numerals in the figures indicate the same or corresponding parts. Patent applicant: New Japan Radio Co., Ltd.

Claims (1)

[Claims] A crystal resonator is connected in parallel to the inverter, and multiple resistors each including a switch connected in series whose on/off is controlled by a decoder are connected in parallel to the inverter, and between the input and the ground of the inverter and the output and the ground. By connecting multiple capacitors in parallel with switches connected in series, each of which is controlled on/off by a decoder, in addition to oscillating with the fundamental wave of the crystal oscillator, the switch can be turned on/off. A crystal oscillation circuit configured to change a feedback resistance value and a capacitance value between the input and ground and between the output and ground of the inverter, thereby making it possible to oscillate even at harmonics of the crystal resonator.