JPH04165809A - Ring oscillator - Google Patents

Abstract

PURPOSE:To change an oscillation frequency as needed by incorporating an analog switch switching the connection of plenty of unit elements constructing an inversion element, a frequency setting circuit setting an optional oscillation frequency, and a frequency deciding/controlling circuit controlling the analog switch based on the compared decision of the oscillation frequency and the set frequency. CONSTITUTION:An inversion element 1 is composed of odd number of inverters. The input/output terminal of an analog switch 2 is connected to the even number-th output terminal of the inverter of the inversion element 1 intermittently connected. A frequency setting circuit 4 setting the optional frequency is connected to the input of a frequency deciding/controlling circuit 3, and the other input of the frequency deciding/controlling circuit 3 is connected to the control terminal of the analog switch 2. When setting the optional frequency in the frequency setting circuit 4, the frequency deciding/controlling circuit 3 compares the frequency set by the frequency setting circuit 4 with the frequency of a ring oscillator, and controls the ON/OFF of the analog switch 2.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a ring oscillator.

[Conventional technology]

Conventional ring oscillators of this type oscillate at a constant oscillation frequency.

[Problem to be solved by the invention]

The conventional ring oscillator described above has a drawback that the oscillation frequency cannot be changed as appropriate because the oscillation frequency is constant.

SUMMARY OF THE INVENTION An object of the present invention is to provide a ring oscillator which solves the above-mentioned drawbacks and whose oscillation frequency can be changed as required.

[Means to solve the problem]

The configuration of the ring oscillator of the present invention includes an analog switch that changes the connection of a large number of unit elements that constitute an inverting element;
The present invention is characterized in that it includes a frequency setting circuit that sets an arbitrary oscillation frequency, and a frequency determination/control circuit that controls the analog spin subordinate based on a comparison determination between the oscillation frequency and the set frequency.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

Figure 1 is the first fruit of the present invention! FIG. 3 is a circuit diagram of a ring oscillator of M.

In FIG. 1, this embodiment has an inverting element 1 consisting of a total of 13 inverters, and a total of 6 analog switches 2.
, a frequency determination/control circuit 3, a frequency setting circuit 4,
It is equipped with a terminal 11.

The inverting element 1 consists of an odd number of inverters. The input/output terminals of the analog switch 2 are connected to even-numbered output terminals of the inverters of the inverting element 1 connected in series. A frequency setting circuit 4 for setting an arbitrary frequency is connected to an input of the frequency judgment/control circuit 3, and the other input of the frequency judgment/control circuit 3 is connected to a ring oscillator. The output is connected to the control terminal of analog switch 2.

Next, the operation of the present invention will be explained. When an arbitrary frequency is set in the frequency setting circuit 4, the frequency judgment/control circuit 3
1 compares the frequency set by the frequency setting circuit 4 with the frequency of the ring oscillator, and controls whether the analog switch 2 is turned on or off.

As a result, the ring oscillator of this embodiment can be configured as shown in FIG.
The objective is to provide waveforms of arbitrary frequencies as shown in A), (B), (C), (D), or (E).

Now, the frequency set by the frequency setting circuit 4 is shown in Fig. 2 (E
), and if the oscillation frequency of the ring oscillator at that time is (A) in Fig. 2, then the frequency judgment/control circuit N3
turns the analog switch 2 on or off to match the set frequency.

The ring oscillator thus provides the set frequency.

FIG. 3 is a circuit diagram of a ring oscillator according to a second embodiment of the present invention.

In this embodiment, the delay times of the inverting elements 1 that constitute the ring oscillator are different. In this embodiment, the inverting elements 1 having different delay times are switched by the analog switch 2. , it has the advantage of being able to obtain fine-grained frequencies.

Incidentally, among the inverting elements 1, the first column has 12 inverters,
The second column consists of nine inverters, the third column consists of six inverters, and the fourth column consists of three inverters. There are three analog switches in each column.

〔Effect of the invention〕

As explained above, the present invention has the advantage that an arbitrary oscillation frequency can be obtained by turning on or off an analog switch.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a ring oscillator according to the first embodiment of the present invention, FIG. 2 is a waveform diagram showing examples of the five types of oscillation waveforms shown in FIG. 1, and FIG. FIG. 2 is a block diagram showing a ring oscillator according to an embodiment.゛1 is an inverting element, 2 is an analog switch, 3 is a frequency judgment/control circuit, 4 is a frequency setting circuit, 11 is a terminal, (A)
, (B), (C), (D), and (E) are examples of the oscillation frequencies of the ring oscillator.

Claims (1)

[Claims] An analog switch that changes the connection of a large number of unit elements constituting an inverting element, a frequency setting circuit that sets an arbitrary oscillation frequency, and a frequency judgment circuit that controls the analog switch based on a comparison judgment between the oscillation frequency and the set frequency. A ring oscillator comprising a control circuit.