JPH05136657A - Ring oscillator circuit - Google Patents

Abstract

PURPOSE:To obtain a variable period type ring oscillator circuit whose layout area is reduced and current consumption is suppressed. CONSTITUTION:Five inverters 101, 102, 201-203 are annularly connected in series while holding an N-channel transistor(TR) therebetween to form a 1st ring oscillator 100. A P-channel TR 33 is provided between the cathode of the inverter 201 and the anode of the inverter 203 as a short-cut path of the series connection of the inverters. The number of inverter stage of the ring oscillator is selected by applying on/off control to each TR.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ring oscillator circuit, and more particularly to improvement of a variable-cycle type ring oscillator circuit.

[0002]

2. Description of the Related Art FIG. 3 is a circuit diagram showing a conventional ring oscillator circuit, in which 1 is an oscillation output φ.
_First and _second ring oscillators 1 that output ₁ and φ ₂
Ring oscillator circuits having 0 and 20, 11 to 13 constitute a ring oscillator 10 that outputs a signal φ ₁ 3
One inverter, 21 to 25 are five inverters that form the ring oscillator 20, and 3 is the ring oscillator 10.
N-channel transistor 4 which receives the oscillation output φ ₁ of the above in the drain and outputs this as the output signal φ to the source receives the oscillation output φ ₂ of the ring oscillator 20 in the drain,
An N-channel transistor 5 that outputs this to the source as an output signal φ controls the transistors 3 and 4 to switch the period of the periodic output signal φ of the ring oscillator circuit 1, and 6 indicates a period control circuit 5 Is an inverter that inverts the output of the above and inputs it to the gate of the transistor 3. FIG. 4 is a waveform diagram showing the waveform of the internal signal in the ring oscillator circuit.

Next, the operation will be described. The three inverters 11 to 13 connected in a ring are ring oscillators 1.
0 to generate a periodic signal φ ₁ having a certain frequency. Similarly, the ring oscillator 20 including the five inverters 21 to 25 also generates the periodic signal φ ₂ . When the inverters 11 to 13 and 21 to 25 forming the ring oscillators 10 and 20 have the same capability, the cycle of the signal φ ₂ generated from the ring oscillator 20 having a large number of inverter stages is generated from the ring oscillator 10. Signal φ ₁ is larger than that of the signal φ ₁ .

Here, when the output of the cycle control circuit 5 is at a high level, the N-channel transistor 4 becomes conductive, but the input of the N-channel transistor 3 is inverted by the inverter 6, so that the N-channel transistor 3 is cut off. Therefore, the signal φ ₂ having a large cycle generated by the ring oscillator 20 is output as the output signal φ _L through the transistor 4.

When the output of the cycle control circuit 5 is low, the N-channel transistor 4 is cut off and the transistor 3 is turned on. Therefore, the signal φ ₁ having a short cycle generated by the ring oscillator 10 is output as the output signal φ _S through the transistor 3.

During the above operation, both the ring oscillator 10 and the ring oscillator 20 are constantly oscillating and consume current.

[0007]

Since the conventional ring oscillator circuit is configured as described above, when changing the cycle of the periodic output signal φ, the ring oscillator circuit is formed by a plurality of independent ring oscillators. However, it is necessary to switch to one of those ring oscillators that outputs a desired cycle, so the layout of the circuit becomes large, and the current also flows to the ring oscillator that does not need to operate, resulting in a large current consumption. There was a problem such as becoming.

The present invention has been made in order to solve the above problems, and an object thereof is to obtain a variable cycle type ring oscillator circuit which can reduce the layout area of the circuit and can reduce the current consumption. And

[0009]

A ring oscillator circuit according to the present invention includes a first ring oscillator formed by connecting an odd number of inverters and a first switch circuit in series and annularly, and the first ring. A second ring oscillator in which an odd number of some inverters constituting the oscillator and a second switch circuit are connected in series and in an annular shape, and the first and second switch circuits are controlled to control the first and second switch circuits. Only one of the outputs of the first and second ring oscillators is selectively output to the outside.

[0010]

According to the present invention, a plurality of inverters are annularly arranged with the first switch circuit sandwiched therebetween to form an inverter series connection body, and a second switch circuit is provided as a shortcut path for the series connection body. Since the number of inverter stages used as a ring oscillator is switched by turning each switch circuit on and off by a control signal, it is possible to control not only the cycle of the output signal of the ring oscillator circuit but also the number of constituent elements. Can be reduced, the layout area of the circuit can be reduced, and current consumption can be reduced.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram showing a ring oscillator circuit according to an embodiment of the present invention. In the figure, reference numeral 2 is a ring having first and second ring oscillators 100 and 200 for outputting oscillation outputs φ ₁₁ and φ ₂₂ , respectively. Oscillator circuit,
201 to 203 are three inverters that form the second ring oscillator 200, and 101 and 102 are inverters 2.
01-203 are connected in series to configure the first ring oscillator 100 together with the above-mentioned three inverters 201-203, and 33 is a drain connected to the anode of the inverter 203 and a source connected to the cathode of the inverter 201. The oscillation output φ ₂₂ of the second ring oscillator 200 is output to the source of the P-channel transistor, and the output of the cycle control circuit 5 is used as the gate input. Reference numeral 44 denotes an N-channel transistor in which the drain is connected to the anode of the inverter 102, the source is connected to the cathode of the inverter 201, and the oscillation output φ ₁₁ of the first ring oscillator 100 is output to the source. It is used as a gate input. FIG. 2 is a waveform diagram showing waveforms of internal signals of the ring oscillator circuit according to the embodiment of the present invention.

Next, the operation will be described. First, when the output of the cycle control circuit 5 is at a high level, the N-channel transistor 44 is conductive and the P-channel transistor 33 is cut off. Therefore, the three inverters 201 to 203 and the two inverters 101 and 102 are connected through the N-channel transistor 44. The ring oscillator 10 is connected in a ring shape.
Form 0. Then, as the oscillation output φ ₁₁ , a waveform with a large cycle of the ring oscillator 100 composed of five inverters is output, and this is output as an output signal φ _L through the N-channel transistor 44.

Next, when the output of the cycle control circuit 5 is at a low level, the N-channel transistor 44 is cut off and the P-channel transistor 33 is turned on, so that the three inverters 201 to 203 are connected in a loop through the transistor 33. Then, the ring oscillator 200 is formed. As the oscillation output φ ₂₂ , a waveform with a short cycle of the ring oscillator 200 is output, and this is output to the signal φ _S through the P-channel transistor 33. Here, the oscillation output φ ₂₂ is input to the two inverters 101.102,
Although the signal φ ₁₁ is output, the signal φ ₁₁ does not affect the cycle of the ring oscillator 200 because the transistor is cut off.

As described above, in this embodiment, the five inverters 101, 102, 201 to 203 are connected in series and annularly with the N-channel transistor interposed therebetween to form the first ring oscillator 100, and at the same time, the above-mentioned inverters are connected. A P-channel transistor 33 is provided between the cathode of the inverter 201 and the anode of the inverter 203 as a path for short-circuiting the series connection body, and the number of inverter stages of the ring oscillator can be switched by controlling ON / OFF of each transistor. Therefore, the number of constituent elements can be reduced to reduce the circuit layout area and the current consumption.

Although the number of inverter stages is limited in the above embodiment, a ring oscillator having another number of stages may be used if it is an odd number. Further, the same effect can be obtained even if a resistance, a capacitance, etc. are added to the ring oscillator other than the inverter.

[0016]

As described above, according to the ring oscillator circuit of the present invention, a plurality of inverters are annularly arranged with the first switch circuit sandwiched therebetween to form an inverter series connection body, which is connected to the series connection body. Since the second switch circuit is provided as a path for short-circuiting and each switch circuit is made conductive or non-conductive by the control signal, the number of stages of the inverter used as the ring oscillator is switched, so that the output signal of the ring oscillator circuit is changed. In addition to controlling the period, the number of constituent elements can be reduced, the circuit layout area can be reduced, and the current consumption can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing a variable cycle ring oscillator circuit according to an embodiment of the present invention.

FIG. 2 is a waveform diagram showing a waveform of an internal signal of the ring oscillator circuit.

FIG. 3 is a diagram showing a conventional variable cycle ring oscillator circuit.

FIG. 4 is a waveform diagram showing a waveform of an internal signal of the ring oscillator circuit.

[Explanation of symbols]

 2 Ring Oscillator Circuit 5 Period Control Circuit 33 P Channel Transistor 44 N Channel Transistor 100 Ring Oscillator 101, 102 Inverter 200 Ring Oscillator 201-203 Inverter

Claims (1)

[Claims] 1. A variable-cycle ring oscillator circuit having a ring oscillator composed of an odd number of inverters, wherein a first ring oscillator in which an odd number of inverters and a first switch circuit are connected in series and in a ring shape. A second ring oscillator formed by connecting an odd number of some of the inverters forming the first ring oscillator and a second switch circuit in series and annularly; A ring oscillator circuit, comprising: a control unit that controls the switch circuit to selectively output one of the first and second ring oscillators to the outside.