JP3434697B2 - Oscillation circuit and semiconductor integrated circuit having the oscillation circuit - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillator circuit for continuously outputting a sinusoidal electric signal, and a semiconductor integrated circuit including the oscillator circuit.

[0002]

2. Description of the Related Art Currently, semiconductor integrated circuits are used in many industrial fields such as microcomputers. Further, this semiconductor integrated circuit is required to have low power consumption and low noise in each industrial field, and various measures have been proposed. However, with respect to the oscillation circuit of the semiconductor integrated circuit, it is difficult to reduce the power consumption and the noise, and measures have not been taken. The oscillator circuit can reduce power consumption and noise by reducing the gain of the amplifier in the circuit. However, reducing the gain of the amplifier causes deterioration of the oscillation characteristics such as the oscillation starting characteristic. For this reason, the oscillator circuit has been delayed in reducing power consumption and noise.

FIG. 1 shows an example of a semiconductor integrated circuit equipped with a conventional oscillator circuit. The oscillation circuit 1 has two input terminals X
An oscillator 2 such as a crystal oscillator or a ceramic oscillator is connected to the input terminals X0 and X1 outside the oscillator circuit 1. Both ends of the oscillator 2 have an oscillating capacitance C
_Grounded via _G and C _D. Three stages of amplifiers A1, A2 and A3 are connected in series between one input terminal X0 and one output terminal XOUT. The feedback resistor R1 is connected in parallel to the first-stage (first-stage) amplifier A1, and the other input terminal X1 is connected to the output stage of the first-stage amplifier A1. Three-stage amplifiers A1 to A3
Amplifies the output signal of the vibrator and removes noise in the signal. This amplifier is not limited to 3 stages,
Although it is possible to have four or more stages, in a normal oscillation circuit,
The third stage is most often used.

[0004]

In the above-mentioned conventional oscillator circuit, the reduction in power consumption and the reduction in noise have not been realized as described above. As a result of the inventor's analysis of this oscillator circuit, the causes of high power consumption and high noise were found as follows. 2 shows current characteristics of the amplifiers A1 to A3, and FIG. 3 shows combined current characteristics of all the amplifiers A1 to A3.

In each of the amplifiers A1 to A3, since the output signal is out of phase with the input signal by 180 °, the first stage amplifier A1 and the third stage amplifier A3 in the oscillator circuit 1 of FIG. As shown in, the phases match. The characteristic of the first-stage amplifier A1 is a current characteristic including the feedback resistor R1. Therefore, all the amplifiers A1 to A
The combined current characteristic of No. 3 is as shown in FIG. 3, and the peak current of the first-stage amplifier A1 and the peak current of the third-stage amplifier A3 overlap each other. This phenomenon raises the peak current value of the oscillation circuit 1 itself, amplifies the consumed current, and causes noise.

An object of the present invention is to reduce the power consumption and the noise of an oscillator circuit. Another object of the present invention is to reduce power consumption and noise of a semiconductor integrated circuit including an oscillation circuit.

[0007]

The present invention has been made to achieve the above object. The present invention provides two input terminals for connecting to a vibrator, one output terminal for outputting a continuous sinusoidal electric signal to the outside, and at least three stages between the input terminal and the output terminal. A connected amplifier, which supplies a feedback signal to the input end by an initial stage amplifier, amplifies and removes noise of an electric signal input from the input end, and outputs the continuous sine wave electric signal. In order to reduce the peak current value of the amplifier and the amplifier for outputting from the end,
It is provided at the node that connects the amplifiers of the second and subsequent stages, and the phase of the output of the amplifiers of the latter stage
Current and the current consumed by the amplifier in the subsequent stage are consumed at the same time.
The oscillation circuit is composed of a circuit that shifts the peaks of the consumption currents from each other within a certain period .

The circuit for shifting the phase shifts the phase relationship between the amplifier arranged in the preceding stage and the amplifier arranged in the latter stage. As a result, it is possible to prevent the peak currents from overlapping in the two amplifiers in which the phases of the peak currents coincide with each other when there is no circuit for shifting the phases. As a result, the peak current value of the oscillation circuit itself is reduced, so that the increase in power consumption due to the increase in the peak current value is suppressed, and the noise component can be reduced.

Further, by adopting this oscillation circuit in a semiconductor integrated circuit, it is possible to realize low power consumption and low noise of the semiconductor integrated circuit.

[0010]

DETAILED DESCRIPTION OF THE INVENTION An embodiment of the present invention will be described with reference to the drawings. FIG. 4 shows an oscillation circuit to which the present invention is applied and a semiconductor integrated circuit including the oscillation circuit according to a first embodiment. In FIG. 4, reference numeral 1 is an oscillator circuit, 2 is an oscillator such as a crystal or ceramic oscillator, and 3 is a semiconductor integrated circuit incorporating the oscillator circuit 1.

The oscillator circuit 1 has two input terminals X0 and X1, and a vibrator 2 is connected to the input terminals X0 and X1 outside the oscillator circuit 1. Both ends of the vibrator 2 are grounded via the oscillation capacitors C _G and C _D. One input terminal X
Between 0 and the output terminal XOUT, three-stage amplifiers A1, A2,
A3 is connected in series. The other input terminal X1 is connected to the output side of the first stage amplifier A1. A feedback resistor R1 is connected in parallel with the first-stage amplifier A1.

The first-stage amplifier A1 in which the feedback resistor R1 is connected in parallel amplifies the electric signal from the vibrator 2 and
A feedback signal is supplied to the vibrator 2. The second-stage and third-stage amplifiers A2 and A3 amplify electric signals and remove noise in the signals. With the above circuit configuration, a sinusoidal electric signal is continuously output from the output terminal XOUT.

The number of stages of the amplifier is not limited to three, and four or more stages can be used, but three stages are most commonly used in a normal oscillator circuit. Further, although a phase inversion type amplifier is used as each of the amplifiers A1 to A3, amplifiers other than the phase inversion type can be used for the amplifiers A2 and A3 in the second and subsequent stages. The capacitor C is connected between the node connecting the second-stage amplifier A2 and the third-stage amplifier A3 and the ground. The capacitance C is provided for the purpose of shifting the phase of the third-stage amplifier A3 with respect to the first-stage amplifier A1. This capacity C is
It can be obtained by patterning the shape of the node into a shape having a large capacitance when forming the node. A patterning method for increasing the capacitance is a method well known in the art, and thus detailed description thereof is omitted here.

The capacitor C may be provided between the node and the power supply, as shown by a broken line in the figure, instead of being provided between the node and the ground. Further, it can be provided both between the node and the ground and between the node and the power supply. The above circuit configuration is the same as that of the conventional oscillation circuit shown in FIG. 1 except that the capacitor C is present.

FIG. 5 shows each amplifier A1 of the oscillator circuit 1 of FIG.
The current characteristics of 3 are shown. In the current characteristics of the amplifiers A1 to A3, the current characteristics of the first-stage amplifier A1 and the second-stage amplifier A2 are the same as those in the conventional oscillation circuit of FIG. 2 described above. That is, the characteristic of the first-stage amplifier A1 is a current characteristic including the feedback resistor R1. Since the output signal of the second-stage amplifier A2 is 180 ° out of phase with the input signal,
180 ° out of phase with the output signal of the first-stage amplifier A1.

The capacitor C delays the electric signal output from the second-stage amplifier A2 by a predetermined amount α. Since the output signal of the third-stage amplifier A3 is 180 ° out of phase with the input signal thereof, it is 180 ° + α from the output signal of the second-stage amplifier A2.
It will only be shifted. Therefore, the third stage amplifier A3
The peak current of 1 shifts from the peak current of the first-stage amplifier A1 by each phase α and does not match.

FIG. 6 shows a combined current characteristic of all the amplifiers A1 to A3. Since the peak currents of the first-stage amplifier A1 and the third-stage amplifier A3 do not overlap, the peak value of the combined current is
This is lower than the conventional combined current in FIG. That is, unlike the conventional oscillator circuit, power consumption is not amplified due to overlapping peak currents. This all amplifier A1
By reducing the peak current value at A3, the power consumption of the oscillation circuit 1 is reduced and the noise component of the oscillation circuit 1 itself can be reduced.

FIG. 7 shows a second oscillator circuit according to the present invention.
2 shows an embodiment of the present invention. In the following description, the first
Only points different from the embodiment will be described. In the example of FIG. 7, a resistor R is inserted between the second-stage amplifier A2 and the third-stage amplifier A3 as a phase shift circuit. This resistance R
Can be formed, for example, by forming all or part of the wiring between the second-stage amplifier A2 and the third-stage amplifier A3 with a high resistance material. As a method of selecting the material and forming the wiring, a technique well known in the art can be used.

The provision of the resistor R causes a wiring delay, and an electric signal deviated from the output signal of the second stage amplifier A2 is input to the third stage amplifier A3. Therefore, as in the first embodiment described above, the first-stage amplifier A1 has three
The phase of the stage amplifier A3 can be shifted. As a result, the current characteristic becomes as shown in FIGS. 5 and 6 described above, and it is possible to realize an oscillation circuit with low power consumption and low noise.

FIG. 8 shows another embodiment of the phase shifting circuit. The circuit for shifting the phase in the present invention is not limited to the capacitor C shown in FIG. 4 or the resistor R shown in FIG. 6 described above, and other circuits can be used. As one example thereof, a circuit in which a capacitor C and a resistor R are combined is shown in FIGS.

(A) shows an example in which a capacitance C is provided between the front stage of the resistor R and the ground, (B) shows an example in which the capacitance C is provided between the rear stage of the resistor R and the ground, and (C) shows An example is shown in which a capacitor C is provided between the front and rear stages of the resistor R and the ground.
Also in these examples, the capacitor C can be provided on the power supply side instead of the ground side. In the above embodiments of the present invention, the oscillator circuit having the three-stage amplifier has been described. In the oscillation circuit having the three-stage amplifier, the phases of the first-stage amplifier and the third-stage amplifier are prevented from being in phase with each other. As described above, the present invention can also be applied to an oscillator circuit having four or more stages of amplifiers. In this case, the circuit for shifting the phase is arranged at an appropriate position between two amplifiers having the same phase, and shifts the phase of the amplifier at the subsequent stage, so that the same operation as that of each of the above-described embodiments is performed. Obtainable.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit configuration of a conventional oscillator circuit and a semiconductor integrated circuit.

FIG. 2 is a diagram showing a current characteristic of each amplifier of the oscillation circuit of FIG.

FIG. 3 is a diagram showing a combined current characteristic of all the amplifiers in FIG.

FIG. 4 is a diagram showing a first embodiment of an oscillator circuit and a semiconductor integrated circuit to which the present invention is applied.

5 is a diagram showing current characteristics of each amplifier of the oscillation circuit of FIG.

6 is a diagram showing a combined current characteristic of all the amplifiers in FIG.

FIG. 7 is a diagram showing a second embodiment of an oscillator circuit and a semiconductor integrated circuit to which the present invention is applied.

FIG. 8 is a diagram showing another embodiment of a phase shifting circuit according to the present invention.

[Explanation of symbols]

1 ... Oscillation circuit 2 ... Transducer 3 ... Semiconductor integrated circuit A1-A3 ... Amplifier C, C1 ... Capacity R, R1 ... Resistance X0, X1 ... Input end XOUT ... Output end

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Claims (5)

(57) [Claims] 1. An input terminal for connecting to a vibrator, an output terminal for outputting a continuous sinusoidal electric signal to the outside, and at least 3 terminals between the input terminal and the output terminal. An amplifier connected in stages, wherein a first stage amplifier supplies a feedback signal to the input end, amplifies and removes noise of an electric signal input from the input end, and outputs the continuous sine wave electric signal to the input signal. An amplifier for outputting from the output end and a node connecting the amplifiers of the second and subsequent stages of the amplifiers are provided, and the phase of the output of the amplifier of the latter stage is set to the amplifier of the former stage.
Current consumed by the amplifier and the current consumed by the amplifier in the subsequent stage
Peaks of each other's current consumption
An oscillating circuit comprising: a circuit for shifting so as not to overlap . 2. The phase shifting circuit comprises a capacitor,
The oscillation circuit according to claim 1, wherein one end of this capacitance is connected to a node between the amplifiers, and the other end is connected to at least one of a power supply and a ground. 3. The phase shifting circuit comprises resistors
The oscillation circuit according to claim 1, wherein the resistor is inserted in a circuit connecting the amplifiers. 4. The oscillator circuit according to claim 3, further comprising a capacitor connected between at least one end of the resistor and at least one of a power supply and a ground. 5. A semiconductor integrated circuit comprising the oscillator circuit according to claim 1. Description: