JP2003224421A - Oscillator and electronic equipment using it - Google Patents

Abstract

(57) [Summary] [Problem] An input waveform with a high frequency of distortion or
An oscillation circuit capable of adjusting or suppressing a duty ratio of an output signal by correcting a reference bias voltage according to a change in an ambient temperature, and an electronic device using the same. An oscillation circuit includes an ECL line receiver, a differential amplifier formed on an IC chip, a switch circuit, and a phase shift circuit for adjusting a phase shift amount.
The bias voltage VBB1 supplied to the inverting input terminal of the oscillation differential amplifier is varied based on the piezoelectric resonator 5, which oscillates at a predetermined oscillation frequency, the impedance circuit 6, and the reference bias voltage VBB output from the IC chip 2. It consists of a voltage variable means that can be used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oscillator circuit and electronic equipment using the oscillator circuit, and more particularly, to an oscillator circuit capable of varying the duty ratio of an output signal output from the oscillator circuit and the same. Regarding electronic devices.

[0002]

2. Description of the Related Art Conventionally, an oscillation circuit using a crystal oscillator or the like has been used as a reference clock source for electronic devices such as microcomputers and mobile phones. Due to recent advances in semiconductor technology, electronic circuits that realize those functions have been integrated, and miniaturization of components and miniaturization of devices have been achieved.

For example, FIG. 7 shows a block diagram of an oscillation circuit including a semiconductor integrated circuit chip (hereinafter referred to as an IC chip) in which a differential amplifier is formed. This oscillator circuit 1C has 3
IC chip 2 in which two differential amplifiers 21 to 23 are integrated
Switch circuit 3, phase shift circuit 4, surface acoustic wave element (hereinafter,
SAW (Surface Acoustic Wav)
e) Called as resonator) 5, and impedance circuit 6
It consists of and. Further, the reference bias voltage VBB is output from the IC chip 2, and the reference bias voltage VBB is supplied to one end of the impedance circuit 6 and to the inverting input terminal D2 of the differential amplifier 21 in the IC chip 2.
Is being supplied.

FIG. 8 shows a differential amplifier 21 in the IC chip 2.
5 is a diagram showing a relationship between a rectangular input waveform Vin and its output waveform Vout as an oscillation signal input to the non-inverting input terminal D1 of FIG.

In FIG. 8, a reference bias voltage VBB is applied to the differential amplifier 21. The threshold voltage VTH on the high voltage side (hereinafter referred to as high) of the reference bias voltage VBB is a voltage level for detecting the rising of the input signal Vin, and the output timing on the output side, that is, the output waveform Vout rises at this timing. Similarly, the threshold voltage VTL on the low voltage (hereinafter, referred to as low) side is a voltage level for detecting the falling of the input signal Vin, and the output signal V falls at the output signal falling timing, that is, at this timing.
out falls.

The voltages VIH and VIL are the input signals V
The amplitude range of in, and the voltages VOH and VOL represent the amplitude range of the output signal Vout.

[0007]

The input terminal D1 is connected to the input terminal D1 shown in FIG.
When a distorted waveform as shown in FIG. 9A is input, the timing of detecting the rising and falling edges of the input waveform changes and the reference bias VBB is fixed, so that the waveform shown in FIG. As described above (the dotted line in the figure is the output waveform when there is no distortion), there is a case where a large deviation (Tup / T <50%) occurs in the duty ratio of the output waveform.

This is a waveform distortion due to impedance mismatch including wiring between components in the positive feedback oscillation loop in the oscillation circuit shown in FIG.

Further, as shown in FIG. 10 (a), if the levels of the high side threshold voltage VTH and the low side threshold voltage VTL of the differential amplifier 21 fluctuate, due to the same cause as described above, FIG. As shown in (b) (the dotted line in the figure is the output waveform when there is no change), there is a case where a large deviation (Tup / T <50%) occurs in the duty ratio of the output waveform.

Further, as shown in FIG. 11A, the reference bias voltage V supplied to the input terminal D2 of the differential amplifier 21.
When the level of BB fluctuates, the input waveform Vin shifts to the high side or the low side accordingly, and as shown in FIG. The dotted line indicates the output waveform when there is no fluctuation), and the duty ratio of the output waveform is largely biased (Tup / T <50.
%) May occur.

The level fluctuations of the threshold voltages VTH and VTL on the high side and the low side and the level fluctuations of the reference bias voltage VBB described above are mainly caused by manufacturing variations of the IC chip 2.

If the duty ratios of the output waveforms are greatly deviated due to the three factors described above, there is no means for adjusting the duty ratios, so that the oscillator circuit 1C is determined to be defective and the yield is increased. There was a problem to make it worse.

Further, there is a problem that when the ambient temperature fluctuates, the duty ratio fluctuates due to the temperature characteristics of the circuit components used in this oscillation circuit.

In particular, in an electronic device using a DDR (Double Data Rate) system which detects both rising and falling of a reference clock signal as clock timing, a large deviation in the duty ratio of the clock signal causes malfunction. Will be a major cause of

The present invention has been made in order to solve the above-mentioned problems, and it relates to the fluctuations related to the above-mentioned input waveform, in particular,
An object of the present invention is to obtain an oscillator circuit capable of adjusting a duty ratio of an output signal by varying a bias voltage according to a distorted input waveform that frequently occurs, and an electronic device using the oscillator circuit.

Further, when the ambient temperature fluctuates and the bias voltage fluctuates due to the temperature characteristics of the circuit parts, the bias voltage is automatically corrected according to the temperature fluctuation and an oscillating circuit capable of preventing malfunction is provided. The purpose is to obtain an electronic device using.

[0017]

An oscillator circuit according to claim 1 is provided with at least a differential amplifier, a piezoelectric vibrator, a phase shift circuit for shifting a phase of an input signal by a predetermined amount, and an impedance circuit. Forming a positive feedback oscillation loop with the differential amplifier, the piezoelectric vibrator, and the phase shift circuit,
The duty ratio of the output signal output from the differential amplifier is adjusted by changing the bias voltage supplied to the differential amplifier.

According to the above configuration, by varying the bias voltage supplied to the differential amplifier, the duty ratio of the output signal can be adjusted to a desired value (usually 50%) at the time of manufacturing this oscillator circuit. In addition, the effect that the yield can be improved can be obtained.

According to a second aspect of the invention, in the oscillator circuit according to the first aspect, the differential amplifier is an ECL (Emitte).
r Coupled Logic: Emitter coupling logic)
It is characterized by being a differential amplifier circuit using a line receiver.

According to the above configuration, the differential amplifier is an EC
Since it is a differential amplifier circuit using an L line receiver, it is possible to obtain an effect that the oscillator circuit can be operated at low power consumption and high speed, and that the level conversion circuit in this differential amplifier circuit can be easily constructed. To be

According to a third aspect of the invention, in the oscillator circuit according to the first or second aspect, the differential amplifier has an inverting input terminal and a non-inverting input terminal, and the inverting input terminal and the non-inverting input terminal. It is characterized in that the variable bias voltage is inputted to one of the two and the other functions as an input for the positive feedback oscillation loop.

According to a fourth aspect of the invention, in the oscillation circuit according to the first to third aspects, the bias voltage is obtained by connecting a voltage varying means to either the inverting input terminal or the non-inverting input terminal of the differential amplifier. It is characterized by changing.

According to the above configuration, as the voltage varying means for supplying a variable bias voltage to the inverting input terminal of the oscillation differential amplifier circuit, for example, a laser trimming resistor,
Since very small individual variable resistors such as variable resistor and fixed resistor, and passive elements such as thermistors are used, when configured as an oscillation circuit, a variable bias voltage can be obtained without taking up much mounting area. The effect that it can be obtained is obtained.

According to a fifth aspect of the present invention, in the oscillator circuit according to the first to fourth aspects, the piezoelectric vibrator is a SAW resonator.

According to a sixth aspect of the invention, in the oscillator circuit according to the first to fourth aspects, the piezoelectric vibrator is a crystal vibrator.

In the above structure, the piezoelectric vibrator is a SAW.
It is preferable to use either a resonator or a crystal oscillator.

According to a seventh aspect of the present invention, there is provided an electronic apparatus according to any one of the first to sixth aspects, which is provided with each oscillation circuit.

According to the above configuration, in an electronic device including the oscillator according to the present invention, for example, an optical interface module for an optical network, a distorted input waveform, a threshold voltage variation with respect to the input waveform, and a reference bias voltage vary. Then, even when the input waveform is shifted to the upper or lower side of the voltage, the bias voltage of the differential amplifier is appropriately corrected by the voltage varying means to suppress the variation of the duty ratio of the clock signal. The timing margin between the clock signals is secured, and an effect of preventing malfunction in the optical network interface module is obtained.

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. (1) First Embodiment (1-1) Configuration of First Embodiment FIG. 1 is a block diagram showing a configuration of an oscillator circuit according to a first embodiment of the present invention.

The oscillation circuit according to the first embodiment of the present invention uses the same IC as the bias voltage obtained by varying the reference bias voltage output from the IC chip by a predetermined voltage varying means (eg, variable resistor). The power is supplied to one of the two differential input terminals of the oscillation differential amplifier mounted on the chip.

In FIG. 1A, the oscillator circuit 1A has an I
An oscillation differential amplifier 21, an output differential amplifier 22, a feedback buffer differential amplifier 23 formed on the C chip 2, a switch circuit 3, a phase shift circuit 4 for adjusting the amount of phase shift, and a predetermined resonance. SAW resonator (piezoelectric resonator) 5a having frequency
(Or the crystal unit 5b) and the impedance circuit 6
(For example, a tank circuit) and the bias voltage V supplied to the inverting input terminal D2 of the oscillation differential amplifier 21 based on the reference bias voltage VBB output from the IC chip 2.
It comprises a resistor (voltage varying means) VR7 capable of varying BB1. A positive feedback oscillation loop is configured by at least the oscillation differential amplifier 21, the feedback buffer differential amplifier 23, the switch circuit 3, the phase shift circuit 4, the SAW resonator 5a, and the impedance circuit 6.

As shown in FIG. 2, the oscillation differential amplifier 21, the output differential amplifier 22, and the feedback buffer differential amplifier 23 are differential amplifier circuits each using an ECL line receiver. This ECL line receiver is a differential amplifier circuit having non-inverting and inverting differential inputs and differential outputs, and has a low power consumption and is used for a circuit that needs to operate at a high speed such as a high frequency oscillation circuit. The obtained output signal can be used for electrical level conversion used in this ECL differential amplifier circuit.

The differential amplifiers 21 to 23 described above are commercialized as general-purpose ICs and are easily available.

In the oscillation differential amplifier 21, the oscillation signal from the SAW resonator 5a is passed through the impedance circuit 6 and the non-inverting input terminal D1 of the oscillation differential amplifier 21.
Entered in. Further, the reference bias voltage VBB is varied by a variable resistor VR7 and is supplied to the inverting input terminal D2 of the oscillation differential amplifier 21 as the bias voltage VBB1. The oscillation signal having the desired frequency f0 is amplified by the oscillation differential amplifier 21 and has a phase difference of 180.
Output to the non-inverted output terminal D1 and the inverted output terminal D2.

The feedback buffer differential amplifier 23 is an amplifier having a buffer function and receives the output signal of the oscillation differential amplifier 21 and outputs it as a differential output signal to the non-inverting output terminal Q1 and the inverting output terminal Q2. To be done.

The switch circuit 3 receives from the signal SQ1 or SQ2 output from the feedback buffer differential amplifier 23, a terminal T1 having a smaller amount of phase shift adjusted by a phase shift circuit 4 described later. Or select T2.

The phase shift circuit 4 is for performing phase adjustment for satisfying the phase condition of the oscillation circuit 1A, and is connected to either the terminal T1 or T2 selected by the switch circuit 3, and this phase shift circuit 4 is used. The phase shift amount is adjusted so that the adjusted phase shift amount becomes smaller.

If the selection of the switch circuit 3 is already known at the design stage, the circuit pattern may be formed by omitting the switch circuit 3.

(1-2) Adjustment of Duty Ratio of Output Signal Here, the duty ratio of the output signal of the oscillation differential amplifier 21 is adjusted based on FIGS. 1B, 1C and 3. Means and methods will be described.

In FIG. 1A, the variable resistor V
R7 is connected between the output terminal VB that supplies the reference bias voltage VBB that is normally output from the IC chip 2 and the inverting input terminal D2 of the oscillation differential amplifier 21. Figure 1
FIG. 1B shows a case where a laser trimming resistor VR71 is used as the variable resistor VR7, and FIG.
Shows the case where the variable resistor VR72 is used.

FIG. 3 is an input / output waveform when the duty ratio of the output signal is adjusted by adjusting the variable resistor VR7 in the distorted input waveform.

Although the duty ratio is treated as a desired value specified by the user, it is usually 50% and will be described here using this value.

In the distorted input waveform of FIG. 3A, the input waveform shown by the dotted line is the waveform before the bias voltage VBB1 is varied, and the duty ratio of the output waveform shown by the dotted line in FIG. 3B is 50. It is the figure which fluctuated below%.
This will be explained using the laser trimming resistor VR71 as shown in FIG. 1B as an example. At the time of manufacturing the oscillation circuit 1A, the resistor VR71 is laser trimmed and biased as shown by an arrow in FIG. 3A. Voltage VBB1
Is varied and the input waveform is shifted to the high side as shown by the solid line, the duty ratio of the output waveform is adjusted to 50% as shown in (b).

When the variable resistor VR72 shown in FIG. 1C is used, the variable resistor VR7 is also used as described above.
The resistance value of 2 is changed to set the duty ratio of the output signal to 50.
% Can be adjusted. This adjustment can also be performed by replacing the fixed resistor VR, which is not shown, when it is used.

FIG. 4 shows the input when the bias voltage VBB1 is varied and the duty ratio of the output waveform is adjusted to 50% when the threshold voltage (VTH and VTL) of the oscillation differential amplifier 21 changes in level. It is a figure showing an output waveform. The dotted line shows the input / output waveform before the bias voltage VBB1 is changed.

When the duty ratio of the output waveform fluctuates due to the fluctuation of the bias voltage VBB1 with respect to the input waveform, as shown by the solid line in FIG.
The level of BB1 is changed in the arrow direction, that is, the high side, and the input waveform is shifted to the high side as shown by the solid line. As a result, as shown in (b), the duty ratio of the output waveform shown by the solid line is adjusted to 50%. Also in this case, the variable resistor VR7 may be either the laser trimming resistor VR71, the variable resistor VR72, or the fixed resistor VR (not shown) replaced.

Further, even when the levels of the threshold voltages VTH and VTL on the high side and the low side of the differential amplifier 21 vary, the duty ratio of the output waveform can be adjusted by the means and method described above. .

(1-3) Effects Obtained by the First Embodiment As described above, according to the first embodiment,
The following effects are achieved.

The oscillation differential amplifier 21, the output differential amplifier 22, the buffer differential amplifier 23, the SAW resonator 5a having a predetermined resonance frequency, and the phase of the input signal are shifted by a predetermined amount and output as an output signal. A positive feedback oscillation is provided by including the phase shift circuit 4 and the impedance circuit 6, and at least the oscillation differential amplifier 21, the feedback buffer differential amplifier 23, the SAW resonator 5a, the phase shift circuit 4 and the impedance circuit 6. By forming a loop and connecting the voltage varying means to the inverting input terminal of the oscillation differential amplifier 21, the bias voltage VBB1 supplied during manufacturing can be varied and the duty ratio of the output signal can be adjusted to 50%. As a result, the yield of the oscillator circuit can be improved.

Further, since the above-mentioned differential amplifier is a differential amplifier circuit using an ECL line receiver, the oscillator circuit can operate at high speed with low power consumption, and as a level conversion circuit in this differential amplifier. The effect is that it can be easily constructed.

Further, as a voltage varying means for supplying a variable bias voltage VBB1 to the inverting input terminal D2 of the oscillation differential amplifier circuit 21, for example, a laser trimming resistor VR71, a variable resistor VR72, a fixed resistor VR, etc. Since a very small individual variable resistor VR7 passive element is used, a variable bias voltage can be obtained without taking up much mounting area (1 mm square meter increase in area) when configured as an oscillation circuit. The effect that can be obtained is obtained.

(2) Second Embodiment FIG. 5 is a block diagram showing a configuration of the oscillator circuit 1B when a bias voltage temperature characteristic adjusting circuit is added according to the second embodiment. The same blocks as those in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

The bias voltage temperature characteristic adjusting circuit 8 (voltage varying means) detects fluctuations in the duty ratio caused by temperature characteristics of the circuit components used, etc., from the ambient temperature of electronic equipment using this SAW resonator. Bias voltage V input to the inverting input terminal D2 of the oscillation differential amplifier 21 due to fluctuations
BB1 is canceled by automatically changing it, thereby suppressing variation in the duty ratio of the output signal.

The bias voltage temperature characteristic adjusting circuit 8 is constituted by, for example, a series voltage dividing circuit of individual resistors and thermistors, a temperature correcting resistor, etc.
By correcting the temperature characteristic of, the fluctuation of the duty ratio of the output signal is suppressed.

As the individual resistors, the laser trimming resistor VR71, the variable resistor VR72, or the fixed resistor VR (not shown) used in the first embodiment can be applied.

As described above, according to the second embodiment,
Even in an environment where the ambient temperature fluctuates, the bias voltage temperature characteristic adjusting circuit 8 automatically adjusts the bias voltage, so that the fluctuation of the duty of the output signal can be suppressed.

Regarding the effect on the mounting area,
It is similar to the first embodiment.

(3) Third embodiment Next, a third embodiment of the present invention will be described.

FIG. 6 is a diagram showing a schematic configuration of an optical interface module for an 10.3125 gigabit optical network using the oscillator circuit according to the first embodiment.

This optical interface module 10
Is to realize an interface function for optical / electrical conversion or electric / optical conversion between, for example, a server computer and an optical network.

As shown in FIG. 6, two positive feedback type oscillation circuits 18-1, 1 which are the same as the oscillation circuit according to the first embodiment.
8-2 is connected via the bit code conversion unit 13.
125 gigabit S / P converter 11, P / S converter 1
2 and 10.3125 Gigabit P / S converter 14,
It is used as a reference clock signal in the S / P converter 15.

As described above, according to the third embodiment,
In the oscillator circuits 18-1 and 18-2, when the input waveform is shifted to the high side or the low side of the voltage due to the input of the distorted waveform, the variation of the threshold voltage with respect to the input waveform, and the variation of the reference bias voltage. However, since the bias voltage is properly adjusted by the variable resistor connected to the oscillation differential amplifier 21 shown in FIG. 1 and the duty ratio of the clock signal is adjusted to 50%, the optical interface module 10 A timing margin is secured between the transmission data and this clock signal, and an effect of preventing malfunction can be obtained.

Further, there is an effect that a stable operation can be easily ensured in a high speed network system capable of transmitting a large amount of data such as a moving image.

Although the above description is for the case where the oscillation circuit of the first embodiment is used, the same effect can be obtained by using the oscillation circuit of the second embodiment.

(4) Modification of Embodiment In the above description, the oscillation signal is biased to the non-inverting input terminal D1 via the impedance circuit 6 and via the variable resistor VR7 or the bias voltage temperature characteristic adjusting circuit. Although the case where the voltage VBB1 is input to the inverting input terminal D2 has been described, the oscillation signal thereof is output to the differential amplifier 21.
Input to the inverting input terminal D2 of the
1 may be input to the non-inverting input terminal D1.

Further, the case where the oscillation circuit is used in the optical interface module for the optical network has been described, but in the case of the oscillation circuit, various electronic devices such as a wireless communication device such as a mobile phone which requires a high frequency oscillation circuit. May be applied to.

Although the oscillation circuit has been described using the SAW resonator as the reference clock source, an AT-cut type crystal resonator may be used instead.

Further, a crystal oscillator, a ceramic oscillator or an SA
Regarding the piezoelectric material forming the piezoelectric resonator such as the W resonator,
In addition to quartz, other piezoelectric materials such as Langasite and LBO
(Lithium Tetraborate: lithium tetraborate) or the like may be used.

[0069]

As described above, according to the present invention, in the oscillation circuit in which the positive feedback oscillation loop is formed by the oscillation differential amplifier, the piezoelectric vibrator, the phase shift circuit and the impedance circuit, By varying the bias voltage supplied to either the non-inverting input terminal or the inverting input terminal of the differential amplifier for use, the duty ratio of the output signal can be adjusted, and the yield can be improved. Further, it is possible to automatically correct the bias voltage even when the ambient temperature fluctuates and suppress the fluctuation of the duty ratio of the output signal.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an oscillator circuit according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a basic configuration of an ECL line receiver.

FIG. 3 is a diagram showing waveforms of input / output signals when a duty ratio of an output signal is adjusted by adjusting a variable resistor VR.

FIG. 4 is a diagram showing an input waveform when the level of the threshold voltage changes in the oscillation differential amplifier and an output waveform obtained by adjusting the bias voltage.

FIG. 5 is a block diagram showing a configuration of an oscillation circuit when a bias voltage temperature characteristic adjusting circuit is added according to a second embodiment of the present invention.

FIG. 6 is a diagram showing a schematic configuration of an optical interface module for an 10.3125 gigabit optical network using the oscillation circuit of the present invention according to the third embodiment.

FIG. 7 is a diagram showing a block diagram of a conventional oscillator circuit.

FIG. 8 is a diagram showing an input waveform of an oscillation signal input to a non-inverting input terminal of a differential amplifier in an IC chip and an output waveform thereof.

FIG. 9 is a diagram showing a distorted input waveform input to a differential amplifier and an output waveform at that time in a conventional oscillation circuit.

FIG. 10 is a diagram showing an input waveform when a level variation occurs in the threshold voltage and an output waveform at that time in the conventional oscillation circuit.

FIG. 11 is a diagram showing an input waveform when a level change occurs in the reference bias voltage and an output waveform at that time in the conventional oscillation circuit.

[Explanation of symbols]

1A, 1B, 1C ... Oscillation circuit 2 ... IC chip, 3 ... Switch circuit, 4 ... Phase shift circuit,
5a ... SAW resonator 5b ... AT cut type crystal oscillator, 6 ... Impedance circuit, 7 ... Variable resistor VR71 ... Laser trimming resistor, VR72 ... Variable resistor 8 ... bias voltage temperature characteristic adjusting circuit, 10 ... optical interface module for optical network.

   ─────────────────────────────────────────────────── ─── Continued front page    F-term (reference) 5J079 AA04 AA06 BA02 BA37 CB02                       FA22 FB02 FB15 GA14 JA06                 5J081 AA01 CC17 CC21 DD11 EE05                       EE19 FF23 FF25 JJ23 KK01                       KK12 KK22 KK23 LL01 MM01                       MM02

Claims (7)

[Claims] 1. A differential amplifier, a piezoelectric vibrator, a phase shift circuit for shifting a phase of an input signal by a predetermined amount, and an impedance circuit, and at least the differential amplifier, the piezoelectric vibrator, and A positive feedback oscillation loop is formed by a phase shift circuit, and a bias voltage supplied to the differential amplifier is varied to adjust a duty ratio of an output signal output from the differential amplifier. 2. The differential amplifier is a differential amplifier circuit using an ECL line receiver.
The described oscillator circuit. 3. The differential amplifier has an inverting input terminal and a non-inverting input terminal, the variable bias voltage is input to one of the inverting input terminal and the non-inverting input terminal, and the other is input to the other. The device functions as an input for the positive feedback oscillation loop.
Alternatively, the oscillator circuit according to claim 2. 4. The bias voltage is varied by connecting a voltage varying means to either the inverting input terminal or the non-inverting input terminal of the differential amplifier. The oscillation circuit according to any one of 1. 5. The oscillator circuit according to claim 1, wherein the piezoelectric vibrator is a SAW resonator. 6. The oscillator circuit according to claim 1, wherein the piezoelectric vibrator is a crystal vibrator. 7. An electronic device comprising the oscillator circuit according to claim 1. Description: