JPH0217713A - Electronic equipment with plural oscillators - Google Patents

Abstract

PURPOSE:To obtain a device stable for external noise by including plural oscillation circuits in which all the constant current circuits, the capacitors, and the switching circuits are constituted of monolithic circuits on the same monolithic substrate. CONSTITUTION:Two oscillators 10 and 20 are formed in the same silicon substrate 160. The oscillators 10 and 20 are provided with oscillation circuit parts 11 and 21, timing capacitors 12 and 22, and buffer output circuits 16 and 26, etc., respectively, and those elements are constituted of the monolithic circuits. Furthermore, the oscillators 10 and 20 are equipped with control input terminals 13 and 23, power source supply terminals 14, 15, 24 and 25, and output terminals 17 and 27, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an It7-device having a plurality of oscillators, and particularly to an electronic device suitable for monolithization.

[Conventional technology]

For precise frequency control systems that require multiple controlled oscillators, if a monolithic pair oscillator circuit can be applied to the oscillator pair circuit, the characteristics will be uniform against Iri source fluctuations, temperature fluctuations, etc., and differential effects will be eliminated. It is desirable that it can be demonstrated.

As such a conventional monolithic oscillator pair, the TTL series 124 type VCO (voltage controlled oscillator) circuit IC shown in the circuit diagram of FIG. 10 is known. This IC includes a monolithic vC in package 150.
o circuit 11゜21 is built-in, and a 5V power supply 11iX35.36 is connected to the digital side and analog side power terminals respectively.
, external timing capacitors 12.22 are connected, and bias input terminals P3. A bias power supply 33 is connected to PL4, and each control input terminal PL, P
By connecting and applying control power supplies 31, 32 to oscillators 2, an oscillation frequency proportional to each control input voltage is obtained at the outputs 17, 27 of each oscillator 1o and 20.

[Problem to be solved by the invention]

However, the above-mentioned conventional technology does not give sufficient consideration to mutual interference of electromagnetic fields between two oscillators, and there is a problem of mutual attraction at close oscillation frequencies. As shown in the characteristic diagram of Fig. 11, when the first oscillator outputs an oscillation frequency fl and the second oscillator outputs a frequency f2 that is close to fx, this is the range in which both frequencies are particularly close. The disturbances caused by each oscillator interfere with each other between the external terminals, and the two oscillators are synchronized at an intermediate output frequency, as shown by the dotted line in FIG. 11, and lose their function as independent oscillators.

The range of this synchronous pull-in usually occurs in a close range where the frequency difference is 10-8 or less, but as the oscillation frequency increases, the induced noise increases, so at high frequencies even a difference of about 10'''2 causes pull-in. There is a risk that this will happen.

An object of the present invention is to provide an electronic device including a plurality of oscillators whose characteristics are well matched and which eliminates mutual interference as described above.

[Means to solve the problem]

Considering that the conventional pull-in phenomenon between multiple oscillators occurs when other oscillator output noise is induced into the timing capacitor terminals, which are sensitive to noise, the timing capacitor is formed as a monolithic circuit on a silicon substrate, and the timing capacitor is The purpose is achieved by not exposing the terminals to the outside.

[Effect]

In other words, in a timing capacitor formed as a monolithic circuit in a silicon substrate, the timing capacitor portion, which is easily susceptible to induction, is not exposed as an external terminal, and the timing capacitor portion is formed on an equipotential substrate of the silicon substrate. Because it receives a good guard shield effect, it is stable against external noise and does not malfunction.

〔Example〕

An embodiment of the present invention will be described below with reference to FIG. 1st
The figure is a circuit block diagram showing an embodiment of the electronic device of the present invention. In the embodiment of FIG. 1, two VCDIo
, 20 are formed in the same silicon substrate 16.
Oscillators 10 and 20 are oscillation circuit portions 11 and 2, respectively.
1, timing capacitors 12, 22. It is composed of buffer output circuits 16, 26, and the like. Furthermore, in the circuit of FIG.
．． 23, power supply terminals 14-15, and 24-25. As the circuit of the oscillation circuit section 11.21 in FIG. 1, a circuit known as an emitter-coupled multivibrator shown in FIG. 2 is used. The main components of oscillation in this circuit are switching transistors 111 and 112 cross-connected by buffer amplifiers 113 and 114, and timing capacitors 12. This is a constant current circuit including transistors 133 and 134, and the oscillation frequency f is generally expressed as follows.

f=I/4CVap where F is the current value of the constant current circuit, C is the value of the timing capacitor, and VBE is the forward voltage drop of the diode 117°118.

In the embodiment of FIG. 1, in order to improve the isolation of each oscillator 10, 20 against mutual induction, the timing capacitors 12, 21 are placed at a distance from each other as shown in the schematic circuit diagram. , external outputs are output via buffer amplifiers 16 and 26. The power supply terminals are also separated.

The operation of the embodiment of FIG. 1 constructed as described above is as follows. 5v from power supply terminal 14-15.24-25
When an operating power source is supplied and control inputs are applied from the control input terminals 13.23, an output frequency proportional to each control input is obtained at the output terminals 17.27. This output frequency is
As described above, the design is such that mutual interference between the two oscillators is sufficiently reduced, so it is stable even when the operating frequencies of the two oscillators are close to each other.

FIG. 3 is a sectional view showing one embodiment of a monolithic capacitor used as a timing capacitor in the present invention. FIG. 3 shows a capacitor structure in which aluminum wiring layers 141 and 142, which are insulated by thin oxide films 143 and 143 on a silicon substrate 140, are used as electrodes.

FIG. 4 shows an example of the structure of another monolithic capacitor called a MOS capacitor that can be applied to the present invention. An n-type diffusion well 149 is formed in a P-type substrate 140, and a capacitor is formed by an n+ diffusion layer 148 therein and an aluminum electrode 148 with a thin oxide film 146 interposed therebetween.

For the capacitor used in the emitter-coupled multivibrator shown in FIG. 2, it is desirable that the strain capacitor be balanced with respect to the substrate in order to obtain a symmetrical oscillation waveform.

Therefore, both the capacitor structure of FIG. 3 and the capacitor structure of FIG. 4 are used by being divided into two parts and then coupled to the substrate so that the parasitic elements are balanced. FIG. 5 shows an equivalent circuit of the divided combination of the capacitor structure shown in FIG. That is, for the main capacitors 123, 123', the parasitic elements 127, 127' 124, 124' 126.12
6' is symmetrical with respect to the board side from the terminals 121 and 122.

FIG. 6 shows an example of an improved oscillator used in the IA device of the present invention. The oscillator in FIG. 6 is basically the emitter-coupled multivibrator shown in FIG.
The collector load resistances 115 and 116 in FIG.
In the figure, active resistors are replaced by MoS transistors 121 and 122. MOS transistors 121 and 122 in FIG. 6 are drive amplifiers 125 and 126, respectively.
is driven by alternate switching. Drive amplifier 1
The voltage amplitude generated by 25.126 is an IR that is linked to the operating constant current of the oscillator. Therefore, the on-resistance values of the MOS transistors 121 and 122 are controlled in inverse proportion to the constant current of the oscillator, and the loop gain of the oscillator does not change even if the operating current of the oscillator, that is, the oscillation frequency changes. This means that the timing capacitor is a monolithic capacitor. This expands the frequency variable range when the capacitor is fixed, and alleviates the limitations associated with fixed capacitors.

FIG. 7 shows a block diagram of an embodiment of an electronic device using multiple oscillators of the present invention. Generally, two PLLs are used in a communication module with integrated transmitter/receiver type 3R function (for example, see Kirihara et al.: 32 Mb/s optical transmission module, 1986 Institute of Electronics and Communication Engineers Conference Ion 2401). Figure 7 shows a module for such communication. 1 shows an example of a module. In FIG. 7, a code decoder (CODEC) 600, - set P
It is composed of LLs 100 and 200, a signal equalization amplifier 615, an output driver 625, an output interface 620, a parallel bus 640, a clock input 650, and the like. Oscillator section 10.2 in PLL100 and 200
0 is a monolithic circuit that is integrally formed including the timing capacitor.

The operation of the circuit of FIG. 7 constructed in this way is as follows. The serial signal sent to the terminal 610 via the transmission line is amplified by the equalizing amplifier 615, and is input to the C0DEC 600 as well as the PLL 100, and the 100 output clocks of the PLL whose timing is extracted are C0DE.
It is used as the decoding sampling clock of C600. On the other hand, the clock on the output side of C0DEC600 is terminal 6.
50 to PLL 200, output bus 650
In order to encode the signal from the C0DEC 600, a double clock is generated and inputted to the CODEC 600. The encoded serial signal is then sent to the transmission line via the driver 625 and the output terminal 620.

In the application example shown in FIG. 7, it is required that the transmitter/receiver integrated module be made smaller and consume less power. In the conventional technology, it was difficult to meet this request due to interference between oscillators, but it is possible according to the present invention.

FIG. 8 is a block diagram showing another embodiment of the present invention. FIG. 8 shows an embodiment of an ultrasonic flowmeter.

In FIG. 8, a pair of ultrasonic transducers 71 and 72 are attached around the circumference of a pipe 70 to be measured. The transducers 71 , 72 are connected to the driver 61 via a changeover switch 63 . The transducers 71, 72 are connected to the receiver circuit 5 via the switch 64.
1, T/V (time-voltage) converter 53, switching circuit 54
．． A pair of integrating circuits 55, 56, variable oscillators 10, 20,
It is output to the frequency difference output circuit 58.

The oscillator 10.20, including the timing capacitor, is monolithic.

In addition, a synchronization circuit 62 that controls the overall timing receives a signal from a changeover switch 57, and a synchronization circuit 62 controls the driver 61 and counter 5.
It is designed to drive 2.

The operation of the ultrasonic flowmeter shown in FIG. 8 will be briefly described.

Transducer 71 .
72 is driven alternately, and the forward propagation time and reverse propagation time of the sound wave are converted into voltage by the T/■ converter 53 according to the flow velocity of the pipe 70, and the switch 54 and the integrator 55 and 56 respectively
The signal is input to a sample-and-hold circuit consisting of a oscillator, and is converted into a frequency when each variable oscillator rises and falls. Therefore, the frequency output by the frequency difference output circuit 58 is proportional to the propagation time difference due to the difference in direction of the transducers 71, 72, ie, the flow rate of the object flowing through the pipe 70.

In such a flowmeter, the propagation velocity of sound waves (several km
/s), the flow velocity of the object to be measured is usually very small (for example, several cm/s) (frequency difference of 10-1' or less). Therefore, it is necessary that the oscillators in the set have similar characteristics with respect to temperature and power supply fluctuations, and that there is no synchronization pull-in phenomenon, and the embodiment of FIG. 8 can satisfy these requirements.

FIG. 9 is a block diagram showing another embodiment of the present invention.

In a digital PLL or some kind of FM demodulator, multiple stable oscillators (clocks) with close output frequencies are used.
Requires. The embodiment of FIG. 9 shows a configuration suitable as such a lock source. In FIG. 9, a control power supply 150 and a bias power supply 250 are shown for each of a set of variable oscillators 10 and 20 constructed of monolithic circuits. It is connected as follows. Buffer amplifier 16.2 at the output
6 is connected, and the output of 1 oscillator 10 is connected to a divider (
A counter) 30 is connected, and the output of the dividing period 300 is input to a phase comparator 400.

A crystal oscillator 500 is connected to the other input of the phase comparator 400, and an output 410 of the phase comparator 400 is connected to the control power supply 1.
50. Sunarichi oscillator 1
02 frequency divider 300, phase comparator 400. Control power supply 150
forms a frequency multiplication PLL. Bias power supply 2
50 is a bias source for making the oscillation frequency of the oscillator 20 slightly larger than that of the oscillator 10.

In the operation of FIG. 8 configured as described above, an output frequency obtained by multiplying the frequency of the crystal oscillator 500 (the multiplication ratio is determined by the frequency divider 300) is obtained from the output terminal 17, and the output frequency is obtained from the other output terminal. obtains a slightly higher frequency. The frequency at terminal 17 is extremely stable because it is controlled by the crystal oscillator, and the frequency output from terminal 27 is also stable because the two oscillators are formed as similar circuits on a monolithic substrate. Therefore, in the embodiment shown in FIG. 9, two closely spaced frequencies can be stably supplied without fear of synchronization.

In the present invention, an emitter-coupled multivibrator type oscillator has been described as an embodiment of the oscillator, but other types of oscillators may be used, such as a Schmitt trigger type oscillator. In a Schmitt trigger type oscillator, the timing capacitor can be a grounded surface, so as a monolithic capacitor, there is less problem of parasitic capacitance with respect to the substrate, and there are a variety of structures that can be used, including semiconductor junction capacitance.

In the embodiment of the present invention, an example is shown in which multiple oscillators including monolithic capacitors are configured on one monolithic substrate, but the silicon substrate is not limited to just one, and multiple monolithic oscillator chips including monolithic capacitors are configured on one monolithic substrate. It may be a collection.

〔Effect of the invention〕

According to the present invention, since the timing capacitors of multiple oscillators are formed as monolithic capacitors to prevent electromagnetic interference, electronic devices equipped with multiple oscillators that are free from synchronization pull even at close operating frequencies can be made compact and have low power consumption. It can be made to.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the present invention. FIG. 2 is a diagram showing an example of a circuit applied to the present invention, FIGS. 3 and 4 are partial cross-sectional views of the circuit applied to the present invention, FIG. 5 is a partial equivalent circuit diagram, and FIG. 6 is a diagram showing an example of a circuit applied to the present invention. 7, 8, and 9 are diagrams showing other embodiments of the present invention; FIG. 10 is a circuit diagram showing a conventional embodiment; FIG. 11 is a circuit diagram showing the applied circuit;
The figure is a characteristic diagram showing a conventional example. 10.20... Oscillator, 12.22... Capacitor, 16... Monolithic chip, 111,112゜1
31-134...transistor, 115,116...
・Resistor, 113, 114.16...Buffer amplifier. Agent: Patent Attorney Katsuo Ogawa, T. (Fig. 3, Fig. 4, Fig. 1/W, Fig. 5, Fig. 2, Section 6, Fig. 7, Fig. 8, Fig. 9, Fig. 10, Fig. 11) VcCj2)

Claims (1)

[Scope of Claims] 1. An electronic device having a plurality of oscillators, characterized in that a plurality of oscillation circuits in which a constant current circuit, a capacitor, and a switching circuit are all constituted by monolithic circuits are included on the same monolithic substrate. 2. An electronic device having a plurality of oscillators according to claim 1, characterized in that the electronic device constitutes a communication transmitting/receiving module. 3. An electronic device having a plurality of oscillators according to claim 1, characterized in that the electronic device constitutes an ultrasonic flow rate (current velocity) meter.