JPH045805A - Crystal oscillation circuit - Google Patents

Abstract

PURPOSE:To restrain the phase of a capacity from being turned and to surely execute a higher harmonic oscillation by a method wherein a coil-shaped body is formed on an IC substrate so as to include a resistance element and a conduction element and they are used as a feedback resistance and a coil inside a resonance circuit. CONSTITUTION:Capacities Cg, Cd are formed of P<+> layers D on poly-Si films B inside an SiO2 film 3. The P<+> layer D and an N<+> layer E inside the film 3 are connected by Al interconnections A and the poly-Si B, and an inverter is formed in the intermediate part. Individual constituent parts are connected by through holes 3a. A coil-shaped body 4 is connected to the capacities and the inverter via the Al interconnections A. That is to say, Al elements 4A are formed on the SiO2 film 3, and poly-Si resistance elements 4B are formed in an inclined shape in such a way that end parts of the elements 4A are overlapped in the prescribed depth of the film; they are connected by the connecting holes 3a. When the coil-shaped body 4 is used, a required feedback resistance Rf is provided by the resistance elements 4B and an inductance component is provided by a coil-shaped body. A quartz oscillator 1 is connected to both ends of the coil-shaped body 4. By this constitution, it is possible to restrain the phase of the capacities from being turned in an equivalent circuit and a higher harmonic oscillation is executed satisfactorily.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention relates to a crystal oscillation circuit, particularly an IC crystal oscillation circuit which can be used as an overtone oscillation circuit by connecting a parallel resonant circuit to a crystal resonator. Concerning configuration.

[Prior Art] Conventionally, crystal oscillation circuits that perform so-called overtone oscillation, which oscillates with harmonics higher than the fundamental wave, such as third and fifth harmonics, have been used. For example, an IC circuit using C-MOS is used.

FIG. 4 shows the configuration of this type of crystal oscillation circuit, and in FIG. 4 (a), the crystal resonator 1 includes a coil LL.
, a feedback resistor Rf, an inverter 2, and two charging/discharging capacitors Cg and Cd.

In addition, in the circuit of Figure (b), the coil L is in the parallel resonant circuit.
The configuration includes a tank circuit which is a parallel tuned circuit in which L is connected in parallel with a capacitor Cg.

FIG. 5 shows an equivalent circuit of the crystal resonator 1, and as shown in the figure, this equivalent circuit is a parallel circuit consisting of a resistor Ro, a coil Lo, a capacitor Co, and a capacitor C1 connected in series. becomes.

By the way, in the oscillation circuit using the above-mentioned crystal resonator 1, there is no problem when oscillating with the fundamental wave.
When performing overtone oscillation with harmonics of z or more, the phase difference around the capacitor C1, that is, the phase difference between the current and voltage (the current lags by 90 degrees) cannot be ignored (and it is said that it will prevent harmonic oscillation). There's a problem.

Therefore, in overtone oscillation, the coil L1 is connected in parallel with 01 of the crystal resonator 1 as shown in FIG.
Coil L1 is connected to capacitor Cg (or Cd may be used) to form a tank circuit. Then, coil Ll
The phase difference between the current and voltage (the voltage is delayed by 90 degrees) generated in the capacitor C1 can be canceled out, thereby improving the phase rotation.
It is possible to oscillate the following harmonics.

[Problem to be solved by the invention] However, in the conventional IC-based crystal oscillation circuit, the coil for improving the phase and performing harmonic oscillation well cannot be formed as an IC circuit. First, there was the problem that it had to be connected externally.

Furthermore, the presence of the external coil becomes an obstacle when forming a hybrid IC including a crystal oscillation circuit, and further prevents cost reduction.

The present invention has been made in view of the above-mentioned problems, and its purpose is to integrate the coil of the resonant circuit into an IC without externally attaching it, and to effectively suppress the phase rotation of the capacitor in the equivalent circuit of the crystal resonator. Our goal is to provide a crystal oscillation circuit that can.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a crystal oscillator circuit in which a resonant circuit is connected to a crystal resonator, and which oscillates at harmonics by this resonant circuit. The present invention is characterized in that a coiled body including a conductive element is formed on an IC substrate, and this coiled body is disposed as a feedback resistor and a coil in the resonant circuit.

[Function] According to the above configuration, for example, a resistor element of a predetermined length provided at a predetermined depth position of an IC board and a conductive element, which is a normal wiring provided on an IC board, are connected by a contact. , a generally helical coiled body is formed. Therefore, this coiled body can function as a coil having inductance, and the resistance element within the coiled body can function as a feedback resistor.

When the coil-shaped body is connected to a crystal resonator, it is equivalent to connecting a coil to a capacitor in the equivalent circuit of the crystal resonator, so the phase rotation of the capacitor is suppressed and harmonic oscillation is improved. It will be held on.

[Embodiments] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a diagram showing the configuration of a crystal oscillation circuit according to an embodiment. In the diagram, an insulating film 3 constituting an IC substrate is, for example, a silicon oxide film (SiO2), and this insulating film 3 includes a resonant circuit shown in FIG. 4 above. That is, on both sides at the bottom of the figure, there is a capacitor C consisting of a rectangular polysilicon portion B formed in the insulating film 3 and a rectangular P11 diffusion formed on the insulating film 3.
g, C, d are provided, and these capacitors Cg, C
d between the P+ diffusion part formed in the insulating film 3 and the N
An inverter is provided in which the first diffusion part E is connected to the metal (aluminum) wiring A and the polysilicon part B. Note that the connections between the illustrated components are made through contacts 3a, which are holes vertically drilled in the insulating film 3.

Then, to the above capacitors Cg and Cd, and the inverter,
A coiled body 4 including a resistive element and a conductive element is connected via metal wiring A. That is, the detailed structure of the coiled body 4 is shown in FIG. 2, and as shown in the figure, a conductive element 4A made of aluminum similar to the metal wiring A is formed obliquely on the insulating film 3, and the insulating A resistive element 4B made of polysilicon is obliquely formed at a predetermined depth position of the film 3 so that the end of the conductive element 4A overlaps when viewed from above. Then, the conductive element 4A and the resistive element 4B are connected to the contact 3a, which is a hole made in the insulating film 3, as shown in the figure.
Finally, a spiral coiled body 4 is formed by the conductive element 4A, the resistive element 4B, and the contact 3a.

In addition to polysilicon, the resistance element 4B can be formed by P+ diffusion, N'' diffusion, P- well, N well, etc.

Such a coiled body 4 has a feedback resistance Rf (FIG. 4) necessary for a resonant circuit due to the presence of the resistance element 4B, and also has an inductance component due to the coil shape. As shown in FIG. 1, a crystal oscillator 1 is connected to both ends 3a of the coiled body 4.

According to the configuration of the above embodiment, the coiled body 4 can first suppress the phase of the capacitor c1 in the equivalent circuit of the crystal resonator 1 due to the presence of the inductor component, and the resonance effect of the resonant circuit can suppress harmonics. oscillation can be performed reliably. For example, if the fundamental wave is 10MHz, it is 30MHz, 50MHz.
MHz (7) It becomes possible to oscillate harmonics.

Furthermore, since the resistive element 4B of the coiled body 4 serves as a feedback resistor Rf, the operating point of the inverter 2 can be adjusted to ensure stable oscillation operation.

Next, FIG. 3 shows another example of a coiled body,
The coiled body 5 shown in the figure includes a conductive element 5A formed on an insulating film 3 and a resistive element 5B formed within the insulating film 3.
The contacts 3a are connected in a spiral (coiled) manner.

Therefore, even with the coiled body 5, as shown in FIGS.
The same effect as the coiled body 4 shown in the figure can be obtained.

Further, in the above embodiment, the coiled body 4.5 is formed by arranging the conductive elements 4A, 5A and the resistive elements 4B, 5B in two levels (two stages) in the insulating film 3, which is an IC substrate.
A coiled body may be formed by arranging conductive elements and resistive elements in three or more layers (the shape of the coiled body may be selected as appropriate depending on the required coil inductance). can do.

[Effects of the Invention] As explained above, according to the present invention, a coiled body including a resistive element and a conductive element is formed on an IC substrate, and this coiled body serves as both a feedback resistor and a coil. Therefore, there is no need to attach a coil externally as in the conventional case, and it is possible to obtain a crystal oscillator in which the coil is also integrated into an IC. Therefore, the above crystal oscillator can satisfactorily suppress the phase shift of the capacitor in the equivalent circuit of the crystal resonator, making it possible to oscillate harmonics.

Furthermore, since the coil can be integrated into an IC, a hybrid IC can also be easily manufactured, which has the advantage of reducing costs.

[Brief explanation of drawings]

FIG. 1 is a configuration diagram showing a crystal oscillation circuit according to an embodiment of the present invention as an IC circuit, FIG. 2 is a diagram showing the detailed configuration of the first coiled body, and FIG. 3 is a diagram showing the detailed configuration of the first coiled body. FIG. 4 is a circuit diagram showing two configurations of a conventional crystal oscillation circuit, and FIG. 5 is an equivalent circuit diagram of a crystal resonator. l...Crystal resonator, 2...Inverter, 3...I
C substrate insulating film, 4.5... Coiled body, 4A, 5A... Conduction element, 4B, 5B... Resistance element, Ll... Coil, Rf -... Feedback resistor, C1, Cg
, Cd... capacitor. Patent applicant New Japan Radio Co., Ltd.

Claims (1)

[Claims] (1) In a crystal oscillation circuit in which a resonant circuit is connected to a crystal resonator and the resonant circuit oscillates at harmonics, a coil-shaped body including a resistive element and a conductive element is used as an I
A crystal oscillation circuit, characterized in that the coil-shaped body is formed on a C substrate and is disposed as a feedback resistor and a coil in the resonant circuit.