JP3160931B2 - Oscillator 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 oscillation circuit, and more particularly to a crystal oscillation circuit capable of changing the oscillation frequency of an oscillator using a piezoelectric vibrator.

[0002]

2. Description of the Related Art An oscillation circuit using a piezoelectric vibrator naturally has a variation in the oscillation frequency due to a variation in the resonance frequency of the piezoelectric vibrator, a variation in the load capacity of the circuit, and a thermal shock at the time of mounting and sealing the oscillation circuit. are doing. Therefore, especially when a high-precision oscillation frequency is required, it may not be possible to enter the target oscillation frequency range without adjustment, and must be adjusted.

FIG. 3 is a circuit diagram of an oscillator using a conventional piezoelectric vibrator. 121 is an inverter amplifier, and 122 is a feedback resistor connected between the gate and drain of the inverter amplifier 121. A gate capacitor 123 is connected to the gate of the inverter amplifier 121, and a drain capacitor 124 is connected to the drain of the inverter amplifier 121. Reference numeral 125 denotes a trimmer capacitor capable of changing a capacitance value, which is connected to the gate of the inverter amplifier 121. 123,
Condensers of 124 and 125 are connected to V _DD or V _SS of one side power is high-frequency grounded. 126 is a piezoelectric vibrator connected between the gate and the drain of the inverter amplifier 121. To adjust the oscillation frequency in the oscillation circuit configured as described above, the trimmer capacitor 1
25 was rotated with a tool such as a screwdriver.

FIG. 4 is a circuit diagram showing another example of a conventional oscillation circuit. 3 is different from the circuit of FIG. 3 in that a capacitor 131 is used instead of the trimmer capacitor 125.
And a variable capacitance group in which a plurality of series members represented by the switches 141 and 141 are arranged in parallel. Adjusting the oscillation frequency in the oscillation circuit configured as described above has been performed by arbitrarily shorting or opening the switches 141, 142, 143, and 144 by soldering.

[0005]

SUMMARY OF THE INVENTION In a conventional oscillation circuit,
Since the oscillation frequency is adjusted by rotating the trimmer capacitor 125, the adjustment process cannot be automated, it takes time, etc. In addition, it is necessary to provide a hole for adjustment, so that the airtightness is lost and the moisture resistance is deteriorated. Due to the mechanism, there is a disadvantage that the rotor rotates due to vibration and impact, and the oscillation frequency shifts.

Further, in the oscillation circuit using the variable capacitance group shown in FIG. 4, it takes time to adjust the frequency by switching, and the capacitance constituting the oscillation loop is wired outside the circuit as a plurality of external terminals. Oscillation characteristics are deteriorated, and if the metal cap is sealed after adjustment or sealed with a mold, the frequency at the time of adjustment is shifted due to a change in stray capacitance or thermal shock, resulting in poor frequency accuracy.

Accordingly, the present invention provides a method of automatically adjusting a frequency and a quick frequency adjustment, reducing the number of external terminals, mounting an oscillation circuit, and enabling a frequency adjustment after sealing. Oscillation characterized by eliminating subsequent frequency shifts, improving airtightness, and eliminating the movable parts such as rotating mechanisms in frequency variable circuits to improve ICs for vibration and shock resistance and miniaturization. It is to provide a circuit.

[0008]

Oscillation circuit of the present invention for achieving the above object, according to an aspect of the an oscillator for oscillating the piezoelectric vibrator, and a capacitor array for varying the load capacitance of the piezoelectric vibrator, the oscillating unit Dividing the source signal output from the
Circuit, a frequency-divided signal divided by the frequency dividing circuit, and the source
Frequency selection circuit that selects and outputs one of the oscillation signals
When a data input circuit for inputting data for controlling said capacitor array and the frequency division selection circuit from outside, a PROM circuit for storing data for controlling said capacitor array and the frequency division selection circuit, at the time of frequency adjustment An operation of transmitting data of the data input circuit to the capacitance array and the frequency division selecting circuit, an operation of transmitting data of the data input circuit to the PROM circuit when storing data, and a data of the PROM circuit during normal operation The capacitance array and the
A data control circuit for controlling the three operations of the operation to be sent to a divider selection circuit, and having a. Ma
Further, the frequency division selection circuit is configured to
After outputting the source vibration signal based on the data of No. 1,
The frequency division based on the second data from the data control circuit.
It is characterized by outputting a signal.

[0009]

Since a capacitor array in which a plurality of series units of a capacitor and a switching transistor are arranged in parallel is used as a variable capacitance element, ON / OFF of the switching transistor can be controlled by digital data and frequency can be adjusted. When the frequency adjustment, capacity array with data from an external
And the frequency division selection circuit.
Select and output the signal, measure this source signal and adjust the frequency
After the frequency adjustment is completed,
Can select the frequency division signal and make the desired frequency division selection.
I can . Next, the data at that time is stored in the PROM circuit. During normal operation, the frequency always so controls the capacitor array and division selection circuit by data stored in the PROM circuit falls within a frequency range of interest. Since operates as described above, the frequency adjustment can be automated, the aging of the frequency
It is small, has excellent vibration resistance and shock resistance, and can be integrated into a circuit, so that it can be made compact and airtight. In addition, high speed and high resolution
Provides an oscillation circuit with a basic configuration that allows frequency adjustment
Wear.

[0010]

Embodiments of the present invention will be described below. FIG. 1 is a block diagram showing an embodiment of the present invention, wherein 1 is a piezoelectric vibrator, 2 is an oscillating unit, and a circuit for oscillating the piezoelectric vibrator. Reference numeral 4 denotes a data input circuit which converts data input from outside the oscillation circuit into data which can be processed internally as frequency adjustment data. As an example, the data input circuit 4 is provided with a shift register. In this case, serial data is input from the outside, converted into parallel data, and transmitted to an internal circuit. Reference numeral 5 denotes a terminal for inputting external data. Reference numeral 6 denotes a capacitor array, which is a circuit in which a plurality of series members of a capacitor and a switching transistor are configured in parallel. One electrode of the capacitor array is connected to the piezoelectric vibrator, and the other electrode is grounded at a high frequency. Reference numeral 6 functions as a variable load capacity of the piezoelectric vibrator. The capacitance array 6 is controlled by controlling the gate of the switching transistor.
Can be varied. Reference numeral 7 denotes a PROM circuit which can store data from the data input circuit 4 and can control the capacity array 6 with the stored data. Numeral 8 denotes a data control circuit which sends data from the data input circuit 4 to the capacitor array 6 and the frequency division selecting circuit 10 during frequency adjustment, and transmits data from the data input circuit 4 to the PROM during data storage.
The data is sent to the circuit 7, and during normal operation of the oscillation circuit, the data stored in the PROM circuit 7 is sent to the capacitor array 6 and the frequency division selecting circuit 10. The above three operations are performed to control the data. 3
Is a terminal for controlling the above data control. Reference numeral 9 denotes a frequency dividing circuit which converts a source oscillation signal from the oscillation unit 2 into 1 /
This is a circuit for dividing the frequency into 2, 1/4, 1/8,. Reference numeral 10 denotes a frequency division selection circuit, which selects a frequency division signal and a source signal of the frequency division circuit 9 based on control data from the data control circuit 8. An output buffer 11 amplifies the signal selected by the frequency division selecting circuit 10 and outputs the amplified signal to the outside of the oscillation circuit. Next, FIG. 2 shows the configurations of the oscillation section 2 and the capacitance array 6 in detail. In this figure, 21 is an inverter amplifier, 22 is a feedback resistor, which is connected to the gate and drain of the inverter amplifier. 23 is a gate capacitance connected to the gate of the inverter amplifier 21, and 24 is a drain capacitance connected to the drain of the inverter amplifier 21. The oscillating unit 2 is composed of at least the above elements, and the piezoelectric vibrator 1 is connected to the gate and the drain in the oscillating unit 2. Next, the inside of the capacitance array 6 will be described. 31 is a capacitor, 41 is a switching transistor, and there is a series body in which these two elements are connected in series.
Similarly, 32, 33, and 34 are capacitors.
43 and 44 are switching transistors connected in series with the respective capacitors. The above-mentioned series body of the capacitor and the switching transistor is connected in parallel, one electrode is connected to the gate side of the oscillating unit 2, and the other B electrode is grounded to the power supply _VDD or _VSS at high frequency. ing. The capacitance value of the capacitance array 6 can be varied by arbitrarily turning on or off each of the switching transistors 41 to 44 by controlling the gates of the switching transistors 41 to 44. As an example of setting the capacitance values of the capacitors 31 to 34, the setting is performed with weighted capacitance values. (Eg, 1pF, 2pF, 4pF,
8 pF) By doing so, a wide capacitance range can be varied with a small number of capacitance elements while maintaining the resolution. Of course,
The number of series bodies of the capacitance and the switching capacitor may be increased.

The method of frequency adjustment and frequency division selection of the oscillation circuit configured as described above, the method of storing the data after adjustment and selection are completed, and the operation of the oscillation circuit during normal operation are described in order. explain.

First, frequency control data and frequency division selection data are input from the data input terminal 5 from outside the oscillation circuit.
The data input circuit 4, which is a shift register, sequentially inputs the input serial data, and changes to parallel data after the input is completed. The data control circuit 8 sends frequency control data to the capacity array 6 and frequency division selection data to the frequency division selection circuit 10 among the data output from the data input circuit. The capacitance array 6 changes the frequency by turning on or off the switching transistor 4 based on the transmitted frequency control data. The frequency division selection circuit 10 selects a frequency division signal or a source signal based on frequency division selection data sent from the data control circuit. The operations from the data input from outside the oscillator to the frequency change and frequency division selection are repeatedly adjusted to a target frequency range while measuring the oscillation frequency.

Next, in order to store the data obtained by the operation of frequency adjustment and frequency division selection, the data of the data input circuit is sent to the PROM circuit via the data control circuit,
The data is stored in the PROM circuit. The PROM circuit is
Once stored data is stored even when the power is turned off, the frequency and frequency division selection can be maintained forever. If a PROM circuit that can be erased by electric or ultraviolet light is used, data can be changed, and the frequency and frequency division selection can be readjusted.

Next, in the normal operation of the oscillator, the PROM
The frequency control and frequency division selection data stored in the circuit is sent to the capacitance array and frequency division selection circuit via the data control circuit, and the capacitance array and frequency division selection circuit operate based on the data.

Since the operation can be performed as described above,
Frequency adjustment can be performed with digital data, and automation is simplified. Also, if data is input by serial data input, the number of terminals going out of the oscillation circuit will be reduced, and if the frequency is adjusted by inputting data from these terminals after sealing with a metal package or transfer molding, airtightness of the oscillation circuit will be obtained. In addition, the shift in frequency due to sealing is eliminated. In addition, since the data is stored by the PROM circuit and the frequency is controlled by the capacitor array including the capacitor and the switching transistor, the vibration resistance, the shock resistance, and the change with time are excellent. Further, since all the circuits can be made into ICs, miniaturization becomes possible. In addition, since the frequency division selection can be controlled by external data, the frequency is adjusted by outputting the source vibration signal, measuring the frequency of the source vibration signal, adjusting the frequency, and selecting the frequency division after the frequency adjustment is completed. Can also be selected. By doing so, the higher the measurement frequency, the higher the measurement speed or the higher the resolution. Therefore, the frequency adjustment can be performed quickly or with high accuracy.

In the above embodiment, the capacitance array 6 is connected to the gate side of the oscillating unit 2, but the same effect can be obtained by connecting it to the drain side.

In this embodiment, both the capacitance array 6 and the frequency division selecting circuit 10 are built in. However, only the capacitance array 6 may be used.

Next, FIG. 5 shows a mounting example of this embodiment. Reference numeral 1 denotes a piezoelectric vibrator, and reference numeral 51 denotes an IC, which includes the oscillating unit, the data input circuit, the capacitor array, the PROM circuit, the data control circuit, the frequency dividing circuit, the frequency dividing selecting circuit, and the output buffer described in the above embodiment. 52 is a package for sealing the oscillation circuit,
It is sealed with a resin mold, ceramic, metal or the like.
53 is a V _DD lead, 54 is a V _SS lead, and 55 is an output lead which is connected to the IC 51 by wire bonding and led out of the package 52. Reference numeral 56 denotes a control lead connected to the control terminal of the IC 51 and led out of the package 52. 57 is a data input lead.
It is connected to the data input terminal of C51 and is led out of the package 52. In order to adjust the frequency of the oscillation circuit configured as described above, power is applied from the _VDD lead 53 and the _VSS lead 54, and the frequency of the oscillation signal output from the output lead 55 is measured. Data is input from the data input lead 57. Repeat this until the frequency is within the desired range. When the frequency adjustment is completed, PRO
Write data to M. During the operation described above, control of data inside the IC is performed from the control lead 56. After the data writing is completed, the control lead 56 and the data input lead 57 are cut from the end face of the package 58. This eliminates unnecessary leads during normal operation and prevents accidents such as lead shorts.

[0019]

According to the present invention, a capacitance array for varying the load capacitance of a piezoelectric vibrator and frequency division of a source vibration signal of an oscillating unit are provided.
A frequency divider, a frequency-divided signal divided by the frequency divider,
Frequency division selection for selecting and outputting one of the recording source signals
Circuit, and controls the capacitance array and the frequency division selection circuit.
A data input circuit for inputting external data,
The data for controlling the quantity array and the frequency division selection circuit is stored.
PROM circuit and data input during frequency adjustment
Circuit data to the capacitance array and the frequency division selection circuit
Sending operation and the data input circuit when storing data
And normal operation.
During operation, the data of the PROM circuit is stored in the capacity array.
The three types of operations, that is, the operation of transmitting to the frequency division selection circuit and
It includes a data control circuit for controlling, and can be controlled by data from outside the capacitor array and division selection circuit, also to store the data in the PROM circuit, in the normal operation with the capacitor array based on the stored data minute by the division selection circuit was set to operate, the frequency adjustment can rapidly frequency adjustment automatable, and storage of data by the PROM circuit, since the frequency control by the capacitance array with a capacitor and a switching transistor It is excellent in vibration resistance and shock resistance , has little change over time, and can be miniaturized because all circuits can be made into ICs. Further, the frequency division selecting circuit is provided with the data control circuit.
Output the source vibration signal based on the first data from
Later, based on the second data from the data control circuit
By outputting the frequency-divided signal, during frequency adjustment
The frequency divider selection circuit selects and outputs the source oscillation signal,
Measure the vibration signal, adjust the frequency, and complete the frequency adjustment.
After that, the frequency division selection circuit selects the frequency division signal and
It is possible to make a selection and this allows
Constant frequency can be increased, so high speed and high resolution
Oscillation circuit with basic configuration that can adjust
You.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a circuit diagram showing an example of a circuit configuration of an oscillation unit and a capacitor array according to the embodiment of the present invention.

FIG. 3 is a circuit diagram showing a first example of a conventional oscillation circuit.

FIG. 4 is a circuit diagram showing a second example of a conventional oscillation circuit.

FIG. 5 is a diagram showing an implementation example of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Piezoelectric vibrator 2 Oscillator 3 Control terminal 4 Data input circuit 5 Data input terminal 6 Capacitance array 7 PROM circuit 8 Data control circuit 9 Divider circuit 10 Divider selection circuit 11 Output buffer 21 Inverter amplifier 22 Feedback resistor 23 Gate capacitance 24 Drain capacitance 31, 32, 33, 34 Capacitor 41, 42, 43, 44 Switching transistor

Claims (2)

(57) [Claims] An oscillator for oscillating a piezoelectric vibrator; a capacitance array for varying a load capacitance of the piezoelectric vibrator; and a frequency divider for dividing a source vibration signal output from the oscillator.
And the divided signal and the source signal divided by the frequency dividing circuit.
And division selection circuit for selecting and outputting either one, and the capacitor array and a data input circuit for inputting data for controlling the frequency dividing selecting circuit from the outside, and the capacitor array and the frequency division selection circuit A PROM circuit for storing data to be controlled; an operation of transmitting data of the data input circuit to the capacitor array and the frequency division selecting circuit when frequency adjustment is performed; and a process of transmitting the data of the data input circuit to the PRO for data storage.
An operation for transmitting to the M circuit, and the PROM during a normal operation.
Oscillation circuit and having a data control circuit for controlling the three operations of the operation data sent to and the frequency division selection circuit and the capacitor array of the circuit. 2. The data dividing circuit according to claim 1 , wherein
Outputting the source signal based on the first data from the road.
After that, based on the second data from the data control circuit
And outputting the frequency-divided signal.
Oscillation circuit as described.