JP3114659B2 - Oscillation circuit frequency adjustment method - 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,
In particular, the present invention relates to a crystal oscillation circuit that can vary the oscillation frequency of an oscillator using a piezoelectric vibrator. The invention also relates to a method for adjusting the frequency of such an oscillation circuit.

[0002]

2. Description of the Related Art Oscillation circuits using a piezoelectric vibrator naturally vary in oscillation frequency due to variations in the resonance frequency of the piezoelectric vibrator, variations in the load capacitance of the circuit, and thermal shocks when the oscillation circuit is mounted and sealed. Have. 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. Reference numeral 121 denotes an inverter-amplifier, and reference numeral 122 denotes a feedback resistor connected between the gate and the 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.

[0004] condensers of 123, 124, and 125 is connected to _{V DD} or _{V SS} of one side is the power supply has been grounded in a high-frequency manner. 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 125 is rotated by 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 is performed by arbitrarily shorting or opening the switches 141, 142, 143, and 144 by soldering.

[0006]

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 an adjustment hole, 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.

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

Accordingly, the present invention provides a method of automatically adjusting a frequency and enabling quick frequency adjustment, reducing the number of external terminals, and mounting and oscillating an oscillation circuit so that the frequency can be adjusted 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. A circuit and a method of adjusting the frequency thereof.

[0009]

In order to achieve the above object, a method for adjusting the frequency of an oscillation circuit according to the present invention comprises an oscillation section for oscillating a piezoelectric vibrator and a load capacitance of the piezoelectric vibrator.
Variable capacitance array and source vibration output from the oscillation unit
Frequency dividing means for dividing the signal, and data for controlling the capacitance array.
A data input circuit for inputting over data from outside, the capacity A
A PROM circuit for storing data for controlling the ray, frequency
When adjusting the number, the data of the data input circuit is
Operation to send data to the
Sending data of the power circuit to the PROM circuit;
During normal operation, the data of the PROM circuit is
A data control circuit for controlling the operation and to be transmitted to Ray, before
Select one of the divided signal and the source signal to output to the outside
A frequency adjustment method of an oscillator circuit having a signal output means for force, and outputs the source oscillation signal from said signal output means to the outside, this <br/> frequency while measuring the frequency of the source oscillator signal after adjusting, and setting the frequency division number before Symbol dividing unit. Further, the frequency dividing means includes the source signal
And output multiple divided signals with different division numbers
A frequency divider circuit for receiving the source oscillation signal and the plurality of frequency-divided signals;
One of the source vibration signal and the plurality of frequency-divided signals
By selecting one and outputting it to the outside
The signal output means is provided by the frequency division selection circuit.
Characterized in that it is configured Te.

[0010]

The present invention employs a method of outputting a source vibration signal instead of a frequency-divided signal at the time of frequency adjustment and performing adjustment. In this way, the measurement frequency can be increased, so that high-speed and high-resolution adjustment can be performed. Further, since the data for controlling the capacitance array is stored after the frequency adjustment, the operation is performed based on the data stored in the storage means during the normal operation. Thus, the frequency can always be within a predetermined frequency range.

[0011]

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 a piezoelectric vibrator,
Since the other electrode is grounded at a high frequency, the capacitance array 6 functions as a variable load capacitance of the piezoelectric vibrator. By controlling the gate of the switching transistor, the capacitance of the capacitance array 6 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 when adjusting the frequency, sends data from the data input circuit 4 to the PROM circuit 7 when storing data, and During normal operation, the stored data of the PROM circuit 7 is sent to the capacity array 6 and the frequency division selecting circuit 10, and the above three operations are performed to control the data. Reference numeral 3 denotes a terminal for controlling the above data control. Reference numeral 9 denotes a frequency dividing circuit which divides the frequency of the oscillation signal from the oscillating unit 2 into 1/2, 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 unit 2 and the capacitance array 6 in detail. In this figure, 21 is an inverter amplifier, 22
Is a feedback resistor connected to the gate and drain of the inverter amplifier. Reference numeral 23 denotes a gate capacitance connected to the gate of the inverter amplifier 21, and reference numeral 24 denotes 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, and 42, 43, and 44 are switching transistors that are connected in series with the respective capacitors. Or more serial body of the capacitor and the switching transistor is connected in parallel with one electrode is connected to the gate side of the oscillator 2 and the other B-side electrode, a high-frequency manner grounded to V _DD or V _SS a power supply 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 the setting of the capacitance values of the capacitors 31 to 34, a weighted capacitance value is set. (For example, 1pF, 2p
F, 4 pF, 8 pF) By doing so, a wide capacitance range can be varied with a small number of capacitance elements while maintaining the resolution. Naturally, 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 can be 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. Also, storage of data by a PROM circuit,
Because the frequency is controlled by a capacitance array composed of capacitors and switching transistors, vibration resistance, shock resistance,
Excellent in aging. Further, since all the circuits can be made into ICs, miniaturization becomes possible. In addition, since the frequency selection can be controlled by external data, the frequency is adjusted by outputting the source signal, measuring the source signal, adjusting the frequency, and selecting the frequency 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 selection circuit 10 are built in. However, only the capacitance array 6 may be used.

Next, FIG. 5 shows an implementation 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,
5 sealed with resin mold, ceramic, metal, etc.
3 _{V DD} lead, 54 _{V SS} leads 55 are connected with IC51 wire bonding at the output leads are led out to the outside 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. A data input lead 57 is connected to the data input terminal of the IC 51 and is led out of the package 52. To adjust the frequency of the oscillation circuit configured as described above, the _VDD lead 53 and the _VSS lead 54
, The frequency of the oscillation signal output from the output lead 55 is measured, and data necessary for frequency adjustment is input from the data input lead 57. Repeat this until the frequency is within the desired range. When the frequency adjustment is completed,
Write data to PROM. During the above operation, the data inside the IC is controlled 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.

[0020]

As described above, according to the present invention, a method of outputting a source vibration signal instead of a frequency-divided signal at the time of frequency adjustment is adopted. By doing so, the measurement frequency can be increased, so that there is an effect that high-speed and high-resolution adjustment is possible. Further, since the data for controlling the capacitance array is stored after the frequency adjustment, the operation is performed based on the data stored in the storage means during the normal operation. Thus, the frequency can always be in a predetermined frequency range. In addition, since there is a capacitance array that makes the load capacitance of the piezoelectric vibrator variable, automation of frequency adjustment is also easy. Also, the sealing of the oscillation circuit
Later, the frequency can be adjusted, thus improving the airtightness of the oscillation circuit.
This eliminates the frequency shift due to sealing. In addition, PR
Storage of data by OM circuit and frequency by capacitance array
Because it is numerical control, it has excellent vibration resistance and impact resistance, and changes over time
Not so easy. Also, all circuits can be made into ICs
Can be downsized.

[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]

 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. Frequency divider selection circuit 11. Output buffer 21. Inverter amplifier 22. Feedback resistor 23. Gate capacitance 24. Drain capacitance 31, 32, 33, 34. Capacitors 41, 42, 43, 44. Switching transistor.

Claims (2)

(57) [Claims] An oscillator for oscillating a piezoelectric vibrator, a capacitor 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 data for externally inputting data for controlling the capacitance array.
Data input circuit and a PROM circuit for storing data for controlling the capacitance array.
And the frequency of the data input circuit during frequency adjustment.
Operation to send the data to the
Of sending data from a data input circuit to the PROM circuit
During normal operation, the data of the PROM circuit is stored in the
Data control circuit for controlling the operation of sending to the quantity array
And selecting one of the frequency-divided signal and the source oscillation signal and
A frequency adjustment method of an oscillator circuit having a signal output means for outputting outputs the source oscillation signal from said signal output means to the outside, this
After adjusting the frequency while measuring the frequency of the source oscillation signal, a frequency adjustment method of an oscillator circuit and sets the frequency division number before Symbol dividing unit. 2. The frequency dividing means according to claim 1 , further comprising:
Divider circuit that outputs a plurality of divided signals with different division numbers
Inputting the source vibration signal and the plurality of frequency-divided signals,
Selecting one of the source oscillation signal and the plurality of frequency-divided signals.
And a divider selection circuit that outputs the selected signal to the outside.
And the signal output means is constituted by the frequency division selection circuit.
2. The method for adjusting the frequency of an oscillation circuit according to claim 1, wherein: