JP3296285B2 - Oscillator with oscillation start 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 oscillating device with an oscillating start-up circuit which is capable of eliminating abnormal oscillation of an oscillating circuit when power is turned on, thereby enabling normal oscillation.

[0002]

2. Description of the Related Art A crystal oscillator using a crystal oscillator can easily obtain a high-precision frequency. For example, a digital clock is typically used as a clock generator for a communication device, a measuring instrument, or a microcomputer / digital circuit. It is heavily used. A conventional oscillation device 1 shown in FIG. 3 has a crystal resonator 3 and a feedback resistor Rf connected in parallel to a feedback path connecting an output terminal and an input terminal of an inverting amplifier 2 composed of a CMOS inverter. The resistor Rf is incorporated in the oscillation circuit 4 integrated in the IC package. The oscillation circuit 4 includes a power supply terminal (power supply voltage Vcc) for the inverting amplifier 2 and a pair of connection terminals for the external crystal resonator 3, and the crystal resonator 3 has vibration electrodes on both sides. Connected to a pair of connection terminals. These connection terminals are grounded via load capacitance capacitors C1 and C2 to stabilize oscillation. The load capacitors C1 and C2 function to adjust the natural oscillation frequency of the crystal unit 3 to the target oscillation frequency.

When the power is turned on to raise the power supply voltage Vcc, the power supply voltage is boosted toward the rated voltage V1, as shown in FIG. 4A, and after reaching the rated voltage V1 at time t1. , The rated voltage V1 is maintained. in this case,
Normally, as shown in FIG. 4C, the oscillation circuit 4 starts oscillating just before the power supply voltage Vcc reaches the rated voltage V1, and starts oscillating at the natural oscillation frequency of the crystal unit 3. I do. After that, it oscillates while gradually increasing the amplitude,
It shifts to the desired oscillation frequency with the passage of time.

[0004]

The above-mentioned conventional oscillation device 1
Although the natural oscillation frequency of the crystal unit 3 is adapted to the oscillation frequency by using the capacitances of the load capacitance capacitors C1 and C2, the oscillation may not be stabilized when the power is turned on. As shown, there were cases where abnormal oscillation occurred at a frequency considerably lower than the intended oscillation frequency even after transition to the steady state. In these cases,
It is necessary to perform a reset operation for forcibly stopping abnormal oscillation and switching to normal oscillation. However, the conventional oscillation circuit 4 does not have such a built-in reset start circuit. There is a problem that such measures may be required.

Japanese Unexamined Patent Publication No. Sho 59-205802 discloses an "oscillation circuit with start trigger" which includes a trigger circuit for detecting a rise of a power supply voltage and generating a trigger pulse at an input side or an output side of an amplifier constituting an oscillation circuit. And a circuit in which an oscillation circuit is activated by a trigger pulse generated by the trigger circuit is disclosed. In this circuit, the transistor which detects that the power supply voltage has reached a voltage value sufficient for the operation of the oscillation circuit is turned on, and the input terminal of the inverting amplifier is instantaneously dropped to 0 volts. The circuit was configured to quickly shift to the oscillation state.

However, the oscillation circuit with a start trigger has a configuration in which the input side of the inverting amplifier is grounded, and a rise detection circuit that detects a rise of the power supply voltage and generates a differential pulse is indispensable. However, it is composed of a series connection circuit of a capacitor and a resistor, and a pair of waveform shaping inverters connected in series to the connection point of the capacitor and the resistor, and has a problem that the circuit configuration is very complicated. Was. Further, in the above-mentioned oscillation device, the oscillator externally connected to the oscillation circuit is formed of a crystal oscillator, the manufacturing cost is higher than that of the ceramic oscillator, and the entire device is formed at a lower cost. Had problems such as not being able to do so.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned conventional problems, and has as its object to promote a normal oscillation by integrating a reset circuit with an oscillator externally attached to an oscillation circuit.

[0008]

To achieve the above object, the present invention provides an oscillation circuit including an amplifier with a feedback resistor,
An oscillator connected in parallel to the feedback resistor outside the oscillation circuit, and one of the oscillators that conducts by an external signal.
A source that grounds the pole and starts oscillation of the amplifier with feedback resistor
And an oscillator having a vibration starting circuit, wherein the oscillator includes:
Package in which the vibrator and the oscillation starting circuit are packaged
It is characterized by being.

Another feature is that the oscillation starting circuit includes a switching element that grounds one end of the vibrator and conducts by the external signal, or that the vibrator is a ceramic vibrator. It is assumed that.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
This will be described with reference to FIG. FIG. 1 is a circuit diagram showing an embodiment of an oscillation device with an oscillation start circuit of the present invention, and FIG.
FIG. 2 is a signal waveform diagram of each section of the circuit shown in FIG. 1.

An oscillating device 11 with an oscillation starting circuit shown in FIG.
Is a device for generating an external interface clock such as a CD-ROM drive. When the power of the CD-ROM drive is turned on, the oscillation is started by the oscillation starting circuit 12, and the normal oscillation state is smoothly achieved. It is configured for migration. The oscillation device 11 includes an oscillation circuit 4 including an inverting amplifier 2 with a feedback resistor Rf, and a ceramic oscillator 13 connected to the feedback resistor Rf outside of the oscillation circuit 4 in parallel.
An oscillator 14 connected to one terminal of the ceramic oscillator 13 and packaged with the oscillator 13; and a pair of capacitors C1 connected to a line connecting the oscillation circuit 4 and the oscillator 14 to provide a load capacitance. , C2.

The oscillation starting circuit 12 includes the ceramic vibrator 1
3 comprises a PNP-type MOS transistor Q having one pole grounded, and a base resistor Rb connected between the base of the MOS transistor Q and an external signal input terminal. The MOS transistor Q has an emitter connected to the input side of the inverting amplifier 2 in the oscillation circuit 4 and a collector grounded. The oscillation starting circuit 12 is housed in the same package together with the ceramic vibrator 13 to form the vibrator 14. Both the ceramic vibrator 13, the MOS transistor Q and the base resistor Rb are of a surface mount type. The oscillator 14 has a four-terminal structure.
One of the remaining two is grounded as a ground terminal, and the other is connected to a start trigger circuit 15 incorporated in the CD-ROM driver. Start trigger circuit 1
Numeral 5 generates a negative reset pulse when the power of the CD-ROM driver is turned on, and serves to make the MOS transistor Q conductive.

Here, when the power supply of the CD-ROM driver is turned on, the power supply voltage Vcc rises while following the progress shown in FIG. When the time t1 has elapsed since the power was turned on, the voltage level reaches the rated voltage V1. After reaching the rated voltage V1 at time t1, the rated voltage V1 is maintained. On the other hand, the oscillation circuit 4
2C, that is, the oscillation output of the inverting amplifier 2 is shown in FIG.
In this case, as shown in FIG.
Oscillation starts slightly before cc reaches the rated voltage V1,
Positive feedback in which the oscillating current is amplified by the mechanical vibration of the oscillator 14 and the piezoelectric effect is cyclically repeated, and oscillation starts at the frequency of the natural frequency of the ceramic oscillator 13.

When a time t2 elapses after the power is turned on, a reset pulse is supplied from the start trigger circuit 15 to the oscillation start circuit 12, as shown in FIG.
MOS transistor Q conducts. As a result, the input terminal of the inverting amplifier 2 in the oscillation circuit 4 is connected to the MOS transistor Q
Grounded. At this time, the input voltage of the inverting amplifier 2 is forced to 0 volt due to a sudden voltage drop due to grounding. As a result, a voltage substantially close to the power supply voltage is applied between the input voltage and the output voltage of the inverting amplifier 2, and this triggers to start normal oscillation. That is, the oscillation is started not at the natural oscillation frequency of the ceramic oscillator 13 but at the intended oscillation frequency adjusted in advance by the capacitors C1 and C2, and after the time t2 elapses after the power is turned on, FIG. Normal oscillation continues as shown in FIG.

As described above, the oscillating device 11 with the oscillation starting circuit includes the oscillator 14 externally connected to the oscillating circuit 4 including the inverting amplifier 2 with the feedback resistor Rf and the ceramic oscillator 13 connected in parallel to the feedback resistor Rf. The oscillation start circuit 12 is connected to one terminal of the ceramic vibrator 13 and is electrically connected by an external signal, grounds the terminal and starts the oscillation of the inverting amplifier 2 with the feedback resistor. Can be packaged together with the ceramic vibrator 13 on the same element instead of inside the oscillation circuit 4. For this reason, by configuring the ceramic resonator 13 and the oscillation starting circuit 12 as surface mount types, it is possible to reduce the size of the package and reduce the cost associated with mass production, and to use an oscillation frequency different from the natural oscillation frequency of the ceramic resonator 13. In a case where a clock pulse is generated by oscillating, abnormal oscillation at power-on, which cannot be dealt with only by adjusting the load capacitance capacitors C1 and C2, is surely shifted to normal oscillation together with the operation of the oscillation starting circuit 12. Can be. Further, since the oscillation starting circuit 12 itself applies a starting trigger in response to an external signal, a special circuit for detecting the rise of the power supply voltage is unnecessary.

Further, the oscillation starting circuit 12 grounds one end of the ceramic vibrator 13 and conducts the current by an external signal.
Since the S transistor Q is included, one end of the ceramic vibrator 13, that is, the input terminal or the output terminal of the inverting amplifier 2 in the oscillation circuit 4 is grounded with the conduction of the MOS transistor Q, and the voltage between the input and output terminals is substantially equal to the power supply voltage. By suddenly applying a voltage, a start trigger can be reliably applied to the oscillation circuit 4, and the MOS transistor Q
Can be configured using surface-mounted transistors,
The size and cost of the oscillator 14 can be reduced.

Further, the vibrator is a ceramic vibrator 1
3, LC, although inferior to quartz resonator,
Ceramic oscillators 13 that have higher frequency stability than oscillation circuits and CR oscillation circuits have good temperature stability, and should be used in various applications if the frequency accuracy and stability are not required as much as crystal oscillators. Taking advantage of the small and inexpensive characteristics of the ceramic vibrator 13 utilizing the mechanical resonance of a piezoelectric ceramic, which is a polycrystalline body,
It is possible to reduce the size and cost of the entire device.

In the above embodiment, the case where the ceramic vibrator 13 is used as the vibrator is taken as an example. However, it goes without saying that the vibrator may be constituted by a quartz vibrator.

[0019]

As described above, according to the present invention,
An oscillator externally connected to an oscillation circuit including an amplifier with a feedback resistor is connected to an oscillator connected in parallel to the feedback resistor, and connected to one terminal of the oscillator. Since the oscillation start circuit is configured with an oscillation start circuit that starts the oscillation of the amplifier with the resistor, the oscillation start circuit can be packaged on the same element with the vibrator instead of inside the oscillator circuit. By using a surface mount type, it is possible to reduce the size of the package and reduce the cost associated with mass production.If a clock pulse is generated by oscillating at an oscillation frequency different from the natural oscillation frequency of the oscillator, load capacitance The abnormal oscillation at power-on, which cannot be dealt with just by adjusting the oscillation, can be reliably shifted to normal oscillation together with the operation of the oscillation start circuit. Since the road itself exerts an activation trigger in response to an external signal, a special circuit for detecting the rise of the supply voltage excellent effects etc. is not required.

Further, since the oscillation starting circuit includes a switching element that grounds one end of the vibrator and conducts by an external signal, one end of the vibrator, that is, an input terminal or an output of an amplifier in the oscillation circuit, is connected with the conduction of the switching element. By grounding the terminal and suddenly applying a voltage almost equal to the power supply voltage between the input and output terminals, a start trigger can be reliably applied to the oscillation circuit, and the switching element uses a surface mount transistor. Since the oscillator can be used, the size of the oscillator can be reduced and the cost can be reduced.

Further, since the vibrator is formed of a ceramic vibrator, the ceramic vibrator having a higher frequency stability than the LC oscillator or the CR oscillator has a better temperature stability, although it is inferior to the quartz oscillator. In applications where frequency accuracy and stability are not required as much as quartz resonators, it can be used in various fields, especially ceramic resonators that use the mechanical resonance of piezoelectric ceramics, which are polycrystalline, and are small and inexpensive. Taking advantage of this feature, it is possible to reduce the size and cost of the entire apparatus, and so on.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of an oscillation device with an oscillation start circuit according to the present invention.

FIG. 2 is a signal waveform diagram of each section of the circuit shown in FIG.

FIG. 3 is a circuit configuration diagram showing an example of a conventional oscillation device.

4 is a signal waveform diagram of each section of the circuit shown in FIG.

[Explanation of symbols]

 2 Inverting amplifier 4 Oscillation circuit 11 Oscillation device with oscillation start circuit 12 Oscillation start circuit 13 Ceramic oscillator 14 Oscillator Rf Feedback resistance C1, C2 Load capacitance capacitor Q MOS transistor Rb Base resistance

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H03B 5/32

Claims (3)

(57) [Claims] An oscillation circuit including an amplifier with a feedback resistor; an oscillator connected outside of the oscillation circuit in parallel with the feedback resistor ;
A source that grounds the pole and starts oscillation of the amplifier with feedback resistor
An oscillator having an oscillation start circuit , wherein the oscillator and the oscillation start circuit are packaged.
With oscillation start-up circuit characterized in that
Oscillation device. 2. The oscillation device with an oscillation start circuit according to claim 1, wherein the oscillation start circuit includes a switching element that grounds one end of the vibrator and conducts by the external signal. 3. The oscillation device according to claim 1, wherein the vibrator is a ceramic vibrator.