CN1649253A - Crystal Accelerated Oscillator Circuit - Google Patents

Abstract

The invention relates to a crystal acceleration oscillation circuit, which comprises a quartz oscillation crystal for generating an oscillation signal, an amplifier group, a feedback resistor, a first trigger, a second trigger and amplifier switch logic. The amplifier group is used for amplifying the oscillation signal; the feedback resistor is used for establishing a direct current working bias voltage of the amplifier group; the input end of the first trigger is connected with the output end of the amplifier group so as to trigger the first trigger by the amplified oscillating signal to generate a first clock output; the input end of the second trigger is connected with the output end of the amplifier group so as to trigger the second trigger by the amplified oscillating signal to generate a second clock output, wherein the second trigger has a hysteresis voltage which is more than a preset value; the amplifier switch is logically connected to the second flip-flop to gradually decrease the amplification intensity of the amplifier group when the second flip-flop is detected to generate the second clock output.

Description

Crystal Accelerated Oscillator Circuit

technical field

The invention relates to a crystal oscillation circuit, especially to a crystal acceleration oscillation circuit capable of ensuring oscillation

Background technique

FIG. 1 shows a traditional crystal oscillator circuit (Crystal Oscillator), which includes an inverting amplifier 11, a feedback resistor 12, a quartz oscillator crystal 13, a group of capacitor pairs 14, and a Schmitt trigger 16, wherein , the inverting amplifier 11 is used for signal amplification to provide the overall crystal oscillator circuit signal gain (Gain), the Schmitt trigger 16 is triggered by the amplified signal generated by the inverting amplifier 11 and outputs the clock signal CLK, and the feedback resistor 12 Used to establish the DC operating bias of the inverting amplifier 11, the quartz oscillator crystal 13 is used to generate an oscillation signal with a resonance frequency, and the capacitor pair 14 is used to make the parallel resonance (Parallelresonance) of the overall crystal oscillator circuit very close to series Resonance (Series resonance), and the oscillation frequency of the crystal oscillation circuit is between the two.

With the aforementioned crystal oscillator circuit, since the signal bandwidth and amplification gain of the inverting amplifier 11 will vary with the operating voltage, process parameters, and load capacitance pairs, and this change will often cause the crystal oscillator circuit to start oscillating too long in many practical applications. long or even unable to oscillate.

In order to solve the aforementioned problems, an improved crystal oscillator circuit as shown in Figure 2 is currently proposed, which uses a plurality of inverting amplifiers 11 in parallel to achieve the purpose of quickly starting the crystal oscillator, and Figure 3 shows its inverting amplifier 11 Switching mode, it first is when the power supply voltage starts (step S301), turns on all inverting amplifiers 11 (this time called Strongmode), because the amplification gain of the amplifier 11 at this time is very high, so it can achieve crystal oscillation The purpose of quick start-up of the device. But the amplifier power consumption of this moment is also very big, in order to reach the demand of power saving, so the clock CLK that will produce is sent into N-bit counter 17 (step S302), after passing through 2 ^N clocks, counter 17 timing finishes, only One basic inverting amplifier 11 that maintains the crystal oscillator circuit to continue to oscillate is reserved (called Weak mode at this time), and the rest of the inverting amplifiers 11 are turned off (step S303 ).

The aforesaid improved crystal accelerated oscillation circuit cone can achieve the purpose of fast start-up by connecting multiple inverting amplifiers 11 in parallel. However, after starting the oscillation, since only one basic inverting amplifier 11 is reserved, the The crystal oscillating circuit is still the same as the traditional crystal oscillating circuit, and the crystal oscillating circuit will not oscillate due to changes in the operating voltage, process parameters, and load capacitance.

Contents of the invention

An object of the present invention is to provide a crystal speed-up oscillation circuit, which can ensure that it will oscillate and will not stop oscillating due to changes in manufacturing process, load capacitance and power supply voltage.

Another object of the present invention is to provide a crystal accelerated oscillator circuit, which can effectively shorten the start-up time.

Another object of the present invention is to provide a crystal speed-up oscillator circuit, which can automatically adjust the current consumption to the minimum.

Another object of the present invention is to provide a crystal speed-up oscillation circuit, which can be replaced with transistor oscillators of different frequencies without causing the problem of non-oscillation or excessive current consumption.

To achieve the above object, the crystal acceleration oscillation circuit of the present invention includes: a quartz oscillator crystal, used to generate an oscillation signal; an amplifier group, used to amplify the oscillation signal, and generate an amplified oscillation signal at its output terminal, wherein , when the power is turned on, the amplifier group has the maximum amplification strength; a feedback resistor, which is connected across the amplifier group, is used to establish the DC working bias voltage of the amplifier group; a first flip-flop, whose input terminal is connected to The output end of the amplifier group, so that the first flip-flop is triggered by the amplified oscillation signal to generate a first clock output; the input end of a second flip-flop is connected to the output end of the amplifier group, so as to be amplified by the amplified oscillation A signal triggers the second flip-flop to generate a second clock output, wherein the second flip-flop has a hysteresis voltage greater than a preset value; and an amplifier switch logic is connected to the second flip-flop to when When it is detected that the second flip-flop generates the second clock output, the amplification strength of the amplifier group is gradually reduced.

Description of drawings

Figure 1 shows a conventional crystal oscillator circuit;

Fig. 2 shows an improved traditional crystal oscillator circuit;

Fig. 3 shows the switching process of the inverting amplifier of the improved traditional crystal oscillator circuit;

Fig. 4 is an embodiment of the crystal accelerated oscillation circuit of the present invention;

Fig. 5 is the switching process of the inverting amplifier of the crystal accelerated oscillation circuit of the present invention;

FIG. 6 is another embodiment of the crystal accelerated oscillation circuit of the present invention.

Detailed ways

In order to better understand the technical content of the present invention, the preferred specific embodiments are illustrated as follows.

Fig. 4 is an embodiment of the crystal acceleration oscillation circuit of the present invention, and it comprises an amplifier group 41, a feedback resistor 42, a quartz oscillator crystal 43, a group of capacitance pair 44, a first flip-flop 46, a second flip-flop 47, and an amplifier switching logic 48. Wherein, the amplifier group 41 includes a plurality of parallel amplifiers 411 for signal amplification to provide the overall crystal oscillator circuit signal gain (Gain), these amplifiers 411 are preferably inverting amplifiers; the feedback resistor 42 is connected across The amplifier group 41 is used to establish the DC operating bias (Direct current operation bias) of the amplifier group; the quartz oscillator crystal 43 is connected across the feedback resistor 42 and the amplifier group 41 to generate a resonance frequency oscillation signal; the capacitance 441 and 442 of the capacitance pair 44 are respectively connected to the two ends of the quartz oscillator crystal 43, so as to make the series resonance (Series resonance) of the overall crystal oscillation circuit very close to the parallel resonance (Parallel resonance), The oscillation frequency of the crystal oscillation circuit is between the two.

Aforesaid first flip-flop 46 is a small-amplitude Smith trigger (Small-swing Schmitt-trigger) with less hysteresis voltage, and its input terminal is connected to the output of this amplifier group 41, so that by this amplifier group 41 output The amplified signal triggers to generate the clock output CLK, and this small-amplitude Smith trigger can also be replaced by a general inverting amplifier. The aforementioned second trigger 47 is a large-amplitude Smith trigger (Large-swing Schmit-trigger) with a larger hysteresis voltage, and its input terminal is connected to the output of the amplifier group 41 to detect the output of the amplifier group 41. When the output amplitude of the amplified signal is greater than the hysteresis voltage of the second dragmitter 47 , an enhanced clock output XCLK is generated to feed into the amplifier switching logic 48 .

The aforementioned amplifier switching logic 48 is used to adjust the number of inverting amplifiers turned on to save current consumption. FIG. 5 shows the switching mode of the aforementioned amplifier switching logic 48. The phase amplifiers are all turned on (step S501), therefore, the crystal acceleration oscillation circuit will start up quickly, and because all the amplifiers 411 are turned on at this time, the current consumption is relatively large, and the crystal acceleration oscillation is caused to avoid closing the amplifiers 411 once The problem that the circuit cannot oscillate after starting to oscillate, therefore, the amplifier switching logic 48 reduces the amplification strength of the amplifier group 41 one by one (step S503) when the second flip-flop 47 generates an enhanced clock output XCLK (step S502). , that is, turn off the amplifiers 411 of the amplifier group 41 one by one until the second flip-flop 47 does not generate the enhanced clock output XCLK or only one amplifier 411 is turned on in the amplifier group 41 (step S504).

In the foregoing switching process, when there is no enhanced clock output XCLK at the beginning, it means that the amplification strength of the amplifier group 41 has been weakened so that the second flip-flop 47 cannot generate the enhanced clock output XCLK, but because the aforementioned second flip-flop 47 is for Large amplitude Smith trigger, its hysteresis voltage is much larger than this first flip-flop 46, therefore, the amplification strength of amplifier group 41 is still enough to make the first flip-flop 46 generate the clock output CLK, thus ensure that the inverting amplifier is turned off to save power consumption. After the current flow, the crystal accelerated oscillation circuit can still oscillate.

The aforementioned amplifier switching logic 48 can be an N-bit counter, which is used to count the number of clock pulses of the boosted clock output XCLK, so that when the count ends, an inverting amplifier of the amplifier group 41 is turned off, and the counter is reset and recount.

Fig. 6 shows another embodiment of the crystal accelerated oscillation circuit of the present invention, and its difference from the previous embodiment is that the amplifier group 61 is composed of a plurality of parallel current sources 611 and an amplifier 612 controlled by these current sources As a result, the amplifier 612 is preferably a current-controlled inverting amplifier, and the amplifier switching logic 48 turns off the current sources 611 of the amplifier group 61 one by one to reduce the amplification strength of the amplifier group 61 one by one.

As can be seen from the above description, the crystal accelerated oscillation circuit of the present invention is to reduce the amplification strength of the amplifiers one by one when the large-amplitude Smith trigger generates a clock signal by simultaneously starting with a large number of amplifiers until the large-amplitude Smith trigger does not There is a clock signal to achieve the purpose of oscillation, which has the following advantages:

1. Ensure that the oscillating circuit will oscillate and will not stop oscillating due to changes in manufacturing process, load capacitance and power supply voltage;

2. It can effectively shorten the start-up time of the oscillating circuit;

3. The number of activated inverting amplifiers of the oscillation circuit will be automatically adjusted to the minimum, so the current consumption will also be automatically adjusted to the minimum; and

4. In some applications, it is necessary to replace the quartz oscillator crystal with a different frequency, and this structure is still applicable.

The above-mentioned embodiments are only examples for convenience of description, and the scope of rights claimed by the present invention should be based on the scope of the patent application, rather than limited to the above-mentioned embodiments.

Claims (10)

1. A crystal accelerated oscillation circuit, characterized in that, comprising; A quartz oscillating crystal is used to generate an oscillating signal; An amplifier group is used to amplify the oscillating signal to generate an amplified oscillating signal at its output terminal, wherein, when the power is turned on, the amplifier group has the maximum amplification strength; a feedback resistor connected across the amplifier group to establish a DC working bias voltage of the amplifier group; A first flip-flop, the input end of which is connected to the output end of the amplifier group, so that the first flip-flop is triggered by the amplified oscillation signal to generate a first clock output; A second flip-flop whose input end is connected to the output end of the amplifier group, so that the second flip-flop is triggered by the amplified oscillating signal to generate a second clock output, wherein the second flip-flop has a value greater than a preset value of the hysteresis voltage; and An amplifier switching logic, connected to the second flip-flop, is used to gradually reduce the amplification strength of the amplifier group when it is detected that the second flip-flop generates a second clock output. 2. The crystal accelerated oscillation circuit according to claim 1, wherein the first trigger is a first Schmitt trigger, the second trigger is a second Schmitt trigger, The hysteresis voltage of the second Schmitt trigger is greater than that of the first Schmitt trigger. 3. The crystal accelerated oscillator circuit as claimed in claim 1, wherein the first flip-flop is an inverting amplifier, and the second flip-flop is a Schmitt trigger. 4. The crystal accelerated oscillation circuit as claimed in claim 2, further comprising a set of capacitor pairs respectively connected to two ends of the quartz oscillator crystal. 5. The crystal accelerated oscillator circuit as claimed in claim 2, wherein the amplifier group comprises a plurality of inverting amplifiers connected in parallel. 6. The crystal accelerated oscillation circuit according to claim 5, wherein the amplifier switching logic is to turn off the inverting amplifiers of the amplifier group one by one when detecting that the second flip-flop generates a second clock output , until the second flip-flop does not generate the second clock output or there is only one inverting amplifier turned on in the amplifier group. 7. The crystal accelerated oscillation circuit according to claim 6, wherein the amplifier switching logic comprises a counter, the counter is used to count the output of the second clock, so that when the count ends, the amplifier group is turned off an inverting amplifier. 8. The crystal accelerated oscillator circuit as claimed in claim 2, wherein the amplifier group includes a plurality of parallel current sources and a current control inverting amplifier, and the current control inverting amplifier is formed by the parallel connection controlled by the current source. 9. The crystal accelerated oscillation circuit according to claim 8, wherein the amplifier switching logic is to turn off the current sources of the amplifier group one by one when detecting that the second flip-flop generates a second clock output, Until the second flip-flop does not generate the second clock output or only one current source is turned on in the amplifier group. 10. The crystal accelerated oscillator circuit according to claim 9, wherein the amplifier switch logic comprises a counter, the counter is used to count the output of the second clock, so that when the count ends, the amplifier group is turned off of a current source.

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