阅读说明：本技术 一种高可靠性低功耗时钟振荡器 (High-reliability low-power consumption clock oscillator ) 是由 张伟 于 2019-09-09 设计创作，主要内容包括：本发明公开了一种时钟振荡器,包括：放大器电路；第一电阻,所述第一电路连接在所述放大电路的两端；水晶晶体振荡电路,所述水晶晶体振荡电路与所述第一电阻耦合,并在输出端产生振荡输出；以及漏电流对策电路,漏电流对策电路连接到所述水晶晶体振荡电路的输入端,当所述输入端有漏电流时,漏电流对策电路提供所述漏电流的流动路径。(The invention discloses a clock oscillator, comprising: an amplifier circuit; the first resistor is connected to two ends of the amplifying circuit; the crystal oscillation circuit is coupled with the first resistor and generates oscillation output at an output end; and a leakage current countermeasure circuit connected to an input terminal of the crystal oscillation circuit, the leakage current countermeasure circuit providing a flow path of the leakage current when the input terminal has the leakage current.)

1. A clock oscillator, comprising:

an amplifier circuit;

The first resistor is connected to two ends of the amplifying circuit;

The crystal oscillation circuit is coupled with the first resistor and generates oscillation output at an output end; and a leakage current countermeasure circuit connected to an input terminal of the crystal oscillation circuit, the leakage current countermeasure circuit providing a flow path of the leakage current when the input terminal has the leakage current.

2. The clock oscillator of claim 1, wherein the amplifier circuit is a first transistor, a source of the first transistor is coupled to a first current source, a drain of the first transistor is coupled to ground, and the first resistor is coupled between the source and the gate of the first transistor.

3. the clock oscillator of claim 2, wherein the dc voltage difference between the source and the gate is zero.

4. The clock oscillator of claim 2, further comprising a first capacitor connected between the input terminal and the gate of the first transistor.

5. The clock oscillator as recited in claim 4, wherein the first capacitor functions as a cut-off capacitor to cut off leakage current from the input terminal from the oscillator, but the oscillating ac signal can pass through the capacitor to the input terminal of the oscillator, so that the crystal oscillator circuit operates normally.

6. the clock oscillator according to claim 1, wherein the leakage current countermeasure circuit includes a second current source, a second resistor, and a second transistor, the second current source being connected to a source of the second transistor, a drain of the second transistor being grounded, the second resistor being connected between the source and an input terminal of the second transistor.

7. The clock oscillator of claim 6, further comprising:

A first diode, the anode of which is connected with the power supply and the cathode of which is connected with the input end; and

And the anode of the second diode is connected to the input end, and the cathode of the second diode is grounded.

8. The clock oscillator of claim 7, wherein a current path of the leakage current is from the second current source to ground via the second resistor, the second diode; or from the first diode, through the second resistor, through the second transistor, to ground.

9. The clock oscillator of claim 1, further comprising:

A third diode, the anode of which is connected with the power supply and the cathode of which is connected with the output end; and

And the anode of the fourth diode is connected to the output end, and the cathode of the fourth diode is grounded.

10. The clock oscillator according to claim 1, wherein the crystal oscillation circuit comprises a crystal, a second capacitor and a third capacitor forming a resonant circuit, one end of the second capacitor and one end of the third capacitor are respectively connected to the crystal, the other end of the second capacitor and the other end of the third capacitor are respectively connected to ground, and the two ends of the crystal are respectively an input end and an output end.

Technical Field

The invention relates to the technical field of clock oscillators, in particular to a high-reliability low-power-consumption clock oscillator.

background

An accurate 32.768KHz clock is required in the Real Time Clock (RTC) system of electronic products. And the RTC generally uses a battery when operating. Therefore, a low power consumption design is required for the RTC circuit system. In particular, 32.768KHz crystal oscillators require ultra-low power consumption designs. Some crystal oscillator manufacturers also have developed ultra-low power crystal oscillators specifically. The corresponding crystal oscillator amplifying circuit also requires a low-power consumption and high-reliability design.

The crystal oscillator is a resonator device manufactured by using the piezoelectric effect of a crystal, and because the crystal has a very high quality factor, the crystal oscillator can generate an oscillation waveform with accurate and stable frequency, and is widely used in the fields of clocks, military industry, communication and the like which have high requirements on oscillation frequency. Fig. 1 shows a typical crystal oscillator amplifier circuit. As shown in fig. 1, the capacitors C1 and C2 form a frequency-selective network together with the crystal, the capacitors M1 and M2 form an inverter as an amplifying circuit, and the feedback resistor Rf provides a dc bias to the amplifier. When the oscillator circuit meets the oscillation starting condition of small signals, transient current starts to be generated due to the noise interference effect in the circuit when a power supply is powered on, the frequency band contained by the transient current is extremely wide, but only a signal of the self resonant frequency is selected due to the frequency selection effect of the frequency selection loop, and the resonant frequency signal is stronger and stronger due to the positive feedback effect, so that oscillation output is generated.

However, the power consumption and oscillation stability of the crystal oscillator are determined by the inverter and the resistor Rf, and when the inverter has a strong driving capability and the resistor Rf has a large resistance, the oscillator can oscillate stably, but the power consumption is high. When the resistance of the resistor Rf is reduced and the driving capability of the inverter is reduced, the power consumption of the oscillator is low, but the stability is poor and even the oscillation cannot occur. For example, when leakage current occurs at the input and output ports of the oscillator, the oscillator may be caused to stop oscillation. Therefore, there is a need in the art for a high reliability low power consumption clock oscillator.

Disclosure of Invention

to solve the problems in the prior art, according to an embodiment of the present invention, there is provided a clock oscillator including:

An amplifier circuit;

The first resistor is connected to two ends of the amplifying circuit;

The crystal oscillation circuit is coupled with the first resistor and generates oscillation output at an output end; and

And the leakage current countermeasure circuit is connected to the input end of the crystal oscillation circuit and provides a flow path of leakage current when the input end has the leakage current.

In one embodiment of the invention, the amplifier circuit is a first transistor, a source of the first transistor is connected to a first current source, a drain of the first transistor is connected to ground, and the first resistor is connected between the source and the gate of the first transistor.

In one embodiment of the invention, the dc voltage difference between the source and the gate is zero.

In one embodiment of the invention, the clock oscillator further comprises a first capacitor connected between the input terminal and the gate of the first transistor.

In one embodiment of the invention, the first capacitor plays a role of cutting off direct current and alternating current, the influence of leakage current at the input end on the performance of the oscillator is cut off, but an oscillating alternating current signal can reach the input end of the oscillator through the capacitor, and the crystal oscillator circuit works normally.

In one embodiment of the present invention, the leakage current countermeasure circuit includes a second current source, a second resistor, and a second transistor, the second current source being connected to a source of the second transistor, a drain of the second transistor being grounded, and the second resistor being connected between the source and an input terminal of the second transistor.

In one embodiment of the invention, the clock oscillator further comprises:

A first diode, the anode of which is connected with the power supply and the cathode of which is connected with the input end; and

And the anode of the second diode is connected to the input end, and the cathode of the second diode is grounded.

In an embodiment of the invention, a current path of the leakage current is from the second current source to the ground terminal via the second resistor and the second diode; or from the first diode, through the second resistor, through the second transistor, to ground.

in one embodiment of the invention, the clock oscillator further comprises:

A third diode, the anode of which is connected with the power supply and the cathode of which is connected with the output end; and

And the anode of the fourth diode is connected to the output end, and the cathode of the fourth diode is grounded.

In an embodiment of the present invention, the crystal oscillation circuit includes a crystal, a second capacitor and a third capacitor, which form a resonant circuit, one end of the second capacitor and one end of the third capacitor are respectively connected to the crystal, the other ends of the second capacitor and the third capacitor are respectively grounded, and two ends of the crystal are respectively an input end and an output end.

In the circuit of the crystal oscillator disclosed by the invention, the resistor is used for conducting alternating current and alternating current at intervals, and the capacitor is used for conducting alternating current and alternating current at intervals. The blocking capacitor is connected to the grid electrode of the transistor, and the blocking capacitor can play a role in filtering, so that the current of the output signal of the crystal oscillator becomes smooth, and the oscillation is more stable.

Drawings

to further clarify the above and other advantages and features of embodiments of the present invention, a more particular description of embodiments of the invention will be rendered by reference to the appended drawings. It is appreciated that these drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. In the drawings, the same or corresponding parts will be denoted by the same or similar reference numerals for clarity.

Fig. 1 shows a typical crystal oscillator amplifier circuit.

Fig. 2 shows a circuit diagram of a crystal oscillator.

fig. 3 shows a graph of leakage current versus source voltage, gate voltage, and voltage difference.

figure 4 shows a circuit diagram of an improved crystal oscillator circuit according to one embodiment of the present invention.

FIG. 5 is a graph showing the relationship between the leakage current and the source voltage, gate voltage and voltage difference in the circuit of FIG. 4.

Detailed Description

In the following description, the invention is described with reference to various embodiments. One skilled in the relevant art will recognize, however, that the embodiments may be practiced without one or more of the specific details, or with other alternative and/or additional methods, materials, or components. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of embodiments of the invention. Similarly, for purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the embodiments of the invention. However, the invention may be practiced without specific details. Further, it should be understood that the embodiments shown in the figures are illustrative representations and are not necessarily drawn to scale.

Reference in the specification to "one embodiment" or "the embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase "in one embodiment" in various places in the specification are not necessarily all referring to the same embodiment.

fig. 2 shows a circuit diagram of a crystal oscillator. In an embodiment of the present invention, as shown in fig. 2, when a current source 201 supplies a current to an amplifier transistor 202. A current source 201 is connected to the source of the amplifier transistor 202. The drain of amplifier transistor 202 is connected to ground. A resistor 203 is connected as a feedback resistor between the source and the gate of the amplifier transistor 202. The crystal 207, the capacitor 206 and the capacitor 208 form a resonant circuit. One end of the capacitor 206 and one end of the capacitor 208 are respectively connected with the crystal 207. The other terminals of the capacitor 206 and the capacitor 208 are respectively connected to ground. Crystal 207 is connected in parallel with resistor 203 between the source and gate of amplifier transistor 202.

The circuit of the crystal oscillator shown in fig. 2 also has an input and an output. The input terminal is a connection node between the gate of the amplifier transistor 202, one terminal of the crystal 207, and one terminal of the resistor 203. The diode 204 has an anode connected to the power supply and a cathode connected to the input terminal. The anode of the diode 205 is connected to the input terminal and the cathode is connected to ground. The output terminal is a connection node of the source of the amplifier transistor 202, the other terminal of the crystal 207, and the other terminal of the resistor 203. The diode 209 has an anode connected to the power supply and a cathode connected to the output terminal. The diode 210 has an anode connected to the output terminal and a cathode connected to ground.

When there is a leakage current at the input terminal, the current can only be provided from the source through the resistor 203, i.e. the current path of the leakage current flows from the source through the resistor 203 and the diode 205 to the ground terminal. Thus, the leakage current is assumed to be 20 nA. Resistor 203 is 20M omega and a voltage drop of 0.4V is generated across the resistor. The difference between the voltages of the source and the grid is 0.4V, so that the gain of the amplifying circuit is reduced, and the signal cannot be amplified. The crystal oscillator circuit is characterized by no oscillation starting or stopping.

Fig. 3 shows a graph of leakage current versus source voltage, gate voltage, and voltage difference. As can be seen from fig. 3, when the leakage current-30 nA to 30nA (negative current indicates that the current is the power supply injection current from the input terminal) at the input terminal varies. The gate voltage curve 301 increases linearly, the source voltage curve 302 does not change, and the source voltage to gate voltage difference curve 303 increases linearly. The variation of the difference between the source voltage and the gate voltage is: -0.5V to 0.5V. This causes the gain of the inverting amplifier to drop sharply, which makes the oscillator unable to oscillate normally.

In order to solve the problem of leakage current, the invention improves the circuit of the crystal oscillator and adds a leakage current countermeasure circuit to the input. Figure 4 shows a circuit diagram of an improved crystal oscillator circuit according to one embodiment of the present invention. When the current source 401 supplies current to the amplifier transistor 402. A current source 401 is connected to the source of the amplifier transistor 402. The drain of the amplifier transistor 402 is connected to ground. A resistor 403 is connected as a feedback resistor between the source and gate of the amplifier transistor 402. The crystal 407, the capacitor 406 and the capacitor 408 form a resonant circuit. One end of the capacitor 406 and one end of the capacitor 408 are respectively connected with the crystal 407. The other terminals of the capacitor 406 and the capacitor 408 are connected to ground, respectively. One end of the crystal 407 is connected to the source of the amplifier transistor 402 and one end of the resistor 403. The other end of the crystal 407 is connected to one end of a capacitor 411. The other terminal of the capacitor 411 is connected to the gate stage of the amplifier transistor 402 and the other terminal of the resistor 403.

The circuit of the crystal oscillator shown in fig. 4 also has an input and an output. The input terminal is a connection node between one terminal of the crystal 407 and one terminal of the capacitor 411. The diode 404 has an anode connected to the power supply and a cathode connected to the input terminal. The anode of diode 405 is connected to the input and the cathode is connected to ground. The output terminal is a connection node of the source of the amplifier transistor 402, the other terminal of the crystal 407, and the other terminal of the resistor 403. The diode 409 has its anode connected to the power supply and its cathode connected to the output terminal. The anode of the diode 410 is connected to the output terminal and the cathode is grounded.

The input terminal of the crystal oscillator circuit is also connected to a leakage current countermeasure circuit 420. The leakage current countermeasure circuit 420 includes a second current source 412, a resistor 413, and a transistor 414. The second current source 412 supplies current to the transistor 414. The second current source 412 is coupled to the source of the transistor 414. The drain of transistor 414 is connected to ground. Resistor 413 is connected between the source and input of transistor 414.

When there is a leakage current at the input terminal, the leakage current is provided by the leakage current countermeasure circuit 420, i.e., the current path of the leakage current is from the current source 412 to the ground terminal via the resistor 413 and the diode 405. Or from diode 404 through resistor 413 through transistor 414 to ground. Thus, leakage current does not flow through the feedback resistor 403 of the amplifier. Therefore, no voltage difference is formed between the source and gate of transistor 402, resulting in no reduction in amplifier gain. The oscillator can be reliably oscillated under the condition of low power consumption.

FIG. 5 is a graph showing the relationship between the leakage current and the source voltage, gate voltage and voltage difference in the circuit of FIG. 4. As can be seen from fig. 5, the gate voltage curve 501 and the source voltage curve 502 overlap each other and remain horizontal, while the source voltage to gate voltage difference curve 503 remains 0. After the leakage current countermeasure circuit is added, when the leakage current changes from-30 nA to 30nA, the linearity of the grid voltage curve 501 and the voltage value of the source voltage curve 502 are not affected, and the difference value between the source voltage and the grid direct current voltage is always 0. Therefore, the operating point and the gain of the inverting amplifier are not affected. Therefore, the countermeasure circuit can completely eliminate the influence of the input terminal leakage current.

In the circuit of the crystal oscillator disclosed in the present invention, the resistor 413 is used for alternating current and alternating current, and the capacitor 411 is used for alternating current and alternating current. By connecting the blocking capacitor 411 to the gate of the transistor 402, the blocking capacitor 411 can perform a filtering function, so that the output signal current of the crystal oscillator becomes smooth and the oscillation becomes more stable.

in other embodiments of the invention, the amplifier circuit of the crystal oscillator may be modified to use other types of amplification circuits. The scope of protection of the invention is therefore not limited to the circuit configuration described in the above embodiments. For example, the leakage current countermeasure circuit may be connected to an input terminal of another crystal oscillator, and the advantageous effects of the present invention can be obtained as well.

while various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not limitation. It will be apparent to persons skilled in the relevant art that various combinations, modifications, and changes can be made thereto without departing from the spirit and scope of the invention. Thus, the breadth and scope of the present invention disclosed herein should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.