TWI746412B - Method for startup of crystal oscillator with aid of external clock injection, crystal oscillator and monitoring circuit - Google Patents

Abstract

A method for startup of a crystal oscillator (XO) with aid of external clock injection, XO and a monitoring circuit therein are provided. The XO includes an XO core circuit, an external oscillator, and an injection switch, where a quality factor of the external oscillator is lower than a quality factor of the XO core circuit. The method includes: utilizing the external oscillator to generate an injected signal; turning on the injection switch to make energy of the injected signal be injected into the XO core circuit, where an amplitude modulation (AM) signal is generated according to combination of the injected signal and an intrinsic oscillation signal from the XO core circuit; and controlling the external oscillator to selectively change an injection frequency of the injected signal according to the AM signal. More particularly, the injection switch is not turned off until the startup process is completed.

Description

The method of starting the crystal oscillator with external clock injection, crystal oscillator and monitoring Visual circuit

The present invention relates to a fast start-up of a crystal oscillator (XO), and more specifically, to a method of starting an XO by means of external clock injection, an associated XO, and a monitoring circuit.

For future communication applications (for example, duty-cycled wireless/wired systems), when there is no data to send or receive, the crystal oscillator (XO) in the communication device can enter sleep mode ( For example, prohibit the oscillation of XO to save power; when there is data to be sent or received, XO can enter the wake-up mode to start the oscillation, and then enter the listen mode with stable oscillation, so that the communication device can send or receive data normally .

For example, the time period corresponding to the listening mode may be 1 millisecond (ms), and the time period corresponding to the wake-up mode (may be referred to as the start-up time TSTART) may be 5 ms, where the wake-up mode consumes power (e.g., consumes total power) 42.7%). Therefore, the start-up time of XO may become a bottleneck in reducing average power. Designers can try to reduce the startup time by controlling the negative resistance in the XO, but this may bring additional power consumption. Therefore, a novel XO startup method and related architecture are needed to solve the related technical problems.

The purpose of the present invention is to provide a method for starting a crystal oscillator (XO) by means of external clock injection, related XO and monitoring circuits, to accelerate the starting of the XO without greatly increasing additional energy consumption.

At least one embodiment of the present invention provides a method for starting XO by means of external clock injection. The method may include: using an external oscillator outside the XO core circuit in the XO to generate the injection signal, where the XO includes the XO core circuit, an external oscillator located outside the XO core circuit, and at least one injection switch. The at least one injection switch is coupled between the injection node of the XO and the output terminal of the XO core circuit, the external oscillator is coupled to the injection node, and the quality factor of the external oscillator is low The quality factor of the XO core circuit; turn on at least one injection switch to inject the energy of the injected signal into the XO core circuit, thereby increasing the energy of the natural oscillation signal of the XO core circuit during the start-up process of the XO, wherein according to the injected signal and The combination of natural oscillation signals generates a modulation signal on the injection node; according to the modulation signal, the external oscillator is controlled to selectively change the injection frequency of the injection signal. More specifically, when the external oscillator selectively changes the injection frequency of the injection signal, at least one injection switch is turned on.

At least one embodiment of the present invention provides an XO. The XO may include an XO core circuit, an external oscillator, at least one injection switch and a frequency controller, wherein the external oscillator is coupled to the injection node of the XO, and at least one injection switch is coupled to the injection node of the XO and the output terminal of the XO core circuit In between, the frequency controller is coupled to an external oscillator. The XO core circuit may be configured to generate a natural oscillation signal within the XO core circuit. The external oscillator may be configured to generate an injection signal in the external oscillator, wherein the quality factor of the external oscillator is lower than the quality factor of the XO core circuit. For example, when at least one injection switch is turned on, the energy of the injection signal is injected into the XO core circuit to increase the energy of the natural oscillation signal during the XO startup process, and the injection signal is injected according to the combination of the injection signal and the natural oscillation signal. A modulated signal is generated on the node. The frequency controller may be configured to receive the modulation signal and control the external oscillator to selectively change the injection frequency of the injection signal according to the modulation signal. More specifically, when the external When the oscillator selectively changes the injection frequency of the injection signal, at least one injection switch is turned on.

At least one embodiment of the present invention provides a monitoring circuit for generating a continuous comparison result of a demodulated voltage sequence, the demodulated voltage sequence carrying information about the relative phase between the XO injection signal and the natural oscillation signal . The monitoring circuit can include amplifiers, capacitors, and loop switches. The amplifier may be configured to receive a demodulated voltage sequence through a first input terminal of the amplifier, wherein the demodulated voltage sequence includes a first voltage and a second voltage following the first voltage. The capacitor is coupled to the second input terminal of the amplifier, and the capacitor may be configured to sequentially store the demodulated voltage sequence. The loop switch is coupled between the second input terminal and the output terminal of the amplifier, and the loop switch is configured to control the configuration of the amplifier. For example, when the loop switch is turned on, the amplifier is configured as a unity gain buffer to transfer the first voltage from the first input terminal of the amplifier to the capacitor. When the loop switch is off, the amplifier is configured as a comparator for comparing the second voltage on the first input terminal of the amplifier with the first voltage stored on the capacitor, and generating all The comparison result of the continuous comparison result, wherein the comparison result carries information about the relative phase between the injection signal and the natural oscillation signal of the XO, and is used to control the injection frequency of the injection signal.

The startup method and the related XO provided by the embodiment of the present invention can use an external oscillator to inject energy into the XO core circuit to accelerate the startup process of the XO. Advantageously, during the startup process, the injection switch coupled between the external oscillator and the XO core circuit can be turned on all the time, so that the efficiency of clock injection can be optimized. In some embodiments, when the injection frequency is adjusted (locked to the natural frequency of the XO core circuit), the injection switch can be turned on all the time, at least for a period of time, or alternately turned on and off to optimize or improve the clock injection efficiency . Compared with the prior art, the overall startup time of XO can be greatly reduced. Therefore, the present invention can optimize the overall performance of the XO without causing any side effects, or optimize the overall performance of the XO in a manner that is unlikely to cause side effects.

After reading the following detailed description of the preferred embodiments shown in the various drawings and drawings, these and other objects of the present invention will undoubtedly become obvious to those with ordinary knowledge in the field. See.

10: XO

11: Active device

20: XO

200: external oscillator

100: XO core circuit

300: frequency controller

S310, S320, S330: steps

210: Low Q oscillator

220: output buffer

310: Demodulation circuit

D0: Diode

C _S : sampling capacitor

330: Finite State Machine

320: monitoring circuit

322: D flip-flop

AMP _COMP : Amplifier

C _COMP : Capacitor

30: XO

COMP: Comparator

320A: Monitoring circuit

RST, RSTB, SH, SHB, VA, VB: signal

CLK _counting : counting clock

40: XO

320B: ADC

FIG. 1 is a schematic diagram showing the concept of starting a crystal oscillator (XO) by means of external clock injection according to an embodiment of the present invention.

Figure 2 is a schematic diagram showing an XO according to an embodiment of the present invention.

Fig. 3 is a flowchart of a method for starting the XO shown in Fig. 2 by means of external clock injection according to an embodiment of the present invention.

FIG. 4 is a schematic diagram showing waveform patterns of some signals with varying relative phases according to an embodiment of the present invention.

Figure 5 shows the relationship between the growth rate and the relative phase of an intrinsic oscillation signal according to an embodiment of the present invention.

Fig. 6 is a schematic diagram showing a detailed implementation of generating a series of demodulated voltages by a demodulation circuit according to an embodiment of the present invention.

Figure 7 shows some details of the relationship between relative phase and distortion according to an embodiment of the present invention.

Figure 8 shows some details of the relationship between the relative phase and the demodulated voltage according to an embodiment of the present invention.

Figure 9 shows some details of the relationship between relative phase and distortion according to an embodiment of the present invention.

Figure 10 shows some details of the relationship between the relative phase and the demodulated voltage according to an embodiment of the present invention.

Fig. 11 is a schematic diagram showing a detailed implementation of the XO shown in Fig. 2 according to an embodiment of the present invention.

Figure 12 shows the operation of the monitoring circuit shown in Figure 11 during the preset phase.

Figure 13 shows the operation of the monitoring circuit shown in Figure 11 during the evaluation phase.

Figure 14 shows a schematic diagram of a detailed implementation of the XO shown in Figure 2 according to an embodiment of the present invention.

Figure 15 shows a schematic diagram of a detailed implementation of the XO shown in Figure 2 according to another embodiment of the present invention.

Fig. 16 is a timing diagram of some signals in the embodiment shown in Fig. 15 according to an embodiment of the present invention.

Fig. 17 is a schematic diagram showing a detailed implementation of the XO shown in Fig. 2 according to another embodiment of the present invention.

Figure 18 shows some details related to controlling the injection frequency according to an embodiment of the present invention.

Figure 19 shows some details related to controlling the injection frequency according to another embodiment of the present invention.

Certain terms indicating specific components are used throughout the following description and request items. As those with ordinary knowledge in the field will understand, electronic device manufacturers can use different names to refer to components. This document does not intend to distinguish between components with different names but the same functions. In the following description and claims, the terms "including" and "including" are used in an open-ended manner, and therefore should be interpreted as meaning "including but not limited to...". Likewise, the term "coupled" is intended to mean an indirect or direct electrical connection. Therefore, if one device is coupled to another device, the connection may be through a direct electrical connection, or through an indirect electrical connection through the other device and connection.

FIG. 1 is a schematic diagram showing the concept of start (for example, fast start) of a crystal oscillator 10 (XO) injected by an external clock according to an embodiment of the present invention. For an oscillator with a high quality factor (which can be called a high-Q oscillator), the performance related to noise (such as phase noise) is better than an oscillator with a low quality factor (which can be called a low-Q oscillator) Many, but the startup time required for the high-Q oscillator may be much longer than the startup time required for the low-Q oscillator. Examples of high-Q oscillators may include, but are not limited to: Pierce XO and Colpitts XO. Examples of low-Q oscillators may include, but are not limited to: ring oscillators and resistor-capacitor (RC) oscillators. The quick start technique shown in Figure 1 can turn on the injection switch coupled between the low-Q oscillator and the high-Q oscillator during the _{period T INJ} , and inject the energy _{of the injection signal V INJ of the low-Q oscillator into} A high-Q oscillator (for example, includes an active device 11 (which has transconductance Gm and a load capacitor C _L ), capacitors C _m and C _o , resistor R _m and inductance L _m ), so that _{The energy of the intrinsic oscillation signal (for example, V m, ss} and _{Im, ss} ) of the high-Q oscillator's intrinsic oscillation signal (for example, V m, ss and Im, ss) is increased during the startup of the XO to accelerate the startup of the XO and allow the XO to output the intrinsic oscillation signal.

In fact, at the beginning of the start-up process, the injection frequency of the low-Q oscillator is usually different from the intrinsic frequency of the high-Q oscillator, such as ±6000 ppm (parts per million), so there is a difference between the injection signal and the intrinsic oscillation signal. The phase error may gradually accumulate. In some embodiments, the quick start technique shown in Figure 1 can also utilize a feedback control mechanism that detects the natural frequency and modifies the low-Q oscillator accordingly to make the injection frequency close to the natural frequency. In detail, the injection switch can be turned on during the first injection period, and the energy of the natural oscillation signal can be increased, wherein, since the natural oscillation signal is not strong enough at the beginning, the injection signal can dominate the low-Q oscillator and the high-Q oscillator. The overall waveform on the connection node (for example, the combination of the injected signal and the natural oscillation signal). In order to detect the intrinsic frequency, the injection switch is then turned off during the lock/synchronization period after the first injection period to allow detection of the intrinsic frequency to control the low-Q oscillator. After the injection frequency approaches the natural frequency, the injection switch is turned on again during the second injection period after the lock/synchronization period, and the clock injection continues.

Figure 2 is a schematic diagram showing an XO 20 according to an embodiment of the present invention. As shown in Figure 2, the XO 20 may include an XO core circuit 100, an external oscillator 200 of the XO core circuit 100 (in particular, the external oscillator 200 is located outside the XO core circuit 100), and at least one injection switch (such as one or Multiple, collectively referred to as _{the injection switch controlled by the signal INJ EN} ) and the frequency controller 300, where the injection switch is coupled between the injection node N _INJ of the XO 20 and the output terminal N _{OUT of the} XO core circuit, and the external oscillator It is coupled to the injection node N _INJ , and the frequency controller 300 is coupled to the external oscillator 200. In this embodiment, the quality factor of the external oscillator 200 is lower than the quality factor of the XO core circuit 100. Among them, the XO core circuit 100 may be an example of a high-Q oscillator, and the external oscillator 200 may be an example of a low-Q oscillator. Fig. 3 is a flowchart showing a method for quickly starting the XO 20 shown in Fig. 2 by means of external clock injection according to an embodiment of the present invention. It should be noted that the workflow shown in Figure 3 is for illustrative purposes only, and is not a limitation of the present invention. In the workflow shown in Figure 3, one or more steps can be added, deleted or modified. In addition, if the same results can be obtained, it is not necessary to perform these steps in the exact order shown in Figure 3. For a better understanding, please refer to Figure 3 in conjunction with Figure 2.

In step S310, the external oscillator 200 may generate an injection signal (for example, a low-Q signal) in the external oscillator 200. In this embodiment, the operating frequency of the frequency controller 300 is controlled by an external oscillator (for example, the operating frequency of the frequency controller 300 may be equal to the injection frequency of the injection signal), but the present invention is not limited thereto.

In step S320, the system including the XO 20 (for example, the duty cycle wireless/wired system) may use the signal INJ _{EN to} turn on the injection switch, so that the energy of the injected signal is injected into the XO core circuit 100, thereby starting the XO 20 In the process, the energy of the natural oscillation signal of the XO core circuit 100 (for example, the energy of the resonator Im(t)) is increased. When the injection switch is turned on, the output terminal N _{OUT is} coupled to the injection node N _INJ , the injection signal and the natural oscillation signal are both present at the injection node N _INJ , and according to the combination of the injection signal and the natural oscillation signal at the injection node N _INJ Amplitude modulation (AM) signal is generated on it. For example, the injection signal (for example, the output square wave) can be modulated by the natural oscillation signal to generate an AM signal, as shown in _{the waveform of the signal V GATE} (t) shown in FIG. 4.

In step S330, the frequency controller 300 may receive the AM signal and _{control the external oscillator 200 according to the AM signal such as the waveform of the signal V GATE} (t) to selectively change the injection frequency of the injection signal. More specifically, during the startup process, when the external oscillator selectively changes the injection frequency of the injection signal, the injection switch is always turned on (for example, not turned off) or at least turned on for a period of time.

It should be noted that the different relative phase (for example, phase error) between the injected signal and the natural oscillation signal may result _{in different waveform patterns of the signal V GATE} (t) shown in Figure 4, which also shows the XO core circuit 100 The energy of the internal resonator I _m (t). For example, when the injection frequency (for example, F _INJ ) is not equal to the natural frequency (for example, F _XO ), the phase error may accumulate over time, and beating behavior may occur. The envelope period T _envelope of the beating behavior can be calculated as follows :

Δf can represent the frequency difference between the injection frequency and the natural frequency. In this embodiment, _{the waveform of the signal V GATE} (t) can be considered to be that the square wave from the external oscillator 200 is _{distorted by the natural oscillation signal (which can be represented by I m} (t)) from the XO core circuit 100, and is different The distortion (for example, the jittery envelope) may correspond to different relative phases between the injected signal and the natural oscillation signal. Therefore, information about the relative phase between the injected signal and the natural oscillation signal is carried by the AM signal _{such as the signal V GATE (t).}

Figure 5 shows the relationship between the growth rate of the natural oscillation signal and the relative phase according to an embodiment of the present invention. As shown in Figure 5, when the relative phase falls in the interval between +90 degrees and -90 degrees, the growth rate of the natural oscillation signal may be positive in response to the external clock injection. When the relative phase falls outside this interval (for example, relative phase>+90° or relative phase<-90°), the growth rate may be negative in response to external clock injection, which means that when the relative phase falls at +90 Outside the interval between ° and -90°, the low-Q oscillator will prevent the XO from starting.

Based on this, in the embodiment shown in FIG. 2, after the startup process of the XO 20 is enabled (for example, after the injection switch is turned on), the injection switch will not be turned off until the startup process is completed. Although the present invention does not interrupt the clock injection of the XO 20 during the required lock/synchronization period, the information related to the relative phase _{can be extracted from the signal V GATE according to the distortion to control the injection frequency.} In addition, the frequency controller 300 can use a control mechanism to ensure that the relative phase always falls within the interval between +90° and -90°, thereby preventing the injection signal from hindering the startup process. Therefore, the efficiency of clock injection is improved, and the startup time can be greatly reduced.

In an embodiment, the frequency controller 300 shown in Figure 2 may include a demodulation circuit, where the demodulation circuit may be configured to receive an AM signal and generate a demodulation voltage sequence based on the AM signal. FIG. 6 is a schematic diagram showing a detailed implementation manner of generating a demodulated voltage sequence by the demodulation circuit 310 according to an embodiment of the present invention, where the demodulation circuit 310 may be an example of the above-mentioned demodulation circuit. In this embodiment, the external oscillator 200 shown in FIG. 2 may include the low-Q oscillator 210 shown in FIG. 6 (for example, a ring oscillator or an RC oscillator) and at least one output buffer (for example, , One or more output buffers, which are collectively referred to as the output buffer 220), wherein the buffer 220 may be coupled between the low-Q oscillator 210 and the injection node N _INJ . In some embodiments, the buffer 220 may be omitted.

In this embodiment, the demodulation circuit 310 can be realized by using a diode with a sample and hold mechanism. As shown in Figure 6, _{the AM signal such as the signal V GATE} (t) is extracted from the AM signal related to the relative phase. Information (for example, the jitter envelope). In detail, the demodulation circuit 310 may include a diode D0, a switch controlled by the reset signal RST (RESET), controlled by the signal RSTB sampling switch and a sampling capacitor C _S, wherein the cathode of the diode D0 body (Cathode) It is coupled to the sampling node of the demodulation circuit 310. In the demodulation circuit 310, the reset switch is coupled between the sampling node and the reference terminal (for example, the ground voltage terminal) of the demodulation circuit 310, and the sampling switch is coupled between the anode of the diode D0 and the injection node N. between _{the INJ} (or in other embodiments, coupled between the anode and the XO diode D0 core circuit output terminal 100 of the N _OUT), and a sampling capacitor C _S is coupled between the sampling node and the reference terminal . For example, in the reset period of the demodulation circuit 310, when the reset switch is turned on and the sampling switch is turned off, the voltage level of the sampling node is reset to the reference The reference level of the terminal. When the reset switch is turned off and the sampling switch is turned on during the sampling period, in response to the voltage level of the AM signal exceeding the threshold corresponding to the diode D0, the charge is accumulated on the sampling node (for example, in response to the signal V _GATE ( The voltage level of t) makes the voltage difference between the cathode and anode of the diode D0 greater than the threshold voltage of the diode D0) to generate the demodulated voltage in the demodulated voltage sequence on the sampling node. The operation of the demodulation circuit 310 is similar to an integrator, so the information related to distortion can correspond to a demodulated voltage sequence, where the demodulated voltage sequence can be represented by the signal V _De-MOD . Note that each demodulated voltage in the demodulated voltage sequence is generated by the same diode (ie, the diode D0), and no mismatch problem is introduced in the demodulated voltage sequence.

Figure 7 shows some details of the relationship between relative phase and distortion (e.g., jitter envelope) according to an embodiment of the present invention. For a better understanding, it is assumed that the energy of a natural oscillation signal _{such as the signal V XO} (for example, the amplitude of the _{signal V XO) does not change.} The jitter envelope with different relative phase Ø can be calculated as follows:

A ₀,-2A ₀,-

A ₀和0，其中A₀可以代表信號V_XO的幅度。基於此，導致跳動包絡Env1(Ø)最小的相對相位Ø _min 可以是0°。因此，如第8圖所示，當相對相位Ø=Ø _min =0°時，諸如信號V_De-MOD的解調電壓序列可以具有最小電壓。 According to this equation, when Ø is -90°, -45°, 0°, +45° and 90°, respectively, the jitter envelope represented by Env1(Ø) can be 0,-

A ₀ ,-2 A ₀ ,-

A ₀ and 0, where A ₀ can represent the amplitude of the _{signal V XO. Based on this, the relative phase Ø min} that causes the minimum jitter envelope Env1(Ø) can be 0°. Therefore, as shown in Fig. 8, when the relative phase Ø=Ø _min =0°, the demodulated voltage sequence such as the signal V _De-MOD can have the minimum voltage.

In fact, as shown in Figure 9, the energy of a natural oscillation signal _{such as the signal V XO (for example, the amplitude of the signal V XO} ) may increase over time. The jitter envelope with different relative phase Ø can be modified as follows:

[A ₀+kØ],-2[A ₀+kØ],-

[A ₀+kØ]和0，其中k可以代表信號V_XO幅度的增長率。基於此，當相對相位Ø在正方向上累積時，當A₀和k為正值時，導致跳動包絡Env1(Ø)最小的相對相位Ø _min 可能落在0°至90°之間的間隔內。因此，如第10圖所示，當Ø=Ø _min 時，諸如信號V_De-MOD的解調電壓序列可以具有最小電 壓。類似地，當相對相位Ø在負方向上累積時，當A₀和k為正值時，導致跳動包絡Env1(Ø)最小的相對相位Ø _min 可能落在0°至-90°之間的間隔內。根據以上描述，可以知道，導致出現了解調電壓序列中的最小電壓(更具體地，局部最小電壓)出現的注入信號與固有振盪信號之間的相對相位，落入+90°和-90°之間的間隔。其中，局部最小電壓可以是在解調電壓序列中解調電壓降低的變化趨勢出現反轉時的電壓。 The jitter envelope with the increased amplitude of the signal V _{XO can be represented by Env1 (Ø).} According to this equation, when Ø is -90°, -45°, 0°, +45° and +90°, the jitter envelope Env1(Ø) can be 0,-

[ A ₀ + k Ø],-2[ A ₀ + k Ø],-

[ A ₀ + k Ø] and 0, where k can represent the growth rate of the _{signal V XO amplitude.} Based on this, when the relative phase Ø accumulates in the positive direction, when A _{0 and k are positive values, the relative phase Ø min} that causes the jitter envelope Env1 (Ø) to be the smallest may fall within the interval between 0° and 90°. Therefore, as shown in FIG. 10, when Ø = Ø _min, such as demodulation sequence voltage signal V _De-MOD may have a minimum voltage. Similarly, when the relative phase Ø accumulates in the negative direction, when A _{0 and k are positive values, the relative phase Ø min} that causes the jitter envelope Env1 (Ø) to be the smallest may fall in the interval between 0° and -90° Inside. According to the above description, it can be known that the relative phase between the injection signal and the natural oscillation signal that caused the minimum voltage (more specifically, the local minimum voltage) in the demodulated voltage sequence to appear falls between +90° and -90° The interval between. Wherein, the local minimum voltage may be the voltage when the change trend of the demodulation voltage decrease in the demodulation voltage sequence is reversed.

FIG. 11 is a schematic diagram showing a detailed implementation of the XO 20 according to an embodiment of the present invention. Note that the injection switch is turned on during the startup process, which is omitted in Figure 11 for brevity. In addition to the demodulation circuit 310 shown in FIG. 6, the frequency controller 300 shown in FIG. 3 may further include: a monitoring circuit 320 coupled to the demodulation circuit, and coupled to the monitoring circuit 320 and an external oscillator The finite state machine (FSM) 330 (FSM with counter) of the device 200 (for example, the low-Q oscillator 210). In this embodiment, the FSM 330 can use the injected signal as a counting clock (for example, CLK _counting ) for the FSM, but the present invention is not limited to this. In this embodiment, the monitoring circuit 320 may be configured to generate a monitoring result according to the demodulated voltage sequence, and the FSM 330 may be configured to control the external oscillator 200 (for example, the low-Q oscillator 210) _{through the signal V control,} In order to selectively change the injection frequency according to the monitoring result, to ensure that the relative phase falls within the interval between +90 degrees and -90 degrees. In the embodiment of FIG. 11, the monitoring circuit 320 may include an amplifier AMP _COMP , a capacitor C _COMP and a loop switch controlled by a signal LOOP _{EN , wherein the first input terminal of the amplifier AMP COMP} (in the amplifier shown in FIG. 11 AMP _COMP marked as "+") can be coupled to the demodulation circuit 310 (for example, the sampling node therein), and the capacitor C _COMP can be coupled to the reference terminal and _{the second input terminal of the amplifier AMP COMP} (shown in Figure 11). The output amplifier AMP _COMP is marked as "-"), and the loop switch can be coupled between the second input terminal and the output terminal _{of the amplifier AMP COMP.} In this embodiment, a _{D flip-flop (DFF) 322 controlled by the signal LOOP EN} may be included in the monitoring circuit 320, where the DFF is coupled between _{the output terminal of the amplifier AMP COMP} and the FSM 330, So that the FSM 330 only receives digital results, but the present invention is not limited to this.

In detail, the amplifier AMP _COMP may be configured to receive the demodulated voltage sequence through its first input terminal, the capacitor C _COMP may be configured to sequentially store the demodulated voltage sequence, and the loop switch may be configured to control the configuration of the monitoring circuit 320. For a better understanding, please refer to Figs. 12 and 13, where Fig. 12 shows the operation of the monitoring circuit 320 shown in Fig. 11 in the pre-setting stage. Figure 13 shows the operation of the monitoring circuit 320 shown in Figure 11 during the evaluation phase. During the preset phase of the monitoring circuit 320, the loop switch is turned on, and the monitoring circuit 320 is configured as a unity gain buffer to go from the first input terminal of the _{amplifier AMP COMP to the capacitor C COMP} (for example, the second _{input terminal of the amplifier AMP COMP).} The input terminal) transmits the first demodulated voltage in the demodulated voltage sequence. In the evaluation phase, the loop switch is turned off, and the monitoring circuit 320 is configured as a comparator to compare _{the second demodulated voltage on the first input terminal of the amplifier AMP COMP} with the first demodulated voltage stored on the capacitor (amplifier AMP _COMP On the second input terminal of) to compare and generate a comparison result, where the monitoring result includes the comparison result. By analogy, continuous comparison results of the demodulated voltage sequence can be generated, where these continuous comparison results can represent monitoring results.

Assuming that the comparison result of the monitoring circuit 320 is "0", it means that the previous demodulated voltage of the two consecutive demodulated voltages in the demodulated voltage sequence (for example, the aforementioned first demodulated voltage) is greater than the two consecutive demodulated voltages in the demodulated voltage sequence. The demodulated voltage after the demodulated voltage (for example, the above-mentioned second demodulated voltage), and the comparison result of the monitoring circuit 320 is "1", which indicates that the previous demodulated voltage of the two consecutive demodulated voltages is smaller than the subsequent demodulated voltage. Adjust the voltage. Therefore, when the comparison result changes from "0" to "1", it means that the local minimum of the demodulated voltage sequence is detected.

In fact, there may be _{an inherent offset V OS} caused by a mismatch between the first input terminal and the second input terminal of the _{amplifier AMP COMP} . Based on the operations shown in Figs. 12 and 13, the influence _{from the inherent offset V OS can be removed from the comparison result.} For example, when the first demodulated voltage (may be represented by "V [n]") is provided in the pre-stage of the transmission from the first input terminal of the amplifier AMP _COMP to a second input of the amplifier AMP _COMP, and the specific offset V _OS can be stored on the capacitor C _COMP together with the first voltage, so the capacitor C _COMP can store the voltage V[n]-V _OS ; in the evaluation phase, the second demodulated voltage (which can be represented by V[n+1]) can be It is present on the first end of the _{amplifier AMP COMP} together with the inherent offset V _OS. Since the first input terminal and the second input terminal of the amplifier AMP _COMP have inherent offsets at their respective ends, the comparison result (for example, AD _RESULT shown in Fig. 13) will not be affected by the inherent offset.

It should be noted that the monitoring circuit 320 is not limited to use in the XO 20 shown in FIG. 11. Any system that requires continuous comparison operations (for example, generating a comparison result about adjacent data (or voltage) in the data (or voltage) sequence) can be implemented by the monitoring circuit 320.

In another embodiment, the diode D0 in the demodulation circuit 310 can be replaced with a transistor M0 (for example, an N-type transistor) as shown in FIG. 14, wherein the gate terminal of the transistor M0 is coupled to the transistor The drain terminal of M0 enables the transistor to act as a diode, but the present invention is not limited to this. Note that the injection switch is turned on during startup and is omitted in Figure 11 for brevity.

In another embodiment, the monitoring circuit 320 can be replaced by a monitoring circuit 320A, as shown in XO 30 shown in Figure 15, where the monitoring circuit 320A can include a comparator COMP, a first sampling switch controlled by the signal SH, The second sampling switch controlled by the signal SHB, the first sampling capacitor C ₁ and the second sampling capacitor C ₂ . Note that the injection switch is turned on during the startup process and is omitted in Figure 11 for brevity. As shown in FIG. 15, a first sample switch and the first sampling capacitors C ₁ forming a first sample and hold circuit, the first sample and hold circuit coupled to the first input terminal of the comparator COMP (comparator COMP in the Marked as "+"), the second sampling switch and the second sampling capacitor C ₂ form a second sampling and holding circuit, which is coupled to the second input terminal of the comparator COMP (on the comparator COMP (Marked as "-"), where the signals VA and VB represent the voltages on the first input terminal and the second input terminal of the comparator COMP.

_{FIG. 16 is a timing diagram of some signals (for example, the counting clock CLK counting} , the signals RST, RSTB, SH, SHB, and the signals VA and VB) in the XO 20 shown in FIG. 15 according to an embodiment of the present invention. In this embodiment, the signals RST, RSTB, SH and SHB may be generated by a timing controller (not shown) according to the counting clock CLKcounting, but the present invention is not limited to this. According to the timing shown in Figure 16, the demodulated voltage of the demodulated voltage sequence can be sampled alternately/in turn on the sampling capacitors C1 and C2, and the corresponding monitoring result of the demodulated voltage sequence can be output from the comparator COMP. For example, the sampling capacitor C1 samples the first demodulation voltage, the sampling capacitor C2 samples the second demodulation voltage, the sampling capacitor C1 samples the third demodulation voltage, and the sampling capacitor C2 samples the fourth demodulation voltage.

In another embodiment, as shown by XO 40 in Figure 17, the monitoring circuit 320 can be replaced with an analog-to-digital converter (ADC) 320B. Please note that the injection switch is turned on during startup and is omitted in Figure 17 for the sake of brevity. For example, the ADC 320B can sequentially convert the demodulated voltage sequence into digital codes, where these digital codes can represent the aforementioned monitoring results, and the FSM 330 can control the low-Q oscillator 210 to selectively change the injection frequency according to these digital codes.

Figure 18 shows some details related to the control of the injection frequency according to an embodiment of the present invention. As shown in Figure 18, the FSM 330 can control the external oscillator (for example, the low-Q oscillator 210) to switch the injection frequency alternately/in turn to one or more target frequencies among the multiple candidate frequencies according to the monitoring result. The injection frequency is stepwise approached to the natural frequency of the natural oscillation signal, wherein multiple candidate frequencies respectively correspond to multiple states of the FSM 330. In this embodiment, it is assumed that the natural frequency (which can be regarded as the target frequency) is equal to the center frequency of the plurality of candidate frequencies (for example, has a frequency error of 0 ppm with respect to the center frequency). When the injection frequency is initially at the first frequency, the first frequency has a frequency error of -5000ppm relative to the center frequency of the multiple candidate frequencies, and the relative phase (for example, phase error) between the natural oscillation signal and the injection signal can start at In the positive direction, the energy of the natural oscillation signal is increasing, while the level of the demodulation voltage sequence (for example, the signal V _De-MOD ) is decreasing. Therefore, the comparison result of the monitoring circuit 320 remains "0" at the beginning. When the monitoring result indicates that the subsequent demodulated voltage at time point t1 is greater than the previous demodulated voltage (for example, the comparison result from the monitoring circuit 320 changes from "0" to "1"), it means that the demodulated voltage is detected The local minimum voltage of the sequence (for example, the signal V _De-MOD ), where the FSM 330 may determine that a candidate frequency less than the first frequency is not available, and control the external oscillator 200 (for example, a low-Q oscillator) to inject the frequency from the first frequency One frequency is switched to a second frequency, which has a frequency error of +5000 ppm relative to the center frequency, and then the comparison result returns to "0". Similarly, when the monitoring result indicates that the comparison result changes from "0" to "1" at time t2, the FSM 330 may determine that a candidate frequency greater than the second frequency is not available, and control the external oscillator 200 (for example, a low-Q oscillator ) Switch the injection frequency from the second frequency to the third frequency, which has a frequency error of -4000 ppm relative to the center frequency. By analogy, the injection frequency can be switched to the fourth frequency, the fifth frequency, the sixth frequency, and the seventh frequency at the time points t3, t4, t5, and t6, respectively. For the sake of brevity, similar descriptions are not repeated here. Accordingly, whenever the demodulated voltage in the demodulated voltage sequence reaches the minimum value, the injection frequency can be appropriately adjusted so that the relative phase can be accumulated in alternating directions, thereby ensuring that the relative phase is limited to within ±90°, (Usually in the range of ±40° or less), so the energy of the natural oscillation signal will always increase.

Figure 19 shows some details related to the control of the injection frequency according to another embodiment of the present invention. In this embodiment, it is assumed that the natural frequency (which can be regarded as the target frequency) has a frequency error of +4500 ppm with respect to the center frequency. As shown in Figure 19, the monitoring result indicates that the comparison result changes from "0" to "1" at time t7 (ie, the demodulated voltage V1 is less than the demodulated voltage V2), and the FSM 330 can determine that the third frequency is less than the third frequency (having The candidate frequency of -4000ppm frequency error) is not available, and the external oscillator 200 (for example, a low-Q oscillator) is controlled to switch the injection frequency from the third frequency to the fourth frequency with +4000ppm frequency error relative to the center frequency. However, because the demodulated voltage V3 is greater than the demodulated voltage V2, the comparison result remains "1" at the time point t8, which means that the switching from the third frequency to the fourth frequency cannot change the accumulation direction of the relative phase. Therefore, the FSM 330 can control the external oscillator 200 (for example, a low-Q oscillator) to further switch the injection frequency from the fourth frequency to the eighth frequency (with +4500ppm frequency error) greater than the fourth frequency (with +4000ppm frequency error) , To change the accumulation direction of the relative phase. Similarly, if after the injection frequency is switched from the ninth frequency to the tenth frequency which is less than the ninth frequency The comparison result remains at "1", the FSM 330 may control the external oscillator 200 (for example, a low-Q oscillator) to further switch the injection frequency from the tenth frequency to the eleventh frequency which is less than the tenth frequency.

In some embodiments, according to the monitoring result, the FSM 330 may control the external oscillator 200 (for example, the low-Q oscillator 210) to alternately switch the injection frequency to the first candidate frequency (for example, the first frequency has a frequency error of -5000ppm) Or the second candidate frequency (for example, the second frequency has a frequency error of +5000 ppm). Note that the first frequency is greater than the natural frequency of the natural oscillation signal, and the second frequency is less than the natural frequency. Therefore, each switch between the first candidate frequency and the second candidate frequency can indeed change the cumulative direction of the relative phase. Therefore, the relative phase can still be limited to within ±90°, and it can be ensured that the energy of the natural oscillation signal with only the two candidate frequencies is always increased during the start-up process.

In some embodiments, the injection switch may be turned on for a predetermined period of time. That is, the time point at which the injection switch is turned off (or the time at which the startup process is completed) can be predetermined. In other embodiments, the system including the XO 20 may monitor at least one signal in the XO 20 to trigger the system to complete the startup process (for example, turn off the injection switch) in response to the above-mentioned at least one signal satisfying a specific condition. In one embodiment, assuming that the initial demodulated voltage represents the first demodulated voltage of the demodulated voltage sequence at the beginning of the start-up process, when the target demodulated voltage of the demodulated voltage sequence is detected, the system can determine that the start-up process is complete , And the injection switch may be turned off, wherein the voltage difference between the target demodulated voltage and the initial demodulated voltage is greater than or equal to a predetermined value. Therefore, when the energy of the natural oscillation signal increases to a specific value that causes the target demodulation voltage to appear, it can be considered that the start-up process has been completed and the injection switch is turned off.

The startup method and the related XO architecture provided by the embodiments of the present invention can control the switching of the injection frequency according to the distorted square wave caused by the amplitude modulation of the injection signal and the natural oscillation signal, so that the relative phase between the injection signal and the natural oscillation signal can be controlled. Limit to the desired interval (e.g., ±90°). Based on this, there is no need to turn off the injection switch during the aforementioned lock/synchronization period, and it is further ensured that the energy of the natural oscillation signal is always increased. Assume that when the injection frequency of the injected signal and the natural frequency of the XO core circuit When the rate is the same, the startup process requires a reference time period. Regarding the method of temporarily interrupting the clock injection in the previous lock/synchronization period, 17.4 times to 90.6 times of the reference time period may be required for the startup process. Regarding the startup method of disconnecting injection until the startup process is completed, a reference time period of 1.05 to 1.5 times may be required, which means that the present invention does greatly improve the clock injection efficiency, and the startup time can be greatly reduced.

Those with ordinary knowledge in the field will easily observe that while maintaining the teachings of the present invention, various modifications and changes can be made to the device and method. Therefore, the above disclosure should be interpreted as being limited only by the bounds of the appended claims.

The foregoing descriptions are only preferred embodiments of the present invention, and all equivalent changes and modifications made in accordance with the scope of the patent application of the present invention shall fall within the scope of the present invention.

S310, S320, S330: steps

Claims (20)

A method for starting a crystal oscillator (XO) by means of an external clock injection, the method comprising: generating an injection signal using an external oscillator outside the crystal oscillator core circuit of the crystal oscillator, wherein the crystal oscillator includes The crystal oscillator core circuit, the external oscillator located outside the crystal oscillator core circuit, and at least one injection switch, the at least one injection switch is coupled to the injection node of the crystal oscillator and the crystal oscillator Between the output terminals of the crystal oscillator core circuit, the external oscillator is coupled to the injection node, and the quality factor of the external oscillator is lower than the quality factor of the crystal oscillator core circuit; The injection switch causes the energy of the injection signal to be injected into the crystal oscillator core circuit, thereby increasing the energy of the natural oscillation signal of the crystal oscillator core circuit, wherein, according to the injection signal and the natural oscillation signal The combination of generating a modulation signal on the injection node; and controlling the external oscillator according to the modulation signal to selectively change the injection frequency of the injection signal; wherein, when the external oscillator selectively changes the injection frequency When the injection frequency of the injection signal is described, the at least one injection switch is turned on. The method according to claim 1, wherein the step of controlling the external oscillator according to the modulation signal to selectively change the injection frequency of the injection signal includes: using the demodulation circuit of the crystal oscillator according to the The modulation signal generates a demodulation voltage sequence, and the demodulation voltage sequence carries information about the relative phase between the injection signal and the natural oscillation signal; using the monitoring circuit of the crystal oscillator, according to the demodulation voltage Sequence to generate monitoring results; and The external oscillator is controlled to selectively change the injection frequency according to the monitoring result. The method according to claim 2, wherein the step of controlling the external oscillator to selectively change the injection frequency according to the monitoring result comprises: alternately switching the injection frequency to the first according to the monitoring result Frequency or second frequency such that the relative phase falls within the interval between +90 degrees and -90 degrees, wherein the first frequency is greater than the natural frequency of the natural oscillation signal, and the second frequency Or, alternately switch the injection frequency to a frequency in a first group of frequencies or a frequency in a second group of frequencies according to the monitoring result, wherein the first group of frequencies are greater than the natural frequency The natural frequency of the oscillating signal, and the second set of frequencies are less than the natural frequency. The method according to claim 2, wherein the step of controlling the external oscillator to selectively change the injection frequency according to the monitoring result comprises: switching the injection frequency among a plurality of candidate frequencies according to the monitoring result Frequency such that the injection frequency is close to the natural frequency of the natural oscillation signal, wherein the multiple candidate frequencies respectively correspond to multiple states of a finite state machine (FSM). The method according to claim 2, wherein the demodulated voltage sequence includes a first demodulated voltage and a second demodulated voltage following the first demodulated voltage, and the external oscillation is controlled according to the monitoring result The step of the device selectively changing the injection frequency includes: in response to the monitoring result indicating that the second demodulation voltage is greater than the first demodulation voltage, switching the injection frequency from the first frequency to the second frequency . The method according to claim 5, wherein the demodulated voltage sequence further includes a third demodulated voltage following the second demodulated voltage, and the external oscillator is controlled to selectively change according to the monitoring result The step of injecting frequency further includes: in response to the monitoring result indicating that the third demodulation voltage is greater than the second demodulation voltage, The injection frequency is switched from the second frequency to the third frequency; wherein, the first frequency is greater than the second frequency, and the second frequency is greater than the third frequency; or, the first frequency Less than the second frequency, and the second frequency is less than the third frequency. The method according to claim 2, wherein the demodulated voltage sequence includes a first demodulated voltage and a second demodulated voltage following the first demodulated voltage, the monitoring circuit includes an amplifier and a capacitor, and uses The step of the monitoring circuit generating a monitoring result according to the demodulated voltage sequence includes: configuring the monitoring circuit to unity gain by turning on a loop switch coupled between the second input terminal and the output terminal of the amplifier A buffer to transmit the first demodulated voltage from the first input terminal of the amplifier to a capacitor coupled with the second input terminal of the amplifier; and configure the monitoring circuit as a comparator to pass Turn off the loop switch to compare the second demodulated voltage on the first input terminal of the amplifier with the first demodulated voltage stored on the capacitor, and generate a comparison result accordingly, wherein, The monitoring result includes: the comparison result. The method according to claim 2, wherein the step of using the demodulation circuit to generate the demodulation voltage sequence according to the modulation signal includes: turning on a reset switch of the demodulation circuit and turning off the demodulation circuit The sampling switch of the modulation circuit to reset the voltage level of the sampling node of the demodulation circuit to the reference level during the reset period; and during the sampling period, the voltage level in response to the modulation signal exceeds and The threshold corresponding to the diode of the demodulation circuit, turn off the reset switch and turn on the sampling switch to accumulate charge on the sampling node to generate the solution on the sampling node Modulate the demodulated voltage of the voltage sequence. The method according to claim 2, wherein the initial demodulated voltage represents the first demodulated voltage in the demodulated voltage sequence, and the method further includes: responding to detecting the target demodulated voltage in the demodulated voltage sequence To indicate that the startup process is completed, at least one injection switch is turned off, wherein the voltage difference between the target demodulated voltage and the initial demodulated voltage is greater than or equal to a predetermined value. A crystal oscillator (XO) includes: a crystal oscillator core circuit for generating a natural oscillation signal; an external oscillator, coupled to an injection node of the crystal oscillator, for generating an injection signal, wherein the external oscillator The quality factor of the oscillator is lower than the quality factor of the crystal oscillator core circuit; at least one injection switch is coupled between the injection node and the output terminal of the crystal oscillator core circuit, wherein when at least one injection When the switch is turned on, the energy of the injection signal is injected into the crystal oscillator core circuit to increase the energy of the natural oscillation signal, and modulation is generated on the injection node according to the combination of the injection signal and the natural oscillation signal Signal; and a frequency controller, coupled to the external oscillator, for controlling the external oscillator to selectively change the injection frequency of the injection signal according to the modulation signal; wherein, when the external oscillator is selected When the injection frequency of the injection signal is changed sexually, the at least one injection switch is turned on. The crystal oscillator according to claim 10, wherein the frequency controller includes a demodulation circuit for receiving a modulation signal and generating a demodulation voltage sequence according to the modulation signal, and the demodulation voltage sequence carries Information about the relative phase between the injection signal and the natural oscillation signal; a monitoring circuit, coupled to the demodulation circuit, for generating a monitoring junction according to the demodulation voltage sequence And a finite state machine (FSM), coupled to the monitoring circuit and the external oscillator, configured to control the external oscillator to selectively change the injection frequency according to the monitoring result. The crystal oscillator according to claim 11, wherein the finite state machine controls the external oscillator to alternately switch the injection frequency to the first frequency or the second frequency according to the monitoring result, so that the The relative phase falls within the interval between +90 degrees and -90 degrees, wherein the first frequency is greater than the natural frequency of the natural oscillation signal, and the second frequency is less than the natural frequency. The crystal oscillator according to claim 11, wherein the finite state machine controls the external oscillator to switch the injection frequency among a plurality of candidate frequencies according to the monitoring result, so that the injection frequency is close to the injection frequency. The natural frequency of the natural oscillation signal, wherein the multiple candidate frequencies respectively correspond to multiple states of the finite state machine. The crystal oscillator according to claim 11, wherein the demodulated voltage sequence includes a first demodulated voltage and a second demodulated voltage following the first demodulated voltage; and when the monitoring result indicates the When the second demodulation voltage is greater than the first demodulation voltage, the finite state machine controls the external oscillator to switch the injection frequency from the first frequency to the second frequency. The crystal oscillator according to claim 14, wherein the demodulated voltage sequence further includes a third demodulated voltage following the second demodulated voltage, and when the monitoring result indicates that the third demodulated voltage is greater than the second demodulated voltage When the voltage is applied, the finite state machine controls the external oscillator to switch the injection frequency from the second frequency to the third frequency, wherein the first frequency is greater than the second frequency, and the second frequency is greater than the third frequency Or, the first frequency is less than the second frequency, and the second frequency is less than the third frequency. The crystal oscillator according to claim 11, wherein the demodulated voltage sequence includes a first demodulated voltage and a second demodulated voltage following the first demodulated voltage, and the monitoring circuit includes: an amplifier, a coupling Connected to the demodulation circuit for receiving the The demodulated voltage sequence; a capacitor, coupled to the second input terminal of the amplifier, for sequentially storing the demodulated voltage sequence; and a loop switch, coupled to the second input terminal and output of the amplifier Between terminals to control the configuration of the monitoring circuit; wherein, when the loop switch is turned on, the monitoring circuit is configured as a unity gain buffer to transfer the first demodulated voltage from the amplifier The first input terminal of the amplifier is transmitted to the capacitor; and when the loop switch is turned off, the monitoring circuit is configured as a comparator for comparing the second demodulated voltage on the first input terminal of the amplifier with The first demodulated voltage stored on the capacitor is compared, and a comparison result is generated, wherein the monitoring result includes the comparison result. The crystal oscillator according to claim 11, wherein the demodulation circuit includes: a diode, the cathode of which is coupled to the sampling node of the demodulation circuit; a reset switch, which is coupled to the sampling node of the demodulation circuit; Between the sampling node and the reference terminal of the demodulation circuit; a sampling switch, which is coupled to the anode of the diode; and a sampling capacitor, which is coupled to the sampling node; wherein, when the reset period is in the reset period, the re When the reset switch is turned on and the sampling switch is turned off, the voltage level of the sampling node is reset to the reference level of the reference terminal; and when the reset switch is turned off and the sampling switch is turned off during the sampling period When turned on, in response to the voltage level of the modulation signal exceeding the threshold corresponding to the diode, charge is accumulated on the sampling node, and the demodulation of the demodulation voltage sequence is generated on the sampling node Voltage. The crystal oscillator according to claim 11, wherein the initial demodulated voltage represents the first demodulated voltage in the demodulated voltage sequence; when the target demodulated voltage in the demodulated voltage sequence is detected to indicate the start When the process is completed, the at least one injection switch is turned off, wherein the target solution The voltage difference between the modulation voltage and the initial demodulation voltage is greater than or equal to a predetermined value. A monitoring circuit for generating a continuous comparison result of a demodulated voltage sequence, the demodulated voltage sequence carrying information about the relative phase between an injection signal and a natural oscillation signal of a crystal oscillator, the monitoring circuit comprising: an amplifier, The demodulated voltage sequence is received through the first input terminal of the amplifier, wherein the demodulated voltage sequence includes a first voltage and a second voltage following the first voltage; a capacitor is coupled to the amplifier The second input terminal of the amplifier is used to sequentially store the demodulated voltage sequence; and a loop switch, coupled between the second input terminal and the output terminal of the amplifier, is used to control the configuration of the monitoring circuit; wherein When the loop switch is turned on, the monitoring circuit is configured as a unity gain buffer for transmitting the first voltage from the first input terminal of the amplifier to the capacitor; when the loop switch When disconnected, the monitoring circuit is configured as a comparator for comparing the second voltage on the first input terminal of the amplifier with the first voltage stored on the capacitor, and generating the continuous comparison result Wherein, the comparison result carries information about the relative phase between the injection signal and the natural oscillation signal of the crystal oscillator, and is used to control the injection frequency of the injection signal. The monitoring circuit according to claim 19, wherein when the loop switch is turned on, the inherent offset caused by the mismatch between the first input terminal and the second input terminal of the amplifier is stored together with the first voltage On the capacitor, thereby preventing the comparison result from being affected by the inherent offset.

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