Numerical control oscillator calibration system

Abstract

The embodiment of the invention discloses a numerical control oscillator calibration system. The system comprises a signal detection assembly, a phase discriminator, a numerically-controlled oscillator gain module, a digital filter and a numerically-controlled oscillator, the numerically-controlled oscillator is connected with the signal detection assembly, the signal detection assembly is connected with the phase discriminator, the phase discriminator is connected with the numerically-controlled oscillator gain module, the numerically-controlled oscillator gain module is connected with the digital filter, and the digital filter is connected with the numerically-controlled oscillator. The digital filter is connected with the numerically-controlled oscillator. According to the embodiment of the invention, the initial control word is not directly adjusted, and the tuning control word is additionally generated for adjustment, so that the adjustment process is not influenced by the size of the initial control word, adjustment can be carried out with a smaller code value, and the calibration precision is improved.

Description

Technical Field

[0001] One or more embodiments of the present specification relate to semiconductor design technology, and more particularly, to a digitally controlled oscillator calibration system. Background Art

[0002] When the All Digital Phase-Locked Loop (ADPLL) is working, the accuracy of the clock depends on the accuracy of the Digital-Controlled Oscillator (DCO). However, in the actual working process, as the temperature, voltage, manufacturing process, etc. change, the output accuracy of the DCO will be affected, resulting in deviations in the accuracy of the clock. The existing technology generally reduces the deviation by directly adjusting and controlling the initial control word of the system. However, in order to ensure the normal operation and stability of the system, the initial control word is relatively large, so that the code value of each change based on the adjustment of the initial control word is also large, and the calibration accuracy is not high. Summary of the invention

[0003] In order to solve the above problems, one or more embodiments of this specification describe a digitally controlled oscillator calibration system.

[0004] According to a first aspect, a digitally controlled oscillator calibration system is provided, the system comprising a signal detection component, a phase detector, a digitally controlled oscillator gain module, a digital filter and a digitally controlled oscillator, the digitally controlled oscillator being connected to the signal detection component, the signal detection component being connected to the phase detector, the phase detector being connected to the digitally controlled oscillator gain module, the digitally controlled oscillator gain module being connected to the digital filter, and the digital filter being connected to the digitally controlled oscillator; The digital controlled oscillator is used to generate an output clock signal under the action of the initial control word, and send the output clock signal to the signal detection component; The signal detection component is used to receive the output clock signal and the reference clock signal and determine the fractional phase of the digitally controlled oscillator; The phase detector is used to determine the total phase error of the digital controlled oscillator based on the output clock signal, the reference clock signal and the fractional phase; The digital controlled oscillator gain module is used to determine the digital controlled oscillator gain according to the total phase error, and send the digital controlled oscillator gain to the digital filter; The digital filter is used to generate a tuning control word according to the gain of the digitally controlled oscillator, and send the tuning control word to the digitally controlled oscillator, so that the digitally controlled oscillator generates a new output clock signal based on the tuning control word and the initial control word.

[0005] Preferably, the signal detection component comprises a reference phase accumulator, a time-to-digital converter and a variable phase accumulator; The reference phase accumulator is used to accumulate the frequency control word; The variable phase accumulator is used to count the number of output clock cycles; The time-to-digital converter is used to determine a fractional phase between a reference clock signal and an output clock signal.

[0006] Preferably, the phase detector is used to determine the integer phase based on the reference clock signal transmitted by the reference phase accumulator and the output clock signal transmitted by the variable phase accumulator, and determine the total phase error based on the sum of the integer phase and the fractional phase.

[0007] Preferably, the initial control word is a physical control word, and the system further comprises an independent control module connected to the digitally controlled oscillator and used to generate the initial controller.

[0008] Preferably, the independent control module is arranged outside the phase-locked loop formed by the signal detection component, the phase detector, the digitally controlled oscillator gain module, the digital filter and the digitally controlled oscillator.

[0009] Preferably, at least two different physical control words are stored in the independent control module, and the independent control module is used to select the initial control word from each of the physical control words according to a system control instruction.

[0010] Preferably, the system further comprises a digitally controlled oscillator gain calibration module, wherein the digitally controlled oscillator gain calibration module is respectively connected to the phase detector and the digitally controlled oscillator gain module; The numerically controlled oscillator gain calibration module is used to determine two test gains that best match the total phase error according to a lookup table method, adjust the numerically controlled oscillator according to the test gains respectively to obtain a test clock signal, and select a target gain from the test gains according to the phase difference between the two test clock signals, and adjust the numerically controlled oscillator gain to the target gain.

[0011] Preferably, the digitally controlled oscillator gain calibration module is used to select a target gain from the test gains according to a phase difference between the two test clock signals within a preset time length.

[0012] Preferably, the target gain is the test gain with a small gain when the phase difference is greater than a preset difference, and the target gain is the test gain with a large gain when the phase difference is not greater than the preset difference.

[0013] The system provided by the embodiment of this specification can determine the gain of the digital controlled oscillator according to the digital controlled oscillator gain module after the phase detector determines the total phase error, and then the digital filter generates a corresponding tuning control word and sends it to the digital controlled oscillator, so that the digital controlled oscillator adjusts the output clock signal according to the tuning control word and the initial control word. In the above process, the initial control word is not directly adjusted, but an additional tuning control word is generated for adjustment, so that the adjustment process is not affected by the size of the initial control word, and can be adjusted with a smaller code value, thereby improving the calibration accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0015] Figure 1 It is a structural schematic diagram of a digital controlled oscillator calibration system in one embodiment of the present specification.

[0016] Figure 2 It is a schematic diagram of phase comparison of test gain within a preset time length in one embodiment of this specification. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application.

[0018] In the following introduction, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance. The following introduction provides multiple embodiments of the present application, and different embodiments can be replaced or combined, so the present application can also be considered to include all possible combinations of the same and / or different embodiments recorded. Therefore, if one embodiment includes features A, B, and C, and another embodiment includes features B and D, then the present application should also be considered to include embodiments containing one or more of all other possible combinations of A, B, C, and D, although the embodiment may not be clearly recorded in the following text.

[0019] The following description provides examples and does not limit the scope, applicability or examples set forth in the claims. Changes may be made to the functions and arrangements of the elements described without departing from the scope of the present application. Various processes or components may be appropriately omitted, substituted or added to each example. For example, the described method may be performed in an order different from the order described, and various steps may be added, omitted or combined. In addition, features described in some examples may be combined in other examples.

[0020] See also Figure 1 , Figure 1 1 is a schematic diagram of the system structure of a digitally controlled oscillator calibration system provided in an embodiment of the present application. In an embodiment of the present application, the system includes a signal detection component, a phase detector, a digitally controlled oscillator gain module, a digital filter and a digitally controlled oscillator, the digitally controlled oscillator is connected to the signal detection component, the signal detection component is connected to the phase detector, the phase detector is connected to the digitally controlled oscillator gain module, the digitally controlled oscillator gain module is connected to the digital filter, and the digital filter is connected to the digitally controlled oscillator; The digital controlled oscillator is used to generate an output clock signal under the action of the initial control word, and send the output clock signal to the signal detection component; The signal detection component is used to receive the output clock signal and the reference clock signal and determine the fractional phase of the digitally controlled oscillator; The phase detector is used to determine the total phase error of the digital controlled oscillator based on the output clock signal, the reference clock signal and the fractional phase; The digital controlled oscillator gain module is used to determine the digital controlled oscillator gain according to the total phase error, and send the digital controlled oscillator gain to the digital filter; The digital filter is used to generate a tuning control word according to the gain of the digitally controlled oscillator, and send the tuning control word to the digitally controlled oscillator, so that the digitally controlled oscillator generates a new output clock signal based on the tuning control word and the initial control word.

[0021] In the embodiment of the present specification, the signal detection component, the phase detector, the digitally controlled oscillator gain module, the digital filter and the digitally controlled oscillator are connected in sequence to form a phase-locked loop. The frequency control word (Frequency Command Word, fcw) will be set in the system to determine the expected frequency of the digitally controlled oscillator DCO output. Assuming that the reference clock signal is 25M and the DCO outputs 2.5G, the frequency control word is equal to 2.5G / 25M=100. In addition, there is an initial control word pbank in the system, which is used to set the corresponding initial value for the digitally controlled oscillator, reduce the initial phase error, and speed up the locking speed. When the system starts working, fcw and pbank are assigned pre-set default values. After the default values ​​are given, the digitally controlled oscillator DCO will oscillate. The output clock signal ckv will pass through the signal detection component to detect the real-time phase corresponding to the output clock signal. At the same time, the reference clock signal refclk and the frequency control word fcw will also pass through the signal detection component to detect the corresponding reference phase. The detected phase data will be input into the phase detector PD to calculate the total phase error between the actual output clock signal and the reference clock signal. Then, the phase detector PD will send the total phase error to the digital control oscillator gain module, which is configured with different mapping relationships between phase differences and gains. Through this mapping relationship, the digital control oscillator gain corresponding to the total phase error can be quickly determined. After the digital control oscillator gain is input into the digital filter (Digital Loop Filter, DLF), it will be smoothed and filtered to further reduce the error. Since the gain is the ratio of the output frequency change to the input control word change, the control word change that needs to be adjusted can be determined according to the specific value of the digital control oscillator gain, and then the corresponding tuning control word abank is generated with this change and input into the digital control oscillator. The tuning control word only indicates the control word corresponding to the part that needs to be adjusted, so the digital control oscillator will still combine the initial control word and the tuning control word, and use the combined control word to perform oscillation control to output a new output clock signal to adjust the DCO output accuracy.

[0022] In one possible implementation, the signal detection component includes a reference phase accumulator, a time-to-digital converter, and a variable phase accumulator; The reference phase accumulator is used to accumulate the frequency control word; The variable phase accumulator is used to count the number of output clock cycles; The time-to-digital converter is used to determine a fractional phase between a reference clock signal and an output clock signal.

[0023] In the embodiment of the present specification, the signal detection component is mainly composed of a reference phase accumulator RPA, a time digital converter TDC and a variable phase accumulator VPA. The reference phase accumulator accumulates the frequency control word to determine the reference clock signal according to the accumulation result, and the accumulated reference clock signal is generally an integer. The time digital converter simultaneously inputs the reference clock signal refclk and the output clock signal ckv to calculate the fractional phase difference between the reference clock signal and the output clock signal. The variable phase accumulator counts the number of output clock cycles to determine the output clock signal according to the counting result, and the counted output clock signal is generally an integer. In this way, the collection of integer signals of the reference clock signal and the output clock signal, as well as the calculation of the fractional phase of the reference clock signal and the output clock signal are realized through the above three components, and the phase detection result is more accurate.

[0024] In one possible implementation, the phase detector is used to determine an integer phase based on a reference clock signal transmitted by a reference phase accumulator and an output clock signal transmitted by a variable phase accumulator, and to determine a total phase error based on a sum of the integer phase and the fractional phase.

[0025] In the embodiment of the present specification, the reference clock signal transmitted by the reference phase accumulator and the output clock signal transmitted by the variable phase accumulator are integer signals, and the phase detector will use this to calculate the integer phase of the reference clock signal and the output clock signal, and combine it with the fractional phase obtained from the time-to-digital converter to determine the total phase error based on the sum of the integer phase and the fractional phase.

[0026] In one possible implementation, the initial control word is a physical control word, and the system further includes an independent control module connected to the digitally controlled oscillator and used to generate the initial controller.

[0027] In the embodiments of this specification, the initial control word is different from the tuning control word. It is a physical control word used to optimize the performance of the phase-locked loop and is generated by an independent control module specifically connected to the digitally controlled oscillator. The independent control module is responsible for generating or adjusting certain control signals, but does not directly participate in the phase detection and frequency adjustment of the loop.

[0028] In one possible implementation, the independent control module is arranged outside a phase-locked loop formed by the signal detection component, the phase detector, the digitally controlled oscillator gain module, the digital filter and the digitally controlled oscillator.

[0029] In the embodiments of this specification, the independent control module will be set outside the phase-locked loop of the system to separate the physical control word from the phase-locked loop, reduce the total delay of the loop, simplify the loop structure, and the physical control word can be optimized and adjusted separately, thereby accelerating the locking process of the phase-locked loop.

[0030] In one possible implementation, at least two different physical control words are stored in the independent control module, and the independent control module is used to select the initial control word from each of the physical control words according to a system control instruction.

[0031] In an embodiment of the present specification, a plurality of physical control words with different initial values ​​may be pre-stored in an independent control module. When the system is running, the system control instruction set by the user will be obtained to determine the approximate output clock range that the user wants the system to achieve, and then the physical control word that best matches the output clock range is selected from each physical control word as the initial control word, thereby improving the stability of the system and avoiding the need to significantly adjust the output clock by tuning the control word.

[0032] In one possible implementation, the system further comprises a digitally controlled oscillator gain calibration module, wherein the digitally controlled oscillator gain calibration module is respectively connected to the phase detector and the digitally controlled oscillator gain module; The numerically controlled oscillator gain calibration module is used to determine two test gains that best match the total phase error according to a lookup table method, adjust the numerically controlled oscillator according to the test gains respectively to obtain a test clock signal, and select a target gain from the test gains according to the phase difference between the two test clock signals, and adjust the numerically controlled oscillator gain to the target gain.

[0033] In the embodiment of the present specification, considering that it is difficult to adjust the loop completely and accurately in one adjustment process in actual conditions, and the total phase error has a decimal value, if a tuning control word is set for each total phase error in consideration of the decimal, too many tuning control words need to be pre-set, and the overly subdivided tuning control words cannot significantly improve the accuracy of the adjustment. Therefore, in order to improve the processing efficiency, a certain number of tuning control words abank can be pre-set in the numerically controlled oscillator gain calibration module, each tuning control word corresponds to a gain, that is, a test gain, and a corresponding mapping table of control words and gains is constructed. The numerically controlled oscillator gain calibration module will query the mapping table through a lookup table method to determine the two test gains that best match the error gain corresponding to the total phase error. Then, the numerically controlled oscillator will be adjusted according to the test tuning control words corresponding to the two test gains, so as to detect the phase of the output clock signal after adjustment, and then calculate the phase difference between the two phase results. If the phase difference is large, it means that the numerically controlled oscillator is very sensitive to the change of the control word, and a smaller gain needs to be used to avoid over-adjustment and maintain the stability of the system. If the phase difference is small, it means that the CNC oscillator is not sensitive to the change of the control word, and using a larger gain can improve the response speed of the system. Therefore, the gain selection strategy will be determined according to the specific size of the phase difference, and then the target gain will be selected from the two test gains, and the CNC oscillator gain will be optimized and calibrated according to the target gain.

[0034] In one possible implementation, the digitally controlled oscillator gain calibration module is used to select a target gain from the test gains according to a phase difference between two test clock signals within a preset time length.

[0035] In the embodiments of this specification, Figure 2 As shown, assuming that the corresponding phase when the tuning control word is abank_a is phe_a, and the corresponding phase when the tuning control word is abank_b is phe_b, the phase diagrams of the two test clock signals will be obtained, and the phase difference between the two phase diagrams within a preset time length will be calculated, and then the gain selection strategy will be determined according to the size of the phase difference, and the target gain will be selected in the test gain.

[0036] In one possible implementation, the target gain is the test gain with a small gain when the phase difference is greater than a preset difference, and the target gain is the test gain with a large gain when the phase difference is not greater than the preset difference.

[0037] In the embodiment of the present specification, a preset difference value will be set. If the phase difference value is greater than the preset difference value, it is considered that the phase difference value is large, and the test gain with a smaller gain will be selected. If the phase difference value is not less than the preset difference value, it is considered that the phase difference value is small, and the test gain with a larger gain will be selected.

[0038] The above is only an exemplary embodiment of the present disclosure, and the scope of the present disclosure cannot be limited thereto. That is, any equivalent changes and modifications made according to the teachings of the present disclosure are still within the scope of the present disclosure. After considering the specification and practicing the disclosure here, those skilled in the art will easily think of the implementation scheme of the present disclosure. This application is intended to cover any modification, use or adaptation of the present disclosure, which follows the general principles of the present disclosure and includes common knowledge or customary technical means in the technical field not recorded in the present disclosure. The description and examples are regarded as exemplary only, and the scope and spirit of the present disclosure are defined by the claims.

Claims

1. A numerically controlled oscillator calibration system, characterized in that: The system comprises a signal detection component, a phase detector, a digitally controlled oscillator gain module, a digital filter and a digitally controlled oscillator, wherein the digitally controlled oscillator is connected to the signal detection component, the signal detection component is connected to the phase detector, the phase detector is connected to the digitally controlled oscillator gain module, the digitally controlled oscillator gain module is connected to the digital filter, and the digital filter is connected to the digitally controlled oscillator; The digital controlled oscillator is used to generate an output clock signal under the action of the initial control word, and send the output clock signal to the signal detection component; The signal detection component is used to receive the output clock signal and the reference clock signal and determine the fractional phase of the digitally controlled oscillator; The phase detector is used to determine the total phase error of the digital controlled oscillator based on the output clock signal, the reference clock signal and the fractional phase; The digital controlled oscillator gain module is used to determine the digital controlled oscillator gain according to the total phase error, and send the digital controlled oscillator gain to the digital filter; The digital filter is used to generate a tuning control word according to the gain of the digital controlled oscillator, and send the tuning control word to the digital controlled oscillator, so that the digital controlled oscillator generates a new output clock signal based on the tuning control word and the initial control word.

2. The system according to claim 1, characterized in that The signal detection component includes a reference phase accumulator, a time-to-digital converter, and a variable phase accumulator; The reference phase accumulator is used to accumulate the frequency control word; The variable phase accumulator is used to count the number of output clock cycles; The time-to-digital converter is used to determine a fractional phase between a reference clock signal and an output clock signal.

3. The system according to claim 2, characterized in that The phase detector is used to determine the integer phase according to the reference clock signal transmitted by the reference phase accumulator and the output clock signal transmitted by the variable phase accumulator, and determine the total phase error according to the sum of the integer phase and the fractional phase.

4. The system according to claim 1, characterized in that The initial control word is a physical control word, and the system further comprises an independent control module connected to the digitally controlled oscillator and used for generating the initial controller.

5. The system according to claim 4, characterized in that The independent control module is arranged outside the phase-locked loop formed by the signal detection component, the phase detector, the digitally controlled oscillator gain module, the digital filter and the digitally controlled oscillator.

6. The system according to claim 4, characterized in that At least two different physical control words are stored in the independent control module, and the independent control module is used to select the initial control word from each of the physical control words according to a system control instruction.

7. The system according to claim 1, characterized in that The system further comprises a digitally controlled oscillator gain calibration module, wherein the digitally controlled oscillator gain calibration module is respectively connected to the phase detector and the digitally controlled oscillator gain module; The numerically controlled oscillator gain calibration module is used to determine two test gains that best match the total phase error according to a lookup table method, adjust the numerically controlled oscillator according to the test gains respectively to obtain a test clock signal, and select a target gain from the test gains according to the phase difference between the two test clock signals, and adjust the numerically controlled oscillator gain to the target gain.

8. The system according to claim 7, characterized in that The digital controlled oscillator gain calibration module is used to select a target gain from the test gains according to a phase difference between two test clock signals within a preset time length.

9. The system according to claim 7, characterized in that The target gain is the test gain with a small gain when the phase difference is greater than a preset difference, and the target gain is the test gain with a large gain when the phase difference is not greater than the preset difference.

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