CN116938233A - Clock center spread spectrum method and device of phase-locked loop - Google Patents
Clock center spread spectrum method and device of phase-locked loop Download PDFInfo
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION, OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L7/00—Automatic control of frequency or phase; Synchronisation
- H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
- H03L7/16—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop
- H03L7/18—Indirect frequency synthesis, i.e. generating a desired one of a number of predetermined frequencies using a frequency- or phase-locked loop using a frequency divider or counter in the loop
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION, OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L7/00—Automatic control of frequency or phase; Synchronisation
- H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
- H03L7/08—Details of the phase-locked loop
- H03L7/085—Details of the phase-locked loop concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION, OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L7/00—Automatic control of frequency or phase; Synchronisation
- H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
- H03L7/08—Details of the phase-locked loop
- H03L7/085—Details of the phase-locked loop concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal
- H03L7/093—Details of the phase-locked loop concerning mainly the frequency- or phase-detection arrangement including the filtering or amplification of its output signal using special filtering or amplification characteristics in the loop
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03L—AUTOMATIC CONTROL, STARTING, SYNCHRONISATION, OR STABILISATION OF GENERATORS OF ELECTRONIC OSCILLATIONS OR PULSES
- H03L7/00—Automatic control of frequency or phase; Synchronisation
- H03L7/06—Automatic control of frequency or phase; Synchronisation using a reference signal applied to a frequency- or phase-locked loop
- H03L7/08—Details of the phase-locked loop
- H03L7/099—Details of the phase-locked loop concerning mainly the controlled oscillator of the loop
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Abstract
The application relates to a clock center spread spectrum method and a device of a phase-locked loop, wherein the method comprises the following steps: the frequency divider of the triangular wave generator controls an input clock signal according to an output clock of a feedback frequency divider of the phase-locked loop and a first preset frequency dividing ratio, the triangular wave signal corresponding to the output of the triangular wave generating circuit is transmitted to the modulating signal module through the gating device, the output identification signal is input to the gating device, the modulating signal module samples and quantizes the triangular wave signal according to the output clock of the feedback frequency divider of the phase-locked loop and then outputs the triangular wave signal to the adder, the gating device inputs a fixed value of the identification signal gating to the adder, the adder outputs a signal representing an output signal value to the feedback frequency divider of the phase-locked loop according to the output of the modulating signal module and the fixed value of the identification signal gating, and the adder outputs the signal representing the output signal value to serve as the feedback frequency dividing ratio of the feedback frequency divider. To achieve a central spread of the output clock of the voltage controlled oscillator of the phase locked loop. The universality of the phase-locked loop is improved.
Description
Technical Field
The present application relates to the field of integrated circuits, and in particular, to a clock center frequency spreading method and apparatus for a phase locked loop.
Background
The energy of the signal is concentrated at the carrier frequency position, so that the energy of the signal generates larger radiation at a certain frequency point.
In order to reduce the effects of electromagnetic interference (Electromagnetic Interference, EMI) in a system, the chip is designed to add the function of a spread spectrum clock (Spread Spectrum Clocking, SSC) to signals that are prone to EMI emissions, thereby reducing electromagnetic interference. For such a frequency-varying spread spectrum clock, energy may be dispersed over a range of frequency spectrums.
The current clock frequency spreading mode mainly adopts a downward frequency spreading mode to spread the frequency of a frequency-spread clock of a phase-locked loop in the system, but the downward frequency spreading mode is adopted to enable the phase-locked loop to be suitable for an application system which is sensitive in frequency and has running at the maximum speed, so that the universality of the phase-locked loop is poor.
Disclosure of Invention
In view of the foregoing, it is desirable to provide a clock center spread spectrum method and apparatus for a phase locked loop that can improve the versatility of the phase locked loop.
A clock-centric spread spectrum method of a phase-locked loop, the method comprising:
the frequency divider of the triangular wave generator controls a clock input signal of a triangular wave generating circuit of the triangular wave generator according to an output clock of a feedback frequency divider of a received phase-locked loop and a first preset frequency dividing ratio;
The triangular wave generating circuit outputs corresponding triangular wave signals and identification signals according to the clock input signals, the preset step height, the preset step starting point value and the preset step number, wherein the preset step starting point value comprises a preset positive triangular wave step starting point value and a preset negative triangular wave step starting point value;
the triangular wave signal output by the triangular wave generating circuit is transmitted to a modulation signal module through a gating device, and the modulation signal module samples and quantizes the triangular wave signal according to the output clock of a feedback frequency divider of the phase-locked loop and then outputs the triangular wave signal to an adder;
the identification signal output by the triangular wave generating circuit is input to a gating device, and the gating device inputs a fixed value gated by the identification signal into the adder according to the input identification signal;
the adder determines an output signal value of the adder according to the output of the modulation signal module and the fixed value of the identification signal strobe;
the adder outputs a signal representing the output signal value to a feedback divider of the phase-locked loop as a feedback division ratio of the feedback divider of the phase-locked loop to achieve center spread of an output clock of a voltage-controlled oscillator of the phase-locked loop.
In one embodiment, the triangular wave generating circuit outputs a corresponding triangular wave signal and an identification signal according to the clock input signal, a preset step height, a preset step starting point value and a preset step number, and the method includes:
in the case of a regular triangle wave output mode, the triangle wave generating circuit outputs a high-level identification signal and outputs a regular triangle wave signal according to a preset step height, a preset regular triangle wave step starting point value and a preset step number;
in the case of the negative triangular wave output mode, the triangular wave generating circuit outputs a low-level identification signal and outputs a negative triangular wave signal according to a preset step height, a preset negative triangular wave step starting value and a preset step number.
In one embodiment, the outputting the regular triangle wave signal according to the preset step height, the preset regular triangle wave step starting point value and the preset step number includes:
when the clock input signal is triggered by the first rising edge in the regular triangle wave output mode, the triangle wave generating circuit takes a preset regular triangle wave step starting point value as a step value at the current moment, and increases a step according to a preset step height on the basis of the step value at the current moment to output a regular triangle wave signal;
After triggering a first rising edge in a regular triangle wave output mode and when the number of the steps does not reach the preset number of steps, the triangle wave generating circuit increases a step according to the preset step height on the basis of the step value at the current moment to output a regular triangle wave signal;
after the first rising edge in the regular triangle wave output mode is triggered and the preset step number is reached, the triangle wave generating circuit outputs a regular triangle wave signal according to a step in a descending mode according to the preset step height on the basis of the step value at the current moment.
In one embodiment, when the step value of the triangular wave generating circuit at the current moment is the last step of the preset positive triangular wave step starting point value, after the next clock rising edge arrives, the positive triangular wave output mode is converted into the negative triangular wave output mode, and the identification signal is converted into the low level.
In one embodiment, the outputting the negative triangular wave signal according to the preset step height, the preset negative triangular wave step starting point value and the preset step number includes:
when the clock input signal is triggered by the first rising edge in the negative triangular wave output mode, the triangular wave generating circuit takes the preset negative triangular wave step starting point value as the step value at the current moment, and on the basis of the step value at the current moment, the step is decreased by one step according to the preset step height to output the negative triangular wave signal;
After triggering a first rising edge in a negative triangular wave output mode and when the number of steps does not reach the preset number of steps, the triangular wave generating circuit outputs a negative triangular wave signal according to a step in a descending mode according to the preset step height on the basis of the step value at the current moment;
after the first rising edge in the negative triangular wave output mode is triggered and the preset step number is reached, the triangular wave generating circuit increases a step according to the preset step height to output a negative triangular wave signal on the basis of the step value at the current moment.
In one embodiment, when the step value of the triangular wave generating circuit at the current moment is the next step of the preset negative triangular wave step starting point value, after the next clock rising edge arrives, the negative triangular wave output mode is converted into the positive triangular wave output mode, and the identification signal is converted into the high level.
In one embodiment, the preset step height and the preset step number are determined according to a spread spectrum depth formula, where the spread spectrum depth formula is:
wherein A_step is the preset step number, A_deep is the preset step height, K is the bit number of the modulation signal module, N is the preset frequency division ratio of the feedback frequency divider, and epsilon is the spread spectrum depth.
In one embodiment, the adder determines an output signal value of the adder according to the output of the modulation signal module and the fixed value of the identification signal strobe, and the method includes:
when the identification signal is at a high level, the fixed value of the identification signal strobe is N, and the output signal value out of the adder is equivalent to:
wherein, a_current is a step value corresponding to a triangular wave signal currently output by the triangular wave generating circuit, N is an original feedback frequency dividing ratio of the feedback frequency divider, and K is a bit number of the modulating signal module;
when the identification signal is at a low level, the fixed value of the identification signal strobe is N-1, and the output signal value out of the adder is equivalent to:
in one embodiment, the preset negative triangle step starting point value is 2 K Wherein K is the bit number of the modulation signal module.
A clock center spread spectrum device of a phase locked loop, the device comprising: the device comprises a triangular wave generator, a modulation signal module, an adder and a gating device;
the triangular wave generator is used for controlling a clock input signal of a triangular wave generating circuit of the triangular wave generator according to an output clock of a feedback frequency divider of a phase-locked loop and a first preset frequency division ratio, and outputting corresponding triangular wave signals and identification signals according to the clock input signal, a preset step height, a preset step starting point value and a preset step number, wherein the preset step starting point value comprises a preset positive triangular wave step starting point value and a preset negative triangular wave step starting point value;
The gating device is used for inputting a fixed value of the gating of the identification signal into the adder according to the input identification signal;
the modulating signal module is used for sampling and quantizing the triangular wave signal according to the output clock of the feedback frequency divider of the phase-locked loop and outputting the triangular wave signal to the adder;
the adder is used for determining an output signal value of the adder according to the output of the modulation signal module and the fixed value of the identification signal strobe; and outputting the signal of the output signal value to a feedback frequency divider of the phase-locked loop as a feedback frequency division ratio of the feedback frequency divider of the phase-locked loop so as to realize center frequency spreading of an output clock of a voltage-controlled oscillator of the phase-locked loop.
According to the clock center spread spectrum method and device of the phase-locked loop, the frequency divider of the triangular wave generator is used for controlling the clock input signal of the triangular wave generating circuit of the triangular wave generator according to the output clock of the feedback frequency divider of the phase-locked loop and the first preset frequency division ratio, the triangular wave generating circuit is used for outputting the corresponding triangular wave signal and the identification signal according to the clock input signal, the preset step height, the preset step starting point value and the preset step number, the preset step starting point value comprises the preset positive triangular wave step starting point value and the preset negative triangular wave step starting point value, the triangular wave signal output by the triangular wave generating circuit is transmitted to the modulating signal module through the gating device, the modulating signal module is used for outputting the triangular wave signal to the adder according to the output clock of the feedback frequency divider of the phase-locked loop, the identification signal output by the triangular wave generating circuit is input to the gating device, the gating device is used for inputting the fixed value of the identification signal gating according to the input identification signal, and the adder is further used for determining the output signal value of the adder according to the output of the modulating signal module and the fixed value of the identification signal gating, and the adder outputs the signal value representing the output signal value to the feedback signal value to the frequency divider of the phase-locked loop, and the frequency divider is used as the frequency divider of the phase-locked loop to realize the frequency spread spectrum of the phase-locked loop. Therefore, the corresponding triangular wave signals and the corresponding identification signals are output according to the clock input signals, the preset step height, the preset step starting point value and the preset step number, and then the feedback frequency division ratio of the feedback frequency divider of the phase-locked loop is determined by the adder after the modulation signal module is sampled and quantized, so that the central frequency expansion of the output clock of the voltage-controlled oscillator of the phase-locked loop is realized, the application of the phase-locked loop is not limited by the frequency of an application system, and the universality of the phase-locked loop is improved.
Drawings
FIG. 1 is a flow chart of a clock center spread spectrum method of a phase locked loop in one embodiment;
FIG. 2 is a process flow diagram of a clock center spread spectrum method of a phase locked loop in one embodiment;
FIG. 3 is a block diagram of a clock center spread spectrum device of a phase locked loop in one embodiment;
fig. 4 is a schematic diagram of a triangular waveform of a clock-centered spread spectrum method of a phase-locked loop in one embodiment.
Detailed Description
The present application will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present application more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the application.
In one embodiment, as shown in fig. 1 and 2, a clock center spread spectrum method of a phase locked loop is provided, including the steps of:
in step S220, the frequency divider of the triangular wave generator controls the clock input signal of the triangular wave generating circuit of the triangular wave generator according to the output clock of the feedback frequency divider of the phase-locked loop and the first preset frequency dividing ratio.
The phase locked loop (phase locked loop, PLL) may be a negative feedback control system that uses a voltage generated by phase synchronization to tune a voltage controlled oscillator to generate a target frequency. The phase-locked loop has a structure as shown in fig. 2, and comprises a Phase Frequency Detector (PFD), a Charge Pump (CP), a Low Pass Filter (LPF), a Voltage Controlled Oscillator (VCO), and a feedback frequency divider connected to an output end of the voltage controlled oscillator, an output end of an adder, and an input end of the phase frequency detector, wherein the input end of the phase frequency detector is connected to a reference frequency signal.
As shown in fig. 3, the triangular wave generator at least includes a frequency divider and a triangular wave generating circuit, wherein an input end of the frequency divider is connected to a clock output end of a feedback frequency divider of the phase-locked loop, and an output end of the frequency divider is connected to a clock input end Clk of the triangular wave generating circuit.
The frequency divider of the triangular wave generator is used for adjusting the clock input signal of the triangular wave generator.
The first preset frequency dividing ratio is set according to the output clock of the feedback frequency divider of the phase-locked loop, and the first preset frequency dividing ratio is greater than or equal to 2 so as to ensure that the output clock of the feedback frequency divider of the phase-locked loop is at least 2 times of the clock input signal of the triangular wave generating circuit. The first preset division ratio may be set by an I2C control word associated with the triangular wave generator.
In step S240, the triangular wave generating circuit outputs the corresponding triangular wave signal and the identification signal according to the clock input signal, the preset step height, the preset step starting point value and the preset step number, wherein the preset step starting point value comprises a preset positive triangular wave step starting point value and a preset negative triangular wave step starting point value.
The preset step height may be a step difference value of the triangular wave signal currently output by the triangular wave generating circuit compared with the triangular wave signal output at the previous moment. The preset step height may be set by an I2C control word associated with the triangular wave generator.
The preset step starting point value can be set through an I2C control word associated with the triangular wave generator. The preset step starting point value comprises a preset positive triangular wave step starting point value and a preset negative triangular wave step starting point value.
The preset starting point value of the step of the regular triangular wave may be a step value of the triangular wave signal output by the triangular wave generating circuit after the triangular wave generating circuit is reset.
The preset negative triangular wave step starting point value can be a step value of a triangular wave signal output by the triangular wave generating circuit when the triangular wave generator finishes positive triangular wave output and the next clock rising edge arrives.
Wherein the preset regular triangle wave step starting point value is set to 0.
The preset negative triangular wave step starting point value is determined according to the bit number of the modulation signal module.
The preset number of steps may be the number of times of continuously increasing or continuously decreasing the triangular wave signal output by the triangular wave generating circuit in each period. The preset number of steps may be set by an I2C control word associated with the triangular wave generator.
As shown in fig. 3, the clock input Clk of the triangular wave generating circuit is connected to the output of the frequency divider, and the preset step height input a_deep, the preset positive triangular wave step starting value input a_start1, the preset negative triangular wave step starting value input a_start2, the preset step number input a_step and the reset end rst of the triangular wave generating circuit are connected to the output of the I2C controller.
In one embodiment, the preset negative triangle step starting point value is 2 K Wherein K is the bit number of the modulation signal module.
In one embodiment, the triangular wave generating circuit outputs a corresponding triangular wave signal and an identification signal according to a clock input signal, a preset step height, a preset step starting point value and a preset step number, and the method comprises the following steps:
in the case of the regular triangle wave output mode, the triangle wave generating circuit outputs a high-level identification signal and outputs a regular triangle wave signal according to a preset step height, a preset regular triangle wave step starting point value and a preset step number; in the case of the negative triangular wave output mode, the triangular wave generating circuit outputs a low-level identification signal and outputs a negative triangular wave signal according to a preset step height, a preset negative triangular wave step starting value and a preset step number.
In one embodiment, outputting the regular triangle wave signal according to the preset step height, the preset regular triangle wave step starting point value and the preset step number comprises:
when the clock input signal is triggered by the first rising edge in the regular triangle wave output mode, the triangle wave generating circuit takes a preset regular triangle wave step starting point value as a step value at the current moment, and increases a step according to the preset step height on the basis of the step value at the current moment to output a regular triangle wave signal; after triggering the first rising edge in the regular triangle wave output mode and when the number of the steps does not reach the preset number of steps, the triangle wave generating circuit increases one step according to the preset step height on the basis of the step value at the current moment to output a regular triangle wave signal; after the first rising edge in the regular triangle wave output mode is triggered and when the preset step number is reached, the triangle wave generating circuit outputs a regular triangle wave signal according to a step in a decreasing mode according to the preset step height on the basis of the step value at the current moment.
When the step value at the current moment is the last step of the preset positive triangular wave step starting point value, the triangular wave generating circuit changes the positive triangular wave output mode into the negative triangular wave output mode after the next clock rising edge arrives, and changes the identification signal into a low level.
In one embodiment, outputting the negative triangular wave signal according to the preset step height, the preset negative triangular wave step starting point value and the preset step number comprises:
when the clock input signal is triggered by the first rising edge in the negative triangular wave output mode, the triangular wave generating circuit takes a preset negative triangular wave step starting point value as a step value at the current moment, and on the basis of the step value at the current moment, the triangular wave generating circuit outputs a negative triangular wave signal according to a step in a descending mode according to the preset step height; after triggering the first rising edge in the negative triangular wave output mode and when the number of the steps does not reach the preset number of steps, the triangular wave generating circuit outputs a negative triangular wave signal according to a step which is decreased by one step on the basis of the step value at the current moment; after the first rising edge in the negative triangular wave output mode is triggered and when the preset step number is reached, the triangular wave generating circuit increases a step according to the preset step height on the basis of the step value at the current moment to output a negative triangular wave signal.
When the step value at the current moment is the next step of the preset negative triangular wave step starting point value, the triangular wave generating circuit changes the negative triangular wave output mode into the positive triangular wave output mode after the next clock rising edge arrives, and changes the identification signal into the high level.
In one example, taking one cycle as an example, the triangular wave generator outputs a triangular wave signal in one cycle to form one positive triangular waveform and one negative triangular waveform. When the triangular wave generator outputs a positive triangular wave signal, the triangular wave generating circuit outputs a high-level identification signal at the same time, and when the triangular wave generator outputs a negative triangular wave signal, the triangular wave generating circuit outputs a low-level identification signal at the same time. As shown in fig. 4, when the first rising edge in the current period is triggered, the triangular wave generator outputs a triangular wave signal, the step value is a preset triangular wave step starting point value, and according to a preset step height (in this example, the preset step height may be set to 1 or greater than 1) and a preset step number, the triangular wave signal is continuously output, when the preset step number is reached, the current step value is a peak value of the triangular wave, and the peak value a_max_current is: the preset number of steps x the preset step height. When the step value returns to the preset positive triangle step starting point value from the highest value, and when the output step value reaches the previous step (step value 1 shown in fig. 3) of the preset positive triangle step starting point value, the triangle wave generating circuit changes into a negative triangle wave signal to output, and the step value jumps to the preset negative triangle step starting point value 2 K According to the preset step height (in this example, the preset step height may be set to 1 or more than 1) and the preset step number, the negative triangular wave signal is continuously output, and when the preset step number is reached, the current step value is the lowest value of the negative triangular wave, and the lowest value is 2 K -a_max_current. When the step value returns to the preset negative threeWhen the output step value reaches the last step value 2 of the preset negative triangular wave step starting value when the angular wave step starting value K At-1, the triangular wave generator immediately converts the triangular wave signal into a regular triangular wave signal, and the identification signal becomes a high level output. To this end, a complete cycle (typically with a cycle time of several tens of μs.) is completed and the next cycle is entered for output.
In one embodiment, the preset step height and the preset step number are determined according to a spread spectrum depth formula, which is:
wherein A_step is the preset step number, A_deep is the preset step height, K is the bit number of the modulation signal module, N is the preset frequency division ratio of the feedback frequency divider, and epsilon is the spread spectrum depth.
Wherein the preset frequency division ratio of the feedback frequency divider is a preset integer frequency division ratio.
Wherein, as shown in FIG. 3, when the triangular waveform is the regular triangular waveform output, namely from 0 to A_max_current, wherein A_max_current=A_step×A_deep, and then to the regular triangular waveform output 1, the identification signal is always at high level, S1a and S1b switches are turned on, S2a and S2b are turned off, up-spread is performed, and the maximum spread depth is When the triangular waveform is output as a negative triangular waveform, namely from 2 K To 2 K -a_max_current, to 2 K When-1, the identification signal is always at low level, the S2a and S2b switches are on, the S1a and S1b are off, the lower spread spectrum is adopted at the moment, and the maximum spread spectrum depth is +.>Because the triangular waveform output is a periodic output, then S1a, S1b and S2a, S2b are periodically turned off and on, thus combining into a center spread output pattern.
It should be appreciated that the bit number K of the modulated signal module is fixed, and the spreading depth can be changed by changing the peak value a_max_current of the positive triangle waveform output and the lowest value of the negative triangle waveform. The change of the value can be realized by changing the preset step height and the preset step number, and a plurality of Bit bits can be used for setting the two parameters respectively, so that different spread spectrum depths are obtained. Setting the spreading depth with two parameters can increase flexibility. Secondly, under the condition that the sampling rate of each step by the modulation signal module is unchanged, namely the preset step number is unchanged, the purpose of adjusting the spread spectrum depth can be achieved by independently setting the preset step height.
In one embodiment, the signal energy can be reduced according to the requirement of the system for reducing electromagnetic interference, and the spread spectrum depth is adjusted by combining the relation between the signal energy reduction and the spread spectrum depth, so as to reduce the signal energy, thereby achieving the requirement of the system for reducing electromagnetic interference, wherein the relation between the signal energy reduction and the spread spectrum depth is as follows: a is that dB =6.5+9log ε+9log (f/1000000), where a dB Epsilon is the spreading depth, and f is the frequency point to be spread. Therefore, the spread spectrum depth is adjusted by changing the preset step height and the preset step number, so that the electromagnetic interference of the system is reduced.
In step S260, the triangular wave signal output by the triangular wave generating circuit is transmitted to the modulating signal module through the gate, and the modulating signal module samples and quantizes the triangular wave signal according to the output clock of the feedback frequency divider of the phase-locked loop, and outputs the sampled and quantized triangular wave signal to the adder.
Wherein the modulation signal module (sigma delta modulate, SDM) is used for sampling and quantizing the input triangular wave signal. The clock signal input by the modulation signal module is the output clock of the feedback frequency divider, the input clock signal is a K-bit multi-bit input signal, and the output of the modulation signal module is a multi-bit signal. Because the modulating signal module can sample each step of the triangular wave signal, the clock signal frequency of the modulating signal module is at least twice the clock input signal frequency of the triangular wave generating circuit of the triangular wave generator, and the modulating signal module can be directly connected with the clock output end of the feedback frequency divider of the phase-locked loop and directly input the output clock output by the feedback frequency divider of the phase-locked loop.
The modulation signal module may be a third-order mesh (cascaded noise shaping structure) structure. The output signal of the modulation signal module of the three-order mesh structure is random output signal in-3-4. When the regular triangular wave signal is input, the identification signal is at a high level, the modulating signal module samples the step value of each triangular wave signal and then carries out quantization output, and the output equivalent value is(the equivalent value is a number less than or equal to 1), wherein A_current is a step value corresponding to the triangular wave signal currently output by the triangular wave generating circuit, namely, the output values-3-4 are randomly combined to obtain an equivalent value->When a negative triangular wave signal is input, the identification signal is at a low level, the modulating signal module samples the step value of each triangular wave signal and then carries out quantization output, and the output equivalent value is +.>(equivalent value is a number less than or equal to 1), namely output values-3-4 are randomly combined to obtain equivalent value +.>
The clock output end of the feedback frequency divider of the phase-locked loop is also connected with the clock input end CLK of the modulation signal module, and the modulation signal module samples and quantizes the triangular wave signal according to the output clock of the feedback frequency divider of the phase-locked loop.
In step S280, the identification signal output by the triangular wave generating circuit is input to the gate, and the gate inputs a fixed value of the identification signal to the adder according to the input identification signal.
As shown IN fig. 3, the gating device may include an inverter L, a switch S1a, a switch S1b, a switch S2a, and a switch S2b, where the switch S1a and the switch S2a are connected IN parallel, that is, input ends of the switch S1a and the switch S2a are connected to a triangular wave signal output end triangule_out of the triangular wave generating circuit, two output ends of the switch S1a and the switch S2a are connected to a signal input end IN of the modulating signal module, an input end of the inverter L is connected to a control end of the switch S1a and an identification signal output end flag_out of the triangular wave generating circuit, an output end of the inverter L is connected to a control end of the switch S2a, a control end of the switch S1b is connected to an identification signal output end flag_out of the triangular wave generating circuit, an input end of the switch S1b is used for inputting a fixed value N of the identification signal gating, an output end of the switch S1b is connected to a first input end of the adder, and an input end of the fixed value of the switch S2b is connected to an output end of the adder A1.
Wherein, the identification signal flag output by the output end flag_out of the triangular wave generating circuit controls the on or off of the switch S1a and the switch S1 b. When the identification signal flag is at a high level, the switch S1a and the switch S1b are switched on; when the identification signal flag is low, the switches S1a and S1b are switched off. The control signals of the on or off of the switch S2a and the switch S2b are controlled by an output signal flagb obtained by the identification signal flagg through an inverter, and when the flagb signal is in a high level, the switch S2a and the switch S2b are switched on; when the flag signal is low, the switches S2a and S2b are switched off.
Here, since the output of the triangular wave generating circuit is a multi-bit output, the switches S1a, S1b, S2a, and S2b, the switches S1a and S2a are multi-bit switches, respectively.
And step S300, the adder determines the output signal value of the adder according to the output of the modulation signal module and the fixed value of the identification signal strobe.
The adder carries out logic addition on the output value of the output end Sdm_out < d:0> of the modulation signal module and the fixed value of the identification signal gating output by the gating device.
In one embodiment, the adder determines an output signal value of the adder based on the output of the modulation signal module and a fixed value of the identification signal strobe, comprising:
in the case where the identification signal is at a high level, the fixed value of the identification signal strobe is N, and the output signal value out of the adder may be equivalent to:
wherein, A_current is the step value corresponding to the triangular wave signal currently output by the triangular wave generating circuit, N is the original feedback frequency dividing ratio of the feedback frequency divider, K is the bit number of the modulation signal module;
in the case where the identification signal is at a low level, the fixed value of the identification signal strobe is N-1, and the output signal value out of the adder may be equivalent to:
wherein the adder can be a multi-bit full adder composed of a plurality of single-bit full adders, and the number of the single-bit adders is that of the output ends Sdm_out of the modulation signal module <d:0>The number of bits to be output is determined, so that d+1 single bit full adders can be used, where d is the highest bit to be output by the modulation signal module. When the triangular wave generating circuit outputs a regular triangular wave signal, the fixed value of the identification signal gating output by the gating device is N, namely the switch S1b is conducted. When the triangular wave generating circuit outputs a negative triangular wave signal, the fixed value of the identification signal gating output by the gating device is N-1, namely the switch S2b is conducted. The output of the adder is also a multi-bit output signal whose value is the divide ratio of the feedback divider in the phase locked loop. When the adder inputs a right triangle wave signal,when the adder inputs the negative triangle wave signal input, < >>
In step S320, the adder outputs a signal representing the output signal value to the feedback divider of the phase-locked loop as a feedback division ratio of the feedback divider of the phase-locked loop, so as to realize center spreading of the output clock of the voltage-controlled oscillator of the phase-locked loop.
According to the clock center spread spectrum method and device of the phase-locked loop, the frequency divider of the triangular wave generator is used for controlling the clock input signal of the triangular wave generating circuit of the triangular wave generator according to the output clock of the feedback frequency divider of the phase-locked loop and the first preset frequency division ratio, the triangular wave generating circuit is used for outputting the corresponding triangular wave signal and the identification signal according to the clock input signal, the preset step height, the preset step starting point value and the preset step number, the preset step starting point value comprises the preset positive triangular wave step starting point value and the preset negative triangular wave step starting point value, the triangular wave signal output by the triangular wave generating circuit is transmitted to the modulating signal module through the gating device, the modulating signal module is used for outputting the triangular wave signal to the adder according to the output clock of the feedback frequency divider of the phase-locked loop, the identification signal output by the triangular wave generating circuit is input to the gating device, the gating device is used for inputting the fixed value of the identification signal gating according to the input identification signal, and the adder is further used for determining the output signal value of the adder according to the output of the modulating signal module and the fixed value of the identification signal gating, and the adder outputs the signal representing the output signal value to the feedback frequency divider of the phase-locked loop as the frequency divider of the feedback frequency divider of the phase-locked loop, and the frequency divider of the phase-locked loop is used for achieving the frequency spread spectrum of the phase-locked loop. Therefore, the corresponding triangular wave signals and the corresponding identification signals are output according to the clock input signals, the preset step height, the preset step starting point value and the preset step number, and then the feedback frequency division ratio of the feedback frequency divider of the phase-locked loop is determined by the adder after the modulation signal module is sampled and quantized, so that the central frequency expansion of the output clock of the voltage-controlled oscillator of the phase-locked loop is realized, the application of the phase-locked loop is not limited by the frequency of an application system, and the universality of the phase-locked loop is improved.
It should be understood that, although the steps in the flowchart of fig. 1 are shown in sequence as indicated by the arrows, the steps are not necessarily performed in sequence as indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least some of the steps in fig. 1 may include multiple sub-steps or stages that are not necessarily performed at the same time, but may be performed at different times, nor do the order in which the sub-steps or stages are performed necessarily performed in sequence, but may be performed alternately or alternately with at least a portion of other steps or sub-steps of other steps.
In one embodiment, as shown in fig. 3, there is provided a clock center spreading device of a phase locked loop, including: triangular wave generator, modulation signal module, adder and gate, wherein:
the triangular wave generator is used for controlling a clock input signal of a triangular wave generating circuit of the triangular wave generator according to an output clock of a feedback frequency divider of the phase-locked loop and a first preset frequency division ratio, and outputting corresponding triangular wave signals and identification signals according to the clock input signal, a preset step height, a preset step starting point value and a preset step number, wherein the preset step starting point value comprises a preset positive triangular wave step starting point value and a preset negative triangular wave step starting point value;
The gating device is used for inputting a fixed value of the identification signal gating into the adder according to the input identification signal;
the modulating signal module is used for sampling and quantizing the triangular wave signal according to the output clock of the feedback frequency divider of the phase-locked loop and outputting the triangular wave signal to the adder;
an adder for determining an output signal value of the adder based on the output of the modulated signal module and a fixed value of the identification signal strobe; and outputting a signal representing the output signal value to a feedback divider of the phase-locked loop as a feedback division ratio of the feedback divider of the phase-locked loop to achieve center spread of an output clock of a voltage-controlled oscillator of the phase-locked loop.
The triangular wave generator at least comprises a frequency divider and a triangular wave generating circuit, wherein the input end of the frequency divider is connected with the clock output end of the feedback frequency divider of the phase-locked loop, and the output end of the frequency divider is connected with the clock input end Clk of the triangular wave generating circuit.
The step height input end A_deep, the positive triangular step starting point value input end A_start1, the negative triangular step starting point value input end A_start2, the step number input end A_step and the reset end rst of the triangular wave generating circuit are connected with the output end of the I2C controller, and the clock input end CLK of the modulating signal module is connected with the clock output end of the feedback frequency divider of the phase-locked loop.
The gating device comprises an inverter L, a switch S1a, a switch S1b, a switch S2a and a switch S2b, wherein the switch S1a and the switch S2a are connected IN parallel, namely, the input ends of the switch S1a and the switch S2a are connected to a triangular wave signal output end Triangle_out of a triangular wave generating circuit, two output ends of the switch S1a and the switch S2a are connected to a signal input end IN of a modulating signal module, the input end of the inverter L is connected with the control end of the switch S1a and an identification signal output end flag_out of the triangular wave generating circuit, the output end of the inverter L is connected with the control end of the switch S2a, the control end of the switch S1b is connected with the identification signal output end flag_out of the triangular wave generating circuit, the input end of the switch S1b is used for inputting a fixed value N of the identification signal gating, the output end of the switch S1b is connected with a first input end of an adder, the control end of the switch S2b is connected with the output end of the inverter L is used for inputting a fixed value N-1 of the identification signal gating signal.
The output end sdm_out < d:0> of the modulation signal module is connected to the second input end of the adder A1, and the output end of the adder A1 is connected to the input end of the feedback frequency divider, so that the adder outputs a signal representing the output signal value to the feedback frequency divider of the phase-locked loop as the feedback frequency division ratio of the feedback frequency divider of the phase-locked loop, so as to realize center frequency spreading of the output clock of the voltage-controlled oscillator of the phase-locked loop.
The clock center frequency spreading device of the phase-locked loop is used for controlling a clock input signal of a triangular wave generating circuit of the triangular wave generator according to an output clock of a feedback frequency divider of the phase-locked loop and a first preset frequency division ratio, and outputting corresponding triangular wave signals and identification signals according to the clock input signal, a preset step height, a preset step starting point value and a preset step number, wherein the preset step starting point value comprises a preset positive triangular wave step starting point value and a preset negative triangular wave step starting point value; the gating device is used for inputting a fixed value of the identification signal gating into the adder according to the input identification signal; the modulating signal module is used for sampling and quantizing the triangular wave signal according to the output clock of the feedback frequency divider of the phase-locked loop and outputting the triangular wave signal to the adder; an adder for determining an output signal value of the adder based on the output of the modulated signal module and a fixed value of the identification signal strobe; and outputs a signal representing the output signal value to a feedback divider of the phase-locked loop as a feedback division ratio of the feedback divider of the phase-locked loop to achieve center spread of an output clock of a voltage-controlled oscillator of the phase-locked loop. Therefore, the corresponding triangular wave signals and the corresponding identification signals are output according to the clock input signals, the preset step height, the preset step starting point value and the preset step number, and then the feedback frequency division ratio of the feedback frequency divider of the phase-locked loop is determined by the adder after the modulation signal module is sampled and quantized, so that the central frequency expansion of the output clock of the voltage-controlled oscillator of the phase-locked loop is realized, the application of the phase-locked loop is not limited by the frequency of an application system, and the universality of the phase-locked loop is improved.
For specific limitations of the clock-centric spreading means of the phase-locked loop, reference may be made to the above limitation of the clock-centric spreading method of the phase-locked loop, which is not described in detail herein. The various modules in the clock center spread spectrum device of the phase-locked loop can be implemented in whole or in part by software, hardware and combinations thereof. The above modules may be embedded in hardware or may be independent of a processor in the computer device, or may be stored in software in a memory in the computer device, so that the processor may call and execute operations corresponding to the above modules.
The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the application. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.
Claims (10)
1. A method of clock-centric spreading of a phase-locked loop, the method comprising:
the frequency divider of the triangular wave generator controls a clock input signal of a triangular wave generating circuit of the triangular wave generator according to an output clock of a feedback frequency divider of a received phase-locked loop and a first preset frequency dividing ratio;
the triangular wave generating circuit outputs corresponding triangular wave signals and identification signals according to the clock input signals, the preset step height, the preset step starting point value and the preset step number, wherein the preset step starting point value comprises a preset positive triangular wave step starting point value and a preset negative triangular wave step starting point value;
the triangular wave signal output by the triangular wave generating circuit is transmitted to a modulation signal module through a gating device, and the modulation signal module samples and quantizes the triangular wave signal according to the output clock of a feedback frequency divider of the phase-locked loop and then outputs the triangular wave signal to an adder;
the identification signal output by the triangular wave generating circuit is input to a gating device, and the gating device inputs a fixed value gated by the identification signal into the adder according to the input identification signal;
the adder determines an output signal value of the adder according to the output of the modulation signal module and the fixed value of the identification signal strobe;
The adder outputs a signal representing the output signal value to a feedback frequency divider of the phase-locked loop as a feedback frequency division ratio of the feedback frequency divider of the phase-locked loop to realize center frequency spreading of an output clock of a voltage-controlled oscillator of the phase-locked loop.
2. The method of claim 1, wherein the triangular wave generating circuit outputs corresponding triangular wave signals and identification signals according to the clock input signal, a preset step height, a preset step starting point value and a preset step number, and comprises:
in the case of a regular triangle wave output mode, the triangle wave generating circuit outputs a high-level identification signal and outputs a regular triangle wave signal according to a preset step height, a preset regular triangle wave step starting point value and a preset step number;
in the case of the negative triangular wave output mode, the triangular wave generating circuit outputs a low-level identification signal and outputs a negative triangular wave signal according to a preset step height, a preset negative triangular wave step starting value and a preset step number.
3. The method of claim 2, wherein the outputting the regular triangular wave signal according to the preset step height, the preset regular triangular wave step starting point value and the preset step number comprises:
When the clock input signal is triggered by the first rising edge in the regular triangle wave output mode, the triangle wave generating circuit takes a preset regular triangle wave step starting point value as a step value at the current moment, and increases a step according to a preset step height on the basis of the step value at the current moment to output a regular triangle wave signal;
after triggering a first rising edge in a regular triangle wave output mode and when the number of the steps does not reach the preset number of steps, the triangle wave generating circuit increases a step according to the preset step height on the basis of the step value at the current moment to output a regular triangle wave signal;
after the first rising edge in the regular triangle wave output mode is triggered and the preset step number is reached, the triangle wave generating circuit outputs a regular triangle wave signal according to a step in a descending mode according to the preset step height on the basis of the step value at the current moment.
4. The method according to claim 3, wherein the triangular wave generating circuit changes the positive triangular wave output mode to the negative triangular wave output mode and changes the identification signal to the low level after the next clock rising edge arrives when the step value at the current time is the last step of the preset positive triangular wave step starting point value.
5. The method of claim 2, wherein the outputting the negative triangular wave signal according to the preset step height, the preset negative triangular wave step starting point value and the preset step number comprises:
when the clock input signal is triggered by the first rising edge in the negative triangular wave output mode, the triangular wave generating circuit takes the preset negative triangular wave step starting point value as the step value at the current moment, and on the basis of the step value at the current moment, the step is decreased by one step according to the preset step height to output the negative triangular wave signal;
after triggering a first rising edge in a negative triangular wave output mode and when the number of steps does not reach the preset number of steps, the triangular wave generating circuit outputs a negative triangular wave signal according to a step in a descending mode according to the preset step height on the basis of the step value at the current moment;
after the first rising edge in the negative triangular wave output mode is triggered and the preset step number is reached, the triangular wave generating circuit increases a step according to the preset step height to output a negative triangular wave signal on the basis of the step value at the current moment.
6. The method according to claim 5, wherein the triangular wave generating circuit changes the negative triangular wave output mode to the positive triangular wave output mode and changes the identification signal to the high level after the next clock rising edge arrives when the step value at the current time is the next step of the preset negative triangular wave step starting point value.
7. The method of claim 1 to 6, wherein the preset step height and the preset step number are determined according to a spread depth formula, the spread depth formula is:
wherein A_step is the preset step number, A_deep is the preset step height, K is the bit number of the modulation signal module, N is the preset frequency division ratio of the feedback frequency divider, and epsilon is the spread spectrum depth.
8. The clock-centric spread spectrum method of claim 2, wherein the adder determines an output signal value of the adder based on the output of the modulation signal module and the fixed value of the identification signal strobe, comprising:
when the identification signal is at a high level, the fixed value of the identification signal strobe is N, and the output signal value out of the adder is equivalent to:
wherein, a_current is a step value corresponding to a triangular wave signal currently output by the triangular wave generating circuit, N is an original feedback frequency dividing ratio of the feedback frequency divider, and K is a bit number of the modulating signal module;
when the identification signal is at a low level, the fixed value of the identification signal strobe is N-1, and the output signal value out of the adder is equivalent to:
9. The method of claim 1, wherein the predetermined negative triangle step starting point value is 2 K Wherein K is the bit number of the modulation signal module.
10. A clock-centric spreading apparatus for a phase-locked loop, the apparatus comprising: the device comprises a triangular wave generator, a modulation signal module, an adder and a gating device;
the triangular wave generator is used for controlling a clock input signal of a triangular wave generating circuit of the triangular wave generator according to an output clock of a feedback frequency divider of a phase-locked loop and a first preset frequency division ratio, and outputting corresponding triangular wave signals and identification signals according to the clock input signal, a preset step height, a preset step starting point value and a preset step number, wherein the preset step starting point value comprises a preset positive triangular wave step starting point value and a preset negative triangular wave step starting point value;
the gating device is used for inputting a fixed value of the gating of the identification signal into the adder according to the input identification signal;
the modulating signal module is used for sampling and quantizing the triangular wave signal according to the output clock of the feedback frequency divider of the phase-locked loop and outputting the triangular wave signal to the adder;
The adder is used for determining an output signal value of the adder according to the output of the modulation signal module and the fixed value of the identification signal strobe; and outputting the signal of the output signal value to a feedback frequency divider of the phase-locked loop as a feedback frequency division ratio of the feedback frequency divider of the phase-locked loop so as to realize center frequency spreading of an output clock of a voltage-controlled oscillator of the phase-locked loop.
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Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20050008113A1 (en) * | 2003-07-09 | 2005-01-13 | Masaru Kokubo | Spread spectrum clock generator and integrated circuit device using the spread spectrum clock generators |
| JP2006067411A (en) * | 2004-08-30 | 2006-03-09 | Renesas Technology Corp | Modulation circuit, phase synchronization circuit with the modulation circuit, and interface device with the phase synchronization circuit |
| EP1858157A1 (en) * | 2006-05-15 | 2007-11-21 | STMicroelectronics Pvt. Ltd. | Spread spectrum clock generation system |
| JP2009004868A (en) * | 2007-06-19 | 2009-01-08 | Toshiba Corp | Spread spectrum clock generator |
| JP2009290733A (en) * | 2008-05-30 | 2009-12-10 | Nec Electronics Corp | Clock generating circuit with frequency modulation function |
| CN101882923A (en) * | 2009-05-04 | 2010-11-10 | 智原科技股份有限公司 | Triangular wave generator, spread spectrum clock generator using same and relevant method |
| US20110204940A1 (en) * | 2010-02-23 | 2011-08-25 | Renesas Electronics Corporation | Clock generator, semiconductor device, and clock generating method |
| US20160049947A1 (en) * | 2014-08-12 | 2016-02-18 | Renesas Electronics Corporation | Spread spectrum clock generator |
-
2023
- 2023-07-28 CN CN202310946631.1A patent/CN116938233A/en active Pending
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20050008113A1 (en) * | 2003-07-09 | 2005-01-13 | Masaru Kokubo | Spread spectrum clock generator and integrated circuit device using the spread spectrum clock generators |
| JP2006067411A (en) * | 2004-08-30 | 2006-03-09 | Renesas Technology Corp | Modulation circuit, phase synchronization circuit with the modulation circuit, and interface device with the phase synchronization circuit |
| EP1858157A1 (en) * | 2006-05-15 | 2007-11-21 | STMicroelectronics Pvt. Ltd. | Spread spectrum clock generation system |
| JP2009004868A (en) * | 2007-06-19 | 2009-01-08 | Toshiba Corp | Spread spectrum clock generator |
| JP2009290733A (en) * | 2008-05-30 | 2009-12-10 | Nec Electronics Corp | Clock generating circuit with frequency modulation function |
| CN101882923A (en) * | 2009-05-04 | 2010-11-10 | 智原科技股份有限公司 | Triangular wave generator, spread spectrum clock generator using same and relevant method |
| US20110204940A1 (en) * | 2010-02-23 | 2011-08-25 | Renesas Electronics Corporation | Clock generator, semiconductor device, and clock generating method |
| US20160049947A1 (en) * | 2014-08-12 | 2016-02-18 | Renesas Electronics Corporation | Spread spectrum clock generator |
Non-Patent Citations (2)
| Title |
|---|
| JENCHIEN HSU: "Timing Jitter and Modulation Profile Extraction for Spread-Spectrum Clocks", IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT, 30 April 2010 (2010-04-30) * |
| 李方博: "高速串行通信链路扩频时钟发生器关键技术研究", 《中国优秀硕士学位论文全文数据库信息科技辑》, 15 June 2020 (2020-06-15) * |
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