阅读说明：本技术 一种数字时钟倍频器 (Digital clock frequency multiplier ) 是由 徐荣金 屠于婷 叶大蔚 史传进 于 2019-10-26 设计创作，主要内容包括：本发明属于集成电路技术领域,具体为一种数字时钟倍频器。本发明的数字时钟倍频器包括：包括若干个级联的二倍频单元,每个二倍频单元由一个占空比恢复电路和一个二倍频器级联而成；占空比恢复电路用于将任意占空比的输入信号恢复至占空比为50%；所述二倍频器：产生50%占空比的输入信号的二倍频信号。本发明通过级联占空比恢复电路和二倍频器,产生输入时钟的多倍频信号。本发明的检测和控制电路均可由标准数字电路实现,可以方便地应用于数字系统或混合信号系统中,提供多个不同频率的时钟。(The invention belongs to the technical field of integrated circuits, and particularly relates to a digital clock frequency multiplier. The digital clock frequency multiplier of the present invention comprises: the frequency doubling circuit comprises a plurality of cascaded frequency doubling units, wherein each frequency doubling unit is formed by cascading a duty cycle recovery circuit and a frequency doubler; the duty ratio recovery circuit is used for recovering the input signal with any duty ratio to the duty ratio of 50%; the frequency doubler: a frequency doubled signal of the input signal with 50% duty cycle is generated. The invention generates a multiple frequency signal of an input clock by cascading a duty cycle recovery circuit and a frequency doubler. The detection and control circuit of the invention can be realized by a standard digital circuit, can be conveniently applied to a digital system or a mixed signal system and provides a plurality of clocks with different frequencies.)

1. A digital clock frequency multiplier is characterized by comprising a plurality of cascaded frequency doubling units, wherein each frequency doubling unit is formed by cascading a duty cycle recovery circuit and a frequency doubler; the duty ratio recovery circuit is used for recovering the input signal with any duty ratio to the duty ratio of 50%; the frequency doubler: for generating a frequency doubled signal of the input signal with 50% duty cycle.

2. The digital clock multiplier of claim 1, wherein the duty cycle recovery circuit comprises: the digital phase detector comprises a first numerical control delay chain, a second numerical control delay chain, a first phase discriminator, a second phase discriminator, an edge synthesizer, a control unit and an output control unit; wherein:

the first numerical control delay chain is used for delaying an input clock ckin and outputting dl 1;

the second numerical control delay chain is used for delaying the output ec of the edge synthesizer, and the output is dl 2;

a first phase detector for detecting whether the falling edge of the input signal dl1 is aligned with the rising edge of dl2, and the output is pd 1;

a second phase detector 2 for detecting whether the rising edge of the input signal dl1 is aligned with the falling edge of dl2, and the output is pd 2;

the edge synthesizer is used for respectively extracting and synthesizing the change edges of the two signals to obtain a group of rising edges and falling edges of output signals, and the output is ec;

the control unit is used for respectively adjusting the time delay of the two numerical control delay chains and judging whether the duty ratio adjustment is finished according to the input enable signal en and the output of the two phase detectors, and the output is delay control words dcw1 and dcw2 and a finished flag signal done;

an output control unit: and the control unit is used for controlling whether to start outputting according to the completion flag signal done of the control unit, and the output is ckout.

3. The digital clock multiplier of claim 2, wherein the digitally controlled delay chain is implemented by: a plurality of logic gate-level co-generators generate time delay, and the multi-path gating device gates appointed different time delay outputs according to the time delay control word; the output is generated by a logic gate or a buffer, a numerical control capacitor array or a variable capacitor with a digital-to-analog converter is used as a load, and different delay outputs are specified according to the size of a delay control word control load.

4. The digital clock multiplier of claim 2, wherein the edge synthesizer generates the changing edge of the output signal from the rising or falling edge of the two input signals; the method specifically comprises the following steps: the rising edge of the input signal 1 determines the rising edge of the output signal, the rising edge of the input signal 2 determines the falling edge of the output signal, and one period of the output signal is synthesized.

5. The digital clock frequency multiplier of claim 2, wherein the control unit controls other circuits to start operating when the external enable signal en is active, and otherwise, all circuits are placed in an idle state; accumulating outputs pd1 and pd2 of the phase detector respectively to obtain delay control words dcw1 and dcw 2; judging whether the duty ratio adjustment is finished or not, wherein the realization mode is that when the outputs of a single phase discriminator in a specified number of adjacent periods are all different, the adjustment of the corresponding delay chain is judged to be finished; and when the adjustment of the two delay chains is finished, judging that the adjustment of the duty ratio is finished, and outputting an effective sign signal done.

6. The digital clock multiplier of claim 1, wherein the frequency doubler doubles by generating a new set of new rising and falling edges from the rising and falling edges, respectively, of the input signal.

7. The digital clock frequency multiplier of claim 1, wherein a multiple power multiplier of 2 is obtained by cascading a plurality of sets of duty cycle recovery circuits and frequency doublers; specifically, the input clock is connected with the input end of the duty cycle recovery circuit, and the output is connected with the input of the frequency doubler to obtain 2 times of frequency clock output; the frequency doubling output is connected with the next group of duty ratio recovery circuit and the frequency doubler to obtain 4 frequency doubling clock output; by analogy, multiple power frequency multiplication clock output of 2 can be obtained; each set includes a completion flag signal done output from the duty recovery circuit as an external enable signal en of the next stage, and the external enable signal of the first stage is supplied from an external input.

Technical Field

The invention belongs to the technical field of integrated circuit design, and particularly relates to a clock frequency multiplier.

Background

The use of clock signals is widely required in integrated circuits, particularly digital integrated circuits. In larger scale systems, such as processors, systems on chip, and mixed signal systems, clock signals of different frequencies are often used to further optimize the energy efficiency of the various modules and subsystems. If the clock signals are respectively input from the outside of the chip, a large number of chip pins and clock buffers are needed, and a large amount of chip area is occupied. If a high-frequency clock is input from the outside of the chip and is realized by an on-chip frequency division network, the power consumption required by the clock buffer can be obviously improved, and the optimization of energy efficiency is not facilitated. Therefore, the clock with lower output frequency outside the chip is adopted to generate different frequency multiplication clocks on the chip to be supplied to different circuits, and the energy efficiency of the clock network can be improved.

Conventional clock multiplier implementations are typically:

1. the high frequency clock counts to generate a new phase, thereby obtaining a multiplied clock signal. The method still needs a high-frequency clock, and the circuit has high working frequency, higher design difficulty and higher power consumption;

2. using phase synthesis based on logic operations, a new clock cycle is generated from the rising and falling edges of the original signal, thereby obtaining a multiplied clock signal. The duty ratio of the output signal generated by the method is inaccurate, which is not beneficial to providing stable time sequence for other circuits, and the duty ratio of the input clock signal is required to be accurate 50%, otherwise, the frequency of the clock after frequency multiplication is unstable;

3. a frequency multiplication system based on a phase-locked loop/a time-delay phase-locked loop and the like utilizes a negative feedback loop to generate a frequency multiplication clock signal. The method has the highest flexibility, but relates to a large number of analog circuits, has higher design difficulty and larger occupied chip area, and is not beneficial to the reconstruction and integration of the system.

Disclosure of Invention

In order to solve the problems of the method, the invention provides the digital clock frequency multiplier which has a simple structure, low power consumption and convenient reconstruction and integration.

The digital clock frequency multiplier provided by the invention realizes the output of different frequency multiplication clocks by cascading the duty cycle recovery circuit and the frequency doubler. The invention can be realized by using a standard digital unit, supports the description by using a hardware description language such as Verilog and the like, can be realized in a programmable device, has simple and flexible system, lower power consumption, convenient reconstruction and integration and can be used in a system needing multiple clocks.

The invention aims to solve the problems that in the traditional clock frequency multiplier implementation mode, a high-frequency clock is needed, the output duty ratio phase is unstable, and an analog circuit is needed, so that the design process of a standard digital integrated circuit is not compatible, the output of different frequency multiplication clocks is realized by cascading a duty ratio recovery circuit and a frequency doubler, the duty ratio is 50%, and the time sequence control of a system is facilitated.

The invention provides a digital clock frequency multiplier, comprising: the frequency doubling units are cascaded, wherein each frequency doubling unit is formed by cascading at least one duty cycle recovery circuit and one frequency doubler; the cascade connection of a plurality of the two unit circuits is used for generating a plurality of frequency multiplication signals of the input signals; the duty ratio recovery circuit is used for recovering the input signal with any duty ratio to the duty ratio of 50%; the frequency doubler is used for generating a frequency doubler signal of the input signal with 50% duty ratio.

In the invention, the duty cycle recovery circuit comprises a first numerical control delay chain 1, a second numerical control delay chain 2, a first phase discriminator 1, a second phase discriminator 2, an edge synthesizer, an output control unit and a control unit. The principle of the circuit is that only according to the rising edge of an input clock, the rising edge of the input clock is used as the reference of an output signal, the time delay between the rising edge and the falling edge of the output signal is adjusted, the time delay is compared with a signal delayed by the circuit by half a period, and if the rising edge and the falling edge of the output signal are respectively aligned, the duty ratio of the output signal is 50%.

To implement the above principle, the first digitally controlled delay chain 1 delays the input clock ckin and outputs dl 1. The edge synthesizer obtains a group of rising edges and falling edges of the output signal according to the rising edge of the input clock ckin and the rising edge of the dl1 respectively, and the output is ec. The second numerically controlled delay chain 2 delays the edge synthesizer output ec to dl 2. The first phase detector 1 detects whether the falling edge of dl1 is aligned with the rising edge of dl2 and the output is pd 1. The second phase detector 2 detects whether the rising edge of the input signal dl1 is aligned with the falling edge of dl2 and the output is pd 2. The control unit respectively adjusts the time delay of two numerical control delay chains according to an input enable signal en and the outputs pd1 and pd2 of the two phase detectors, the outputs are delay control words dcw1 and dcw2, so that the rising edge of dl1 is aligned with the falling edge of dl2, the falling edge of dl1 is aligned with the rising edge of dl2, and an effective completion flag signal done is output at the moment. And the output control unit controls whether to start outputting according to the completion flag signal done of the control unit, and the output is ckout.

The numerical control delay chain (comprising a first numerical control delay chain and a second numerical control delay chain) can be realized by a standard digital unit, for example, a plurality of logic gate-level joint generation delays, and the multi-channel gating device gates different specified delays to output according to the delay control word. The method can also be realized in a digital-analog mixed mode, a logic gate or a buffer is used for generating output, a numerical control capacitor array or a variable capacitor with a digital-analog converter is used as a load, and different delay outputs are specified according to the size of a delay control word control load.

The control unit controls other circuits to start working when the external enable signal en is effective, otherwise, the control unit is in an idle state; accumulating outputs pd1 and pd2 of the phase detector respectively to obtain delay control words dcw1 and dcw 2; and judging whether the duty ratio adjustment is finished or not. The implementation mode of the phase discriminator can be, but is not limited to, when the outputs of a single phase discriminator in the specified number of adjacent cycles are different, the adjustment of the corresponding delay chain is judged to be finished; and when the adjustment of the two delay chains is finished, judging that the adjustment of the duty ratio is finished, and outputting an effective sign signal done.

The frequency doubler provided by the invention realizes frequency doubling by respectively generating a new group of new rising edges and new group of new falling edges from the rising edges and the falling edges of input signals. The specific implementation manner includes, but is not limited to, phase synthesis implemented by performing logic operation on the input signal and the delayed signal thereof.

In the invention, multiple power frequency multipliers of 2 are obtained by cascading a plurality of groups of duty ratio recovery circuits and frequency doublers; specifically, the input clock is connected with the input end of the duty cycle recovery circuit, and the output is connected with the input of the frequency doubler to obtain 2 times of frequency clock output; the frequency doubling output is connected with the next group of duty ratio recovery circuit and the frequency doubler to obtain 4 frequency doubling clock output; by analogy, multiple power frequency multiplication clock output of 2 can be obtained; each set includes a completion flag signal done output from the duty recovery circuit as an external enable signal en of the next stage, and the external enable signal of the first stage is supplied from an external input.

The digital clock frequency multiplier provided by the invention comprises a numerical control delay chain and a detection control circuit which can be realized by a standard digital circuit, can be conveniently applied to a digital system or a mixed signal system and provides a plurality of clocks with different frequencies.

Drawings

Fig. 1 is a top-level structural block diagram of a clock multiplier according to an embodiment of the present invention.

Fig. 2 is a block diagram of a structure of a duty recovery circuit according to an embodiment of the present invention.

Fig. 3 is a timing diagram of a duty recovery circuit according to an embodiment of the present invention.

Fig. 4 is a circuit diagram of a digitally controlled delay chain according to an embodiment of the present invention.

Fig. 5 is a circuit diagram of a phase detector according to an embodiment of the present invention.

Fig. 6 is a circuit diagram of an edge synthesizer according to an embodiment of the present invention.

Fig. 7 is a block diagram of a control unit according to an embodiment of the present invention.

Fig. 8 is a block diagram of a frequency doubler according to an embodiment of the present invention.

Fig. 9 is a timing diagram of a frequency doubler according to an embodiment of the present invention.

Detailed Description

The present invention will be described more fully hereinafter in the reference to the accompanying drawings, which provide preferred embodiments of the invention, and which are not to be considered as limited to the embodiments set forth herein.

Fig. 1 is a top-level structural block diagram of a clock multiplier according to an embodiment of the present invention, which includes a plurality of cascaded frequency doubling units, where each frequency doubling unit is formed by cascading a duty cycle recovery circuit and a frequency doubler. The input of the first frequency doubling unit is input clock ckin, the output is ck21 with the frequency being twice the frequency of the input clock, and in turn, the output of the previous frequency doubling unit is used as the input of the next frequency doubling unit, and then the output of each frequency doubling unit is the frequency doubling of the input. In order to control each unit to start operating, an enable signal en is inputted from the outside, and when it is active, the first frequency doubling unit starts operating. Each frequency doubling unit outputs a complete signal done which can be used as an input enable signal of the next stage, for example, the complete signal done21 of the first frequency doubling unit can be used as an enable signal en22 of the second frequency doubling unit, and the complete signal done2n of the last frequency doubling unit can be input to the outside and provided to an upper system as a mark signal.

Fig. 2 is a block diagram of a structure of a duty recovery circuit according to an embodiment of the present invention. The method comprises the following steps: numerical control delay chain 1, namely DCDL 1; numerical control delay chain 2, namely DCDL 2; phase detector 1, i.e., PD 1; phase detector 2, i.e., PD 2; edge synthesizers, i.e., EC; an Output control unit, namely Output Enable; and a control unit, i.e., a Controller. The numerical control delay chain 1 delays the input clock ckin and outputs dl 1. The edge synthesizer obtains a group of rising edges and falling edges of the output signal according to the rising edge of the input clock ckin and the rising edge of the dl1 respectively, and the output is ec. The output ec of the edge synthesizer takes the rising edge of the input clock ckin as the falling edge and the rising edge of dl1 as the rising edge, and a one-cycle waveform is obtained. The numerical control delay chain 2 delays the output ec of the edge synthesizer, and the output is dl 2. The phase detector 1 detects whether the falling edge of dl1 is aligned with the rising edge of dl2 and the output is pd 1. The phase detector 2 detects whether the rising edge of the input signal dl1 is aligned with the falling edge of dl2 and the output is pd 2. The control unit respectively adjusts the time delay of the two numerical control delay chains according to an input enable signal en and outputs pd1 and pd2 of the two phase detectors, wherein the outputs are delay control words dcw1 and dcw2, so that the rising edge of dl1 is aligned with the falling edge of dl2, the falling edge of dl1 is aligned with the rising edge of dl2, and an effective completion flag signal done is output at the moment. When the done signal is valid, the output control unit outputs a clock ckout.

Fig. 3 is a timing diagram of a duty recovery circuit according to an embodiment of the present invention. dl1 is the delay of the input clock ckin, the magnitude of which is controlled by a delay control word dcw1 provided by the control unit. The output ec of the edge synthesizer takes the rising edge of the input clock ckin as the falling edge and the rising edge of dl1 as the rising edge, and a one-cycle waveform is obtained. dl2 is the delay of ec, the size of which is controlled by a delay control word dcw2 provided by the control unit. The phase detector 1 and the phase detector 2 respectively detect whether the falling edge of dl1 is aligned with the rising edge of dl2 and the rising edge of dl1 is aligned with the falling edge of dl2, and the output is pd 2. When the controller detects that the output polarities of two adjacent periods of the two phase detectors are alternately opposite, the duty ratio is judged to be recovered, an effective done signal is output, and the output control unit outputs dl2 as an output clock ckout.

Fig. 4 is a circuit diagram of the digitally controlled delay chain according to the embodiment of the present invention, which can be implemented as the digitally controlled delay chain 1 and the digitally controlled delay chain 2, that is, the delay control word controls the gating of the mux to gate different numbers of delay cells, so as to adjust the delay from the input in to the output out. Because the delay unit and the gate mux can be realized by a digital standard unit, the numerical control delay chain can be realized by comprehensive layout and wiring of a digital integrated circuit, and system integration is facilitated.

Fig. 5 is a circuit diagram of a phase detector provided in an embodiment of the present invention, where two phase detectors are implemented by D flip-flops, where phase detector 1, i.e., PD1, is triggered by a rising edge of dl2 to sample dl1, and its QB output PD1 is the inverse of dl1 at the arrival time of the rising edge of dl2, if the falling edge of dl1 leads the rising edge of dl2, the output of PD1 is 1, otherwise, the output of PD1 is-1; the phase detector 2, PD2, is triggered by the falling edge of dl2 to sample dl1, the Q output PD2 is the value of dl1 at the arrival time of the falling edge of dl2, if the rising edge of dl1 leads the falling edge of dl2, the PD2 output is 1, otherwise the PD2 output is-1.

Fig. 6 is a circuit diagram of an edge synthesizer according to an embodiment of the present invention. The D flip-flop 2, namely the trigger clock of the DFF2 is the input clock ckin, the reset signal is the inverted signal ckin _ ndly of the input clock ckin delay signal, and the data end D is connected with the power supply. The flip-flop generates a narrow pulse rst _ pulse as the reset signal of the D flip-flop 1, i.e., DFF1, at the rising edge of the input clock ckin. The trigger clock of the DFF1 is dl1, the data terminal is connected with the power supply, the output ec of the DFF1 is a signal with the rising edge defined by dl1 and the falling edge defined by ckin, and the function of edge synthesis is realized.

Fig. 7 is a block diagram of a control unit according to an embodiment of the present invention, which employs two integrators, namely ACC1 and ACC2, to integrate pd1 and pd2 under the triggering of a rising edge of dl2 and a falling edge of dl2, respectively, and the integrated values are encoded as delay control words of the nc delay chain 1 and the nc delay chain 2, respectively. Meanwhile, the control unit judges whether the values of pd1 or pd2 of two adjacent periods are different from the values of the respective previous periods, if the two periods both meet the condition that the adjacent periods are changed alternately, the duty ratio is considered to be recovered, and a done flag signal done is output. This function is implemented by a logic unit consisting of a register formed by two D flip-flops, two exclusive-OR gates XOR, an AND gate AND AND a counter.

Fig. 8 is a block diagram of a frequency doubler according to an embodiment of the present invention, and a timing diagram thereof is shown in fig. 9. And carrying out exclusive OR (XOR) operation on the input signal in of the frequency doubler and the delay signal in _ dly thereof, and outputting out to obtain a period at the rising edge and the falling edge of the input signal in respectively so as to realize frequency doubling.

While the embodiments of the present invention have been described with reference to specific examples, those skilled in the art will readily appreciate that the various illustrative embodiments are capable of providing many other embodiments and that many other advantages and features of the invention are possible. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.