阅读说明：本技术 噪声消除电路以及数据传输电路 (Noise cancellation circuit and data transmission circuit ) 是由 船桥正美 加藤秀司 新名亮规 于 2018-04-17 设计创作，主要内容包括：噪声消除电路(110)具备：第1并行串行变换电路(21),将所输入的2N位并行数据变换为串行数据；反转电路(20),使所输入的2N位并行数据的奇数位以及偶数位中的某一方反转；第2并行串行变换电路(22),将反转电路(20)输出的并行数据、和所输入的2N位的并行数据的奇数位以及偶数位中的某另一方的没有反转的并行数据变换为串行数据；第1缓冲器(23),被输入第1并行串行变换电路(21)的输出数据；以及第2缓冲器(24),被输入第2并行串行变换电路(22)的输出数据。(A noise cancellation circuit (110) is provided with: a 1 st parallel-serial conversion circuit (21) for converting the input 2N-bit parallel data into serial data; an inversion circuit (20) for inverting either the odd-numbered bit or the even-numbered bit of the input 2N-bit parallel data; a 2 nd parallel-serial conversion circuit (22) for converting parallel data outputted from the inversion circuit (20) and parallel data of either the odd-numbered bit or the even-numbered bit of the inputted 2N-bit parallel data, which is not inverted, into serial data; a 1 st buffer (23) to which the output data of the 1 st parallel-serial conversion circuit (21) is input; and a 2 nd buffer (24) to which the output data of the 2 nd parallel-serial conversion circuit (22) is input.)

1. A noise cancellation circuit includes:

a 1 st parallel-serial conversion circuit for converting 2N-bit parallel data into serial data in synchronization with a clock signal, wherein N is a natural number of 1 or more;

an inversion circuit for inverting either one of an odd-numbered bit and an even-numbered bit of the 2N-bit parallel data;

a 2 nd parallel-serial conversion circuit for converting the parallel data output from the inversion circuit and the parallel data of the other of the odd-numbered bits and the even-numbered bits of the 2N-bit parallel data, which is not inverted, into serial data in synchronization with a clock signal;

a 1 st buffer to which the output data of the 1 st parallel-serial conversion circuit is input; and

a 2 nd buffer to which the output data of the 2 nd parallel-serial conversion circuit is input;

the 1 st parallel-serial conversion circuit and the 2 nd parallel-serial conversion circuit are substantially constituted by the same circuit,

the 1 st buffer and the 2 nd buffer are substantially constituted by the same circuit,

the 1 st buffer and the 2 nd buffer are connected to a common power supply and to a common ground.

2. A noise cancellation circuit includes:

a 1 st parallel-serial conversion circuit for converting N-bit parallel data, N being an odd number of 1 or more, into serial data in synchronization with a clock signal;

a selector unit to which the N-bit parallel data is input, and which outputs parallel data by alternately switching a mode of outputting odd-numbered bits that are not inverted and even-numbered bits that are not inverted with respect to the input N-bit parallel data and a mode of outputting odd-numbered bits that are not inverted and even-numbered bits that are not inverted with respect to the input N-bit parallel data at an update cycle of the N-bit parallel data;

a 2 nd parallel-serial conversion circuit for converting the parallel data output from the selector unit into serial data in synchronization with a clock signal;

a 1 st buffer to which the output data of the 1 st parallel-serial conversion circuit is input; and

a 2 nd buffer to which the output data of the 2 nd parallel-serial conversion circuit is input;

the 1 st parallel-serial conversion circuit and the 2 nd parallel-serial conversion circuit are substantially constituted by the same circuit,

the 1 st buffer and the 2 nd buffer are substantially constituted by the same circuit,

the 1 st buffer and the 2 nd buffer are connected to a common power supply and to a common ground.

3. The noise canceling circuit of claim 1 or 2,

the output terminal of the 2 nd buffer is connected to the same load as the output terminal of the 1 st buffer.

4. The noise cancellation circuit according to any one of claims 1 to 3,

and a capacitor for smoothing power supply noise, the capacitor being connected between a power supply and a ground connected to the 1 st buffer and the 2 nd buffer.

5. A data transmission circuit is provided with:

the noise cancellation circuit of any one of claims 1 to 4;

a 3 rd buffer connected to an output terminal of the 1 st buffer included in the noise canceling circuit and outputting a differential signal; and

and a 4 th buffer connected to an output terminal of the 2 nd buffer included in the noise canceling circuit, and configured by substantially the same circuit as the 3 rd buffer.

6. The data transmission circuit of claim 5,

the 3 rd buffer and the 4 th buffer are connected to a common power supply and to a common ground.

7. A data transmission circuit is provided with:

a plurality of the noise canceling circuits of any one of claims 1 to 4;

a 5 th buffer to which a plurality of serial data output from the 1 st parallel-to-serial conversion circuit provided in each of the plurality of noise cancellation circuits are input and which outputs a multilevel signal; and

a 6 th buffer to which a plurality of serial data output from the 2 nd parallel-serial conversion circuit provided in each of the plurality of noise cancellation circuits are input and which outputs a multilevel signal;

the same load as the output terminal of the 5 th buffer is connected to the output terminal of the 6 th buffer.

Technical Field

The present invention relates to a noise canceling circuit and a data transmission circuit, and more particularly to a technique for suppressing power supply noise generated in a circuit including a parallel-serial converter circuit.

Background

In recent years, data communication capacity handled between electronic devices has been increasing, and in order to meet such a demand, it is necessary to increase data communication speed and further to increase the multi-level of signals to be transmitted. One of the causes of deterioration of signal quality in high-speed data transmission is jitter (jitter). It is known that a main cause of deterioration of the jitter characteristic is power supply noise. The power supply noise is generated by a variation in instantaneous current flowing at a timing at which a plurality of logic circuits, buffer circuits, and the like in the transmission circuit simultaneously change.

The data to be communicated may be continuously changed, or the same value may be continuous and the data may not be changed. When data is not changed, the instantaneous current flowing is also smaller than when data is changed, and therefore the period of the waveform of the current noise fluctuates depending on the pattern of data at the time of communication.

The magnitude of the power supply noise is determined by the product of the instantaneous current value at the time of data change and the power supply impedance. The power supply impedance is typically designed to have a resonance point between several MHz to several hundred MHz. It is known that, assuming that the peak value of the instantaneous current is always the same, when the frequency component of the current noise generated by the instantaneous current is a frequency close to the resonance point, the power supply noise becomes large, and when the current noise is generated at a frequency higher than the resonance point, the generated power supply noise becomes relatively small.

In the past, the following studies have been made: the peak current value of the instantaneous current flowing between the power supply and the ground is reduced by shifting the timing of simultaneous change for each data, or a large number of bypass capacitors are arranged between the power supply and the ground, thereby reducing the power supply noise. However, as the communication speed increases, the instantaneous current value increases, and a timing margin for shifting the timing of data cannot be obtained sufficiently, and it becomes very difficult to suppress the instantaneous current itself. Therefore, when the frequency of the current noise of a large instantaneous current fluctuates in the vicinity of the resonance point, it is difficult to sufficiently suppress the power supply noise.

Therefore, patent document 1 provides a noise canceling circuit that generates a continuous signal when communication data continuously changes and generates a signal when data continuously changes, drives the same load (load) connected to the same power supply as a path of the communication data by the noise canceling signal, and generates a transient current regularly regardless of a pattern of the communication data by the noise canceling signal when the communication data does not change. Since the instantaneous current changes at the same cycle as the data communication speed, the fluctuation frequency of the instantaneous current shifts to the high frequency side and becomes a constant frequency, so that the power supply noise can be effectively suppressed by the optimum design of the power supply impedance.

Disclosure of Invention

Problems to be solved by the invention

However, the noise cancellation circuit of patent document 1 generates a noise cancellation signal using data after parallel-serial conversion and a clock signal for driving the parallel-serial conversion circuit, and has the following problems: as the data communication speed increases, the difficulty of timing design of a noise cancellation circuit using a clock signal and a flip-flop circuit has dramatically increased.

The present invention has been made in view of the above-described problems, and an object thereof is to provide a noise canceling circuit and the like capable of easily generating a noise canceling signal even when an operation speed is increased.

Means for solving the problems

In order to solve the above problem, a noise cancellation circuit according to an aspect of the present disclosure includes: a 1 st parallel-serial conversion circuit for converting 2N-bit (N is a natural number of 1 or more) parallel data into serial data in synchronization with a clock signal; an inversion circuit for inverting either one of an odd-numbered bit and an even-numbered bit of the 2N-bit parallel data; a 2 nd parallel-serial conversion circuit for converting the parallel data output from the inversion circuit and parallel data of the other of odd-numbered bits and even-numbered bits of the 2N-bit parallel data, which is not inverted, into serial data in synchronization with a clock signal; a 1 st buffer to which the output data of the 1 st parallel-serial conversion circuit is input; and a 2 nd buffer to which the output data of the 2 nd parallel-serial conversion circuit is input; the 1 st parallel-serial conversion circuit and the 2 nd parallel-serial conversion circuit are substantially configured by the same circuit, the 1 st buffer and the 2 nd buffer are substantially configured by the same circuit, and the 1 st buffer and the 2 nd buffer are connected to a common power supply and to a common ground.

In order to solve the above problem, a data transmission circuit according to an aspect of the present disclosure includes: the noise cancellation circuit described above; a 3 rd buffer connected to an output terminal of the 1 st buffer included in the noise canceling circuit and outputting a differential signal; and a 4 th buffer connected to an output terminal of the 2 nd buffer included in the noise canceling circuit, and substantially composed of the same circuit as the 3 rd buffer.

Effects of the invention

According to the present disclosure, it is possible to provide a noise canceling circuit and the like capable of easily generating a noise canceling signal even when the operation speed is increased.

Drawings

Fig. 1 is a diagram showing a configuration of a data transfer circuit according to embodiment 1.

Fig. 2 is a timing chart showing an operation of the data transfer circuit according to embodiment 1.

Fig. 3 is a schematic timing chart showing the relationship between noise cancellation data and power supply current in the data transfer circuit according to embodiment 1.

Fig. 4 is a diagram showing a configuration of a data transfer circuit according to embodiment 2.

Fig. 5 is a timing chart showing an operation of the data transfer circuit according to embodiment 2.

Fig. 6 is a diagram showing a configuration of a data transfer circuit according to embodiment 3.

Fig. 7 is a timing chart showing an operation of the data transfer circuit according to embodiment 3.

Fig. 8 is a diagram showing a configuration of a data transfer circuit according to embodiment 4.

Fig. 9 is a diagram showing a configuration of a data transfer circuit according to embodiment 5.

Fig. 10A is a diagram showing a configuration of a data transfer circuit according to embodiment 6.

Fig. 10B is a diagram showing an example of a detailed configuration of the selector unit according to embodiment 6.

Fig. 11A is a timing chart showing an example of the operation of the data transfer circuit according to embodiment 6.

Fig. 11B is a timing chart showing another example of the operation of the data transfer circuit according to embodiment 6.

Fig. 12 is a diagram showing a configuration of a data transfer circuit according to embodiment 7.

Detailed Description

Hereinafter, a noise canceling circuit and a data transmission circuit according to an embodiment of the present disclosure will be described with reference to the drawings. The following embodiments are specific examples of the present invention, and the numerical values, shapes, materials, constituent elements, arrangement positions and connection forms of the constituent elements, steps, order of the steps, and the like are examples and are not intended to limit the present invention. In addition, the drawings are not necessarily strictly illustrated. In the drawings, the same reference numerals are assigned to substantially the same components, and redundant description is omitted or simplified.

(embodiment mode 1)

Fig. 1 is a diagram showing a configuration of a data transfer circuit 111 including a noise canceling circuit 110 according to embodiment 1. In the figure, the data transmission circuit 111 having the same configuration is provided for each of the plurality of lines (Lane1 to Lane z). Hereinafter, the data transmission circuit 111 provided in one line will be described (the same applies to other embodiments). Unless otherwise specified, each data and signal is 2-value data and a 2-value signal.

The data transfer circuit 111 includes a noise cancellation circuit 110, a 3 rd buffer 25, and a 4 th buffer 26. In addition, in fig. 1, the 2N-bit (bit) parallel data input to the data transfer circuit 111 is illustrated as being divided into N signal lines that transfer odd bits ("2N-bit parallel data (odd bits)") and N signal lines that transfer even bits ("2N-bit parallel data (even bits)").

The noise cancellation circuit 110 includes: a 1 st parallel-serial conversion circuit 21 that converts input 2N-bit (N is a natural number equal to or greater than 1) parallel data into serial data in synchronization with a clock signal; an inverting circuit 20 that inverts one of odd bits and even bits (odd bits in the present embodiment) of the input 2N-bit parallel data; a 2 nd parallel-serial conversion circuit 22 for converting the parallel data output from the inverter circuit 20 and the non-inverted parallel data of either one of the odd-numbered bits and the even-numbered bits (even-numbered bits in the present embodiment) of the input 2N-bit parallel data into serial data in synchronization with the clock signal; a 1 st buffer 23 to which the output data of the 1 st parallel-serial conversion circuit 21 is input; and a 2 nd buffer 24 to which the output data of the 2 nd parallel-serial conversion circuit 22 is input.

In the figure, the 1 st parallel-serial conversion circuit 21 and the 2 nd parallel-serial conversion circuit 22 are substantially constituted by the same circuit. Here, "substantially constituted by the same circuit" means having a circuit configuration in which substantially the same consumption current flows at the same timing, and typically, being connected to the same power supply and the same ground terminal, and being constituted by the same circuit.

Serial data after parallel-serial conversion in the 1 st parallel-serial conversion circuit 21 and the 2 nd parallel-serial conversion circuit 22 are input to the 1 st buffer 23 and the 2 nd buffer 24, respectively. The 1 st buffer 23 and the 2 nd buffer 24 are connected to a common power supply (here, a power supply for supplying the voltage VDD1) and to a common ground (here, a ground for the voltage VSS 1). A bypass capacitor (not shown) for smoothing power supply noise is connected between the power supply and the ground.

The 3 rd buffer 25 is connected to the output terminal of the 1 st buffer 23, and the 4 th buffer 26 is connected to the output terminal of the 2 nd buffer 24 so as to be equal to the load (load) of the 1 st buffer 23. Here, the 3 rd buffer 25 and the 4 th buffer 26 are differential output buffers. The 3 rd buffer 25 and the 4 th buffer 26 are connected to a common power supply (here, a power supply for supplying the voltage VDD2) and to a common ground (here, a ground for the voltage VSS 2). A bypass capacitor (not shown) for smoothing power supply noise is connected between the power supply and the ground.

The voltage of the power supply connected to the 1 st buffer 23 and the 2 nd buffer 24 (here, the voltage VDD1) and the voltage of the power supply connected to the 3 rd buffer 25 and the 4 th buffer 26 (here, the voltage VDD2) are different depending on the specification. When the 3 rd buffer 25 and the 4 th buffer 26 can be supplied with the same power supply voltage as the 1 st buffer 23 and the 2 nd buffer 24, the power supply and the ground line to which the 3 rd buffer 25 and the 4 th buffer 26 are connected are common to the power supply and the ground line to which the 1 st buffer 23 and the 2 nd buffer 24 are connected. On the other hand, when the 3 rd buffer 25 and the 4 th buffer 26 need to be supplied with power supply voltages different from those of the 1 st buffer 23 and the 2 nd buffer 24, the 3 rd buffer 25 and the 4 th buffer 26 are supplied with power supply voltages different from those of the 1 st buffer 23 and the 2 nd buffer 24.

The output signal of the 4 th buffer 26 is a signal unnecessary for the actual transmission circuit, and is not output to the outside of the transmission circuit. That is, the 4 th buffer 26 is configured as a dummy circuit. The 3 rd buffer 25 and the 4 th buffer 26 are substantially constituted by the same circuit. That is, the 3 rd buffer 25 and the 4 th buffer 26 may have the same circuit or different circuit configurations as long as substantially the same consumption current flows at the same timing when outputting data synchronized with the clock signal. In fig. 1, the 3 rd buffer 25 and the 4 th buffer 26 are differential output buffers, but may be single-ended output buffers.

Fig. 2 is a timing chart showing the operation of the data transfer circuit 111 according to embodiment 1. In this figure, "data bit" indicates data in which the 0 th to 9 th bits are repeated as 1 word. "parallel data" means 2N-bit parallel data input to the data transfer circuit 111. "noise-canceling parallel data" means parallel data obtained by combining inverted odd-numbered parallel data output from the inverting circuit 20 and non-inverted even-numbered parallel data with respect to input 2N-bit parallel data, that is, input data to the 2 nd parallel-serial converting circuit 22. "serial data" represents output data of the 1 st parallel-to-serial conversion circuit 21. "noise removal data" represents output data of the 2 nd parallel-serial conversion circuit 22.

As is apparent from this drawing, the odd-numbered bits of the input 2N-bit parallel data are inverted by the inverting circuit 20, while the even-numbered bits are not inverted, and the parallel data obtained by combining these inverted odd-numbered bits and even-numbered bits that are not inverted is subjected to parallel-serial conversion by the 2 nd parallel-serial converting circuit 22 to generate noise-canceled data (i.e., a noise-canceled signal). The noise removal data is a serial signal in which data does not transition at a portion where data transitions (a change from 1 to 0, or a change from 0 to 1) in the serial data output from the 1 st parallel-serial conversion circuit 21, and data transitions at a portion where data does not transition in the serial data.

Such noise canceling data is generated from parallel data (i.e., noise canceling parallel data) at a data rate of Fc/2N [ Hz ] without using serial data at a data rate Fc [ bps ] after parallel-serial conversion. Therefore, according to the data transfer circuit 111 including the noise cancellation circuit 110 of the present embodiment, it is possible to generate noise cancellation data very easily without using a high-speed clock signal and high-speed serial data in signal processing after parallel-to-serial conversion as in patent document 1. In addition, the generation of the noise canceling data may be performed not only by using the odd bits after inversion and the even bits without inversion for the input 2N-bit parallel data as in the present embodiment, but also by using the even bits after inversion and the odd bits without inversion.

Fig. 3 is a schematic timing chart showing the relationship between noise cancellation data and power supply current in the data transfer circuit 111 according to embodiment 1. In the present figure, "serial data" represents "serial data" in fig. 2, that is, output data of the 1 st parallel-serial conversion circuit 21. The "power-ground consumption current" below the buffer indicates the current flowing between the power and the ground in the 1 st buffer 23 and the 3 rd buffer 25. The "noise removal data" represents "noise removal data" of fig. 2, that is, output data of the 2 nd parallel-serial conversion circuit 22. The "power-ground consumption current" below the buffer indicates the current flowing between the power and the ground in the 2 nd buffer 24 and the 4 th buffer 26. The "total of power-ground consumption currents" indicates the total of currents flowing between the power and the ground in the 1 st buffer 23, the 2 nd buffer 24, the 3 rd buffer 25, and the 4 th buffer 26. The operation and effect of the noise cancellation circuit 110 will be described with reference to this drawing.

As shown in "current consumption between power supply and ground" in the 2 nd row from the top in fig. 3, when the data transfer circuit 111 outputs serial data in synchronization with a clock signal, instantaneous current flows between the power supply and ground of the 1 st buffer 23 and the 3 rd buffer 25 at the transition point. When the output data changes out of synchronization with the clock signal, no instantaneous current flows between the power supply and the ground of the 1 st buffer 23 and the 3 rd buffer 25. On the other hand, as shown in "power-ground current consumption" in the 4 th row from the top in fig. 3, when the serial data is shifted in synchronization with the clock signal, the 2 nd buffer 24 and the 4 th buffer 26 to which the noise removal data is input do not have a transition in output, and therefore, no instantaneous current flows between the power-ground lines of the 2 nd buffer 24 and the 4 th buffer 26. In the case where the serial data changes out of synchronization with the clock signal, the noise cancellation circuit 110 outputs noise cancellation data synchronized with the transition of the clock signal, and instantaneous currents flow between the power supply and the ground lines of the 2 nd buffer 24 and the 4 th buffer 26.

Since the 1 st buffer 23 and the 2 nd buffer 24 are connected to a common power supply and a common ground, and the 3 rd buffer 25 and the 4 th buffer 26 are also connected to a common power supply and a common ground, instantaneous current always flows between the power supply and the ground at timing synchronized with the clock signal regardless of the serial data pattern, as shown by "power-ground current consumption sum" in fig. 3, and the frequency of power supply noise is limited to a frequency band depending on the edge of the clock signal.

In general, the resonance point of the power supply impedance is designed to be several tens MHz to several hundreds MHz, and noise at a frequency higher than the resonance point is absorbed by a bypass capacitor connected between the power supply and the ground in the circuit. In the case where there is no noise cancellation circuit, power supply noise depends on the mode of serial data, and therefore, the frequency component thereof spreads over a wide range from the edge period (data rate) of the clock signal to the frequency of 1/D thereof (D is an integer of 1 or more). When the instantaneous current value is set to be the same at the edge timing of any clock signal, instantaneous current noise of the same level occurs in the above frequency range, and power supply noise increases as the frequency approaches the resonance point.

By using the noise canceling circuit 110 of the present invention, transient current noise occurs only at the edge period (data rate) of the clock signal, and is therefore reliably absorbed by the bypass capacitor, and power supply noise hardly occurs in the vicinity of the resonance point of the power supply impedance, and power supply noise can be relatively suppressed compared to the case where no noise canceling circuit is provided.

As described above, the noise canceling circuit 110 of the present embodiment includes: a 1 st parallel-serial conversion circuit 21 that converts input 2N-bit (N is a natural number equal to or greater than 1) parallel data into serial data in synchronization with a clock signal; an inversion circuit 20 for inverting either one of an odd-numbered bit and an even-numbered bit of the input 2N-bit parallel data; a 2 nd parallel-serial conversion circuit 22 for converting the parallel data output from the inversion circuit 20 and the parallel data of the other of the odd-numbered bits and the even-numbered bits of the input 2N-bit parallel data, which is not inverted, into serial data in synchronization with the clock signal; a 1 st buffer 23 to which the output data of the 1 st parallel-serial conversion circuit 21 is input; and a 2 nd buffer 24 to which the output data of the 2 nd parallel-serial conversion circuit 22 is input. The 1 st parallel-serial conversion circuit 21 and the 2 nd parallel-serial conversion circuit 22 are substantially constituted by the same circuit, the 1 st buffer 23 and the 2 nd buffer 24 are substantially constituted by the same circuit, and the 1 st buffer 23 and the 2 nd buffer 24 are connected to a common power supply and to a common ground.

Thus, the noise-canceled data output from the 2 nd parallel-serial converter circuit 22 becomes a serial signal in which data does not transition at a portion where data transitions (transition, jump) in the serial data output from the 1 st parallel-serial converter circuit 21 and data does not transition at a portion where data does not transition in the serial data. Therefore, the 1 st buffer 23 connected to the output of the 1 st parallel-to-serial converter 21 allows a transient current to flow to a portion where there is a transition in serial data, while the 2 nd buffer 24 connected to the output of the 2 nd parallel-to-serial converter 22 allows a transient current to flow to a portion where there is no transition in serial data. As a result, the instantaneous current noise generated by the noise canceling circuit 110 occurs only at the edge period (data rate) of the clock signal, and is therefore reliably absorbed by the bypass capacitor connected between the power supply and the ground.

Further, according to the noise canceling circuit 110 of the present embodiment, noise canceling data is generated not by signal processing after parallel-serial conversion as in patent document 1 but by using parallel data before parallel-serial conversion. Therefore, it is not necessary to use a high-speed clock signal and high-speed serial data, and noise-canceled data can be generated very easily compared with the conventional one. That is, a noise canceling circuit capable of easily generating a noise canceling signal even when the operation speed is increased can be realized.

The same load as the output terminal of the 1 st buffer 23 is connected to the output terminal of the 2 nd buffer 24. Thus, the consumption current in the 1 st buffer 23 is the same as the consumption current in the 2 nd buffer 24, and the current consumed in the noise cancellation circuit is constant regardless of the parallel data to be input.

The noise cancellation circuit 110 includes a capacitor for smoothing power supply noise, which is connected between the power supply and the ground connected to the 1 st buffer 23 and the 2 nd buffer 24. Thus, the capacitor connected between the power supply and the ground functions as a bypass capacitor, and instantaneous current noise occurring in the noise cancellation circuit 110 in a certain period is significantly suppressed.

The data transfer circuit 111 of the present embodiment includes: a noise cancellation circuit 110; a 3 rd buffer 25 connected to an output terminal of the 1 st buffer 23 included in the noise canceling circuit 110, the 3 rd buffer 25 outputting a differential signal; and a 4 th buffer 26 connected to the output terminal of the 2 nd buffer 24 included in the noise canceling circuit 110, and substantially constituted by the same circuit as the 3 rd buffer 25. Thus, the data transfer circuit 111 including the noise cancellation circuit 110 capable of easily generating a noise cancellation signal even when the operation speed is increased can be realized.

The 3 rd buffer 25 and the 4 th buffer 26 are connected to a common power supply and to a common ground. Thus, transient current noise occurring in the 3 rd buffer 25 and the 4 th buffer 26 in a constant cycle between the power supply and the ground can be suppressed significantly by the bypass capacitor connected between the power supply and the ground.

(embodiment mode 2)

Here, as embodiment 2, a configuration in which the parallel-to-serial conversion circuit of embodiment 1 outputs multi-bit serial data will be described.

Fig. 4 is a diagram showing the configuration of a data transfer circuit 121 including the noise canceling circuit 120 according to embodiment 2. The data transmission circuit 121 has the following structure: the 1 st parallel-serial conversion circuit 21 and the 2 nd parallel-serial conversion circuit 22 in the data transmission circuit 111 of embodiment 1 are replaced with a 1 st parallel-serial conversion circuit 210 and a 2 nd parallel-serial conversion circuit 220, respectively, which output multi-bit serial data; a plurality of 1 st buffers 23 and 2 nd buffers 24 are provided, and 3 rd buffers 25 and 4 th buffers 26 in embodiment 1 are replaced with 3 rd buffers 35 and 4 th buffers 36 of a multi-bit input, respectively.

Both the 1 st parallel-serial conversion circuit 210 and the 2 nd parallel-serial conversion circuit 220 in fig. 4 are parallel-serial conversion circuits having a Y tap emphasis function (Y tap emphasis function) for outputting serial data in parallel with Y bits (Y is a natural number of 2 or more) from 2N-bit parallel data.

In high-speed data communication, since bits that change more contain more high-frequency components and bits that change less contain less high-frequency components, the waveform attenuates as the high-frequency components are closer to the receiving circuit side according to the attenuation characteristics of the transmission path. Therefore, the waveform is relatively small for bits that change more than for bits that change less. Therefore, pre-emphasis and post-emphasis are performed as measures for making the waveform received at the receiving side constant. Therefore, the present embodiment includes a parallel-to-serial conversion circuit that combines the emphasis signals as shown in fig. 4. That is, the 1 st parallel-serial conversion circuit 210 and the 2 nd parallel-serial conversion circuit 220 output an emphasis signal (i.e., serial data to be added for use) in addition to normal serial data.

Fig. 5 is a timing chart showing the operation of the data transfer circuit 121 according to embodiment 2. Here, the emphasis data output from the 1 st parallel-to-serial conversion circuit 210 and the 2 nd parallel-to-serial conversion circuit 220 is serial data that has been delayed by 1 cycle (i.e., 1 clock amount) from the serial data. Fig. 5 illustrates a case where the 1 st parallel-serial conversion circuit 210 and the 2 nd parallel-serial conversion circuit 220 operate as a post emphasis circuit with Y being 2. That is, both the 1 st parallel-serial conversion circuit 210 and the 2 nd parallel-serial conversion circuit 220 output 2-bit serial data. One bit is serial data and the other bit is serial data delayed by 1 cycle of the data rate.

In fig. 5, "data bit" indicates data in which 0 th to 9 th bits are repeated as 1 word. The "parallel data" represents 2N-bit parallel data input to the data transfer circuit 121. The "noise-removed parallel data" is parallel data obtained by combining inverted odd-numbered parallel data output from the inverting circuit 20 and non-inverted even-numbered parallel data with respect to input 2N-bit parallel data, and is input data to the 2 nd parallel-serial converting circuit 220. "serial data" represents output data of one of the 1 st parallel-to-serial conversion circuits 210. The "post emphasis signal" indicates the other output data of the 1 st parallel-to-serial conversion circuit 210, and is data obtained by delaying the serial data by 1 clock. The "noise removal data" indicates output data of one of the 2 nd parallel-serial conversion circuits 220. The "post-emphasis signal noise removal data" indicates the other output data of the 2 nd parallel-serial conversion circuit 220, and is data obtained by delaying the noise removal data by 1 clock. "the 3 rd buffer 35 outputs a waveform" indicates a waveform of a signal output from the 3 rd buffer 35.

The 2-bit serial data output from the 1 st parallel-serial conversion circuit 210 and the 2 nd parallel-serial conversion circuit 220 are input to the 1 st buffer 23 and the 2 nd buffer 24 arranged in 2 bits, respectively, and output signals from the 1 st buffer 23 and the 2 nd buffer 24 are input to the 3 rd buffer 35 and the 4 th buffer 36 which are output buffers having a weighting function. At this time, the output waveform of the 3 rd buffer 35 is a waveform in which the signal of the data rate 1 cycle is emphasized and the signal intensity of the continuous data of 2 cycles or more is relatively reduced, as shown in "the output waveform of the 3 rd buffer 35" in fig. 5. Thus, a transmission signal suitable for high-speed data communication is generated in which the signal intensity of the high-frequency component is emphasized over that of the low-frequency component.

In the case of the noise canceling circuit described in patent document 1, if the output bit width of the parallel-serial conversion circuit increases, a noise canceling circuit corresponding to the bit width is required, and it is necessary to design a plurality of noise canceling circuits that operate at high speed. In contrast, according to the present embodiment, noise cancellation data corresponding to each emphasis data signal can be easily generated without adding a noise cancellation circuit to the 1 st parallel-to-serial conversion circuit 210 and the 2 nd parallel-to-serial conversion circuit 220 that output multiple bits of emphasis serial data from 2N-bit parallel data.

(embodiment mode 3)

Here, as embodiment 3, a configuration in which the generation of the noise canceling data of embodiment 1 is added to the parallel-serial conversion circuit will be described.

Fig. 6 is a diagram showing the configuration of a data transfer circuit 131 including a noise canceling circuit 130 according to embodiment 3. The data transmission circuit 131 has the following structure: the 1 st parallel-serial conversion circuit 21 and the 2 nd parallel-serial conversion circuit 22 in the data transmission circuit 111 of embodiment 1 are replaced with three parallel-serial conversion circuits (i.e., a 2N: 2M parallel-serial conversion circuit 43, a 1 st parallel-serial conversion circuit 41, and a 2 nd parallel-serial conversion circuit 42). In the present specification, the symbol "a: b "means to convert a-bit parallel data into B-bit parallel data.

That is, the noise canceling circuit 130 includes 2N for converting 2N-bit parallel data into 2M-bit (M is a natural number equal to or less than N) parallel data (in other words, 2M-bit parallel serial data when M is smaller than N): a 2M parallel-serial conversion circuit 43, and a 1 st parallel-serial conversion circuit 41 and a 2 nd parallel-serial conversion circuit 42 for converting 2M-bit parallel data into 1-bit serial data.

According to the present embodiment, by 2N: the 2M parallel-serial conversion circuit 43, the inverter circuit 20, and the 2 nd parallel-serial conversion circuit 42 can generate noise-canceled data by performing parallel-serial conversion on parallel data of the 2N-bit parallel data, which is the odd-numbered bit after inversion and the even-numbered bit without inversion, or the odd-numbered bit without inversion and the even-numbered bit after inversion. At this time, if the data rate of the serial data output from the 1 st parallel-to-serial conversion circuit 41 is set to Fc [ bps ], the generation of noise cancellation data is performed at F/2M [ Hz ].

The operation of the data transfer circuit 131 when N is 5 (i.e., 2N is 10 bits) and M is 1 (i.e., 2M is 2 bits) will be described with reference to fig. 7. Fig. 7 is a timing chart showing the operation of the data transfer circuit 131 according to embodiment 3. In this figure, "data bit" indicates data in which 0 th to 9 th bits are repeated as 1 word. "serial data (even bit string)" indicates 2N: one of the 2-bit outputs of the 2M parallel-serial conversion circuit 43 is output data. "serial data (odd bit string)" represents 2N: the other of the 2-bit outputs of the 2M parallel-serial conversion circuit 43 outputs data. "serial data" represents output data of the 1 st parallel-to-serial conversion circuit 41. "serial data (even bit string)" indicates 2N: one of the 2-bit outputs of the 2M parallel-serial conversion circuit 43 is output data. "inverted serial data (odd bit string)" indicates output data of the inverting circuit 20. "noise removal data" represents output data of the 2 nd parallel-serial conversion circuit 42.

2N: the 2M parallel-serial conversion circuit 43 converts the input 10-bit parallel data into 2-bit parallel data. At this time, the 2-bit parallel data is odd-numbered serial data ("serial data (odd bit string)" in fig. 7) and even-numbered serial data ("serial data (even bit string)" in fig. 7), respectively, and has a frequency 1/2 times the data rate. Next, the 2 nd parallel-serial conversion circuit 42 performs parallel-serial conversion on the data obtained by inverting the odd-numbered serial data by the inverter circuit 20 and the even-numbered serial data that is not inverted, thereby generating noise-canceled data ("noise-canceled data" in fig. 7) in the same manner as in embodiment 1.

In contrast to the present embodiment, when the even-numbered bits after inversion and the odd-numbered bits without inversion are used for the input 2N-bit parallel data, the noise canceling data can be generated similarly.

In addition, N and M can be designed to have arbitrary values.

In the present embodiment, the ratio of 2N: 2M, 2M: although the 2-stage (stage) parallel-serial conversion circuit 1 has been described, even with a configuration in which the parallel-serial conversion circuit is divided into a plurality of stages (stages), noise canceling data can be generated if one of odd-numbered bits and even-numbered bits of 2N-bit parallel data can be inverted and parallel-serial conversion can be performed on parallel data combined with the other data that is not inverted.