JP3247045B2 - Time counting circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to a time counting circuitry which measures the time such as a pulse interval of the pulse signal.

[0002]

2. Description of the Related Art A time counting circuit for measuring a time such as a pulse interval of a pulse signal is expected to be used for digital communication and the like. In recent years, the time counting circuit can be arranged on the same chip as other digital circuits by being constituted by CMOS transistors. As a result, the cost of the semiconductor device has been greatly reduced.

Further, the time counting circuit can be applied to various fields such as demodulation of FM waves and demodulation of LSI bus signals by further improving accuracy and stabilizing operation. In particular,
If a time counting circuit capable of measuring a minute time accurately and stably can be used for demodulating the bus signal of the LSI, the number of buses of the LSI can be greatly reduced.

FIG. 21 is a block diagram showing an example of a conventional time counting circuit. In FIG. 21, 51 is a delay circuit ring, 54 is a holding circuit row, 55 is an arithmetic circuit, 56a is a counter, and 56b is a counter output holding circuit. A pulse signal to be measured is input from the pulse signal input terminal, and time data representing a pulse interval of the input pulse signal to be measured is output from the operation result output terminal.

The time counting circuit shown in FIG. 21 is obtained by connecting seven delay circuits each composed of two inverters and one delay circuit composed of three inverters (the eighth stage in FIG. 21) in a ring shape. The configured delay circuit ring 51 is used. The delay circuit ring 51 has an odd number (2 ×
Since it is composed of (7 + 3 = 17) inverters, so-called oscillation occurs, and signal transitions sequentially move with time and circulate through the delay circuit ring 51. Therefore, time can be measured by observing the change in the output signal of each delay circuit.

The output signal of each delay circuit constituting the delay circuit ring 51 is held by a flip-flop (FF) constituting a holding circuit row 54. When the pulse signal to be measured rises, the arithmetic circuit 55 Is output to Further, the counter 56a measures the number of turns of the signal transition in the delay circuit ring 51, and outputs the measured number of turns to the arithmetic circuit 55 via the counter output holding circuit 56b. The arithmetic circuit 55 converts the signal output from the holding circuit array 54 into numerical data, calculates the pulse interval of the pulse signal to be measured based on the numerical data and the number of turns of the signal transition, and outputs a calculation result output terminal. (IEICE, IEICE Technical Report, ICD93-77 (1993-
08), “Time / numerical conversion LSI”).

[0007]

However, the conventional time counting circuit has the following problems.

FIG. 22A is a graph showing a change in output voltage of each delay circuit constituting the delay circuit ring 51.
In FIG. 22A, a straight line 1 indicates a change in the output voltage of the first-stage delay circuit, and similarly, straight lines 2 to 7 indicate changes in the output voltage of the second- to seventh-stage delay circuits, respectively. Is shown.

As shown in FIG. 22A, the output voltage of each delay circuit is changed from VSS ("0" at a logic level) to V
It takes some time to change to DD ("1" at the logic level). This is because each delay circuit drives a load appearing at the input terminal of the next-stage delay circuit, that is, the input capacitance, and corresponds to a charging time for charging the input terminal of the next-stage delay circuit.

For example, when the output voltage of the first-stage delay circuit starts to change from "0" to "1", the output voltage of the second-stage delay circuit changes from "0" to "1" after a certain delay time. Begins to change. Further, after a certain delay time, the output voltage of the third-stage delay circuit starts to change from “0” to “1”. As described above, the output voltage of each delay circuit changes sequentially. As shown in FIG. 22A, there are a plurality of delay circuits whose output voltage changes at a certain timing.

The operation of the flip-flop (FF) forming the holding circuit row 54 and the operation of the delay circuit ring 51 are not synchronized. Therefore, in the flip-flop, not only a voltage representing a so-called logic level “0” or “1” is input, but also an intermediate voltage during a transition from “0” to “1” may be input. Since the flip-flop is a circuit that holds and outputs an input signal at one of logic levels “0” and “1”, the intermediate voltage is also at a logic level of either “0” or “1”. And hold it. That is, there is an input voltage range in which the probability that the flip-flop holds “0” and the probability that it holds “1” are both present. This range of the input voltage is called an uncertain region.

Assume that a pulse signal to be measured rises at time T in FIG. At this time,
Since the output voltage of the first-stage delay circuit and the output voltage of the second-stage delay circuit are both in the uncertainty region, the first-stage flip-flop is “0” with probability A (0 <A <1). Hold and
“1” is held at the probability B (0 <B <1, where B = 1−A). The second-stage flip-flop has a probability C
(0 <C <1) holds “0” and the probability D (0 <D <
1, where D = 1−C) holds “1”.

While the time counting circuit as shown in FIG. 21 is operating normally, the outputs of the first to fifth flip-flops are "00000" → "10000" → "11".
000 ". However, at time T, A × D
Is output with a probability of "01000". At this time, the arithmetic circuit 55 cannot calculate correctly,
Generates an error. This is called erroneous holding of the holding circuit array.

Further, due to the influence of noise on the power supply voltage supplied to the delay circuit and the flip-flop, etc.,
In some cases, the output voltage of the delay circuit changes slowly and the uncertainty region expands. FIG. 22B is a graph showing a change in the output voltage of each delay circuit in such a case. Assume now that the pulse signal to be measured rises at time Te in FIG. At this time, since the output voltages of the delay circuits of the second to fifth stages are in the uncertain region, the possibility that the holding circuit row may cause erroneous holding increases and the erroneous holding increases as compared with the case of FIG. The error generated by holding also increases.

Further, the conventional time counting circuit has another problem.

In an actual semiconductor manufacturing process, the performance of a transistor to be manufactured varies. For this reason,
The actual threshold voltage of each flip-flop varies.

FIG. 23A is a graph showing a change in output voltage of each delay circuit constituting the delay circuit ring 51.
In FIG. 23A, a straight line 1 indicates a change in the output voltage of the first stage delay circuit, and similarly, straight lines 2 to 7 indicate a change in the output voltage of the second to seventh stage delay circuits, respectively. Is shown. In addition, the first stage and the third stage to the seventh stage flip
Let the threshold voltage of the flop be Va, and let the threshold voltage of the second stage flip-flop be Vb.

FIG. 23B is a graph showing a change in the time code output from each flip-flop constituting the holding circuit array 54. In FIG. 23B, after the output voltage of the first-stage delay circuit reaches the threshold voltage Va of the first-stage flip-flop, the output voltage of the second-stage delay circuit is changed to the second-stage flip-flop. The time required until the flop reaches the threshold voltage Vb (time code 1) is represented by t1. Also,
After the output voltage of the second-stage delay circuit reaches the threshold voltage Vb of the second-stage flip-flop, the output voltage of the third-stage delay circuit is changed to the threshold voltage of the third-stage flip-flop. The time required to reach Va (time code 2) is defined as t2.

Since the threshold voltage Va of the first-stage and third-stage flip-flops is different from the threshold voltage Vb of the second-stage flip-flop, the time t1 indicating the time code 1 and the time code 2 differs from time t2. For this reason, there is a problem that the linearity of time data with respect to real time deteriorates, and the accuracy of time measurement decreases.

In view of the above problems, an object of the present invention is to provide a time counting circuit with higher accuracy than before .

[0021]

In order to solve the above-mentioned problems, according to the present invention, an output signal of each delay circuit is provided between a delay circuit ring and a row of holding circuits by a logic indicated by the output signal and each holding circuit. By providing a conversion means comprising a conversion circuit for converting the logic represented by the logic level signal output from the circuit to be equal, the erroneous holding of the holding circuit row is prevented, and the linearity in the relationship between time data and real time is provided. Is guaranteed.

More specifically, a solution of the present invention is that a time counting circuit for measuring a pulse interval of a pulse signal is constituted by a plurality of delay circuits connected in a ring shape. A delay circuit ring in which a transition of a signal whose output signal transitions from one logic level to another logic level circulates, and a plurality of conversion circuits each having an input of an output signal of a delay circuit constituting the delay circuit ring,
A conversion unit configured to convert and output an output signal of a delay circuit input to each conversion circuit according to an instruction based on at least one of the rising and falling timings of a pulse signal to be measured; and the conversion unit. A holding circuit comprising a plurality of holding circuits each having an input of an output signal of the conversion circuit, wherein each holding circuit converts the output signal of the conversion circuit to be input into a logic level signal and outputs the signal at a timing different from the above timing Column, converting the logic level signal output from the holding circuit column into numerical data,
An arithmetic circuit for calculating a pulse interval of the pulse signal to be measured based on the numerical data, wherein each converting circuit constituting the converting means samples the input signal.
And the difference between the sampled signal and a common reference potential
Amplify the voltage and apply the amplified difference voltage to a constant potential.
Output .

According to the first aspect of the present invention, the signal transition circulates through the delay circuit ring including the delay circuits connected in a ring. That is, the logic level of the output signal of each delay circuit changes over time. Each conversion circuit constituting the conversion means converts and outputs the output signal of the delay circuit to be input according to an instruction based on at least one of the rising and falling timings of the pulse signal to be measured. The arithmetic circuit converts the logical level signal obtained based on the signal output from the conversion means into numerical data, and calculates the pulse interval of the pulse signal to be measured based on the numerical data.

However, since the transition of the signal in the delay circuit ring and the pulse signal to be measured are asynchronous, when the pulse signal to be measured rises or falls, the output signal of a certain delay circuit changes from one logical level to another. It may be in the process of transitioning to a logic level. Here, each conversion circuit samples the input signal and outputs the sampled signal.
And the difference voltage between them and the common reference potential
The difference voltage is applied to a constant potential and output. For this reason,
The holding circuit does not cause erroneous holding even when the output signal of the delay circuit transitions from one logic level to another logic level, and is a logic representing the same logic as the logic indicated by the output signal of the delay circuit. The level signal can be input to the arithmetic circuit. Therefore, it is possible to realize a time counting circuit with higher accuracy than before.

According to a second aspect of the present invention, in the time counting circuit of the first aspect, a pulse signal to be measured is input, and a pulse signal is measured based on at least one of the rising and falling timings of the pulse signal to be measured. A switch signal generating circuit for generating a first switch signal and a second switch signal;
In accordance with an instruction of the first switch signal generated by the switch signal generation circuit, an output signal of a delay circuit to be input is converted and output, and a holding circuit forming a holding circuit row includes the switch signal generation circuit. According to an instruction of the second switch signal generated by the circuit, an output signal of the conversion circuit to be input is converted into a logic level signal and output.

According to a third aspect of the present invention, the conversion circuit in the time counting circuit of the second aspect outputs a signal of a constant potential when there is no instruction by the first switch signal. When instructed, the conversion circuit samples the output signal of the delay circuit as an input, amplifies the difference voltage between the potential of the sampled signal and a predetermined reference potential, and converts the amplified difference voltage to the constant potential. And a sampling circuit for applying the signal to the output.

According to the third aspect of the present invention, in the sampling circuit of the conversion circuit, when indicated by the first switch signal, the signal at the output terminal of the delay circuit to which the conversion circuit is connected is sampled. . Further, a difference voltage between the potential of the sampled signal and a predetermined reference potential is amplified, and the amplified difference voltage is applied to a constant potential output when no instruction is given by the first switch signal. Is done. For this reason, the potential of the output signal of the sampling circuit is higher than the potential of the sampled signal when the potential of the sampled signal is higher than a predetermined reference potential, and the potential of the sampled signal. Is lower than a predetermined reference potential, the potential is further lower than the potential of the sampled signal. That is,
The logic of the sampled signal is determined by comparison with a predetermined reference potential, and a signal is output such that the holding circuit does not cause erroneous holding.

Therefore, even if the output signal of the delay circuit connected via the conversion circuit is in the process of transition from one logic level to another logic level, the holding circuit has the same logic as the signal indicated by this signal. A logic level signal representing logic can be reliably output. Further, even if the threshold voltage of the holding circuit varies, the influence can be reduced.

According to a fourth aspect of the present invention, the sampling circuit in the time counting circuit according to the third aspect generates a predetermined reference potential internally.

According to the fourth aspect of the present invention, even if the potential of the sampled signal fluctuates due to the fluctuation of the power supply voltage, the predetermined reference potential also fluctuates, so that no error occurs in the determination of logic. Therefore, the holding circuit can stably output a logic level signal representing the same logic as the logic indicated by the output signal of the delay circuit connected via the conversion circuit.

According to a fifth aspect of the present invention, in the time counting circuit according to the third aspect, the sampling circuit includes an external input terminal to which a signal is externally input, and a first circuit to which a signal from the external input terminal is input. A second circuit that receives a signal output from the first circuit as an input; and a second circuit that is provided between the external input terminal and an input terminal of the first circuit. First switch means set to one of a conduction state for connecting an input terminal of the first circuit and a non-conduction state of disconnecting the external input terminal and the input terminal of the first circuit; and A conductive state provided between an input terminal of the second circuit and an output terminal of the second circuit for connecting an input terminal of the first circuit and an output terminal of the second circuit, and the first circuit Of the second circuit and the output terminal of the second circuit Assume that a second switching means which is set to one of a conductive state.

The first circuit inverts and amplifies a voltage at a first capacitor whose one terminal is connected to an input terminal of the first circuit and a voltage at another terminal of the first capacitor. A first inverting amplifier for outputting to an output terminal of the first circuit, and an input terminal of the first inverting amplifier provided between an input terminal and an output terminal of the first inverting amplifier; And a third switch means that is set to one of a conduction state for connecting an output terminal and a non-conduction state for disconnecting an input terminal and an output terminal of the first inverting amplifier circuit. The second circuit inverts and amplifies a voltage at another terminal of which one terminal is connected to an input terminal of the second circuit and an output terminal of the second circuit by inverting and amplifying a voltage at another terminal of the second capacitance. A second inverting amplifier circuit for outputting to a terminal, and an input of the second inverting amplifier circuit A conductive state provided between the input terminal and the output terminal of the second inverting amplifier circuit for connecting the input terminal and the output terminal of the second inverting amplifier circuit, and a non-conductive state for disconnecting the input terminal and the output terminal of the second inverting amplifier circuit. And fourth switch means set to either one of the above.

Further, when there is no instruction by the first switch signal, the first switch means and the third switch means are in a conductive state, and the second switch means and the fourth switch means are non-conductive. State, the first
Once instructed by the switch signal of the above, once the first switch means and the third switch means are turned off and the second switch means and the fourth switch means are turned on, Again, the first switch means and the third switch means are turned on, and the second switch means and the fourth switch means are turned off.

According to the fifth aspect of the present invention, when there is no instruction by the first switch signal, the external input terminal is connected to the input terminal of the first circuit because the first switch means is in the conductive state. Since the second switch is non-conductive, the input terminal of the first circuit is disconnected from the output terminal of the second circuit, so that the potential of the external input signal (V
is applied to one terminal of the first capacitor. Further, since the third switch means is in a conductive state, the input potential and the output potential of the first inverting amplifier circuit become equal, and the potential (Va1) is applied to the other terminal of the first capacitor. . That is, a potential difference (Vin-Va1) is given to the first capacitor.

When instructed by the first switch signal,
Since the first switch is turned off, the external input terminal is disconnected from the input terminal of the first circuit, and the second input terminal is disconnected from the second input terminal.
Is turned on, the input terminal of the first circuit is connected to the output terminal of the second circuit.
Is applied to one terminal of the first capacitor. In addition, since the fourth switch is turned on, the input potential and the output potential of the second inverting amplifier circuit become equal, and the potential (Va2) becomes the potential of the output signal of the second circuit. That is, the potential Va2 is applied to one terminal of the first capacitor. Since the charge accumulated in the first capacitor is stored, a potential obtained by subtracting the potential difference (Vin−Va1) from the potential Va2 appears at the other terminal of the first capacitor. Since the third switching means is non-conductive, the input terminal and the output terminal of the first inverting amplifier circuit are separated, so that the potential at the other terminal of the first capacitor is reduced by the first inverting amplifier circuit. It is inverted and amplified. As a result, the potential (referred to as Vmid) of the output signal of the first circuit becomes G1 (Vin).
−Va2) + Va2. Here, G1 is the voltage gain of the first inverting amplifier circuit. The potential Vmid is applied to one terminal of the second capacitor, and the potential Va2 is applied to the other terminal.
That is, a potential difference (Vmid-Va2) is given to the second capacitor.

Further, the third switching means is turned on again, so that the input potential and the output potential of the first inverting amplifier circuit become equal, and the potential Va1 is applied to one terminal of the second capacitor. Will be. Since the electric charge accumulated in the second capacitor is preserved, the potential difference (Vmid-Va2) is maintained. The input terminal of the first circuit is disconnected from the output terminal of the second circuit because the second switch is non-conductive, and the second inverting amplifier circuit is non-conductive because the fourth switch is non-conductive. Is separated from the input terminal of the second capacitor, the potential at the other terminal of the second capacitor is inverted and amplified by the second inverting amplifier circuit. As a result, the potential (referred to as Vout) of the output signal of the second circuit becomes G2 (Vmi
d−Va1) + Va2 = G2 G1 (Vin−Va2) + Va2. Here, G2 is the voltage gain of the second inverting amplifier circuit.

As can be seen from the above equation, when indicated by the first switch signal, the potential of the input signal is sampled, and the difference voltage between the potential Vin and the potential Va2 of the sampled signal is amplified. At the same time, the amplified difference voltage is applied to the potential Va2 and output. For this reason, the potential of the output signal of the sampling circuit becomes higher than the potential Vin when the potential Vin of the sampled signal is higher than the potential Va2, and becomes higher than the potential Vin when the potential Vin is lower than the potential Va2. Will be even lower. That is, the output potential of the second inverting circuit when the input terminal and the output terminal are connected is set to a predetermined reference potential, the logic of the sampled signal is determined by comparison with the predetermined reference potential, and the holding circuit Will be output so as not to cause erroneous holding. Therefore, the holding circuit
Even if the output signal of the delay circuit connected via the conversion circuit is in the process of transitioning from one logic level to another logic level, a logic level signal representing the same logic as the logic indicated by this signal is reliably generated. Can be output. Further, even if the threshold voltage of the holding circuit varies, the influence can be reduced. Furthermore, even if the potential of the sampled signal fluctuates due to the fluctuation of the power supply voltage, the predetermined reference potential also fluctuates, so that no error occurs in the logic judgment. Therefore, the holding circuit can stably output a logic level signal representing the same logic as the logic indicated by the output signal of the delay circuit connected via the conversion circuit.

According to the invention of claim 6, the conversion circuit in the time counting circuit of claim 2 outputs a signal of a constant potential when there is no instruction by the first switch signal. When instructed, the conversion circuit amplifies the difference voltage between the potential of the output signal of the delay circuit input to the conversion circuit and a predetermined reference potential, and applies and outputs the amplified difference voltage to the constant potential. It has a cascade circuit.

According to the invention of claim 6, in the hold cascade circuit included in the conversion circuit, when indicated by the first switch signal, the potential of the signal at the output terminal of the delay circuit to which the conversion circuit is connected is reduced. The difference voltage from the predetermined reference potential is amplified, and the amplified difference voltage is applied to the constant potential output when there is no instruction by the first switch signal. Therefore, when the potential of the output signal of the hold cascade circuit is higher than the predetermined reference potential, the potential of the output signal of the delay circuit becomes higher than the potential of the output signal of the delay circuit. Is lower than the predetermined reference potential, the potential becomes lower than the potential of the output signal of the delay circuit. That is, the logic of the output signal of the delay circuit is determined by comparison with a predetermined reference potential, and a signal is output such that the holding circuit does not cause erroneous holding. Therefore,
The holding circuit keeps the same logic as the logic indicated by the output signal of the delay circuit even when the output signal of the delay circuit connected via the conversion circuit is in the process of transitioning from one logic level to another logic level. The logical level signal represented can be output reliably. Further, even if the threshold voltage of the holding circuit varies, the influence can be reduced.

According to a seventh aspect of the present invention, in the time counting circuit of the first aspect, the phase of the signal at the output terminal of one of the delay circuits constituting the delay circuit ring is compared with the phase of the reference clock signal, and the phase correction instruction is issued. A phase comparator for outputting a control signal for controlling a signal delay time to a delay circuit constituting the delay circuit ring in accordance with an instruction of the signal output from the phase comparator. It is assumed that the delay circuit ring, the phase comparator, and the loop filter form a phase locked loop (PLL).

According to the seventh aspect of the present invention, in the phase comparator, the phase of the reference clock signal is compared with the phase of the signal at the output terminal of one of the delay circuits forming the delay circuit ring.
A signal for instructing phase correction is output. The loop filter outputs a control signal for controlling the signal delay time to a delay circuit constituting a delay circuit ring according to an instruction of a signal output from the phase comparator. That is, a phase locked loop (PLL) is configured by the delay circuit ring, the phase comparator, and the loop filter. Therefore, the transmission time of the signal transition in the delay circuit ring is controlled to be constant .

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a configuration diagram of a time counting circuit according to one embodiment of the present invention. In FIG. 1, 11 is a delay circuit ring, 12 is a switch signal generation circuit, 13 is a sampling circuit array as a conversion means including a sampling circuit 13a as a conversion circuit, and 14 is a flip-flop 1 as a holding circuit.
A holding circuit array composed of 4a, 15 is an arithmetic circuit, 16a is a counter, and 16b is a counter output holding circuit. Also,
A pulse signal to be measured is input from the pulse signal input terminal, and time data representing a pulse interval of the pulse signal to be measured is output from the calculation result output terminal.

The delay circuit ring 11 is composed of eight delay circuits connected in a ring. That is,
The first to eighth stage delay circuits are connected in series, and the output terminal of the eighth stage delay circuit is connected to the first stage input terminal. The delay circuits of the first to seventh stages are constituted by two inverters connected in series, and the delay circuit of the eighth stage is constituted by three inverters connected in series. That is, the delay circuit ring 11
It is configured by connecting 17 (= 2 × 7 + 3) inverters in a ring shape.

The switch signal generation circuit 12 receives a pulse signal to be measured and outputs a first switch signal 12a to the sampling circuit array 13 based on the rising timing of the pulse signal to be measured. The second switch signal 12b is also output to the holding circuit array 14 based on the rising timing of the pulse signal to be measured. Arithmetic circuit 1
5 and the counter output holding circuit 16b also output a clock signal based on the rising timing of the pulse signal to be measured.

The sampling circuit array 13 includes a delay circuit ring 11
And a sampling circuit (SH) 13a as eight conversion circuits respectively connected to the output terminals of the delay circuit constituting. Each sampling circuit 13a receives the first switch signal 1 input from the switch signal generation circuit 12.
According to the instruction of 2a, the output signal of the delay circuit is sampled.

The holding circuit array 14 is a flip-flop (F) as eight holding circuits connected to the output terminals of the sampling circuit 13a constituting the sampling circuit array 13.
F) 14a. Each flip-flop 14a holds the signal output from the sampling circuit 13a, and outputs the held signal when the second switch signal 12b is input from the switch signal generation circuit 12.

One sampling circuit 13a and this sampling circuit 1
A logic decision circuit is constituted by the flip-flop 14a connected to the output terminal 3a.

The counter 16a is connected to the output terminal of the eighth stage delay circuit (the input terminal of the first stage delay circuit) of the delay circuit ring 11, and counts the number of signal transitions in the delay circuit ring 11. I do. The counter output holding circuit row 16b holds the 2-bit count data output from the counter 16a, and outputs the held count data when a clock signal is input from the switch signal generation circuit 12.

The arithmetic circuit 15 converts the signal output from the holding circuit array 14 into numerical data, performs an arithmetic operation together with the count data output from the counter output holding circuit array 16b, and outputs 5-bit time data. I do.

The operation of the time counting circuit shown in FIG. 1 will be described in more detail with reference to Table 1.

Since an odd number (17) of inverters are connected in a ring shape in the delay circuit ring 11, so-called oscillation occurs, and signal transitions sequentially move with time and circulate through the delay circuit ring 11. I do. 1st to 7th
Since the delay circuit of the stage is constituted by two inverters, a signal representing the same logic level as the input signal is output after a certain delay time. Further, since the eighth stage delay circuit is constituted by three inverters, a signal representing a logic level different from the input signal is output after a certain delay time. Each inverter is configured such that the delay times in the delay circuits of each stage are equal.

Table 1 is a table showing temporal changes of output signals of the respective delay circuits constituting the delay circuit ring 11, and numerical data when the pulse signal to be measured rises at each time. In Table 1, with respect to the output signal of each delay circuit, the H level is represented by “1” and the L level is represented by “0”. The time interval is a signal delay time in one delay circuit, and is assumed to be 1 ns here.

[0054]

[Table 1]

Now (time 0), it is assumed that the output signals of the delay circuits of the first to seventh stages are at the L level and the output signal of the delay circuit of the eighth stage is at the H level. When 1 ns has elapsed (time 1), the output signal of the first-stage delay circuit changes from the L level to the H level because the input signal (that is, the output signal of the eighth-stage delay circuit) is at the H level. 2nd to 7th
The output signal of the delay circuit at the stage remains at the L level. After another 1 ns (time 2), the output signal of the second-stage delay circuit changes from the L level to the H level because the input signal (that is, the output signal of the first-stage delay circuit) is at the H level. In this way, every time 1 ns elapses, the signal transitions by 1
Step by step. The output signal of the delay circuit is input to the arithmetic circuit 15 via the sampling circuit array 13 and the holding circuit array 14, and is converted into 3-bit numerical data as shown in the right column of Table 1.

The counter 16a counts the number of signal transitions at the output terminal of the eighth stage delay circuit. When the transition of the signal makes one round of the delay circuit ring 11 (time 8)
Since the output signal of the delay circuit at the eighth stage changes from H level to L level, the counter 16a adds 1 to the count data. The counter output holding circuit 16b outputs the held count data to the arithmetic circuit 15 when the pulse signal to be measured rises. The arithmetic circuit 15 obtains time data representing the time when the pulse signal to be measured rises from the 3-bit numerical data and the count data.

The feature of this embodiment is that the sampling circuit train 1 is located between the delay circuit ring 11 and the holding circuit train 14.
3 is that erroneous holding of the holding circuit array 14 is prevented. Hereinafter, the operation of the sampling circuit array 13 will be described.

FIG. 2A is a circuit diagram showing a configuration example of the sampling circuit. In FIG. 2A, reference numeral 21 denotes a capacity;
Is an inverting amplifier circuit, S1 is a first switch, S2 is a second switch, and S3 is a third switch. The input terminal is connected to one terminal of the capacitor 21 via the first switch S1, and the reference potential input terminal is connected to the third switch S3.
Is connected to one terminal of the capacitor 21 via the. Capacity 2
The other terminal is connected to the input terminal of the inverting amplifier circuit 22. Further, the input terminal and the output terminal of the inverting amplifier circuit 22 are connected via the second switch S2.

When the sampling circuit shown in FIG. 2A is used for the time counting circuit shown in FIG. 1, the input terminal is connected to the output terminal of the delay circuit constituting the delay circuit ring 11, and the output terminal is held. It is connected to the input terminal of the flip-flop constituting the circuit row 14. The operation of each switch is controlled by a first switch signal 12a input from the switch signal generation circuit 12.

The operation of the sampling circuit shown in FIG.
This will be described with reference to FIG. First, in the sampling operation,
The first switch S1 and the second switch S2 are turned on, and the third switch S3 is turned off. At this time, the input potential Vin is applied to one terminal of the capacitor 21. This input voltage Vin is the potential of the output signal of the delay circuit. The same potential Va is output to the input terminal and the output terminal of the inverting amplifier circuit 22, and the potential Va is applied to the other terminal of the capacitor 21. Therefore, charges are accumulated in the capacitor 21 by the potential difference (Vin−Va). Further, the output potential Vout becomes equal to the potential Va.

Next, in the amplification operation, the first switch S1 and the second switch S2 are turned off and the third switch S1 and the second switch S2 are turned off.
Switch S3 is turned ON. At this time, the reference potential Vref is applied to one terminal of the capacitor 21. Since the electric charge accumulated in the capacitor 21 is preserved, the potential difference (Vin−Va) in the sampling operation is kept as it is, and the potential of the other terminal of the capacitor 21 is changed from Va to (Vref− (Vin−Va)).
= (Vref-Vin + Va). Therefore, the output potential Vout is Becomes Here, G is the voltage gain of the inverting amplifier circuit 22.

As can be seen from equation (1), the output signal of the delay circuit is sampled by the sampling operation, and the difference voltage between the potential Vin of the sampled signal and the reference potential Vref is amplified and fixed by the amplification operation. It is applied to the potential Va and output to the holding circuit.

FIG. 3 is a graph showing a change in voltage in the sampling circuit shown in FIG. 2, where (a) shows the input voltage Vin,
(B) shows the voltage of the input terminal of the capacitor 21, (c) shows the voltage of the output terminal of the capacitor 21, and (d) shows the output voltage Vout.

As shown in FIG. 3A, it is assumed that the signal A indicated by the solid line is ahead of the signal B indicated by the dashed line in time. As shown in FIG. 3B, the input voltage Vin at the end of the sampling operation is held as the input-side voltage of the capacitor 21 until the transition from the sampling operation to the amplification operation. In FIG. 3B, the voltage V1 is held for the signal A, and the voltage V2 is held for the signal B.

As shown in FIG. 3C, the difference between the input voltage of the capacitor 21 and the reference voltage Vef is applied to the output voltage of the capacitor 21 by the amplification operation. As shown in FIG. 3D, the output voltage of the capacitor 21 is inverted and amplified by the inverting amplifier 22 to become the output voltage Vout. The output voltage Vout of the signal A is substantially equal to the power supply voltage VDD, and the output voltage Vout of the signal B is substantially equal to the ground voltage VSS.

FIG. 4A is a graph showing a change in the potential of the output signal of each delay circuit constituting the delay circuit ring 11. In FIG. 4A, a straight line 1 indicates a change in the potential of the output signal of the first-stage delay circuit.
Reference numeral 8 denotes a change in the potential of the output signal of each of the second to eighth delay circuits. FIG. 4B is a graph showing a change in the potential of the output signal of each sampling circuit 13a constituting the sampling circuit array 13. In FIG. 4B, curves 2 to 7 indicate changes in the potentials of the output signals of the second to seventh sampling circuits, respectively. The time T indicates the time when the pulse signal to be measured rises.

Each sampling circuit 13a constituting the sampling circuit array 13 outputs a certain reference potential Va before the pulse signal to be measured rises. When the pulse signal to be measured rises (time T), the first switch signal 12a is input from the switch signal generation circuit 12 to each sampling circuit 13a, and each sampling circuit 13a outputs the output signal of the connected delay circuit. Are sampled respectively. In FIG. 4A, the potential of the sampled signal is indicated by a circle. Each sampling circuit 13a further amplifies the difference voltage between the potential of the sampled signal and the reference potential Va, and then applies the amplified difference voltage to the reference potential Va and outputs it.

Therefore, the potential of the output signal of each sampling circuit 13a exists in a range where both the probability that the flip-flop holds “0” and the probability that the flip-flop holds “1” exist, that is, in the so-called uncertain region. Will not be done. Therefore, only the signal that is always held as "0" or the signal that is always held as "1" is input to the flip-flop 14a constituting the holding circuit array 14.

As a result, the holding circuit array 14 does not cause erroneous holding. In addition, each flip flop 14
Even if the threshold voltage varies in a, linearity can be guaranteed in the relationship between real time and time data.

Although the sampling circuit shown in FIG. 2 has a general configuration, a sampling circuit having a higher amplification factor is also conceivable.

FIG. 5A is a circuit diagram showing another example of the configuration of the sampling circuit. In FIG. 5A, 31 is a first capacitor, 32 is a second inverting amplifier circuit, 33 is a second capacitor,
34 is a second inverting amplifier circuit, S1 is a first switch, S1
2 is a second switch, S3 is a third switch, and S4 is a fourth switch. The input terminal is connected to one terminal of the first capacitor 31 via the first switch S1, and the other terminal of the first capacitor 31 is connected to the input terminal of the first inverting amplifier circuit 32. I have. An output terminal of the first inverting amplifier circuit 32 is connected to one terminal of the second capacitor 33,
The other terminal of the second capacitor 33 is connected to the input terminal of the second inverting amplifier circuit 34. The input terminal of the first capacitor 31 and the output terminal of the second inverting amplifier 34 are connected via a second switch S2. The input terminal and the output terminal of the first inverting amplifier circuit 32 are connected to a third switch S3.
And a first capacitor 31, a first inverting amplifier circuit 32 and a third switch S3 constitute a first circuit. The input terminal and the output terminal of the second inverting amplifier circuit 34 are connected via a fourth switch S4. The second capacitor 33, the second inverting amplifier circuit 34 and the fourth switch S4 control the second terminal. Circuit is configured.

When the sampling circuit shown in FIG. 5A is used for the time counting circuit shown in FIG. 1, the input terminal is connected to the output terminal of the delay circuit constituting the delay circuit ring 11, and the output terminal is held. It is connected to the input terminal of a flip-flop 14a constituting the circuit row 14. The operation of each switch is controlled by a first switch signal 12a input from the switch signal generation circuit 12.

The operation of the sampling circuit shown in FIG.
This will be described with reference to FIG. First, in the sampling operation of the first circuit, the first switch S1 and the third switch S1
3 is turned on, and the second switch S2 and the fourth switch S4 are turned off. At this time, the first capacitance 31
The input potential Vin is applied to one terminal. This input potential Vin is the potential of the output signal of the delay circuit. Also, the first
The input terminal and the output terminal of the inverting amplifier circuit 32 have the same potential Va1, and the potential Va1 is applied to the other terminal of the first capacitor 31. Therefore, the potential difference (V
In-Va1) accumulates charges.

Next, in the amplification operation of the first circuit, the first switch S1 and the third switch S3 are turned off, and the second switch S2 and the fourth switch S4 are turned on. At this time, the same potential Va2 is output to the input terminal and the output terminal of the second inverting amplifier circuit 34,
a2 is applied to one terminal of the first capacitor 31. Since the charge accumulated in the first capacitor 31 is stored, the potential difference (Vin−Va1) in the sampling operation is maintained as it is, and the potential of the other terminal of the first capacitor 31 is changed from Va1 to (Va2− ( V
in-Va1)). Therefore, the output potential Vmid of the first circuit is as follows: Vmid = -G1 (Va2- (Vin-Va1) -Va1) + Va1 = G1 (Vin-Va2) + Va1. Here, G1 is the voltage gain of the first inverting amplifier circuit 32.

At this time, the output potential Vmid of the first circuit is applied to one terminal of the second capacitor 33, and the potential Vmid at the input terminal of the second inverting amplifier circuit 34 is applied to the other terminal.
a2 is applied. Accordingly, charges are accumulated in the second capacitor 33 due to the potential difference (Vmid-Va2). That is, the second circuit performs a sampling operation.

Next, in the amplification operation of the second circuit, the first switch S1 and the third switch S3 are turned on, and the second switch S2 and the fourth switch S4 are turned off.
It becomes FF. At this time, the same potential Va1 is output to the input terminal and the output terminal of the first inverting amplifier circuit 32,
a1 is applied to one terminal of the second capacitor 33. Since the electric charge accumulated in the second capacitor 33 is stored, the potential difference (Vmid−Va2) in the sampling operation is maintained as it is,
The potential of the other terminal of the second capacitor 33 is changed from Va2 to (Va1−
(Vmid-Va2)). Therefore, the output potential Vout is as follows: Vout = -G2 (Va1- (Vmid-Va2) -Va2) + Va2 = G2 (Vmid-Va1) + Va2 = G2.SIGMA.G1 (Vin-Va2) + Va1-Va1 + Va2 = G2 G1 (Vin −Va2) + Va2 (2) Here, G2 is the voltage gain of the second inverting amplifier circuit 34.

As can be seen from equation (2), the output signal of the delay circuit is sampled by the sampling operation, and the potential Vin of the sampled signal is kept constant by the amplification operation of the first circuit and the second circuit. The difference voltage of the potential Va2 is amplified to a constant potential Va2
And output to the holding circuit. Further, when the expressions (1) and (2) are compared, it is understood that the amplification factor is increased.

FIG. 6 is a circuit diagram showing an example of the internal configuration of the switch signal generation circuit 12. In FIG. 6, a pulse signal to be measured is input to an input terminal 51, and a sampling circuit 13a is output from output terminals 52a, 52b, 52c, and 52d.
A first switch signal 12a for controlling the operation of the flip-flop 14 is output from the output terminals 53a and 53b.
A second switch signal 12b for controlling the operation of a is output.

A signal for controlling the first switch S1 of the sampling circuit 13a is output from the output terminal 52a, and a signal for controlling the second switch S2 of the sampling circuit 13a is similarly output from the output terminal 52b. A signal for controlling the third switch S3 of the sampling circuit 13a is output from the output terminal 52c, and a signal for controlling the fourth switch S4 of the sampling circuit 13a is output from the output terminal 52d. Also,
A signal for controlling the master latch of the flip-flop 14a is output from the output terminal 53a, and a signal for controlling the slave latch of the flip-flop 14a is output from the output terminal 53b.

FIG. 7 shows signals output from the switch signal generation circuit 12 shown in FIG.
FIG. 3 is a timing chart showing the operations of a sampling circuit 13a and a flip-flop 14a controlled by the sampling circuit 13; First switch signal 1 generated based on a pulse signal to be measured
According to 2a, the first and second circuits of the sampling circuit 13a repeatedly perform the sampling operation and the amplification operation. The hatched area indicates a period in which the sampling operation shifts to the amplification operation or the amplification operation shifts to the sampling operation. Further, the flip-flop 14a repeatedly performs the through and the latch according to the second switch signal 12b generated based on the pulse signal to be measured.

The sampling circuits shown in FIGS. 2 and 5 can be easily realized by using a CMOS inverter as an inverting amplifier. FIG. 8 is a circuit diagram showing a configuration example of a sampling circuit using a CMOS inverter. The first inverting amplifier circuit 32 and the second inverting amplifier circuit 34 in the sampling circuit shown in FIG. Are constituted by CMOS inverters. In addition, two CMOs
An output buffer configured by connecting S inverters in series is provided in front of the output terminal. Since the operation of this sampling circuit is the same as that of the sampling circuit shown in FIG. 5, the description is omitted here.

The sampling circuit shown in FIG. 5 is excellent not only in terms of the amplification factor but also in terms of stability against fluctuations in the power supply voltage. This will be described.

FIG. 9 is a graph showing characteristics of the CMOS inverter. In FIG. 9, the horizontal axis represents the input voltage of the CMOS inverter, the vertical axis represents the output voltage of the CMOS inverter, and solid line A represents the relationship between the input voltage and the output voltage. The reference voltage Va is obtained by the intersection of the solid line A and the straight line indicating the input voltage = the output voltage. The slope of the solid line A is steep near the reference voltage Va, and it can be seen that the voltage gain of the CMOS inverter increases near the reference voltage Va. Therefore, when the input voltage is close to the reference voltage, the difference voltage between the input voltage and the reference voltage Va is greatly amplified.

The inverting amplifier circuit 2 of the sampling circuit shown in FIG.
2 uses a CMOS inverter, the input voltage of the CMOS inverter is (Vref−Vin +
Va)), when (Vref-Vin + Va) is close to the reference voltage Va, the difference voltage is greatly amplified and the output voltage becomes XA.

However, when the power supply voltage changes from VDD to V'DD
In this case, the relationship between the input voltage and the output voltage of the CMOS inverter is as shown by a broken line B. Therefore, the reference voltage also drops from Va to V'a. When the power supply voltage drops to V'DD in the amplifying operation, as shown in FIG. 9, the reference voltage V'a is changed to the input voltage (Vref
−Vin + Va). At this time, the difference voltage is greatly amplified to the opposite side, and the output voltage becomes XB. That is, the logic indicated by the output voltage is reversed, which is not preferable.

On the other hand, the sampling circuit shown in FIG. 5 is hardly affected by the fluctuation of the power supply voltage. FIG.
6 is a graph showing characteristics of the MOS inverter, and is a diagram for explaining an operation when a CMOS inverter is used for the first inverting amplifier circuit 32 and the second inverting amplifier circuit of the sampling circuit shown in FIG. is there. As in FIG. 9, the horizontal axis is C
The input voltage of the MOS inverter, the vertical axis is the output voltage of the CMOS inverter, the solid line A indicates the relationship between the input voltage and the output voltage, and the broken line B indicates the power supply voltage from VDD to V'DD.
Shows the relationship between the input voltage and the output voltage at the time when the voltage drops to.

Here, a first CMOS inverter is used as the first inverting amplifier circuit 32, and a second CMOS inverter is used as the second inverting amplifier. Also, a first CMOS inverter and a second CMOS
The inverters have characteristics as shown in FIG. 10, and the reference voltages are both equal to Va.

In the amplification operation of the first circuit, the first C
The input voltage of the MOS inverter is Va− (Vin−Va) = Va−Vin + Va. The input voltage (Va-Vin + Va) is equal to the reference voltage Va.
, The difference voltage is greatly amplified, and the output voltage becomes XA.

When the power supply voltage drops from VDD to V'DD, the relationship between the input voltage and the output voltage of the CMOS inverter becomes as shown by the broken line B, and the reference voltage also drops from Va to V'a. However, even if the power supply voltage drops to V'DD in the amplification operation of the first circuit, as shown in FIG. 10, the reference voltage drops to V'a and the input voltage also drops to (V'DD).
a−Vin + V′a). Therefore, the differential voltage is not greatly amplified to the opposite side, the output voltage becomes XB, and the logic indicated by the output voltage does not reverse. Therefore, the sampling circuit shown in FIG. 5 is superior to the sampling circuit shown in FIG. 2 in terms of stability against fluctuations in the power supply voltage.

Further, the function of the sampling circuit in the time counting circuit of the present invention can be realized by using a circuit other than the sampling circuit.

FIG. 11A is a circuit diagram showing a configuration example of a hold cascade circuit. Although this circuit is not a sampling circuit, it has the function of outputting a constant voltage when the switch is ON, and amplifying and outputting the difference voltage between the input voltage and the reference voltage when the switch is OFF. ,
It can be used instead of the sampling circuit in the time counting circuit shown in FIG.

In FIG. 11, reference numeral 41 denotes a PMOS whose source is connected to a power supply;
PMOS 43 connected to the drain of MOS 41
a is an NMOS whose drain is connected to the drain of the PMOS 42a and whose source is grounded; 43b is an NMOS whose drain is connected to the drain of the PMOS 42b and whose source is grounded;
4b is a PMOS whose source is connected to the power supply, 45a
Is an NMOS whose drain is connected to the drain of the PMOS 44a and whose source is connected to the drain of the NMOS 43a, and 45b is an NMOS whose drain is connected to the drain of the PMOS 44b and whose source is the NMOS 43a.
NMOS connected to the drain of b, 46 is a PMO
This is a PMOS in which the source and the drain are connected to the drains of S44a and the PMOS 44b. PMOS 46
Plays the role of a switch in the hold cascade circuit.

The input voltage Vin is applied to the gate of the PMOS 42a.
Is applied, and the reference voltage Vre is applied to the gate of the PMOS 42b.
f is applied. The gate of the PMOS 44a has a PMOS
The drain voltage of the PMOS 44b is applied to the gate of the PMOS 44b.
A constant voltage VB1 is applied to the gate of the PMOS 41, and NM
A constant voltage VB2 is applied to the gates of the OSs 43a and 43b, and a constant voltage VB3 is applied to the gates of the NMOSs 45a and 45b.
Is applied. The switching voltage Vφ is applied to the gate of the PMOS 46. The drain voltage of the PMOS 44b is output as an output voltage Vout.

The operation of the hold cascade circuit shown in FIG. 11A will be described with reference to FIG. As shown in FIG. 11B, the switch voltage Vφ
Is at L level, the PMOS 46 is turned on and the switch is turned on. At this time, the hold cascade circuit is said to be in the set state. Switch voltage Vφ
Is at the H level, the PMOS 46 is turned off and the switch is turned off. At this time, the hold cascade circuit is in an amplification state.

Since the PMOS 41 works as a constant current source,
A constant current I1 flows through the drain. When the input voltage Vin is equal to the reference voltage Vref, the PMOS 42a and the PMOS
A current of I1 / 2 flows through each of 42b. PMOS
Since 43a and 43b function as constant current sources having the same characteristics, a constant current I2 flows. Since the PMOSs 45a and 45b also function as constant current sources having the same characteristics, a constant current I3 flows. Here, I1 / 2 + I3 = I2.

It is assumed that the input voltage Vin is different from the reference voltage Vref. Assuming that Vin> Vref, the PMOS 42a
Of the current flowing through the PMOS 42b
Is I1 / 2 + Δ. Δ is a minute value. When the hold cascade circuit is in the set state, the PMOS 46 is in a conductive state, so that a current Δ corresponding to the change flows from the terminal B to the terminal A through the PMOS 46. Therefore, the current flowing through the PMOSs 44a and 44b does not change, so that the output voltage Vout does not change.

When the hold cascade circuit is in the amplifying state, the PMOS 46 is in a non-conductive state, so that the change current Δ cannot flow from the terminal B to the terminal A through the PMOS 46 and flows out to the output terminal. become. Therefore, the output voltage Vout increases. That is, the potential difference between the input voltage Vin and the reference voltage Vref is amplified and output.

In the time counting circuit according to the present embodiment, a phase lock loop (PLL) is used.
The transmission time of the signal transition in the delay circuit ring may be controlled to be constant. FIG. 12 shows a configuration diagram of such a time counting circuit. 12, the phase comparator 17 compares the phase of the signal at the input terminal of the first stage delay circuit of the delay circuit ring 11 with the phase of the reference clock signal. The loop filter 18 receives the instruction signal from the phase comparator 17 and outputs a signal for adjusting the delay time to each of the delay circuits forming the delay circuit ring 11. The delay circuit ring 11, the phase comparator 17 and the loop filter 18
A lock loop (PLL) is configured.

FIG. 13 is a circuit diagram showing a delay circuit in a time counting circuit using a PLL as shown in FIG. In the figure, (a) is a delay circuit per stage, and (b) is a transistor-level circuit diagram of the delay circuit shown in (a).

In FIG. 13, a signal for adjusting the signal delay time from the terminal I1 to the terminal I2 is input to the terminal a1, and a signal for adjusting the signal delay time from the terminal I2 to the terminal I3 is input to the terminal a2. You. In the case of the time counting circuit as shown in FIG. 12, a signal output from the loop filter 18 is input to terminals a1 and a2.

When the voltage at the terminal a1 rises, the drain current of the transistor M1 decreases, so that the rise time of the signal at the terminal I2 becomes longer. On the other hand, when the voltage at the terminal a1 drops, the drain current of the transistor M1 increases, so that the rise time of the signal at the terminal I2 is shortened. When the voltage at the terminal a2 changes, the drain current of the transistor M4 similarly changes, and the rise time of the signal at the terminal I3 changes.

Now, consider the case where the signal at terminal I1 rises. At this time, the voltage at the terminal I2 falls, then the voltage at the terminal I3 rises, and the signal propagates.

First, it is assumed that the voltages at the terminals a1 and a2 have risen. The fall time of the signal at the terminal I2 is dominated by the drain current of the transistor M3.
The fall time change due to the rise in the voltage of 1 is small. However, the rise time of the signal at the terminal I3 is delayed due to a decrease in the drain current of the transistor M4 due to an increase in the voltage at the terminal a2. Therefore, the signal delay time becomes longer.

Assume that the voltages at the terminals a1 and a2 have dropped. The fall time of the signal at the terminal I2 is dominated by the drain current of the transistor M3.
The fall time change due to the voltage drop of 1 is small. However, the rise time of the signal at the terminal I3 is accelerated by the increase in the drain current of the transistor M4 due to the drop in the voltage at the terminal a2. Therefore, the signal delay time is shortened.

Similarly, when the signal at terminal I1 falls, the delay time of the signal changes. As described above, the signal delay time of the delay circuit can be adjusted by the signals input to the terminals a1 and a2.

As described above, according to the time counting circuit according to the present embodiment, the conversion circuit composed of the sampling circuit or the hold cascade circuit is provided between the delay circuit ring and the holding circuit row. The erroneous holding of the holding circuit row can be prevented, and the occurrence of an error due to the variation in the threshold voltage of the flip-flop constituting the holding circuit row can be prevented.

The sampling circuit or the hold cascade circuit does not necessarily need to be provided for every delay circuit, but may be provided for every other delay circuit, for example.

(Application Example) In the time counting circuit according to the above-described embodiment, a logic judging circuit is constituted by the sampling circuit 13a and the flip-flop 14a. The logic determination circuit amplifies a difference voltage between a signal potential at a designated timing and a first predetermined potential, and applies the amplified difference voltage to a second predetermined potential based on a potential obtained. Thus, the logic of the signal is determined. Such a logic judgment circuit can be applied to other uses. The following application example relates to a skew adjustment circuit using a logic determination circuit.

When a clock pulse signal output from one circuit and a clock pulse signal output from another circuit are supplied to a certain digital circuit, the digital circuit malfunctions when there is a delay time difference between the clock pulse signals. . This is a malfunction of a digital circuit due to so-called clock skew or data skew.

It has been pointed out that erroneous operation due to skew becomes more serious as the operating frequency of the digital circuit becomes higher. Even if the delay time difference of the clock pulse signal is small (1 ns or less), the digital circuit may malfunction. Can cause. The skew adjustment circuit reduces a skew by reducing a delay time difference between a plurality of clock pulse signals.

FIG. 14 is a block diagram showing a configuration of a skew adjustment circuit according to this application example. In FIG. 14, 6
Reference numeral 0 denotes a skew adjustment circuit which supplies a circuit C after reducing the delay time difference between the clock pulse signal output from the circuit A and the clock pulse signal output from the circuit B.

Reference numerals 61 and 62 denote first and second delay circuits for delaying the input clock pulse signal and outputting the delayed clock pulse signal.
63 and 64 are first and second sampling circuits as first and second conversion circuits, 65 and 66 are first and second flip-flops as first and second holding circuits, and 67 is a first and second flip-flop. A control for supplying the first clock pulse signal 61A output from the first delay circuit 61 to the first sampling circuit 63 and controlling the second sampling circuit 64, the second flip-flop 66 and the arithmetic circuit 69 The circuit 68 includes a second clock pulse signal 61B output from the second delay circuit 62.
Is supplied to a second sampling circuit 64 and a control circuit for controlling the first sampling circuit 63 and the first flip-flop 65, and 69 is a control circuit for the first and second flip-flops 65,
66 and a first delay circuit 6 based on the output signal
An arithmetic circuit for calculating and outputting first and second control signals 69A and 69B for controlling the delay times of the first and second delay circuits. First
5 and the second sampling circuits 63 and 64 respectively
It is configured as shown in FIG. The first sampling circuit 63 and the first flip-flop 65 constitute a first logic decision circuit, and the second sampling circuit 64 and the second
And the flip-flop 66 constitute a second logic decision circuit.

First, an outline of the operation of the skew adjustment circuit 60 will be described with reference to FIG. FIG. 15 is a graph showing a time change when the first and second clock pulse signals 61A and 61B rise, and a solid line A indicates the first clock output from the circuit A and delayed by the first delay circuit 61. The pulse signal 61A and the solid line B indicate the second clock pulse signal 61B output from the circuit B and delayed by the second delay circuit 62. In the figure, (a) shows that the first clock pulse signal 61A is ahead of the second clock pulse signal 61B, and (b) shows that the first clock pulse signal 61A is more advanced than the second clock pulse signal 61B. Also shows a case where it is late.

In the skew adjustment circuit 60, when the first clock pulse signal 61A exceeds the threshold voltage Vth (time tA), the voltage of the second clock pulse signal 61B is held by the second sampling circuit 64. Is done. On the other hand, when the second clock pulse signal 61B exceeds the threshold voltage Vth (time tB), the first clock pulse signal 61B
The voltage of A is held by the first sampling circuit 63.

When the first clock pulse signal 61A is ahead of the second clock pulse signal 61B, as shown in FIG. 15A, the voltage V1 of the second clock pulse signal 61B at time tA is increased. Second sampling circuit 6
4, and the held voltage V1 is held by the second flip-flop 66 as the ground voltage VSS (logic level "0"). On the other hand, at time tB, the voltage V2 of the first clock pulse signal 61A is held by the first sampling circuit 63, and the held voltage V2
2 is the power supply voltage VDD by the first flip-flop 65.
(Logic level “1”).

On the other hand, when the first clock pulse signal 61A lags behind the second clock pulse signal 61B, as shown in FIG.
Of the clock pulse signal 61A is held by the first sampling circuit 63, and the held voltage V3 is held by the first flip-flop 65 as the power supply voltage VSS (logic level "0"). On the other hand, at time tA, the voltage V4 of the second clock pulse signal 61B is held by the second sampling circuit 64, and the held voltage V4 is supplied by the second flip-flop 66 to the power supply voltage VDD (logic level "1"). ).

Therefore, the first flip-flop 65
Is "1" and the second flip-flop 6
When the held data of No. 6 is "0", it means that the first clock pulse signal 61A is ahead of the second clock pulse signal 61B. When the data held in the first flip-flop 65 is “0” and the data held in the second flip-flop 66 is “1”, the first clock pulse signal 61A is changed to the second clock pulse signal 61B. It will be behind.

The arithmetic circuit 69 performs the first operation in accordance with the data held in the first and second flip-flops 65 and 66.
And the function of adjusting the delay time of the second delay circuits 61 and 62, so that the skew adjustment circuit 60 performs the first clock pulse signal 61A and the second clock pulse signal 61B.
Can be reduced.

Next, the internal configuration of control circuits 67 and 68 will be described.

FIG. 16 is a circuit diagram showing an example of the internal configuration of the control circuit 67. In FIG. 16, reference numeral 71 denotes a signal input terminal to which a first clock pulse signal output from the circuit A and delayed by the first delay circuit 61 is input;
a, 72b, 72c, 72d are output terminals for outputting control signals for controlling the second sampling circuit 64, 73a, 73b
Is an output terminal for outputting a control signal for controlling the second flip-flop 66, and 74 is a signal output terminal for outputting the clock pulse signal input to the signal input terminal 71.

The output terminal 72a outputs a signal for controlling the switch S1 of the second sampling circuit 64. Similarly, an output terminal 72b receives a signal for controlling the switch S2, an output terminal 72c receives a signal for controlling the switch S3, and an output terminal 72c.
d outputs a signal for controlling the switch S4.
The output terminal 73a outputs a signal for controlling the master latch of the second flip-flop 66, and the output terminal 73a
b outputs a signal for controlling the slave latch of the second flip-flop 66. The signal output from the output terminal 73a is also supplied to the arithmetic circuit 69 to control the operation. The clock pulse signal output from the signal output terminal 74 is output to the first sampling circuit 63.

FIG. 17 shows the change of the input / output signal of the control circuit 67 shown in FIG. 16 and the second sampling circuit 64 and the second flip-flop 6 controlled by the control circuit 67.
6 is a timing chart showing the operation of Example No. 6. The second sampling circuit 64 holds the input signal at the falling timing of the control signal of the switch S1. The second flip-flop 66 holds the output signal of the second sampling circuit 64 at a logic level “1” or “0”.

The control circuit 68 is also constituted by a circuit as shown in FIG. In the control circuit 68, the second clock pulse signal 61B output from the circuit B and delayed by the second delay circuit 62 is input to the signal input terminal 71, and the clock pulse signal output from the signal output terminal 74 is Is output to the second sampling circuit 64. Terminal 72
a, 72b, 72c, 72d from the first sampling circuit 6
3 is output, and terminals 73a and 73b
Outputs a control signal for controlling the first flip-flop 65.

Next, the first and second delay circuits 61 and 62
Will be described.

FIG. 18 is a circuit diagram showing an example of the internal configuration of the first delay circuit 61. In FIG. 18, reference numeral 81 denotes an input terminal to which a clock pulse signal output from the circuit A is input, and reference numeral 82 denotes a delayed second clock pulse signal 61.
Reference numeral 83 denotes a control signal input terminal to which the first control signal 69A output from the arithmetic circuit 69 is input. Reference numerals 84a to 84h denote inverter trains composed of inverters connected in series and having different delay times. Each of the inverter rows 84a to 84h has an input terminal 81.
The first control signal 69A input to the control signal input terminal 83 is connected between the output terminal 82 and each of the inverter rows 84a to 84h in parallel.
The switches S1 to S8 whose opening and closing are controlled by the switches are arranged.

Table 2 is a table showing an example of the delay time of each of the inverter rows 84a to 84h.

[0127]

[Table 2]

As shown in Table 2, the inverter trains 84a to 84a
The delay time of 84h is 0.4 ns to 1.8 ns.
It is set in increments of 2 ns. By selecting the signal path from the input terminal 81 to the output terminal 82 by opening and closing the switches S1 to S8, the delay time in the first delay circuit 61 is adjusted from 0.4 ns to 1.8 ns in increments of 0.2 ns. Becomes possible. For example, switch S2
When only the switch is closed, the delay time in the first delay circuit 61 is 0.6 ns.

The second delay circuit 62 is also constituted by a circuit as shown in FIG.

Next, the internal configuration and operation of the arithmetic circuit 69 will be described.

FIG. 19 is a circuit diagram showing an example of the internal configuration of the arithmetic circuit 69. 19, reference numeral 91a denotes an input terminal to which output data of the first flip-flop 65 is input, 91b denotes an input terminal to which output data of the second flip-flop 66 is input, and 92 denotes a terminal 73 of the control circuit 67.
93, an input terminal to which the control signal output from a is input
a is an output terminal for outputting a first control signal 69A for setting the delay time of the first delay circuit 61, and 93b is an output for outputting a second control signal 69B for setting the delay time of the second delay circuit 62. Terminals, 94a and 94b are logic gates, 95
a and 95b are flip-flops; 96 is a 4-bit counter for adding the output data of the flip-flop 95a while subtracting the output data of the flip-flop 95b;
Is a decoder for decoding the count data of the 4-bit counter 96 to generate a first control signal 69A for setting the delay time of the first delay circuit 61, and 98 is a second delay circuit 62
Is a ROM for storing a second control signal 69B for setting the delay time of the second control signal.

It is assumed that the output data of the first flip-flop 65 input from the input terminal 91a is "1" and the output data of the second flip-flop 66 input from the input terminal 91b is "0" ( When tA <tB), the output data of the logic gate 94a becomes "1" and the output data of the logic gate 94b becomes "0". At this time, the 4-bit counter 96 adds 1 to the previous output data at the falling timing of the control signal input to the input terminal 92.

On the other hand, the first input from the input terminal 91a
The output data of the flip-flop 65 is "0" and the second flip-flop 6 inputted from the input terminal 91b
6 is "1"(tA> tB)
Then, the output data of the logic gate 94a becomes "0", and the output data of the logic gate 94b becomes "1". At this time, the 4-bit counter 96 subtracts 1 from the previous output data at the falling timing of the control signal input to the input terminal 92.

The decoder 97 converts the output data of the 4-bit counter 96 into an 8-bit first control signal 69A. Table 3 shows the output data of the 4-bit counter 96 and the first data.
6 is a table showing a relationship with a switch selected in the delay circuit 61 of FIG.

[0135]

[Table 3]

For example, when the output data of the 4-bit counter 96 is "0100" or "0101", the switch S3 is selected, so that the delay time in the first delay circuit 61 is 0.8 ns.

On the other hand, the ROM 98 stores a second control signal 69B for selecting the switch S4. Therefore, the delay time in the second delay circuit 62 is 1.
0 ns.

FIG. 20 is a timing chart showing the operation of the skew adjustment circuit 60 according to this application example.

When the first clock pulse signal 61A output from the circuit A and delayed by the first delay circuit 61 rises (time tA), the first circuit of the second sampling circuit 64 is The output second delay circuit 62
Holds and amplifies the potential N1 of the second clock pulse signal 61B delayed by the above. On the other hand, when the second clock pulse signal 61B rises (time tB), the first circuit of the first sampling circuit 63 holds and amplifies the potential M1 of the first clock pulse signal 61A.

First flip-flop 65 holds the output signal of the second circuit of first sampling circuit 63 at the next rise of time tB of second clock pulse signal 61B. Since the potential M1 is high, the data held in the first flip-flop 65 becomes "1". The second flip-flop 66 activates the second sampling circuit 64 at the second rising of the first clock pulse signal 61A at time tA.
Holds the output signal of the circuit of FIG. Since the potential N1 is low, the data held in the second flip-flop 66 becomes "0".

Since the data held in the first flip-flop 65 is “1” and the data held in the second flip-flop 66 is “0”, the 4-bit counter 96 of the arithmetic circuit 69 adds 1 to the output data. I do. As a result, the arithmetic circuit 69 outputs to the first delay circuit 61 a first control signal 69AD1 for setting a longer delay time. Accordingly, the first clock pulse signal 61A is further delayed, and approaches the timing of the second clock pulse signal 61B.

By repeating the above operation, the time difference between the first clock pulse signal 61A and the second clock pulse signal 61B is reduced, and the problem of clock skew is eliminated.

In this application example, the potential of the first clock pulse signal 61A is changed to the second clock pulse signal 61B.
Are sampled at the timing of the rising edge of the first clock pulse signal 61B, and the potential of the second clock pulse signal 61B is sampled at the timing of the rising edge of the first clock pulse signal 61A.

Note that the function of the sampling circuit in the skew adjustment circuit according to this application example can be realized by using a circuit other than the sampling circuit, like the time counting circuit according to the above-described embodiment. A hold cascade circuit as shown in FIG. 11A may be used instead of the sampling circuit.

[0145]

As described above, according to the time counting circuit of the present invention, the provision of the conversion circuit makes it possible to reliably supply the arithmetic circuit with a logic level signal representing the same logic as that indicated by the output signal of the delay circuit. Therefore, linearity can be guaranteed in the relationship between the time data and the real time. Therefore, it is possible to realize a time counting circuit with higher accuracy than before. In addition, by configuring the conversion circuit with a sampling circuit that is resistant to fluctuations in power supply voltage, it is possible to reliably realize a time counting circuit that has higher accuracy and is more resistant to fluctuations in power supply voltage .

[ Brief description of the drawings]

FIG. 1 is a configuration diagram of a time counting circuit according to an embodiment of the present invention.

2A is a circuit diagram showing a configuration example of a sampling circuit in a time counting circuit according to an embodiment of the present invention, and FIG. 2B is an operation diagram thereof.

3A and 3B are graphs showing a change in voltage in the sampling circuit shown in FIG. 2, wherein FIG. 3A shows an input voltage Vin, FIG. 3B shows a voltage of an input terminal of a capacitor 21, and FIG. The voltage of the terminal on the output side, and (d) shows the output voltage Vout.

FIG. 4 is a diagram for explaining the operation of the sampling circuit in the time counting circuit according to one embodiment of the present invention, and (a).
Is a graph showing a change in output voltage of each delay circuit, and (b) is a graph showing a change in output voltage of each sampling circuit.

FIG. 5A is a circuit diagram illustrating another configuration example of a sampling circuit in a time counting circuit according to an embodiment of the present invention;
(B) is an operation diagram thereof.

FIG. 6 is a circuit diagram showing an internal configuration of a switch signal generation circuit.

7 is a timing chart showing signals output from the switch signal generation circuit shown in FIG. 6, and operations of a sampling circuit and a flip-flop controlled by the switch signal generation circuit.

FIG. 8 is a circuit diagram of a sampling circuit when a CMOS inverter is used.

FIG. 9 is a graph showing characteristics of a CMOS inverter.

FIG. 10 is a graph showing characteristics of a CMOS inverter.

11A is a circuit diagram of a hold cascade circuit, and FIG. 11B is an operation diagram thereof.

FIG. 12 is a configuration diagram when a phase locked loop (PLL) is used in a time counting circuit according to an embodiment of the present invention.

13A and 13B are diagrams illustrating a delay circuit in a time counting circuit using a PLL, where FIG. 13A illustrates a delay circuit per stage,
FIG. 2B is a circuit diagram of the delay circuit shown in FIG.

FIG. 14 is a block diagram illustrating a configuration of a skew adjustment circuit according to an application example of the present invention.

FIG. 15 is a graph showing a time change at the time of rising of the clock pulse signal output from the circuits A and B,
(A), when the clock pulse signal output from the circuit A is ahead of the clock pulse signal output from the circuit B, (b), the clock pulse signal output from the circuit A is output from the circuit B This shows a case where it is behind the clock pulse signal.

FIG. 16 is a circuit diagram showing an example of an internal configuration of a control circuit in a skew adjustment circuit according to an application example of the present invention.

17 shows changes in input / output signals of the control circuit shown in FIG. 16;
FIG. 3 is a timing chart showing operations of a sampling circuit and a flip-flop controlled by the control circuit.

FIG. 18 is a circuit diagram illustrating an example of an internal configuration of a delay circuit in a skew adjustment circuit according to an application example of the present invention.

FIG. 19 is a circuit diagram illustrating an example of an internal configuration of an arithmetic circuit in a skew adjustment circuit according to an application example of the present invention.

FIG. 20 is a timing chart showing an overall operation of a skew adjustment circuit according to an application example of the present invention.

FIG. 21 is a configuration diagram of a conventional time counting circuit.

FIG. 22 is a diagram for explaining a problem in the conventional time counting circuit, and is a graph showing a change in output voltage of each delay circuit.

23A and 23B are diagrams for explaining a problem in the conventional time counting circuit, in which FIG. 23A is a graph showing a change in output voltage of each delay circuit, and FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Delay circuit ring 12 Switch signal generation circuit 12a 1st switch signal 12b 2nd switch signal 13 Sampling circuit sequence (conversion means) 13a Sampling circuit (conversion circuit) 14 Holding circuit sequence 14a Flip-flop (holding circuit) 15 Arithmetic circuit 16a Counter 16b Counter output holding circuit 17 Phase comparator 18 Loop filter 21 Capacitance 22 Inverting amplifier circuit 31 First capacitor 32 First inverting amplifier circuit 33 Second capacitor 34 Second inverting amplifier circuit 41, 42a, 42b, 44b, 44a PMOS 43a, 43b, 45a, 45b NMOS 51 delay circuit ring 54 holding circuit row 55 arithmetic circuit 56a counter 56b counter output holding circuit

────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ Identification symbol FI H03K 23/00 H03K 23/00 B (56) References JP-A-7-99450 (JP, A) JP-A-6-283984 ( JP, A) JP-A-60-59813 (JP, A) JP-A-63-49825 (JP, U) JP-A-6-500680 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , (DB name) H03M 1/00-1/88 H03K 5 / 00,5 / 08 H03L 7/00 G01R 25/04 G01R 29/02

Claims (7)

(57) [Claims] 1. A time counting circuit for measuring a pulse interval of a pulse signal, comprising: a plurality of delay circuits connected in a ring shape;
A delay circuit ring in which a transition of a signal in which an output signal of each delay circuit transitions from one logic level to another logic level is circulated; and a plurality of conversions each having an output signal of the delay circuit constituting the delay circuit ring as an input. A conversion unit configured of a circuit, wherein each conversion circuit converts and outputs an output signal of a delay circuit to be input according to an instruction based on at least one of timings of rising and falling of a pulse signal to be measured; and It is composed of a plurality of holding circuits each having an input of an output signal of a conversion circuit constituting the conversion means, and the timing and
At different timings , each holding circuit converts the output signal of the conversion circuit as an input into a logic level signal and outputs the logic level signal, and converts the logic level signal output from the holding circuit row into numerical data. An arithmetic circuit for calculating a pulse interval of the pulse signal to be measured based on the numerical data, wherein each conversion circuit constituting the conversion means converts the input signal
Sampling, the sampled signal and a common reference potential
And amplify the difference voltage to a constant potential.
A time counting circuit characterized by applying and outputting . 2. The time counting circuit according to claim 1, wherein a pulse signal to be measured is input, and the first switch is set based on at least one of rising and falling timings of the pulse signal to be measured. A switch signal generation circuit for generating a signal and a second switch signal, wherein the conversion circuit forming the conversion means has a delay as an input according to an instruction of the first switch signal generated by the switch signal generation circuit. A holding circuit forming a holding circuit array, the output signal of a conversion circuit to be input according to an instruction of a second switch signal generated by the switch signal generation circuit; Is converted to a logic level signal and output. 3. The time counting circuit according to claim 2, wherein the conversion circuit outputs a signal of a constant potential when there is no instruction by the first switch signal, and the conversion circuit outputs the signal of the constant potential when the instruction is given by the first switch signal. Then, the output signal of the delay circuit input to the conversion circuit is sampled, the difference voltage between the potential of the sampled signal and a predetermined reference potential is amplified, and the amplified difference voltage is applied to the constant potential. A time counting circuit, comprising a sampling circuit for outputting the result. 4. The time counting circuit according to claim 3, wherein the sampling circuit internally generates a predetermined reference potential. 5. The time counting circuit according to claim 3, wherein the sampling circuit comprises: an external input terminal to which a signal is externally input; a first circuit to which a signal from the external input terminal is input; A second circuit that receives a signal output from the first circuit as an input; and a second circuit that is provided between the external input terminal and an input terminal of the first circuit, the external input terminal and the first circuit. And the external input terminal is connected to the first input terminal.
A first switch means which is set to one of a non-conductive state for disconnecting the input terminal of the first circuit, and a first switch means provided between the input terminal of the first circuit and the output terminal of the second circuit. A conductive state in which the input terminal of the first circuit is connected to the output terminal of the second circuit, and a non-conductive state in which the input terminal of the first circuit is separated from the output terminal of the second circuit. A second switch means set to either one of the first circuit and the first circuit, wherein the first circuit has a first terminal connected to an input terminal of the first circuit.
A first inverting amplifier circuit that inverts and amplifies a voltage at another terminal of the first capacitor and outputs it to an output terminal of the first circuit; and an input terminal of the first inverting amplifier circuit. A conductive state provided between the input terminal and the output terminal of the first inverting amplifier circuit, and a non-conductive state separating the input terminal and the output terminal of the first inverting amplifier circuit. And a third switch means set to either one of the second circuit and the second circuit, wherein the second circuit has one terminal connected to an input terminal of the second circuit.
A second inverting amplifier circuit that inverts and amplifies a voltage at another terminal of the second capacitor and outputs the voltage to an output terminal of the second circuit; and an input terminal of the second inverting amplifier circuit. A conductive state provided between the input terminal and the output terminal of the second inverting amplifier circuit and a non-conductive state separating the input terminal and the output terminal of the second inverting amplifier circuit. And a fourth switch means set to either one of the first and second switches, and when there is no instruction by the first switch signal, the first switch means is provided.
The switch means and the third switch means are in a conductive state, and the second switch means and the fourth switch means are in a non-conductive state. Once instructed by the first switch signal, once the After the first switch means and the third switch means are turned off and the second switch means and the fourth switch means are turned on, the first switch means and the third switch are turned on again. A time counting circuit wherein the means is turned on and the second switch means and the fourth switch means are turned off. 6. The time counting circuit according to claim 2, wherein the conversion circuit outputs a signal of a constant potential when there is no instruction by the first switch signal, and the conversion circuit outputs the signal of the constant potential when the instruction is given by the first switch signal. Then, a hold cascade circuit that amplifies a difference voltage between a potential of an output signal of the delay circuit input to the conversion circuit and a predetermined reference potential, and applies the amplified difference voltage to the constant potential to output the same. A time counting circuit comprising: 7. The time counting circuit according to claim 1, wherein a phase of a signal at an output terminal of one of the delay circuits constituting the delay circuit ring is compared with a phase of a reference clock signal, and a signal for instructing phase correction is provided. A phase comparator for outputting, and a loop filter for outputting a control signal for controlling a signal delay time to a delay circuit configuring the delay circuit ring according to an instruction of a signal output from the phase comparator, A time counting circuit, wherein a phase locked loop (PLL) is constituted by the delay circuit ring, the phase comparator, and the loop filter.