Control circuit and semiconductor memory device

Abstract

To provide a control circuit that can prevent the delay operation from becoming long and complete a sequence for adjusting the delay of an internal clock signal using a DLL circuit within a specified execution period.SOLUTION: A control circuit 1 includes a control unit that sets a delay amount on the basis of the phase difference between an input clock signal clk and an output clock signal, and a delay line unit 14 that performs a delay operation of delaying the input clock signal clk in accordance with the delay amount to generate an output clock signal, the delay line unit 14 includes a plurality of delay units each having one or more delay elements that delay the input clock signal clk, and the number of delay elements in one delay unit is greater than the number of delay elements in another delay unit.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a control circuit and a semiconductor memory device. [Background technology]

[0002] A dynamic random access memory (DRAM), which is a type of semiconductor storage device, is a volatile memory that stores information by storing electric charges in a capacitor, and loses the stored information when power is cut off. A delay locked loop (DLL) circuit is provided in the DRAM as a phase-locked loop circuit. The DRAM uses the DLL circuit to generate an internal clock signal for outputting a data signal in synchronization with an input clock signal input from the outside (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2015-35241 A Summary of the Invention [Problem to be solved by the invention]

[0004] Incidentally, when adjusting the delay of an internal clock signal using a DLL circuit, a sequence is executed that includes, for example, a reset operation of the DLL circuit, a delay (lock) operation of the DLL circuit (for example, an operation of synchronizing an external clock and an internal clock while activating the delay lines one by one), and an operation of detecting an N value that indicates the number of delay clock cycles between an input clock signal and an internal clock signal.

[0005] Here, the lock time Tdll due to the delay operation of the DLL circuit can be expressed by the following formula. Tint+Tdll=N×tCK

[0006] In the above formula, Tint indicates the inherent delay time in the DLL circuit, and tCK indicates the clock cycle. For example, if the clock cycle (tCK) becomes longer than the inherent delay time (Tint) due to the temperature in the semiconductor memory device, the lock time (Tdll) due to the delay operation of the DLL circuit will also become longer as shown in the above formula. If the lock time becomes longer in this way, the execution time of the entire sequence will become longer, and there is a risk that the execution of the next sequence will be delayed or that the execution period (tDLLK) of the sequence will be exceeded.

[0007] The present invention has been made in consideration of the above-mentioned problems, and has an object to provide a control circuit, a semiconductor memory device, and a control method for a semiconductor memory device that are capable of suppressing the prolongation of delay operations and completing a sequence for adjusting the delay of an internal clock signal using a DLL circuit within a specified execution period. [Means for solving the problem]

[0008] The control circuit of the present invention is a control circuit comprising a control unit that sets a delay amount based on the phase difference between an input clock signal and an output clock signal, and a delay line unit that performs a delay operation to delay the input clock signal corresponding to the delay amount to generate the output clock signal, wherein the delay line unit comprises a plurality of delay units having one or more delay elements that delay the input clock signal, and the number of delay elements in one of the delay units is greater than the number of delay elements in another of the delay units.

[0009] Since the number of the delay elements in one of the delay units is greater than the number of the delay elements in another of the delay units, many delay elements can be used by simply activating one unit, and the delay amount can be achieved quickly. Therefore, the lock time required to eliminate the same delay amount can be shortened, the delay operation is prevented from becoming longer, and the sequence for adjusting the delay of the internal clock signal using the DLL circuit can be completed within a predetermined execution period.

[0010] The delay units are connected in series and are used in sequence from one end to the other end according to the set delay amount, and it is preferable that the number of delay elements in the delay unit on the other end is greater than the number of delay elements in the delay unit on the one end.

[0011] It is preferable that the number of the delay elements included in each of the delay units from the other end side to a predetermined position is greater than the number of the delay elements included in each of the delay units from the predetermined position to the one end side.

[0012] It is preferable that the number of the delay units from the other end side to a predetermined position is greater than the number of the delay units from the predetermined position to the one end side. It is preferable that the number of delay elements included in the delay units adjacent to each other across the predetermined position differs by one. It is preferable that a plurality of the predetermined positions are provided, and the number of the delay units between each of the predetermined positions is the same. It is preferable that a plurality of the predetermined positions are provided, and the number of delay elements included in the delay units adjacent to each other via the predetermined position differs by one.

[0013] It is preferable that the control section sets the number of the delay units to be used in the delay operation in accordance with the amount of delay.

[0014] It is preferable that the delay line section activates delay units connected in series, from the delay unit at one end where the input clock signal is input, up to a number of delay units corresponding to the set number of delay units, and delays the input clock signal using these activated delay units.

[0015] It is preferable that the delay line section activates a delay unit among the delay units connected in series that corresponds to the number of delay units, and delays the input clock signal from the activated delay unit using the delay unit at the one end from which the output clock signal is output.

[0016] Preferably, the delay element comprises a NAND gate. It is preferable that the delay element included in the delay unit is composed of two NAND gates or three NAND gates.

[0017] A semiconductor memory device of the present invention preferably includes any one of the control circuits described above. The semiconductor memory device is preferably a dynamic random access memory. Effect of the Invention

[0018] According to the control circuit and semiconductor memory device of the present invention, it is possible to prevent the delay operation from becoming long, and to complete a sequence for adjusting the delay of an internal clock signal using a DLL circuit within a predetermined execution period. [Brief description of the drawings]

[0019] [Figure 1] 2 is a block diagram showing an example of the configuration of a control circuit according to an embodiment of the present invention; [Diagram 2] FIG. 2 is a diagram showing a configuration of a delay line section. [Diagram 3] 10 is a diagram illustrating a relationship between a unit of a delay line section and a NAND gate in the present embodiment. FIG. [Figure 4] FIG. 13 is a diagram illustrating the number of stages of NAND gates required for a delay amount. [Diagram 5] FIG. 13 is a diagram showing a schematic diagram of a required delay amount. [Figure 6] FIG. 13 is a diagram showing the configuration of another delay line section. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Hereinafter, a control circuit, a semiconductor memory device, and a control method for a semiconductor memory device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. However, the embodiment is merely an example, and the present invention is not limited thereto.

[0021] (Embodiment 1) 1 shows an example of the configuration of a control circuit according to an embodiment of the present invention. In this embodiment, the control circuit 1 is provided in a semiconductor memory device such as a DRAM. In this embodiment, well-known configurations (e.g., a command decoder, a memory cell array, an input / output interface unit, etc.) provided in a semiconductor memory device such as a DRAM are not shown in order to simplify the explanation.

[0022] The control circuit 1 includes an input buffer 11, a phase detection unit 12, a DLL control unit 13, a delay line unit 14, a replica unit 15, and an output buffer 16.

[0023] The input buffer 11 buffers an external clock signal CK input to the input buffer 11 to generate an input clock signal clk. The generated input clock signal clk is transmitted to the delay line unit 14 and the phase detection unit 12. As will be described in detail later, the delay line unit 14 generates a delayed signal (output clock signal) dll_clk by delaying the input clock signal clk input, and transmits the delayed signal to the output buffer 16 and the replica unit 15. The replica unit 15 outputs the delayed signal dll_clk generated by the delay line unit 14 to the phase detection unit 12 as a feedback signal fb_clk.

[0024] The phase detector 12 detects the phase difference between the input clock signal clk and the feedback signal fb_clk. The input clock signal clk and the feedback signal fb_clk are input to the phase detector 12. The phase detector 12 generates a phase signal up / down indicating the phase lead or lag of the feedback signal fb_clk relative to the input clock signal clk, and inputs the phase signal up / down to the DLL controller 13.

[0025] The DLL control unit 13 determines the amount of delay from the phase difference detected by the phase detection unit 12. The DLL control unit 13 then generates and outputs a control signal dll_code and a selection control signal select (described later) composed of multiple bits as signals indicating the amount of delay in the lock operation (one example of the "delay operation" of the present invention). The output control signal dll_code and selection control signal select are input to the delay line unit 14.

[0026] The delay line unit 14 is a variable delay unit that performs a locking operation by delaying the input clock signal clk based on the delay amount set by the DLL control unit 13 to generate a delayed signal dll_clk (output clock signal) and outputting it to the output buffer 16.

[0027] The configuration of the delay line unit 14 will be described with reference to Fig. 2. As shown in Fig. 2, the delay line unit 14 includes a multiplexer 21 and a NAND gate array 22 configured by connecting a plurality of NAND gates N (hereinafter, when distinguishing between individual gates, a number will be added after N) in series. The delay element is made up of a component (NAND gate N) that delays the clock signal, and in this embodiment, it is made up of two NAND gates N connected in series. Note that only a portion of the NAND gate array 22 is shown in Fig. 2.

[0028] In each NAND gate N, the input clock signal clk is input to the NAND gate N1 on the most upstream side (the leftmost side in the figure) in the NAND gate string 22, and the other NAND gates N receive the output from the immediately preceding NAND gate N connected in series. Here, the end of the NAND gate string 22 where the input clock signal clk is input is referred to as the upstream side, and the opposite side is referred to as the downstream side.

[0029] The NAND gate array 22 is divided into a number of units U (delay units; hereinafter, when distinguishing between individual units, a number will be added after U). That is, in this embodiment, not only the NAND gates N but also the units U are connected in series. The units U are configured such that the unit numbers increase from unit U1 on the upstream side to unit U1, unit U2, and so on downstream.

[0030] Here, the code signal of the control signal dll_code composed of multiple bits generated by the DLL control unit 13 is <n>is input to each unit U. In other words, the unit Un receives the code signal <n>is input, and the same code signal is input to the NAND gates N in one unit U. <n>This code signal is input. <n>determines which units are activated, <n>If the value of the control signal dll_code is "1", the unit Un is activated. For example, the NAND gates N1 and N2 included in the unit U1 are respectively connected to the same control signal dll_code code signal. <1> is input, and if the value of the code signal is "1", the NAND gates N1 and N2 (unit U1) are activated.

[0031] In each unit U, the output of the last-stage (most downstream) NAND gate N is input as a unit signal unit to the multiplexer 21. A selection control signal select is input to the multiplexer 21. The selection control signal select is a signal indicating which unit U's unit signal unit is to be selected. Of the unit signals unit to the multiplexer 21, the unit signal unit selected by the selection control signal select is input and output as a delayed signal dll_clk.

[0032] In the lock operation, the input clock signal clk is sequentially activated from the unit U1 on the upstream side (one end side. In the present invention, the unit U that is used first among the units U connected in series corresponds to the one end side) where the input clock signal clk is input, to the unit Un corresponding to the number of NAND gates N required to achieve the delay amount set by the DLL control unit 13, and the input clock signal clk is delayed using these activated units U. For example, when the DLL control unit 13 sets that the unit U9 is activated to achieve the delay amount, the DLL control unit 13 generates a selection control signal select indicating that the unit U9 is selected, and generates a control signal dll_code including a code signal that activates the units U1 to U9, and these are input to the delay line unit 14. In this case, the units U1 to U9 are activated, and a unit signal unit9 in which the input clock signal clk is delayed is generated. Then, the multiplexer 21 selects the unit signal unit9 from the unit U9 and outputs it as the delay signal dll_clk.

[0033] Here, in this embodiment, the number of stages of NAND gates N differs for each unit U. For example, unit U1 is composed of two stages of NAND gates (NAND gates N1 and N2), and unit U8 is composed of four stages of NAND (NAND gates N7, N8, N9, and N10). An explanation will be given with reference to FIG. 3. FIG. 3 is a diagram showing a schematic diagram of the relationship between the units U and the NAND gates N of the delay line section 14 of this embodiment, in which each square indicates a unit U, the number of the unit U (for example, "1" indicates unit U1) is indicated in the upper left corner of the square, and the number of stages of NAND gates N included in the unit U is indicated within the square, and the larger the number of NAND gates N included in each unit U, the larger the unit is displayed. As shown in FIG. 3, in this embodiment, the NAND gate array 22 is configured so that each of the units U1 to U8 has two stages of NAND gates N, each of the units U9 to U16 has four stages of NAND gates N, each of the units U17 to U24 has six stages of NAND gates N, and each of the units U25 to U32 has eight stages of NAND gates N.

[0034] The conventional delay line section is also composed of a plurality of NAND gates N connected in series and divided into a plurality of units U, but the conventional delay line section differs from this embodiment in that all units in the conventional delay line section are composed of two-stage NAND gates. In such a conventional control circuit having a delay line section, it took a long time to activate the desired number of delay units when the delay amount was large. In other words, conventionally, even when the delay amount was large, each unit was activated in order from one end side, and the input clock signal was delayed and a lock operation was performed until it matched the output clock signal. In this case, when the delay amount was large, it took a long time to lock the operation if a large number of units were activated in order from the end side until the input clock signal matched the clock signal and used for the delay operation.

[0035] In contrast, in this embodiment, unlike such a conventional delay line section, the number of stages of NAND gates N varies depending on the unit U, so that it is possible to suppress the lengthening of the lock time Tdll. That is, when activating the units U in order from one end side in order to activate the units U corresponding to the number of NAND gates N required to achieve the delay amount, since there is a portion in the unit U that has a large number of stages of NAND gates N, it is possible to activate many NAND gates N by simply activating one unit U, so that the delay amount can be achieved quickly. This point will be explained using Figures 4 and 5. Figure 4 shows the number of stages of NAND gates required for the delay amount, and Figure 5 shows the lock time (Tdll) required for the delay amount.

[0036] In the case of a lock operation for a delay amount that requires a delay using 36 stages of NAND gates N, in the conventional delay line section shown in Fig. 4(1), it is necessary to activate 18 units U in order from unit U1 to unit U18. However, in the case of the delay line section 14 of this embodiment shown in Fig. 4(2), in the case of a lock operation for a delay amount that requires a delay using 36 stages of NAND gates N, it is sufficient to activate 13 units U in order from unit U1 to unit U13. This is because, in this embodiment, the number of NAND gates N in each unit U is two stages up to unit U8, but the number of NAND gates N in each unit U is four stages from unit U9 onwards, and it is sufficient to activate 13 units to activate 36 stages of NAND gates N.

[0037] In this case, as shown in FIG. 5(1), in the case of a conventional delay line section, a locking time of 18 units was required to complete the locking operation, but in the delay line section 14 of this embodiment, it is only necessary to activate 13 units, so that the locking operation can be completed in the locking time of 13 units.

[0038] In this embodiment, since the number of stages of the NAND gates N constituting the downstream unit U is greater than the number of stages of the NAND gates N in the upstream unit U, the activation of the number of NAND gates N required to eliminate the delay time can be achieved quickly, and the lock time Tdllk can be shortened. As a result, the execution time Tdllk of the sequence corresponding to the lock time can also be shortened. When increasing the number of stages of the NAND gates N, the number of NAND gates N is increased by two for each delay element, that is, in this embodiment, two NAND gates N are one set (delay element).

[0039] Furthermore, in this embodiment, the delay circuit can be constructed by simply changing the number of stages of the NAND gates N in the unit U (i.e., by simply changing the wiring) from the conventional delay circuit without changing the control in the DLL control unit 13, and the lock time Tdll can be shortened, so that the circuit can be implemented very simply.

[0040] In this embodiment, the number of stages of NAND gates N in the downstream unit U is greater than that in the upstream unit, but it is sufficient if there is at least a unit U in which the number of NAND gates N is greater than the number of NAND gates N in the other units U in the NAND gate array 22. Even in this case, it is possible to quickly achieve activation of the number of NAND gates N required to eliminate the delay time.

[0041] Considering only the shortening of the locking time, it is possible to increase the number of stages of the NAND gates N in all the units U compared to the conventional method, but it is preferable to increase the number of NAND gates N in at least some of the units U as described above, since it is possible to perform appropriate control according to the amount of delay. In particular, by increasing the number of NAND gate stages in the downstream unit U compared to the upstream unit as in this embodiment, it is possible to perform more appropriate control according to the amount of delay. That is, in this embodiment, the number of stages of the NAND gates N in each unit U is set to be small in the upstream unit U (for example, 2 stages as in the conventional method), and the number of stages is increased in the downstream unit U. When the amount of delay is small, the locking operation can be performed adequately by using only these upstream units U, and when the amount of delay is large, the downstream unit U with a large number of stages is used, but since the downstream unit U has a large number of NAND gates N, it is possible to end the locking operation earlier than in the conventional method.

[0042] 3, two stages of NAND gates N are added for every eight units in this embodiment, but the present invention is not limited to this, and it is sufficient to configure the number of NAND gates N in the units U to be increased at least on the downstream side (the other end side) from the upstream side (one end side). That is, one predetermined position is set, and all the units U included from the upstream side to the predetermined position have the same number of stages of NAND gates N, and all the units U included from the predetermined position to the downstream side have the same number of stages of NAND gates N.

[0043] Moreover, it is preferable to set such a predetermined position relatively downstream (on the other end side). For example, one predetermined position is set after the unit U16, and each unit U from unit U1 to unit U16 includes two stages of NAND gates N, and only the last unit U17 to unit U includes four stages of NAND gates N. With this configuration, since the downstream units U have many stages of NAND gates N, it is possible to end the locking operation earlier than in the past even when the delay amount is very large, such as when unit U17 is used. Also, the predetermined position may be irregularly set in the NAND gate array 22. For example, if a predetermined position is set at the 8th unit and the 12th unit, each unit U from unit U1 to unit U8 includes two stages of NAND gates N, each unit U from unit U9 to unit U12 includes four stages of NAND gates N, and only the last unit U13 to unit U24 includes six stages of NAND gates N. Even with this configuration, the downstream units U have a greater number of stages of NAND gates N, so that it is possible to complete the locking operation earlier than in the past.

[0044] In addition, in this embodiment, the number of stages of the NAND gates N is increased by one delay element at each predetermined position, or two stages in terms of the number of NAND gates N, but this is not limited thereto. For example, if one predetermined position is set after the unit U16, the first to 16th units may all include two stages of NAND gates N in each unit U, and only the last 17th to 24th units may include eight stages of NAND gates N. It is preferable to gradually increase the number of stages in order to perform fine control, but when performing a locking operation using the latter units U, the locking time is prolonged, so the number of stages may be increased significantly at once.

[0045] (Embodiment 2) In the above-described embodiment, the multiplexer 21 is provided on the output side, but in this embodiment, the delay line unit 14 is configured using a selector on the input side instead of the multiplexer 21, which is different from the first embodiment. The delay line unit 14 of this embodiment will be explained with reference to FIG. 6. In this embodiment, the delay line unit 14 includes a selector (not shown) and a NAND gate array 32 consisting of a plurality of NAND gates N. Note that only a portion of the NAND gate array 32 is shown in FIG. 6.

[0046] The NAND gate array 32 consists of two NAND gate arrays. Specifically, the NAND gate array 32 includes a first NAND gate array 33 and a second NAND gate array 34. The first NAND gate array 33 is configured with a plurality of NAND gates N connected in series, and has odd-numbered NAND gates NA and even-numbered NAND gates NB. The second NAND gate array 34 is configured with a plurality of NAND gates NC connected in parallel, each of which is connected to an even-numbered NAND gate NB. These NAND gates NA, NB, and NC are configured as one delay element.

[0047] In this embodiment, each unit U is configured by dividing the NAND gate array 32 so as to include one or more delay elements. That is, in this embodiment, the units U are also connected in series, and the number of NAND gates N differs for each unit U. Also, in this embodiment, the units U are numbered from the downstream side (one end side) opposite to the upstream side (other end side) where the input clock signal clk is input. For example, the number of NAND gates N included in the downstream unit U8 is three in total, but the number of NAND gates N in the adjacent unit U9 is six. Thus, in this embodiment, the predetermined position is in the unit U8, and the units U16 (not shown) to U9 on the upstream side across the predetermined position all have four stages of NAND gates N, and the units U8 to U1 on the downstream side (one end side) across the predetermined position all have two stages of NAND gates N.

[0048] The output of the odd-numbered NAND gate NA and the output of the NAND gate NC are input to the even-numbered NAND gate NB of the first NAND gate array 33. The input clock signal clk and the code signal or 0 signal of the control signal dll_code are input to the NAND gate NC. The code signal is a code signal with the same number as the number of the corresponding unit U. <n>For example, the unit U7 receives the code signal <7> is entered.

[0049] In this embodiment, only the unit U selected by the control signal input to the selector is activated. In the activated unit U, the input clock signal clk is delayed through the NAND gate NC and NAND gate NB of the unit U, and the input clock signal clk input to the NAND gate NB is further input to the adjacent NAND gate NA, delayed while passing through the unit U of the NAND gate array 33, and output as a delayed signal dll_clk.

[0050] That is, in this embodiment, the delay line unit 14 activates only the units U corresponding to the number of NAND gates N necessary to achieve the delay amount set according to the delay amount among the units U connected in series, and delays the input clock signal clk using the activated units U to the unit U1 at the downstream end where the delay signal dll_clk is output. For example, when the DLL control unit 13 sets that the unit U9 is to be activated, a selection control signal select indicating that the unit U9 is selected is input, and the unit U9 is activated, and as a result, the units U1 to U9 are used for the delay operation, and the delay signal dll_clk in which the input clock signal clk is delayed is generated and output. At this time, the number of stages of the NAND gates N of the unit U8 used for the delay operation is two stages, and the number of stages of the NAND gates N of the unit U9 used for the delay operation is four stages, and the delay amount is the same as the units U8 and U9 of the first embodiment. In the unit U including a plurality of delay elements such as the unit U9, the input clock signal clk and the 0 signal are input to the NAND gates NC other than the upstream NAND gate NC.

[0051] In this manner, in this embodiment, since the number of NAND gates N constituting the unit U from the predetermined position is greater than the number of NAND gates N of other units U up to the predetermined position, a desired number of NAND gates N can be used early when the delay amount is large, and as a result, the lock time Tdll can be shortened. As a result, the execution time (Tdllk) of the sequence corresponding to the lock time can also be shortened. (Modification)

[0052] In the above-described embodiments, the delay element is a NAND gate N, but this is not limiting. Furthermore, the configuration of the delay line section 14 is not limited.

[0053] In the above embodiment, the semiconductor recording device having the control circuit is a DRAM, but the present invention is not limited to this. For example, the semiconductor memory device may be a static random access memory (SRAM), a flash memory, or another semiconductor memory device.

[0054] The above-described embodiment and modifications are described for the purpose of facilitating understanding of the present invention, and are not described for the purpose of limiting the present invention. Therefore, the elements disclosed in the above embodiment and modifications are intended to include all design modifications and equivalents that fall within the technical scope of the present invention.

[0055] The configuration of the DLL circuit 10 in the above-described embodiment is merely an example, and may be modified as appropriate, or various other configurations may be adopted. [Explanation of symbols]

[0056] 1 Control circuit 10 DLL circuit 11 Input Buffer 12 Phase detection section 13 DLL control section 14 Delay Line Section 15 Replica Section 16 Output Buffers 21 Multiplexer 22 NAND gate array 24 Delay Line Section 32 NAND gate array 33 First NAND gate row 34 Second NAND gate row CK External clock signal N NAND gates U-Unit clk Input clock signal dll_clk delayed signal (output clock signal) dll_code control signal fb Feedback signal select Selection control signal unit Unit signal up / down phase signal< / n> < / n> < / n> < / n> < / n> < / n>

Claims

1. A control circuit including a control unit that sets a delay amount based on a phase difference between an input clock signal and an output clock signal, and a delay line unit that performs a delay operation that delays the input clock signal in response to the delay amount to generate the output clock signal, the delay line section includes a plurality of delay units each having one or more delay elements that delay the input clock signal; A control circuit, characterized in that the number of said delay elements in one of said delay units is greater than the number of said delay elements in another of said delay units.

2. 2. The control circuit according to claim 1, wherein the delay units are connected in series and are used in sequence from one end to the other end according to the set delay amount, and the number of delay elements in the delay unit on the other end is greater than the number of delay elements in the delay unit on the one end.

3. 3. The control circuit according to claim 2, wherein the number of said delay elements in each of said delay units from said other end side to a predetermined position is greater than the number of said delay elements in each of said delay units from said predetermined position to said one end side.

4. 3. The control circuit according to claim 2, wherein the number of each of said delay units from said other end side to a predetermined position is greater than the number of each of said delay units from said predetermined position to said one end side.

5. 4. The control circuit according to claim 3, wherein the number of said delay elements included in said delay units adjacent to each other via said predetermined position differs by one.

6. A plurality of the predetermined positions are provided, 4. The control circuit of claim 3, wherein the number of said delay units between each of said predetermined positions is the same.

7. A plurality of the predetermined positions are provided, 4. The control circuit according to claim 3, wherein the number of delay elements included in the delay units adjacent to each other via the predetermined position differs by one.

8. 3. The control circuit according to claim 2, wherein the control section sets the number of the delay units to be used in the delay operation in accordance with the amount of delay.

9. 9. The control circuit according to claim 8, wherein the delay line section activates delay units from the delay unit at one end side to which the input clock signal is input up to a number of delay units corresponding to the set number of delay units among the delay units connected in series, and delays the input clock signal using these activated delay units.

10. 9. The control circuit according to claim 8, wherein the delay line section activates the delay units corresponding to the number of the delay units among the delay units connected in series, and delays the input clock signal from the activated delay unit using the delay unit at the end side from which the output clock signal is output.

11. 3. The control circuit of claim 2, wherein said delay element comprises a NAND gate.

12. 10. The control circuit according to claim 9, wherein the delay element included in the delay unit is composed of two NAND gates.

13. 11. The control circuit according to claim 10, wherein the delay element included in the delay unit is composed of three NAND gates.

14. A semiconductor memory device comprising the control circuit according to any one of claims 1 to 13.

15. 15. The semiconductor memory device according to claim 14, wherein the semiconductor memory device is a dynamic random access memory.

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