JP3729582B2 - Semiconductor device, semiconductor device system, and digital delay circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor device that outputs an externally input signal at a predetermined accurate phase, a semiconductor device system using such a semiconductor device, and a digital delay circuit used therein, and more particularly to ambient temperature and The present invention relates to a synchronous semiconductor memory in which a signal is always output at a predetermined phase with respect to an external clock regardless of fluctuations in power supply voltage.
[0002]
[Prior art]
Usually, in a semiconductor integrated circuit (LSI), a signal is input from the outside, a processing operation corresponding to the input signal is performed, and an output signal is output. Therefore, it is important at what timing the output signal can be obtained with respect to the external input signal. In general-purpose LSIs, this timing is generally determined by the specifications. For example, in a dynamic random access memory (DRAM), the timing at which data is output from the changing edge of the address signal and the data setup time for writing data are defined along with the maximum frequency of the address signal.
[0003]
In recent years, the speed of the CPU in a computer system or the processing speed of various other electronic circuits has been urged to increase the interface portion. For example, although CPUs with a clock of 100 MHz or more have appeared, the access speed and data transfer speed of DRAMs widely used as main memory are operating speeds that are an order of magnitude lower. Therefore, various new DRAM systems such as a synchronous DRAM (SDRAM) that enables a data transfer rate of 100 MHz or higher have been proposed.
[0004]
The SDRAM performs data input / output in synchronization with a high-speed clock input from the outside. The SDRAM has a plurality of units that can input / output a plurality of bits of data in parallel. A method that speeds up the interface with the outside by converting this multi-bit data to serial data, and a method that speeds up the operation by pipelining internal operations and performing each pipe operation in parallel. There is. In the following, a pipelined DRAM will be described as an example.
[0005]
FIG. 1 is a block diagram of a SDRAM of 16M, 2 banks, 8 bits wide, which is an example of a pipelined synchronous DRAM (hereinafter simply referred to as SDRAM).
In addition to the DRAM cores 108a and 108b of general-purpose DRAM, the SDRAM includes a clock buffer 101, command decoder 102, address buffer / register & bank address select (hereinafter simply referred to as address buffer) 103, I / O data buffer / register 104, control. It has signal latches 105a and 105b, a mode register 106, and column address counters 107a and 107b. Unlike the conventional operation, the / CS, / RAS, / CAS, and / WE terminals are configured such that the operation mode is determined by inputting various commands in combination. Various commands are decoded by the command decoder, and each circuit is controlled according to the operation mode. The / CS, / RAS, / CAS, and / WE signals are also input to the control signal latches 105a and 105b, and their states are latched until the next command is input.
[0006]
On the other hand, the address signal is amplified by the address buffer 103 and used as a load address for each bank, and also used as an initial value for the column address counters 107a and 107b. The signals read from the DRAM cores 108a and 108b are amplified by the I / O data buffer / register 104 and output in synchronization with the rising edge of the external clock CLK input from the outside. The same operation is performed for the input, and the input data is written to the I / O data buffer / register 104.
[0007]
FIG. 2 is a diagram showing the timing of a general SDRAM read (read) operation.
The external clock CLK is a signal supplied from a system in which the SDRAM is used, and operates to take in various commands, address signals, input data, or output output data in synchronization with the rising edge of the CLK. .
[0008]
When reading data from the SDRAM, an active (ACT) command is input to the command terminal from a combination of command signals (/ CS, / RAS, / CAS, / WE signal), and a row address signal is input to the address terminal. To do. When this command and row address are input, the SDRAM enters an active state, selects a word line corresponding to the row address, outputs cell information on the word line to the bit line, and amplifies it with a sense amplifier.
[0009]
On the other hand, a read command (Read) and a column address are input after the operation time (tRCD) of the portion related to the row address. According to the column address, the selected sense amplifier data is output to the data bus line, amplified by the data bus amplifier, further amplified by the output buffer, and output to the output terminal (DQ). A series of these operations is exactly the same as that of a general-purpose DRAM. In the case of an SDRAM, a circuit related to a column address is pipelined, and read data is output continuously every cycle. . Thereby, the data transfer cycle becomes the cycle of the external clock.
[0010]
There are three types of access time in the SDRAM, and all are defined on the basis of the rising edge of CLK. In FIG. 2, tRAC indicates a row address access time, tCAC indicates a column address access time, and tAC indicates a clock access time. When this SDRAM is used in a high-speed memory system, tRAC and tCAC, which are times from when a command is input to when data is first obtained, are important, but in order to increase the data transfer speed, the clock access time tAC It is also important.
[0011]
FIG. 3 is a block diagram for explaining the pipeline operation in the SDRAM, and shows a case where three stages of pipes are provided as an example.
The processing circuit related to the column address in the SDRAM is divided into a plurality of stages along the flow of processing, and the divided circuit of each stage is called a pipe. In the clock buffer 101, an internal clock signal to be supplied to each pipe is generated from CLK, and each pipe is controlled in accordance with the supplied internal clock signal. Switches that control signal transmission timing between the pipes are provided between the pipes, and these switches are also controlled by an internal clock signal generated by the clock buffer 101.
[0012]
In this example, in the pipe-1, the address signal is amplified by the column address buffer 116, the address signal is sent to the column decoder 118, and the information of the sense amplifier circuit 117 corresponding to the address address selected by the column decoder 118 is sent to the data bus. Until the data bus information is amplified by the data bus amplifier 119. Pipe-2 is composed of only the data bus control circuit 120, and pipe-3 is composed of only the I / O buffer 104. If the circuits in any of the pipes complete the operation within the clock cycle time, data can be sent out in a relay manner by opening and closing a switch between the pipes in synchronization with CLK. As a result, processing in each pipe is performed in parallel, and data is continuously output to the output terminal in synchronization with CLK.
[0013]
[Problems to be solved by the invention]
FIG. 4 is a diagram for explaining a problem when the conventional SDRAM described in FIGS. 1 to 3 is used in a high-speed memory system.
In FIG. 4, tAC represents the clock access time from the system clock CLK, and tOH represents the output data holding time to the previous cycle or the next cycle. Considering the variation in SDRAM characteristics, temperature dependence, and power supply voltage dependence, tAC and tOH do not match and have a certain width. The time corresponding to this width is a time when data is indefinite, meaning a time when it is not known what data is output, and is a time that cannot be used in the memory system, which is a so-called dead band. In addition, although not shown, this dead band includes wiring delay time and variation on the board.
[0014]
On the other hand, in order to capture (receive) SDRAM output on the system side, a setup time (tSI) and a hold time (tHI) are required, and these times must be within the time when the data of the memory output is fixed. . The time is (tCLK + tOH−tAC) from the figure.
For example, when considering a system operating at 100 MHz, if the cycle time (tCLK) is 10 ns, the memory access time (tAC) is 6 ns, and the hold time is 3 ns, the subtraction 7 ns is a time that can be used on the system side. The total setup time and hold time (tSI + tHI) of the receiving logic in a system using a normal input circuit is 3 ns, and the remaining 4 ns is a system margin time such as signal delay on the board and variations between DQ terminals. Become. Considering the signal propagation time on the board, this value is very strict for the system. Needless to say, even higher speed systems will require more stringent timing adjustments. Therefore, it has become important to make the data indeterminate time shown in FIG. 4 as small as possible.
[0015]
In order to shorten the data indeterminate time, data is always output in a predetermined phase with respect to the external clock CLK even if there is a variation in characteristics, a temperature change, or a power supply voltage change, that is, the clock access time tAC is It may be always constant. If it is desired that the data output be performed in synchronization with the rising edge of the external clock CLK, the clock access time tAC may be always zero.
[0016]
As described above, the necessity of outputting an output signal in synchronization with an externally input signal has been described by taking a synchronous DRAM as an example. However, this is not limited to a synchronous DRAM and can be said to be common to many semiconductor devices. It is. Various measures can be taken with respect to the inside of the semiconductor device so that a desired operation can be performed in each semiconductor device. However, in the case of outputting the processing result inside each semiconductor device, other semiconductor devices Therefore, it is important to make the output timing constant.
[0017]
The present invention has been made in view of the above problems, and realizes a semiconductor device in which data is output in a predetermined phase with respect to the external clock CLK regardless of variations in characteristics, temperature changes, and power supply voltage changes. With the goal. In particular, an object is to realize a synchronous semiconductor memory in which the clock access time tAC is always controlled to be constant.
[0018]
[Means for Solving the Problems]
FIG. 5 is a diagram showing a basic configuration of a semiconductor device of the present invention.
As shown in FIG. 5, in the semiconductor device of the present invention, an external input signal is input, an input circuit 13 that outputs a reference signal and an output timing signal are received, and an output signal is output at a timing according to the output timing signal. And an output timing control circuit 20 that controls the output timing of the output signal from the output circuit 14 so as to be in a predetermined phase with respect to the external input signal. The circuit 20 has a selectable delay amount, delays the reference signal by the selected delay amount, and compares the phase of the reference signal and the output timing signal with the delay circuit 21 applied to the output circuit 14 as an output timing signal. A delay control circuit that selects a delay amount of the delay circuit 21 based on a comparison result between the phase comparison circuit 22 and the phase comparison circuit 22. Characterized in that it comprises a 23.
[0019]
In the semiconductor device of the present invention, the delay amount for timing adjustment in the output timing control circuit 20 is not fixed, and the actual circuit signal is compared with the external clock signal (corresponding to the reference signal) output from the input circuit 13. Therefore, even if there are variations in the characteristics of semiconductor devices, temperature changes, power supply voltage changes, etc., the phase relationship of the output signal with respect to the external clock signal is set to a predetermined value. It is possible to maintain it accurately.
[0020]
The comparison with the external clock signal requires that the signal be delayed by an amount equal to the delay amount in the actual circuit. The external clock signal is input to the input circuit 13 of the semiconductor device and subjected to processing such as amplification. Therefore, the external clock signal that can be compared is the external clock signal output from the input circuit, and this has a phase difference from the actual external clock signal by the delay in the input circuit 13. Therefore, a dummy input circuit 24 that generates the same delay amount as that of the input circuit 13 is provided, and a signal obtained by passing the output timing signal through the dummy input circuit 24 is compared with an external clock signal output from the input circuit 13. It is desirable to cancel the delay amount in the input circuit 13.
[0021]
In the configuration of FIG. 5, the output of the delay circuit 21 is input to the dummy input circuit 24. Therefore, the comparison target signal to be compared with the external clock signal by the phase comparison circuit 22 does not include a delay in the output circuit 14. Of course, the phase relationship to be controlled is determined in consideration of this amount of correction, but the delay in the output circuit 14 is larger than the delay amount in other parts, the variation in the characteristics of the semiconductor device, the temperature change, the change in the power supply voltage, etc. There is a problem that the change in the delay amount in the output circuit 14 is relatively large and cannot be ignored.
[0022]
FIG. 6 is a diagram for explaining this problem. Here, description will be made assuming that control is performed so as to output in synchronization with the rising edge of external clock signal CLK. The output timing signal that is supplied from the delay circuit 21 to the output circuit 14 and defines the output timing of the signal from the output circuit 14 rises before a predetermined amount of the rising edge of CLK in anticipation of the delay in the output circuit 14. If the delay amount in the output circuit 14 is a predetermined value, the output changes in synchronization with the rising edge of CLK. However, if the delay amount in the output circuit 14 changes due to the above factors, the output timing from the output circuit will be shifted from the rising edge of the CLK accordingly. If there is such a variation, it is necessary to allow for a margin, and it is difficult to increase the speed accordingly.
[0023]
In order to solve such a problem, the output signal of the output circuit 14 may be input to the dummy input circuit 24 and the phase with the external clock signal may be compared. In order to perform the phase comparison, the output signal of the output circuit 14 needs to change. During normal operation, output data is output from the output circuit 14, but this output data is a random signal, and the “high” level or the “low” level may continue. Therefore, in order to compare the phase of the output signal of the output circuit 14 with respect to the external clock signal during normal operation, the phase comparison circuit 22 determines whether or not the output signal has changed, and performs phase comparison only when the output signal has changed, thereby performing delay control. When the output signal does not change, the circuit 23 performs control so that the delay amount until then is maintained, and when the output signal does not change, feedback control is performed so that the phases match based on the comparison result of the phase comparison circuit 22. To do.
As another configuration, an initialization operation is performed before starting a normal operation, and dummy data that changes in a predetermined cycle is output in the initialization operation. Are compared, and feedback control is performed so that the phases match. After matching, the adjusted delay amount is maintained. Since the dummy data always changes in a predetermined cycle, the phase comparison circuit 22 can compare the phases by determining which of the changes.
[0024]
Further, as shown in FIG. 7, a dummy output circuit having characteristics equivalent to those of the output circuit 14 may be provided, and the phase comparison between the output signal of the dummy output circuit and the external clock signal may be performed. The semiconductor device of FIG. 7 is provided with a dummy output circuit 35 in addition to the configuration of FIG. 5, and the output timing signal from the delay circuit 31 is also input to the dummy output circuit 35. The difference is that the dummy output signal output in response to the signal is input to the phase comparison circuit 32 via the dummy input circuit 34 and compared with the external clock signal from the input circuit.
[0025]
With the configuration of FIG. 7, the dummy output circuit can always output a signal suitable for phase determination independent of the output signal from the output circuit. Therefore, it is possible to perform the feedback control by always outputting the dummy data as described above. Moreover, if the dummy data is a signal that changes more slowly than the cycle of the clock signal, the power consumption of the circuit can be reduced.
[0026]
Further, a second output timing control circuit for the dummy output circuit is provided separately from the first output timing control circuit for the output circuit, and the output signal and the dummy output signal are respectively synchronized with the external clock signal at the time of initialization. This means that the output signal and the dummy output signal are also synchronized, and thereafter, the dummy output signal is fed back to the first output timing control circuit for control. With such a configuration, even if a dummy output circuit is used, adjustment including the influence of a load connected to the actual output circuit is possible.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
In the following description, an embodiment in which the present invention is applied to a synchronous DRAM will be described. As described above, the present invention is not limited to a synchronous DRAM, and an output signal is output in synchronization with an externally input signal. Any semiconductor integrated circuit can be applied.
[0028]
A synchronous DRAM (SDRAM) according to an embodiment of the present invention has an overall configuration as shown in FIG. FIG. 8 is a diagram illustrating the timing of the read operation of the SDRAM of the embodiment.
As apparent from comparison between FIG. 3 and FIG. 8, the SDRAM of the embodiment has almost the same configuration as the conventional SDRAM, but the configuration of the clock buffer 101 is different. In the SDRAM of the embodiment, the clock buffer 101 has an internal clock generation circuit 121 and an output timing control circuit 122. The internal clock generation circuit 121 is the same as the conventional SDRAM, generates an internal clock signal from the external clock CLK, and supplies it to the pipe-1 and pipe-2. The output timing control circuit 122 has the basic configuration shown in FIG. 7, and controls the output timing of data from the output circuit 14 so as to always have a predetermined phase with respect to the external clock CLK.
[0029]
FIG. 9 is a diagram showing the configuration of the output timing control circuit 122 of the first embodiment, and also shows the terminal 11 to which the external clock CLK is input, the output circuit 14 and the data output terminal 12 together.
As shown in FIG. 9, the output timing control circuit of the first embodiment delays the input circuit 13 that receives the external clock CLK input to the external clock input terminal 11 and the CLK that is input from the input circuit 13 and outputs it. A DLL (Delay Lock Loop) circuit 40 that generates an output clock that defines the output timing of data from the circuit 14, a dummy input circuit 34 having the same circuit configuration as the input circuit 13, and the output circuit 14 A dummy output circuit 37 having a circuit configuration equivalent to the above, a dummy signal wiring 36 provided between the DLL circuit 40 and the dummy output circuit 37, equivalent to the signal wiring from the DLL circuit 40 to the output circuit 14, and a data output terminal 12 and a dummy output load 38 having a load equivalent to that assumed.
[0030]
The input circuit 13 includes an electrostatic protection circuit (ESD) 131, a current mirror circuit 132 that amplifies CLK, a latch circuit 133, a CLK control circuit 134, and a 1 / N frequency divider 135. Since the input circuit 13 is an external clock input circuit that is widely used except for the 1 / N frequency divider 135, the 1 / N frequency divider 135 will be described later, and a detailed description thereof will be omitted here. . Like the input circuit 13, the dummy input circuit 34 includes a dummy ESD 341, a dummy current mirror circuit 342, a dummy latch circuit 343, and a dummy CLK control circuit 344, and each circuit is the same as that of the input circuit 13. The signal delay amount is the same.
[0031]
The DLL circuit 40 includes a delay circuit 41a that delays a signal input from the CLK control circuit 134 by a selected amount, and a dummy delay circuit that delays a signal input from the 1 / N frequency divider 135 by a selected amount. 41b, the phase comparison circuit 42 that compares the signal of the 1 / N frequency divider 135 and the signal of the dummy CLK control circuit 344, and the delay amount of the delay circuit 41a and the dummy delay circuit 41b based on the comparison result of the phase comparison circuit 42 And a delay control circuit 43 for selecting.
[0032]
FIG. 10 is a diagram showing circuit configurations and operation waveforms of the delay circuit 41a and the dummy delay circuit 41b. (1) shows a configuration of a delay circuit for 1 bit, and (3) shows a plurality of delay circuits for 1 bit. The configuration and operation explanation when connected in stages are shown, and (2) is a time chart showing the operation of the delay circuit for one bit.
As shown in (1) of FIG. 10, the delay circuit for 1 bit includes two NAND circuits 401 and 402 and an inverter 403. The operation of the delay circuit for 1 bit will be described with reference to (2) in FIG. 10. The input φE is an activation signal, and the delay circuit operates when it is at “H” level. (2) shows a state in which φE becomes “H” and signal reception is possible. The signal IN is an input signal to the delay circuit for 1 bit, φN is the signal from the adjacent right side connected in multiple stages, OUT is the output signal of the delay circuit for 1 bit, 4a-1 and 4a-2 Shows the waveform of the corresponding internal terminal in the circuit of (1). Therefore, OUT becomes φN to the left.
[0033]
When φN is “L”, OUT is always “L”. When φN is “H” and φE is “L”, OUT is “H”. When φN is “H” and φE is “H”, OUT is “H” if the input signal IN is “L”, and “L” if IN is “H”. (2) in FIG. 10 shows that when IN rises from L to H in the state of φE = H and φN = H, the input signal IN is inverted by the NANAD gates 401 and 402 and the inverter 403 and transmitted to the output OUT. It shows how it is being done.
[0034]
(3) in FIG. 10 is an example in which the delay circuit for 1 bit of (1) is cascade-connected in a plurality of stages, and corresponds to an actual delay circuit. Although only three stages are shown in the figure, they are actually connected in multiple stages. The activation signal φE has a plurality of signal lines such as φE-1, φE-2, and φE-3 for each circuit element, and these signals are controlled by the delay control circuit 43.
[0035]
In the figure, the delay circuit for one bit in the middle is activated, and φE-2 is “H”. In this case, when the input signal IN changes from “L” to “H”, φE-1 and φE-3 of the leftmost one-bit delay circuit and the rightmost one-bit delay circuit are “L”. The input signal IN is stopped by the NAND circuits 401-1 and 401-3, as indicated by the bold line. On the other hand, since φE-2 of the activated delay circuit for one bit in the middle is “H” level, the input signal IN passes through the NAND circuit 401-2. Since the output OUT of the right one-bit delay circuit is “H”, the input signal IN also passes through the NAND circuit 402-2 and is transmitted to OUT as the signal “L”. As described above, when OUT on the right side, that is, φN is “L”, OUT is always “L”, so this “L” signal is sequentially applied to the NAND circuit and inverter of the delay circuit for 1 bit on the left side. Is transmitted and taken out as a final OUT signal.
[0036]
In this way, the input signal IN is transmitted through the activated delay circuit for 1 bit so as to be folded back to become a final OUT signal. That is, the delay amount can be controlled depending on which part of the activation signal φE is set to “H”. The delay amount for one bit is determined by the total signal propagation time of the NAND circuit and the inverter, and this time becomes the delay unit time of the DLL circuit. The overall delay time is an amount obtained by multiplying the delay amount for one bit by the number of stages to be passed.
[0037]
FIG. 11 is a diagram showing a circuit configuration of the delay control circuit, and FIG. 12 is a time chart showing its operation. As shown in FIG. 11, the delay control circuit is also configured by connecting 1-bit delay control circuits 430-2 surrounded by a dotted line by the number of stages of the delay circuit, and the output of each stage is the activity of each stage of the delay circuit. Signal .phi.E.
The one-bit delay control circuit 430-2 includes transistors 435-2, 437-2, 438-2, and 439 connected in series to both ends of a flip-flop composed of a NAND 432-2 and an inverter 433-2. -2 and a NOR circuit 431-2. The gate of the transistor 438-2 is connected to the terminal 5a-2 at the preceding stage, and the gate of the transistor 439-2 is connected to the terminal 5a-5 at the succeeding stage so as to receive the signals at the preceding and succeeding stages. On the other hand, set signals φSE and φSO for counting up and reset signals φRE and φRO for counting down are connected to the other transistor connected in series every other circuit. As shown in the figure, in the delay control circuit 430-2 for the middle one bit, the transistor 435-2 is connected to φSO and the transistor 437-2 is connected to φRO, and the circuits on both sides of the delay control circuit 430-2 are each φSE. And φRE. The NOR circuit 431-2 is configured to receive the left 5a-1 and 5a-4 signals of this circuit. Note that φR is a signal for resetting the delay control circuit, and temporarily becomes “L” level after power-on, and thereafter is fixed to “H”.
[0038]
FIG. 12 is a diagram illustrating the operation of the delay control circuit of FIG.
First, φR temporarily becomes “L”, and the terminals 5a-1, 5a-3, 5a-5 are reset to “H”, and 5a-2, 5a-4, 5a-6 are reset to “L”. . When counting up, the count up signals φSE and φSO repeat “H” and “L” alternately. When φSE changes from “L” to “H”, 5a-1 is grounded and changes to “L”, and 5a-2 changes to “H”. In response to the change of 5a-2 to “H”, φE-1 changes from “H” to “L”. Since this state is latched by the flip-flop, the output φE-1 remains “L” even when φSE returns to “L”. Then, in response to the change of 5a-1 to “L”, the output φE-2 changes from “L” to “H”. Since 5a-2 changes to "H", the transistor 434-2 is turned on, and when φSO is changed from "L" to "H", 5a-3 is grounded to "L" and 5a-4 is " Change to H ". In response to the change of 5a-4 to "H", φE-2 changes from "H" to "L". Since this state is latched by the flip-flop, the output φE-2 remains “L” even if φSO returns to “L”. Then, in response to the change of 5a-3 to “L”, the output φE-3 changes from “L” to “H”. In the figure, φSE and φSO are only output one pulse at a time, but the delay control circuit is connected in multiple stages, and if φSE and φSO alternately repeat “H” and “L”, the output φE The position of the stage where becomes “H” is sequentially shifted to the right. Therefore, if it is necessary to increase the delay amount based on the comparison result of the phase comparison circuit 42, the pulses of φSE and φSO may be input alternately.
[0039]
If the count-up signals φSE and φSO and the count-down signals φRE and φRO are not output, that is, the “L” state is maintained, the position of the stage where the output φE becomes “H” is fixed. Accordingly, when it is necessary to maintain the delay amount based on the comparison result of the phase comparison circuit 42, the pulses of φSE, φSO, φRE, and φRO are not input.
[0040]
When counting down, if the φRE and φRO pulses are alternately input, the position of the stage where the output φE becomes “H” is sequentially shifted to the left as opposed to counting up.
As described above, in the delay control circuit shown in FIG. 11, by inputting a pulse, the position of the stage where the output φE becomes “H” can be moved one by one, and these outputs φE Thus, if the delay circuit shown in FIG. 10C is controlled, the delay amount can be controlled to increase or decrease by one unit.
[0041]
Here, the delay circuit and the delay control circuit will be described in more detail. In the first embodiment, a circuit as shown in (3) of FIG. 10 is used as the delay circuit, and control is performed by a delay control circuit as shown in FIG. In order to realize a circuit in which the delay amount can be changed step by step by a unit amount, it has a plurality of signal paths connected in series, and a signal is selectively output from a part of the plurality of signal paths. In general, a delay line whose delay amount can be selected is used. In such a delay line, it is necessary to avoid a state in which no signal path is selected even in a transient state in which a signal is output from an adjacent signal path in order to change the delay amount. Therefore, a delay control circuit that controls such a delay line needs to always output a signal for selecting one of the signal paths even in a transient state. In the delay control circuit of FIG. 11, each stage outputs two complementary signals. That is, the output of the NAND gate and the output of the inverter are complementary signals. Then, up to a certain stage, a complementary signal in one state is output, the subsequent stages output inverted complementary signals, and the stage that outputs the inverted complementary signal first shifts. In other words, the delay control circuit in FIG. 11 performs the same operation as the shift register. In the circuit of FIG. 11, the NOR gate calculates a negative logical sum of two different stages of complementary signals among the complementary signals of such a shift register for each stage, and outputs the result as (3) in FIG. Are connected to the selection signal line of each stage. In the MOS transistor, the falling speed from the logic value “H” to the logic value “L” is generally faster than the rising speed from the logic value “L” to the logic value “H”. In the circuit of FIG. 11, the output of the NOR gate whose logic value is both “L” indicates the selection position of the delay line, and one of the inputs of this NOR gate changes to the logic value of “H”. Slowly, the “H” input of the NOR gate that indicates the next selected position of the delay line changes to “L” at a faster speed. Therefore, before the output of the NOR gate that has instructed the selection position stops the instruction of the selection position, the output of the NOR gate that indicates the selection position next indicates the selection position. A state where the NOR gate does not indicate the selection position can also be avoided.
[0042]
FIG. 13 is a diagram showing an output change when the position of the NOR gate indicating the selection position is changed in order in the delay control circuit of FIG. As illustrated, the next selection signal rises before the previous selection signal falls. Therefore, there is no problem that no path of the delay line is selected.
For example, in the circuit of FIG. 11, a delay is provided such that an AND gate having the nodes 5a-2 and 5a-3, 5a-4 and 5a-5 as inputs is provided, and the outputs are φE-1 and φE-2. Although a control circuit is also conceivable, such a circuit has a problem that the outputs of all the AND gates become “L” in a transient state.
[0043]
FIG. 14 is a diagram illustrating an example in which an AND gate (a combination of a NAND gate and an inverter) is used instead of the NOR gate in the circuit of FIG. In this circuit, the input of the AND gate is a complementary signal different in every other stage. With such a configuration, the outputs of two adjacent AND gates are simultaneously “H”, that is, a state in which the selected position is designated. Since the two AND gates indicating the selected position change one by one, one AND gate always remains “H”, and a state where neither of the AND gates indicates the selected position is avoided. When the outputs of the two AND gates are “H”, in the delay line of (3) in FIG. 10, since the two paths are activated simultaneously, the signal changes slightly in shape. If the stage delay is small, it can be ignored.
[0044]
The phase comparison circuit 42 includes two circuit parts, a phase comparison unit and an amplification circuit unit. 15 is a diagram showing a circuit configuration of the phase comparison unit, FIG. 16 is a time chart showing an operation of the phase comparison unit, FIG. 17 is a diagram showing a circuit configuration of the amplification circuit unit, and FIG. 18 is an amplification circuit. It is a time chart which shows operation | movement of a part.
In FIG. 15, φout and φext are an output signal and an external clock to be compared by this phase comparison circuit 42, the phase of φout is determined with reference to φext, and φa to φe are output signals connected to the amplifier circuit. Yes. As shown in FIG. 15, the phase comparison unit includes flip-flop circuits 421 and 422 configured by two NAND circuits, latch circuits 425 and 426 that latch the state, and a circuit 424 that generates an activation signal for the latch circuit. , And a delay circuit 423 for one delay for obtaining a phase allowable value of the external clock φext.
[0045]
In FIG. 16, (1) shows a case where the phase of the comparison target signal φout is ahead of the comparison reference signal φext and φout changes from “L” to “H” before φext. When both φout and φext are “L”, the terminals 6a-2, 6a-3, 6a-4, and 6a-5 of the flip-flop circuits 421 and 422 are both “H”. When φout changes from “L” to “H”, both the terminals 6a-2 and 6a-4 change from “H” to “L”. After that, φext is changed from “L” to “H” by one delay, and the terminal 6a-1 is changed from “L” to “H”. However, the potentials at both ends of the flip-flop are already determined. Will not change. Eventually, 6a-2 maintains “L”, 6a-3 maintains “H”, 6a-4 maintains “L”, and 6a-5 maintains “H”. On the other hand, as φext changes from “L” to “H”, φa of the circuit 424 changes from “L” to “H”, and 6a-6 has a pulse that temporarily becomes “H” level. Is applied. Since 6a-6 is input to the NAND circuits of the latch circuits 425 and 426, the NAND circuit is temporarily activated, and the potential states at both ends of the flip-flop circuits 421 and 422 are taken into the latch circuits 425 and 426. It will be. Finally, φb becomes “H”, φc becomes “L”, φd becomes “H”, and φe becomes “L”.
[0046]
Next, (2) shows a case where the phase of the comparison target signal φout and the comparison reference signal φext are substantially the same, and φout changes from “L” to “H” almost simultaneously with φext. This is when φout changes from “L” to “H” within the time difference between the rising time of φout and the rising time of 6a-1. In this case, first, φext changes from “L” to “H” to change the terminal 6 a-3 of the flip-flop 421 from “L” to “H”, but in the flip-flop 422, 6 a-1 is “L”. On the contrary, 6a-4 changes from “H” to “L”. Thereafter, 6a-1 changes from "H" to "L", but since the state of the flip-flop 422 has already been determined, no change occurs. Thereafter, 6a-6 temporarily becomes “H”, and this state is stored in the latch circuit. Eventually, φb becomes “L”, φc becomes “H”, φd becomes “H”, and φe becomes “L”.
[0047]
Further, (3) shows a case where the phase of the comparison target signal φout is delayed from that of the comparison reference signal φext, and φout changes from “L” to “H” after φext. In this case, changes occur in the two flip-flop circuits 421 and 422 due to φext, and 6a-3 and 6a-5 change from “H” to “L”. Finally, φb becomes “L”, φc becomes “H”, φd becomes “L”, and φe becomes “H”.
[0048]
In this way, it is possible to detect whether the rising time of φout has become “H” before that, is almost the same time, or has become “H” with a delay, based on the rising time of φext. These detection results are latched as values of φb, φc, φd, and φe, and based on these values, it is determined whether to count up or count down the delay control circuit.
[0049]
FIG. 17 is a diagram showing a circuit configuration of the amplifier circuit section of the phase comparison circuit 42.
The amplifying circuit unit includes two parts, a JK flip-flop 427 and an amplifying unit 428 including a NAND and an inverter. The signal φa is input to the JK flip-flop 427 from the phase comparison unit in FIG. 15, and the potentials of 7a-9 and 7a-11 are alternately changed depending on whether φa is “L” or “H”. It is a mechanism that repeats “L” and “H”. The amplifying unit 428 receives and amplifies the output signal of the JK flip-flop 427 and the signal from φb to φd.
[0050]
First, the operation of the JK flip-flop 427 will be described with reference to the timing chart of FIG. When φa changes from “H” to “L” at time T1, the terminals 7a-17a-10 change from “L” to “H”. On the other hand, the state changes in 7a-5, 7a-6, and 7a-7 according to the change in 7a-1, but since φa is “L”, no change occurs in 7a-8. Eventually, the output 7a-9 does not change, and only 7a-11 changes from "L" to "H". Next, when φa changes from “L” to “H” at time T2, the terminal 7a-8 changes from “H” to “L” and 7a-10 changes to 7a− contrary to the movement at time T1. Since 7 does not change, the output 7a-9 does not change, the output 7a-9 changes from "L" to "H", and 7a-11 does not change. In this way, the JK flip-flop circuit 427 moves the outputs 7a-9 and 7a-11 alternately to repeat "H" and "L" according to the movement of φa.
[0051]
Next, the operation of the amplifying unit 428 will be described with reference to FIGS. FIG. 19 shows a case where the comparison target signal φout first changes from “L” to “H” with respect to the rising edge of the comparison reference signal φext. In this case, the input signals from the phase comparison unit are φb “H”, φc “L”, φd “H”, and φe “L”. Eventually, 7a-12 is fixed to “H”, 7a-13 is fixed to “L”, and φSO and φSE change according to the state of the JK flip-flop, but φRO and φRE have 7a-13 set to “L”. Therefore, it does not change.
[0052]
FIG. 20 shows a case where the comparison target signal φout changes from “L” to “H” almost simultaneously with the comparison reference signal φext. In this case, the input signals from the phase comparison unit are φb “L”, φc “H”, φd “H”, and φe “L”. Eventually, 7a-12 and 7a-13 are fixed to “L”, and φSO and φSE are not affected by the output of the JK flip-flop, and φSO, φSE, φRO, and φRE are fixed to “L”. Will remain.
[0053]
FIG. 21 illustrates a case where the comparison target signal φout changes from “L” to “H” with a delay from the rising edge of the comparison reference signal φext. In this case, the input signals from the phase comparison unit are φb “L”, φc “H”, φd “L”, and φe “H”. Eventually, 7a-12 is fixed to “L”, 7a-13 is fixed to “H”, and φRO and φRE change depending on the state of the JK flip-flop, but φSO and φSE are 7L-13 is “L”. Therefore, it does not change.
[0054]
FIG. 22 is a diagram illustrating a circuit configuration of the output circuit 14.
In FIG. 22, Data1 and Data2 are signals corresponding to the storage data read from the cell array 115 and output via the sense amplifier 117, the data bus amplifier 119, and the data bus control circuit 120, and Data1 and Data2 are When the output data is “H”, both are “L”, and when the output data is “L”, both are “H”. Note that it is possible to take a high impedance state in which the output data is neither “H” nor “L”. In this case, in the data bus control circuit 120, Data1 becomes “H” and Data2 becomes “L”. Is converted as follows. φoe is an output signal of the delay circuit 40, and the output timing from this output circuit is controlled in accordance with φoe. When φoe becomes “H”, it operates so as to output information of Data 1 and Data 2 to the data output terminal 14. Assuming that “H” is output to the data output terminal 14, φoe changes from “L” to “H”, 8a-1 becomes “L”, 8a-2 becomes “H”, The transfer gate is turned on, and Data1 and Data2 are transmitted to 8a-3 and 8a-6. Eventually, 8a-5 becomes "L" and 8a-8 becomes "H", the output P-channel transistor is turned on, the N-channel transistor is turned off, and "H" output is output to the data output terminal 14. Will appear. When φoe becomes “L”, the transfer gate is turned off, and the output state until then is maintained.
[0055]
FIG. 23 is a diagram showing a circuit configuration of the dummy output circuit 37, and also shows a capacitive element 38 provided as a dummy output load. FIG. 24 is a diagram showing the operation of the dummy output circuit 37 of FIG. 23, and shows the relationship between the internal clock signal and the dummy output signal of 8a-9. 24A shows a case where the 1 / N frequency divider 135 is not provided, and FIG. 24B shows a case where the frequency division ratio is 4. FIG.
[0056]
As apparent from the comparison with the output circuit 14 of FIG. 22, the dummy output circuit 37 has a circuit configuration similar to that of the output circuit 14, but unlike the output circuit 14, the dummy output circuit does not need to output data. Both signals input to the transfer gate are fixed to “L”. Thus, when outputting data, the dummy output 8a-9 is always "H". Further, Int-CLK is an internal clock, and in addition to opening / closing the transfer gate for controlling the output timing from the dummy output circuit, a feedback inverter is input to one terminal as a NAND circuit. As shown in (1) of FIG. 24, when Int-CLK becomes “H”, 8a-9 becomes “H” by the same operation as the output circuit 14. On the other hand, when Int-CLK returns to "L", the transfer gate is closed, and at the same time, both 8a-3 and 8a-6 become "H", and the dummy output 8a-9 is returned to "L".
[0057]
FIG. 24 (1) shows a waveform when the 1 / N frequency divider 135 is not provided, and Int-CLK is a signal having the same cycle as the external clock signal CLK. FIG. 24 (1) shows a case where the load capacity 38 of the dummy output load is very small. In practice, the capacity of the wiring to which the output circuit of the SDRAM is connected or an element that needs to be driven is shown. It is necessary to provide an appropriate load, and the rise and fall times of 8a-9 become very slow, and the operation of this dummy output circuit is limited by the rise and fall rates of 8a-9. Therefore, if the cycle of the external clock signal CLK is shortened, this dummy output circuit may not operate.
[0058]
Therefore, in this embodiment, as shown in FIG. 9, a 1 / N frequency divider 135 is provided. The 1 / N frequency divider 135 divides the output of the latch circuit 133 to generate Int-CLK shown in (2) of FIG. 24 for the external clock signal. This Int-CLK is a signal that becomes “H” for one cycle with respect to four pulses of the external clock signal. By using such Int-CLK for the dummy output circuit, it is possible to avoid the problem that the operable frequency of the dummy output circuit is limited by the rising and falling speeds.
[0059]
When the 1 / N frequency divider 135 is provided, the dummy output 8a-9 is as shown in (2) of FIG. 24. Therefore, the phase comparison between the dummy output and the external clock signal in the phase comparison circuit 42 is performed using the external clock signal. Therefore, the power consumption is reduced by that amount.
The above is the description of each part of the SDRAM of the first embodiment. In the SDRAM of the first embodiment, the delay amounts in the delay circuits 41a and 41b are selected by one stage so that a predetermined phase relationship is obtained based on the phase comparison result after first resetting to select the initial position. This is done by shifting the selection position one by one. Therefore, a certain amount of time is required until the optimum delay amount is selected after the delay amount is reset when the power is turned on. Therefore, when using the SDRAM of the first embodiment, it is necessary to provide a predetermined initialization period after power-on and to apply a predetermined number or more of external clock signals during that period.
[0060]
In the SDRAM of the first embodiment, the internal processing system is divided into a plurality of pipes that are continuously processed, and operate in parallel. In the above description, only the output has been described, but the input is similarly piped. As a result, data input / output can be performed in synchronization with a high-speed external clock signal, and the transfer speed is greatly increased.
[0061]
As described above, in the SDRAM of the first embodiment, since the data output timing is controlled to be a predetermined phase of the external clock signal, even if there is a temperature change during use or a power supply voltage change, Data is always performed in synchronization with a predetermined phase of the external clock signal. In addition, dummy circuits equivalent to the input circuit and output circuit are provided and controlled so as to have a predetermined phase including changes in the delay amount thereof, so that the phase relationship can be controlled very accurately. is there. As a result, the transfer speed can be further increased.
[0062]
In current semiconductor devices, output signal standards are determined in order to ensure signal compatibility with other semiconductor elements. In a semiconductor device used in combination with SDRAM or SDRAM, two standards of “Low Voltage Transistor Transistor Logic (LVTTL)” and “Series Stub Termination Logic (SSTL)” are generally used. There is an output circuit that can output any one of the two standards, and the output circuit can be set to one of the two standards by applying a selection signal from the outside. If the output circuit can be switched so that the output can be performed with different standards, the characteristics of the output circuit change due to the switching. As described above, it is important to provide a dummy output circuit equivalent to the output circuit and compare the phase with the signal that passed through it because the change in the delay amount in the output circuit is large. When the value changes, it is necessary to switch the characteristics of the dummy output circuit accordingly. The second to fourth embodiments are SDRAM embodiments in which the characteristics of the output circuit can be changed by switching.
[0063]
FIG. 25 is a diagram showing a circuit configuration of the dummy output circuit of the SDRAM of the second embodiment. The SDRAM of the second embodiment has the same configuration as the SDRAM of the first embodiment except for the dummy output circuit.
As apparent from the comparison with FIG. 23, the difference of the dummy output circuit of the SDRAM of the second embodiment from that of the first embodiment is that a driver circuit composed of an N-channel transistor and a P-channel transistor has a reference number. Two driver circuits are provided for LVTTL indicated by 371 and for SSTL indicated by 372, and either of the driver circuits is selected for the NAND circuit and the NOR circuit connected to the gates of the N channel transistor and the P channel transistor, respectively. That is, the selection signal cttZ is instructed. The sizes of the P-channel transistor and the N-channel transistor that constitute the CVTTL driver circuit 371 are different from the sizes of the P-channel transistor and the N-channel transistor that constitute the SSTL driver circuit 372. The size of the ton radiator is appropriately defined according to the output mode. The selection signal cttZ is “H” when designating the SSTL standard, and is “L” when designating the LVTTL standard. The voltage applied to the reference power supply terminal from the outside is a predetermined value Vref. It is generated by determining whether this is the case. In the circuit of FIG. 23, when the selection signal cttZ is “L”, the signals applied to the gates of the N-channel transistor and the P-channel transistor of the LVTTL driver circuit 371 vary depending on 8a-4 and 8a-7, and are dummy signals. However, the “L” and “H” signals are applied to the gates of the N-channel transistor and the P-channel transistor of the SSTL driver circuit 371, respectively, and the N-channel transistor and the P-channel transistor of the SSTL driver circuit 371 are output. Are both turned off, so-called high impedance state. On the other hand, when the selection signal cttZ is “L”, the LVTTL driver circuit 371 is in a high impedance state, and the SSTL driver circuit 371 outputs a dummy signal.
[0064]
In this manner, the characteristics of the dummy output circuit are switched in the SDRAM of the second embodiment.
FIG. 26 is a diagram showing a circuit configuration of the dummy output circuit of the SDRAM of the third embodiment. The SDRAM of the third embodiment has the same configuration as that of the SDRAM of the first embodiment except for the dummy output circuit.
[0065]
The SSTL standard and the LVTTL standard differ in the current that flows to the output transistor of the driver circuit, and the SSTL standard requires a larger current to flow. Since the current flowing through the output transistor varies depending on the size of the transistor, the SSTL standard transistor needs to be larger. In general, the transistor of the driver circuit has a large size. When two driver circuits for SSTL and LVTTL are provided as shown in FIG. 25, a large area is required. Therefore, in the SDRAM dummy output circuit of the third embodiment, the LVTTL driver circuit 373 and the driver circuit 374 that allows the SSTL standard current to flow by matching with the LVTTL driver circuit 373 are provided, and the driver when the LVTTL standard is instructed The circuit 374 is set in a high impedance state, and when the SSTL standard is instructed, both the LVTTL driver circuit 373 and the driver circuit 374 are set in an operating state so that an SSTL standard current can flow.
[0066]
The SSTL standard and the LVTTL standard also define the output load. Therefore, the SDRAM of the fourth embodiment can switch the dummy output load.
FIG. 27 is a diagram showing a circuit configuration of the dummy output circuit of the SDRAM of the fourth embodiment. The SDRAM of the fourth embodiment has the same configuration as the SDRAM of the third embodiment except for the dummy output load.
[0067]
As shown in FIG. 27, in the dummy output circuit of the SDRAM of the fourth embodiment, two loads of an SSTL load 377 and an LVTTL load 378 are provided as dummy output loads, and only one of them is selected by the selection signal cttZ. Can be selectively connected to the dummy output terminals 8a-24. A 30 pF capacitive element is used as the SSTL load 377 and a 50 pF capacitive element is used as the LVTTL load. Further, when the SSTL load 377 is selected, a termination resistor 379 having one end connected to the power supply VccQ is connected to the dummy output terminal 8a-24.
In the first to fourth embodiments, the dummy output circuit outputs only rising data that changes to "L" or "H", and detects the phase of the rising edge with respect to the external clock signal. However, the change in the delay amount in the output circuit differs between the rising data where the output signal changes from “L” to “H” and the falling data where the output signal changes from “H” to “L”. For this reason, in the configurations of the first to fourth embodiments, there is a difference in phase with respect to the external clock signal between rising data and falling data. In general, as a driver circuit for an output circuit, an N-channel transistor and a P-channel transistor are connected in series between a power supply terminal and the ground as shown in FIGS. The configuration to turn on is used. In such a driver circuit, a difference is likely to occur particularly when the driving capabilities of the N-channel transistor and the P-channel transistor are unbalanced due to a difference in process conditions between the N-channel transistor and the P-channel transistor. The fifth embodiment is an embodiment that solves such a problem.
[0068]
FIG. 28 is a diagram showing the configuration of the output timing control circuit of the SDRAM of the fifth embodiment.
As apparent from comparison between FIG. 9 and FIG. 28, the fifth embodiment of the SDRAM differs from the first embodiment of the SDRAM in that the delay circuit can adjust the phase of the rising data and the falling data independently. Each of the dummy delay circuits has two delay circuits. Hereinafter, differences from the first embodiment will be described.
[0069]
The first delay circuit 41a-H is a delay circuit for adjusting the output timing of rising data, and the second delay circuit 41a-L is a delay circuit for adjusting the output timing of falling data. CLK is input from the output of the CLK control circuit 134. The output of the first delay circuit 41a-H is input to the output circuit 14 and used as a timing signal when outputting “H” data. The output of the second delay circuit 41a-L is input to the output circuit 14 and used as a timing signal when outputting “L” data. Similarly, the first dummy delay circuit 41b-H is a dummy delay circuit for adjusting the output timing of rising dummy data, and the second delay circuit 41b-L is for adjusting the output timing of falling dummy data. Int-CLK is input from the output of the 1 / N frequency divider 135. The output of the first dummy delay circuit 41b-H is input to the dummy output circuit 37 via the dummy signal wiring 36-H and used as a timing signal when outputting "H" dummy data. The output of the second dummy delay circuit 41b-L is input to the dummy output circuit 37 via the dummy signal wiring 36-L and is used as a timing signal when outputting “L” dummy data. Each delay circuit is made in the same way.
[0070]
The delay control circuit is composed of two circuits 43-H and 43-L, each having the configuration shown in FIG. The delay amount of the first delay circuit 41a-H and the first dummy delay circuit 41b-H is selected by the output of the delay control circuit 43-H, and the second delay circuit is selected by the output of the delay control circuit 43-L. The delay amount of 41a-L and the second dummy delay circuit 41b-L is selected.
[0071]
FIG. 29 is a diagram showing the configuration of the phase comparison circuit in the fifth embodiment. As apparent from comparison with FIG. 15 and FIG. 17, the difference from the first embodiment is that the signal φddq is always set to “L” and “H” by the signal data before the comparison part of the phase comparison circuit. A switch circuit 412 for “H” is provided, and two “H” output amplifying units 414 and “L” output amplifying units 415 are provided.
[0072]
In the switch circuit 412, for example, when data is “H” and “H” is output, φddq also changes from “L” to “H”. Since data is “H”, the transfer gate 416 is turned on and φddq is input to the phase comparator 413 as the signal φout. Conversely, when data is “L”, the transfer gate 417 is turned on, so that a signal obtained by inverting φddq is input to the phase comparator 413 as the signal φout. Thus, the input φout of the phase comparator 413 is always input as a signal that changes from “L” to “H”. Note that the same circuit as shown in FIG. 15 is used as the phase comparison unit 413.
[0073]
The two amplifying units 414 and 415 have the same configuration as the circuit configuration shown in FIG. 17, respectively, except that a NAND gate to which inputs φb to φe are input can be controlled by a signal data using a three-input gate. different. When the data is “H”, the “H” output amplifying unit 414 is activated and operates. When the data is “L”, the “L” output amplifying unit 415 is activated and operates. The internal operation is the same as the circuit of FIG.
[0074]
FIG. 30 is a diagram showing the configuration of the dummy output circuit 37 of the fifth embodiment.
The dummy output circuit 37 receives two activation signals φdoeH and φdoeL, which are timing signals output from the first and second dummy delay circuits 41b-H and 41b-L. φdoeH is an activation signal used when outputting “H”, and φdoeL is an activation signal used when outputting “L”. Which activation signal is used is selected by the signals data and / data.
[0075]
Now, assuming that data is “H” and / data is “L”, φdoeH becomes valid, and a switching signal for terminals 10-1 and 10-2 is output so that the upper transfer gate in the figure operates. On the other hand, when data is “L” and / data is “H”, φdoeL becomes valid, and a switching signal for terminals 10-10 and 10-11 is output so that the lower transfer gate operates. Once the data is output to the dummy output circuit, it is latched and held in the latch circuit, so that the output is maintained until the next activation signal is input even when the activation signal becomes “L”.
[0076]
The output circuit 14 has the same configuration as that of FIG. 26 except that the timing signals output from the first and second delay circuits 41a-H and 41a-L are input instead of the activation signals φdoeH and φdoeL. It is.
FIG. 31 is a waveform diagram showing the operation of each part in the fifth embodiment. The upper side shows the case of “H” output, and the lower side shows the case of “L” output.
[0077]
In the case of “H” output, the external clock signal CLK changes from “L” to “H”, and the signal is amplified by the input circuit 13. φ1 / N is a signal that has passed through the frequency divider 135 and is input to the dummy delay circuits 41b-H and 41b-L. φdoeH is a signal after passing through the dummy delay circuit 41b-H and becomes an activation signal input to the dummy output circuit 37. By this activation signal, the dummy output circuit 37 operates to output the dummy output 10-9. This signal is input to the dummy input circuit 34 and becomes the input signal φout of the phase comparison circuit 42. Eventually, the phase comparison circuit compares the rising edge of (a) surrounded by ◯ with the rising edge of (b) surrounded by ◯ which is the input signal φout of the phase comparison circuit.
[0078]
In the case of “L” output, the description up to φ1 / N is the same as described above, and φdoeL is a signal that has passed through a dummy delay circuit 41b-L different from the above, and this signal is sent to the dummy output circuit 37 as an activation signal. In response to this, the dummy output circuit 37 outputs “L”. This signal is input to the dummy input circuit 34 and becomes φddq. This is inverted by the switch circuit 412 of FIG. 29 and input to the phase comparison circuit 42 as the signal φout. Eventually, the phase comparison circuit compares the rising edge of (a) surrounded by ◯ with the rising edge of (c) surrounded by ◯ which is the input signal φout of the phase comparison circuit.
[0079]
As described above, in the fifth embodiment, the delay amount can be controlled separately for the “H” output and the “L” output. Therefore, the clock access time at the “H” output and the clock access at the “L” output. It is possible to match the time. Thereby, the timing margin in the system using this SDRAM is expanded, and the system can be operated at high speed.
[0080]
In the first to fifth embodiments, a delay circuit for outputting output data, a dummy delay circuit similar to the output circuit, a dummy output circuit are provided, and a dummy load similar to the load connected to the output terminal is provided. A dummy output signal similar to the actual output signal is generated, and the phase of the external clock signal is compared with the dummy output signal. As a result, the phase relationship of the output signal with respect to the external clock signal is maintained more accurately than in the conventional example. However, in a system in which such a semiconductor device is used, the routing of wiring actually connected to the output terminal is not constant, and it is rare that the load (capacitance, output impedance) is always constant. Therefore, it is extremely rare for the load of the actual output circuit and the dummy load to coincide with each other, and a minute time error occurs between the actual output waveform and the dummy output waveform.
[0081]
FIG. 32 is a diagram for explaining the generation of such an error.
The delay circuit operates after the operation time completion time T2 of the input circuit with reference to the rising time T1 of the external clock signal CLK, delays the output timing signal, and outputs data from the output circuit. Here, the time required for this is T4. Here, the clock access time is indicated by T6. Even if a similar dummy delay circuit is manufactured, there is a slight error, and even if the same position is selected, a difference occurs in the delay amount. Further, since there is a difference in delay amount due to manufacturing errors of the dummy output circuit and the dummy load, the delay amount of the dummy circuit is T5. The error is indicated by T7 in the figure.
[0082]
Such errors are slight, and in the past, such a slight time lag was not a problem, but in recent high-speed systems, this slight error has been affecting the speed limit of operation. It has become a problem.
The sixth embodiment is an SDRAM in which such a slight error is reduced. In the first to fifth embodiments, the same delay amount is selected for the delay circuit and the dummy delay circuit according to the selection signal from the common delay control circuit. On the other hand, in the sixth embodiment, a phase comparison circuit and a delay control circuit are provided separately for the delay circuit and the dummy delay circuit, respectively. A considerable number of dummy cycles are performed in the initialization period immediately after the power is turned on. In this dummy cycle, dummy data is also output from the output circuit, and the delay circuit is controlled so that the phase of the dummy data and the external clock signal is synchronized. . Independently of this, the dummy delay circuit is controlled so that the phase of the dummy data output from the dummy output circuit and the external clock signal is synchronized. In this state, the delay amount of the delay circuit is controlled to a value in which the phase of the output data from the output circuit including the influence of the actually connected load and the phase of the external clock signal are synchronized. Similarly, the dummy delay circuit is also controlled to a value in which the phases of the dummy output data and the external clock signal are synchronized. In this state, if dummy output data is input to the phase comparison circuit on the regular delay circuit side, control is performed so that the phase of the output data and the external clock signal are synchronized even if there is a subsequent fluctuation. become. Such a configuration can also be applied to the SDRAM of the first embodiment shown in FIG. 9. However, in the sixth embodiment described below, such a configuration is applied to the SDRAM of the fifth embodiment of FIG. This is an applied example.
[0083]
FIG. 33 is a block diagram of the SDRAM of the sixth embodiment.
As shown in the figure, in the sixth embodiment, a DLL circuit 44 that generates a timing signal that defines the output timing of the output circuit 14 that outputs normal data, and an output of a dummy output circuit 37 that outputs a dummy output. A dummy DLL circuit 45 for generating a dummy timing signal for defining timing is provided. The DLL circuit 44 includes an “H” delay circuit 441a, an “L” delay circuit 441b, a phase comparison circuit 442, and a delay control circuit 443a. The dummy DLL circuit 45 includes an “H” dummy delay circuit 451a, an “L” dummy delay circuit 451b, a phase comparison circuit 452, and a delay control circuit 453a. Dummy input circuits 34 c and 34 d are provided corresponding to the DLL circuit 44 and the dummy DLL circuit 45. A signal corresponding to the external clock signal from the input circuit 13 is input to each delay circuit. In addition, a signal from the dummy input circuit corresponding to the signal from the input circuit 13 is input to each phase comparison circuit. A power supply voltage VccQ is applied to the output circuit 14 and an output timing signal from the DLL circuit 44 is supplied. The output of the output circuit 14 is connected to the output terminal 12 and supplied to the switching circuit 39. A board wiring 151 and another LSI input circuit receiver 152 are connected to the output terminal 12, and these become actual output loads. Similarly, the power supply voltage VccQ is applied to the dummy output circuit 37 and the dummy output timing signal from the dummy DLL circuit 45 is supplied. The output of the dummy output circuit 37 is supplied to the dummy input circuit 34d through the dummy output load 38 and also supplied to the switching circuit 39. The switching circuit 39 switches the signal supplied to the dummy input circuit 34 c between the output of the output circuit 14 and the output of the dummy output load 38. The dummy circuit and the regular circuit corresponding to the dummy circuit described above are configured to be similar with the same circuit configuration.
[0084]
In addition, a dummy data generation circuit 53 for generating dummy data for forcibly outputting “L” and “H” outputs from the output circuit 14 and the dummy output circuit 37 in a dummy cycle immediately after power-on, A power-on detection circuit 52 that detects power-on and a command decoder circuit 51 are provided.
The operation of the circuit of the sixth embodiment will be described below.
[0085]
When the change edge of the output signal and the dummy output signal is earlier with respect to the rising point of the external clock signal, the phase comparison circuits 442 and 452 conversely increase the delay amount of the delay circuit. If it is later than the rise time of, control is made to reduce the delay amount. Of course, this control is performed independently for both “H” and “L” transition edges.
[0086]
In such a memory system in which SDRAM is used, immediately after the system power is turned on, the memory system starts a clock operation, and confirms and adjusts the operation of various logic and PLL circuits mounted on the system. A dummy cycle is performed and an external clock signal is input. During this dummy cycle, if the operation of shifting the delay amount of each delay circuit is repeated so that the change edge of the output signal and the dummy output signal has a predetermined phase with respect to the external clock signal, the DLL circuit and the dummy DLL The circuit can be adjusted. However, immediately after the power is turned on, no information is written in the memory. Therefore, the output signal and the dummy output signal are constant, and the adjustment operation cannot be performed as it is. For this reason, it is necessary to internally generate data for delay circuit adjustment in the dummy cycle. In this embodiment, a dummy data generation circuit 53 is newly provided for this purpose, and the output waveforms of the power-on detection circuit 52 and the command decoder circuit 51 previously provided in the conventional SDRAM are used forcibly. Generate dummy data and adjust the delay circuit.
[0087]
FIG. 34 is a diagram showing a circuit configuration of the dummy data generating circuit in the sixth embodiment.
The dummy data generation circuit includes two parts, an activation signal generation unit 371 and a flip-flop unit 372. The activation signal generator 371 includes a signal φext obtained by amplifying the external clock signal CLK by an input circuit, φR notifying that the power has been turned on, and a signal φMRS for actually starting the operation after the initialization of the memory is completed. Entered. These operations will be described with reference to the operation waveforms in FIG.
[0088]
At time T1, the Vcc voltage is applied and the Vcc voltage rises. After a while, the power-on detection circuit 52 operates to output φR. When the dummy data generation circuit 53 receives this signal, φSW becomes “H” and / φSW becomes “L”. Next, at time T2, φext serving as a reference signal is input from the outside. By this signal, the flip-flop unit 372 outputs φD and / φD at a period twice that of the external clock signal. These signals are input to the output circuit and the dummy output circuit and used as output data.
[0089]
In the case of the SDRAM, it is necessary to set the operation mode in the mode register in the memory before starting the actual operation. In order to set the operation mode in the mode register, a mode register set instruction is inserted and set. When this command comes in, the command decoder 51 outputs a signal φMRS. If φMRS is output at time T3, in response to this signal, φSW becomes “L”, / φSW becomes “H”, and 10a-2 becomes constant. Thereafter, the dummy data becomes a constant value.
[0090]
FIG. 36 is a diagram showing a circuit configuration of the output circuit 14 of the sixth embodiment, and FIG. 37 is a time chart showing its operation. The dummy output circuit 37 has the same circuit configuration as the output circuit, and only the dimensions are similar and small. Therefore, the operation is exactly the same.
The dummy data generated by the dummy data generation circuit 53 is input to the output circuit 14. The output circuit 14 includes a high impedance control unit 141, a dummy data switch unit 142, and an output amplification unit 143. The dummy data is input to the high impedance control unit 141. / ΦZ is a signal for setting the output to a high impedance state. When the output is set to high impedance, / φZ is set to “L”, but becomes invalid in a dummy cycle period immediately after power-on when φSW is “H”. -1 becomes "L" and 12a-2 becomes "H". On the other hand, since the dummy data switch unit 142 has / φSW at “L”, the dummy data φD is in a passing state. On the contrary, the signal DB of the actual data bus is not swept out to 5a-11 and 5a-12 because φSW is “H”.
[0091]
In this state, since the dummy data φD is valid, both 5a-11 and 5a-12 become “H” when φD is “H”. When the output circuit activation signal φoe (a signal that has passed through the DLL circuit 44) synchronized with the external clock signal φext becomes “H”, “H” is output as an output signal. Conversely, when φD is “L”, both 5a-11 and 5a-12 become “L”, and when RI and φoe are “H”, “L” is output as an output signal.
[0092]
As described above, by using the dummy cycle immediately after the power is turned on, the DLL circuit 44 determines when the external clock signal rises and when the output signal becomes “H” and “L”, and the dummy output signal becomes “H”. Also, the dummy DLL circuit 45 coincides with the time point when it becomes “L”. Of course, since the waveform of the output signal and the waveform of the dummy output are slightly different, the set values of the delay circuits of the DLL circuit 44 and the dummy DLL circuit 45 are different, but at this time, the external clock signal, the output signal, The three signals of the dummy output signal are synchronized.
[0093]
After the dummy cycle is completed (after φMRS is output), the memory operation is actually started, and the data stored in the memory is output to the output terminal 12. These data are completely random, and it is not known what data is output. Further, in the SDRAM, since the data input terminal and the data output terminal 12 are I / O common terminals, input data may be input. That is, the series of the DLL circuit 44 cannot be used for adjusting the delay circuits 441a and 441b. Therefore, the switching circuit 39 is switched to switch the comparison target signal of the DLL circuit 44 from the output signal to the dummy output signal.
[0094]
FIG. 38 is a diagram showing a circuit configuration of the switching circuit 39. Two transfer gates in which an N-channel transistor and a P-channel transistor are connected in parallel are provided, and one of them is controlled to pass by a signal φSW.
As a result, when a variation in temperature or the like occurs during the memory operation and the delay amount of the delay circuit of the DLL circuit 44 needs to be adjusted, a dummy output signal is used as a comparison target signal. Since the three waveforms of the external clock signal, the output signal, and the dummy output signal are matched during the dummy cycle immediately after being turned on, the deviation of the waveform of the external clock and the dummy output signal is detected and adjusted based on the detection result. In this case, the output signals also match.
[0095]
In the sixth embodiment, it is possible to synchronize the external clock signal and the output signal in a series of operations, including the difference in board wiring and wiring load actually used. As a result, a sufficient margin can be ensured even in a system that operates at a higher speed, and the operation is stabilized even in a higher-speed system.
In the first to sixth embodiments, a dummy output circuit is provided to output dummy data, and the phase of the output signal and the phase of the external clock signal are compared. However, the output of the output circuit is not provided without providing the dummy output circuit. It is also possible to compare the phase of the signal and the external clock signal. The seventh embodiment is an example in which phase comparison of output signals is performed.
[0096]
FIG. 39 is a diagram showing the configuration of the output timing control circuit of the seventh embodiment. As shown in FIG. 39, the output timing control circuit of the seventh embodiment includes an input circuit 13, an output circuit 14, a delay circuit 501, a delay control circuit 502, a phase comparison circuit 503, and an output of the input circuit 13. A half-phase shift circuit 504 for generating a half-shift clock having a phase difference of 180 degrees from the clock signal CLK1, a first dummy input circuit 505 and a second dummy input circuit 506, and a first, second and third Latch circuits 507, 508, and 509 are included. The input circuit 13 and the output circuit 14 are the same as those of the embodiments described so far. In the seventh embodiment, the phase comparison circuit 503 determines whether the output signal has changed, outputs a hold signal when the output signal does not change, performs phase comparison only when the output signal has changed, and based on the comparison result. Then, a control signal (UP / DOWN) signal is output to instruct the delay control circuit 502 to increase or decrease the delay amount. The 1/2 phase shift circuit 504 and the first, second, and third latch circuits 507, 508, and 509 use signals for determining whether the phase comparison circuit 503 has changed the output signal and comparing the phases. This is a circuit to be generated. As the latch circuit, a normal latch circuit is used, and its configuration is widely known, and therefore, the description thereof is omitted here.
[0097]
FIG. 40 is a diagram illustrating a configuration example of the first delay circuit 501 and the delay control circuit 503. The second delay circuit 502 is also controlled by the same output of the delay control circuit 503, but the illustration is omitted here. As shown in the figure, the delay circuit 501 includes an inverter row 521 in which a plurality of inverters are connected in series, and a plurality of AND gates 522-1 provided so that one of the inputs receives the output of every two stages of the inverter row 521. 52-n and an N-channel transistor 523-1 in which the output of each AND gate is applied to the gate, the source is grounded, and the drain is commonly connected. 523-2,... 523-n, a resistor 524 connected between the signal line to which the drains of the N-channel transistors are connected in common and the high potential side of the power supply, and an input Includes a buffer 525 connected to the signal line and outputting the internal clock CLK2. The delay control circuit 502 includes an up / down counter 526 and a decoder 527. The up / down counter 526 does not count when the hold signal HOLD is “L”, and when the hold signal HOLD is “H”, A count operation is performed in synchronization with the rise of φ1 / 2CLK1, and the count-up is performed when the up / down signal UP / DOWN is “H”, and the count-down is performed when the signal is “L”. The decoder 527 decodes the output of the up / down counter 29, sets one of the outputs to “H”, and sets the other output to “L”. When the up / down counter 526 counts up, the output position to be set to “H” is shifted to the right, and when it is counted down, the output position to be set to “H” is shifted to the left. The output of the decoder 527 is sequentially connected to the other input of each AND gate 522-1, 522-2,... 522-n, and only the AND gate to which “H” is input from the decoder 527 is activated. Is done. Of the outputs from the inverter train, the signal input to the activated AND gate is output as the internal clock CLK2, and the number of stages passing through the inverter train varies depending on which AND gate is activated. Therefore, the delay amount of the internal clock can be selected. Therefore, the adjustment unit of the delay amount control is a delay amount for two inverters. Note that the delay control circuit 503 needs to be considered so that any one of the paths is always selected by the delay circuit 501 as described with reference to FIGS.
[0098]
FIG. 41 is a diagram showing the configuration of the ½ phase shift circuit 504. As shown in FIG. 41, the 1/2 phase shift circuit 504 includes a current mirror circuit 511, a clock input buffer circuit 512, first and second 1 / 2φ delay circuits 513 and 516 having the same configuration, Buffer circuits 514 and 517, a phase comparison circuit 518, a delay control circuit 519, and a buffer circuit 515 for outputting a φ1 / 2 clock signal φ1 / 2CLK1. The current mirror circuit 511 and the clock input buffer circuit 512 are parts constituting the input circuit. The first and second 1 / 2φ delay circuits 513 and 516 are digital delay lines in which the delay amount is selectively changed, and are controlled so as to have the same delay amount. The phase comparison circuit 518 compares the phases of the clock signal output from the buffer circuit 512 and the clock signal output from the buffer circuit 517, and outputs the phase comparison result to the delay control circuit 519. Based on the comparison result of the phase comparison circuit 518, the delay control circuit 519 makes the first and second 1/2 so that the clock signal output from the buffer circuit 512 and the clock signal output from the buffer circuit 517 match. The 2φ delay circuits 513 and 516 are controlled. The phase comparison circuit 518 uses a circuit shown in FIG. 42 described later, and the delay circuits 513 and 516 use the circuit shown in FIG.
[0099]
The clock signal output from the buffer circuit 512 is delayed by the first delay circuit 513 and then input to the second delay circuit 516 via the buffer circuit 374, and is the same as the delay amount of the first delay circuit 513. The signal is delayed by an amount and input to the phase comparison circuit 518 via the buffer circuit 517. The phase comparison circuit 518 compares the phases of the clock signals output from the buffer circuits 512 and 517, and the delay control circuit 519 compares the first and second delay circuits so that the two phases match based on the comparison result. The delay amount of 513 and 516 is changed. When the two phases coincide, the path from the first delay circuit 513 to the second delay circuit 516 via the buffer 514 and the phase comparison circuit 518 from the second delay circuit 516 via the buffer 517 Since the path until the signal is input to the second delay circuit 516 is the same, the phase of the signal input to the second delay circuit 516 is exactly half a cycle different from the phase of the signal input to the first delay circuit 513. Therefore, the phases of the clocks output from the buffer circuits 514 and 517 are also shifted by a half cycle, and the buffer circuit 515 outputs a 1/2 shift clock φ1 / 2 obtained by shifting the clock signal by a half cycle. Thus, by using a 1/2 phase shift circuit as shown in FIG. 40, a 1/2 shift clock φ1 / 2 obtained by accurately shifting the clock signal by 1/2 phase can be obtained.
[0100]
In the seventh embodiment, the circuit as shown in FIG. 41 is used because the ½ shift clock φ1 / 2 obtained by shifting the clock signal accurately by ½ phase is required in other portions. In the embodiment, since an exactly 1/2 phase shifted signal is not required, an inverter may be simply used.
In any case, the latch circuit 507 latches the output of the dummy output circuit 505 in synchronization with the rising edge of CLK1, the latch circuit 508 latches the output of the dummy output circuit 506 in synchronization with the falling edge of CLK1, and the latch circuit 509. Latches the output of the latch circuit 508 in synchronization with the fall of CLK1. Therefore, the latch circuit 509 latches the output of the dummy output circuit 506 one cycle after the falling edge of CLK1 latched by the latch circuit 508. The output of the latch circuit 507 is input to the phase comparison circuit 503 as RG1, the output of the latch circuit 508 as RG2, and the output of the latch circuit 509 as RG0.
[0101]
FIG. 42 is a circuit diagram showing the configuration of the phase determination circuit 503. The operation of the phase determination circuit 503 will be described with reference to FIGS. 43 to 45. FIG.
In a state where there is no phase shift, the output signal is assumed to change at the rising edge of the clock signal CLK1φ1 output from the input circuit 13. The positions indicated by arrows in the figure are the timings at which the latch circuits latch the output signals, and are RG0, RG1, and RG2 in order from the left. State 1 in FIG. 43 is when the output signal remains “H” and does not change. At this time, RG0, RG1, and RG2 are all “H”, the hold signal HOLD becomes “L”, and the phase is shifted. Since it cannot be determined, the count operation is not performed. Similarly, state 2 is when the output signal remains “L” and does not change. At this time, RG0, RG1, and RG2 are all “L”, and similarly, the hold signal HOLD becomes “L” and the count is performed. Do not work.
[0102]
States 3 and 4 shown in FIG. 44 are when the output signal changes from “H” to “L”, and when the change edge of the output signal is delayed with respect to the rising edge of CLK1 as in state 3. , RG0, RG1, and RG2 become “H”, “H”, and “L”, respectively. In this case, the hold signal HOLD becomes “H”, the up / down signal UP / DOWN becomes “L”, and the delay amounts of the delay circuits 501 and 502 are reduced. When the change edge of the output signal is advanced with respect to the rising edge of CLK1 as in state 4, RG0, RG1, and RG2 become “H”, “L”, and “L”, respectively. In this case, HOLD becomes “H”, UP / DOWN becomes “H”, and the delay amounts of the delay circuits 501 and 502 are increased.
[0103]
States 5 and 6 shown in FIG. 45 are cases where the output signal changes from “L” to “H”, and when the change edge of the output signal is delayed with respect to the rising edge of CLK1 as in state 5. , RG0, RG1, and RG2 become “L”, “L”, and “H”, respectively. In this case, HOLD becomes “H”, UP / DOWN becomes “L”, and the delay amounts of the delay circuits 501 and 502 are reduced. When the change edge of the output signal is advanced with respect to the rising edge of CLK1 as in state 6, RG0, RG1, and RG2 become “L”, “H”, and “H”, respectively. In this case, HOLD becomes “H”, UP / DOWN becomes “H”, and the delay amounts of the delay circuits 501 and 502 are increased.
[0104]
Each state described above, the values of RG0, RG1, and RG2 at that time, and necessary operations are shown in the truth table of FIG.
As described above, in the output timing control circuit of the seventh embodiment shown in FIG. 39, the phase comparison between the output signal and the clock signal is performed, and the phase of the output signal is controlled to be synchronized with the clock signal. The output signal is a random signal, and the “high” level or the “low” level may continue. However, the phase comparison circuit 503 of the seventh embodiment determines whether the output signal has changed, and when the output signal has changed. Only when the output signal does not change, the delay control circuit 502 performs control so that the delay amount until then is maintained, and when the output signal does not change, the delay control circuit 502 is based on the comparison result of the phase comparison circuit 503. Thus, the feedback control is performed so that the phases coincide with each other, so that phase comparison is possible even for output signals.
[0105]
FIG. 47 is a block diagram showing the configuration of the output timing control circuit of the eighth embodiment. The output timing control circuit according to the eighth embodiment is similar to the output timing control circuit according to the seventh embodiment when the output signal changes from “L” to “H” and from “H” as described in the fifth embodiment. This is an example in which different timing control is applied when changing to “L”. The seventh embodiment is different from the seventh embodiment in that two delay circuits 501-H and 501-L and two delay control circuits 502-H and 502-L for controlling them independently are provided. Here, further explanation is omitted.
[0106]
Even when the phase of the output signal with respect to the external clock signal is compared, a phase adjustment mode can be provided to perform phase adjustment. To do this, a dummy data output circuit for outputting dummy data that changes in a predetermined cycle shown in FIG. 34 is provided. In the phase adjustment mode, the output circuit outputs dummy data, and the output signal and the external clock signal are output. And phase control are performed, and feedback control is performed so that the phases match. Then, after matching, the mode is switched to the normal mode, where the adjusted delay amount is maintained. In this case, the phase can be adjusted by feedback control as in the first to sixth embodiments.
[0107]
FIG. 48 is a block diagram showing the configuration of the output timing control circuit of the ninth embodiment. The output timing control circuit of the ninth embodiment is an example in which another phase comparison circuit is applied to the basic configuration of the output timing control circuit having the dummy output circuit shown in FIG. As described above, in the case where the dummy output circuit is provided, dummy data that changes in a predetermined cycle generated by the dummy data generation circuit is output, and a phase comparison with this output signal is performed. Since the dummy data changes in a predetermined cycle, the phase determination circuit 532 determines whether or not the output signal changes, and when it does not change, it is not necessary to output a hold signal so as not to change the delay amount of the delay circuit. Therefore, in the circuit of the ninth embodiment, a latch circuit 533 that latches the output signal of the dummy input circuit 505 in synchronization with CLK1, and a latch circuit 534 that latches the output signal of the dummy input circuit 506 in synchronization with φ1 / 2CLK1. And the output of the latch circuit 533 is input to the phase determination circuit 532 as RG1 and the output of the latch circuit 534 is input as RG2. The phase determination circuit 532 determines the phase based on RG1 and RG2.
[0108]
FIG. 49 is a diagram showing a circuit configuration of the phase comparison circuit 532 used in the output timing control circuit of the ninth embodiment. As is apparent from the figure, this phase comparison circuit is composed of a circuit only on the side of calculating the up / down signals UP / DOWN of the phase comparison circuit shown in FIG. As described above, in the ninth embodiment, it is determined whether or not the output signal changes. When the output signal does not change, there is no need to output the hold signal, and therefore the portion for generating the hold signal HOLD is excluded.
[0109]
FIG. 50 is a diagram showing a determination operation of the phase determination circuit 532 of FIG. As shown in (1) of FIG. 50, when the output signal DQ (here, the output of the dummy input circuit) is delayed with respect to the clock signal CLK1, RG1 and RG2 have different values. When DQ is advanced with respect to CLK1, RG1 and RG2 have the same value. Therefore, the phase determination circuit 532 sets the up / down signal UP / DOWN to “L” so that the delay amount of the clock is decreased when RG1 and RG2 are different values, and the delay amount of the clock when RG1 and RG2 are the same value. UP / DOWN is set to “H” so as to increase.
Each state described above, the values of RG1 and RG2 at that time, and necessary operations are shown in the truth table of FIG.
[0110]
Returning to FIG. 48, as the delay circuit 501 and the delay control circuit 531, the same circuit as that of the seventh embodiment shown in FIG. 40 is used. However, as shown in FIG. The hold signal HOLD is not input and no hold function is required.
FIG. 53 is a block diagram showing the configuration of the output timing control circuit of the tenth embodiment. The output timing control circuit of the tenth embodiment has a configuration in which the change period of the output signal from the dummy output circuit is set to 1 / N by using the 1 / N frequency dividing circuit described in the first embodiment. This is applied to the circuit. As shown in the figure, a 1 / N frequency dividing circuit 542, a CLK control circuit 541 that delays the clock signal by the 1 / N frequency dividing circuit 542, and a delay circuit 501b that delays the 1 / N frequency divided clock CLK1 / N. In addition, dummy CLK control circuits 543 and 544 having the same delay amount as the CLK control circuit 541 are provided at the outputs of the dummy input circuits 505 and 506, and the latch circuit 533 is synchronized with CLK1 / N in the dummy CLK control circuit 543. The latch circuit 534 is different from the ninth embodiment in that the dummy CLK control circuit 544 is latched in synchronization with / CLK1 / N obtained by inverting CLK1 / N. The structure of other parts is the same as that of the ninth embodiment.
[0111]
FIG. 54 is a diagram showing the determination operation of the tenth embodiment. As shown in the figure, even when the external clock signal CLK is not a signal with a duty of 50% due to deterioration during transmission or the like, the changing edge of the signal CLK1 / N divided by 1 / N is synchronized with the rising edge of CLK. If the output from the dummy output circuit 37 is performed in synchronization with CLK1 / N, the dummy output signal changes in synchronization with the rising edge of CLK1 / N as shown in the figure. Therefore, the timing at which the latch circuit 533 latches is around the rising edge of CLK1 / N, and the timing at which the latch circuit 534 latches is around the rising edge of CLK1 / N. That is, the timing at which the latch circuit 534 latches is near the midpoint of the change edge of the dummy output signal. When DQ is delayed, RG1 and RG2 have different values, and when DQ is advanced, RG1 and RG2 have the same value.
[0112]
FIG. 55 is a block diagram showing the configuration of the output timing control circuit of the eleventh embodiment. The output timing control circuit of the eleventh embodiment is similar to the output timing control circuit of the tenth embodiment when the output signal changes from “L” to “H” and from “H”, as described in the fifth embodiment. This is an example in which different timing control is applied when changing to “L”. Here, further explanation is omitted.
[0113]
As described above, in the first to eleventh embodiments, the output timing control circuit of the semiconductor device of the present invention has been described. However, how to apply such an output timing control circuit in such a semiconductor device is described. An example will be described.
56 shows the clock input circuit 13, the output timing control circuit 30, the first to mth output circuits 571-1, 571-2,... 571-m, and the clock signal in the semiconductor device of the twelfth embodiment. 6 is a diagram illustrating an arrangement configuration of a distribution circuit 580. FIG.
[0114]
As shown in the figure, a plurality of signals OS-1, OS-2,..., OS-n are output from this semiconductor device, so that output circuits 571-1, 571-2,. -M is provided. The clock distribution circuit 580 arranges the clock signal supplied from the clock input circuit 13 via the output timing control circuit 30 in the semiconductor device via a plurality of buffer circuits (CB1, CB21,..., CBnm) 581 to 583. Are distributed to the output circuits 571-1, 571-2,. It is an equidistant wiring in which the wiring length to the distribution destination is the same as the number of buffer circuits that pass through. Therefore, in FIG. 56, the phases of the clock signals input to the output circuits 571-1, 571-2,. The clock input circuit 13 and the output timing control circuit 30 are arranged in one of the output circuits 571-1, 571-2, ..., 571-m, here, in the vicinity of the first output circuit 571-1. Then, the output timing control circuit 30 performs control so that the phase of the output signal from the first output circuit 571-1 is synchronized with the external clock CLK. As described above, since the clock distribution circuit 580 has equidistant wiring, the phases of the clock signals input to the respective output circuits are all the same, and the phase of the output signal of the first output circuit 571-1 is the same. When synchronized with the external clock CLK, the phases of the output signals from all the output circuits are synchronized with the external clock CLK.
[0115]
In the semiconductor device to which the circuits of the first to twelfth embodiments described above are applied, the accuracy of synchronization of the output signal with respect to the external clock is greatly improved as compared with the conventional example. An embodiment in which a semiconductor device system is configured using a semiconductor device that outputs with high synchronization accuracy to such an external clock will be described.
First, conventional output timing and its problems will be described. FIG. 57 is a diagram for explaining the output timing of a conventional semiconductor device that outputs data in synchronization with an external clock signal. In the conventional example, an operation for outputting data is started in response to the rising edge of the external clock signal CLK (t0). The output actually appears at the output terminal after a certain time. This time varies depending on process variations, power supply variations, temperature, etc., and the output appears at t1 at the shortest and at t2 at the longest. That is, the clock access time is in the range of tOH and tAC from the rising edge of the external clock signal. These tOH and tAC are defined by the specifications of the semiconductor device, and the period between t1 and t2 is a time when data that cannot be actually used is uncertain.
[0116]
On the side receiving such an output, a setup time tIS and a hold time tIH are required, and tIS and tIH are defined with respect to the rising edge of the external clock signal. The start time of the setup time tIS is indicated by t3, and the end time of the hold time tIH is indicated by t5. Therefore, in the figure, the difference between the time t2-t6 and t3-t5 is the system timing margin. This timing margin is necessary to some extent in order to absorb errors due to various factors of the system.
[0117]
In recent years, the frequency of the external clock signal has been increasing, and there has been a problem that this timing margin cannot be secured sufficiently.
FIG. 58 is a diagram showing output timing of the semiconductor device of the present invention. In the conventional example, as shown in FIG. 57, the output operation is started from the rising edge of the external clock signal. On the other hand, in the semiconductor device of the present invention, the output signal is output in synchronization with the falling edge of the external clock signal. Of course, it is assumed that the rising and falling edges of the external clock signal are signals having a phase difference of 180 degrees and a duty ratio of 50%. As already described, in the semiconductor device of the present invention, the output timing of the output signal can be accurately controlled so as to have a predetermined phase with respect to the external clock signal. Therefore, the output signal immediately appears at the output terminal in synchronization with the falling edge of the external clock signal. Therefore, the center of the period in which the output signal is determined coincides with the rising edge of the external clock signal, and the same timing margin can be taken before and after the input. Here, considering the case where the period of the external clock signal becomes narrower and narrower, the advantage of outputting at such timing becomes clear.
[0118]
FIG. 59 shows a memory system according to a thirteenth embodiment constructed using semiconductor memories 610 to 613 capable of accurately controlling the output timing of an output signal so as to have a predetermined phase with respect to an external clock signal. It is a figure which shows the arrangement | positioning of an element, and the mode of signal wiring. FIG. 60 is a diagram showing the phase relationship between the clock signal CLK and data in the memory system of the thirteenth embodiment.
[0119]
In the figure, reference numeral 601 is a controller of this memory system. The semiconductor memories 610 to 613 are arranged as shown, and the data stored in each of the semiconductor memories 610 to 613 is output to the data bus 602 in synchronization with the clock signal CLK applied to the clock signal line 603. Here, if the direction in which the clock signal CLK propagates through the clock signal line 603 is the direction from the right side to the left side as shown in the figure, the time for the CLK to reach each memory is the fastest in the right memory-3. The left side memory becomes slower. However, the time for the data output in synchronization with CLK to reach the controller 601 is shorter for the left side memory. If the propagation speed of the clock signal CLK on the clock signal line 603 and the propagation speed of the data signal on the data bus 602 are the same, as shown in FIG. The controller 601 is reached at the timing of reaching 601. Therefore, the controller 601 may take in data based on CLK.
[0120]
FIG. 61 is a diagram showing element arrangement and signal wiring in the memory system of the fourteenth embodiment.
In the memory system of the fourteenth embodiment, CLK is first input to the controller 601, and the controller 601 generates a write clock signal Write-LK and a read clock signal Read-CLK from this CLK. The clock signal line through which Read-CLK is propagated is once propagated to the position of the right end memory 613 through the signal line 605 and then returned to the controller 601 through the signal line 606. Supply of Read-CLK to each memory is performed from a signal line 606. Thus, the data output from each memory is taken into the controller 601 as in the thirteenth embodiment.
[0121]
In the fourteenth embodiment, Read-CLK propagated through the signal line 606 is input to the controller 601 as Read-Receive. Then, the delay amount of Read-CLK is adjusted so that Read-CLK and Read-Receive match.
FIG. 62 is a diagram showing a clock signal system in the controller 601 in the fourteenth embodiment.
[0122]
As shown in FIG. 42, CLK input from the outside enters the output buffer 621 and is then output as Write-CLK. Write-CLK passes through the current mirror circuit 622 and the driver 623, is amplified, delayed by an amount selected by the delay circuit 624, and then output from the output buffer 625 as Read-CLK. The returned Read-CLK is received as Read-Receive, passes through the current mirror circuit 626 and the driver 627, and is then input to the phase comparison circuit 628. The output of the driver 623 is also input to the phase comparison circuit 628 and the phases are compared. The delay control circuit 629 selects a delay amount of the delay circuit based on the comparison result. In this way, the delay amount of Read-CLK is adjusted so that Read-CLK and Read-Receive coincide.
[0123]
FIG. 63 is a diagram showing element arrangement and signal wiring in the memory system of the fifteenth embodiment.
In the memory system of the fifteenth embodiment, similarly to the thirteenth embodiment, the controller 601 receives the clock signal CLK propagating in the direction in which the output data from the memory propagates as Read-Receive. The controller 601 generates a write clock signal Write-CLK from this Read-Receive. Reading from the memory is performed in synchronization with CLK. The delay amount of the output Write-CLK is adjusted so that the phase of Read-Receive matches that of Read-Receive.
[0124]
FIG. 64 is a diagram showing a clock signal system in the controller 601 in the fifteenth embodiment.
As shown in FIG. 64, the CLK-Receive input from the outside is amplified by passing through the current mirror circuit 631 and the driver 632, delayed by the amount selected by the delay circuit 633, and then written from the output buffer 634. Output as -CLK. This Write-CLK passes through the current mirror circuit 635 and the driver 636 and then is input to the phase comparison circuit 637. The output of the driver 632 is also input to the phase comparison circuit 637 and the phases are compared. The delay control circuit 638 selects the delay amount of the delay circuit 633 based on the comparison result. In this way, the phase of Write-CLK is adjusted so as to coincide with Read-Receive.
[0125]
FIG. 65 is a diagram showing element arrangement and signal wiring in the memory system of the sixteenth embodiment.
In the memory system of the sixteenth embodiment, the clock terminal of the controller 601 is used both as a read clock and a write clock. As in the seventh embodiment, the controller 601 receives the clock signal CLK propagating in the direction in which the output data from the memory propagates as R / W-CLK. Therefore, the data output from the memory is taken into the controller 601 as in the seventh embodiment. The clock signal CLK is branched to the clock signal line 607 immediately before being input to the controller 601, and returns in the reverse direction, which becomes a clock signal for writing. Therefore, the data written to the memory output from the controller 601 and the write clock signal propagate in parallel. The problem is to match the phase of the data to be written to the memory and the clock signal for writing.
[0126]
FIG. 66 is a diagram showing a clock signal system in the controller 601 in the sixteenth embodiment.
As shown in FIG. 66, R / W-CLK input from the outside is amplified by passing through a current mirror circuit 641 and a driver 642, and after being delayed by an amount selected by a delay circuit 643, a data output buffer 644. The data output buffer 644 outputs the data of the write data register 640 in synchronization with the timing signal supplied from the delay circuit 643. This timing signal is delayed by the same delay amount as the data output buffer 644 by the dummy output buffer 649 and then input to the current mirror circuit 645. The output of the current mirror circuit 645 is input to the phase comparison circuit 647 after passing through the driver 646. The output of the driver 642 is also input to the phase comparison circuit 647 and the phases are compared. The delay control circuit 648 selects the delay amount of the delay circuit 643 based on the comparison result. In this way, the write data Write-Data is synchronized with R / W-CLK, that is, the write clock signal.
[0127]
【The invention's effect】
As described above, according to the present invention, the delay amount is adjusted so that a signal of an actual circuit is compared with an external clock signal so as to have a predetermined phase relationship. Even if there is a change in the power supply voltage or the like, the phase relationship of the output signal with respect to the external clock signal can be accurately maintained at a predetermined value.
[0128]
Further, since an input dummy circuit and an output dummy circuit are provided and a signal to be compared with the external clock signal is a signal close to the actual output signal, the phase can be accurately adjusted.
Furthermore, since the phase is adjusted for each of the rising output data and the falling output data, the phase error can be further reduced.
[0129]
Furthermore, even if the dummy circuit is made similar, there is a difference from the circuit related to the actual output, and the load actually connected to the output terminal cannot be predicted, and a difference from the assumed dummy load occurs. Is inevitable. Such a difference becomes an error in phase adjustment. However, according to the present invention, since such an error is adjusted, the error can be further reduced. Further, by using such a semiconductor device, a semiconductor system capable of operating at high speed can be realized.
[Brief description of the drawings]
FIG. 1 is a block diagram showing an overall configuration of a synchronous DRAM (SDRAM).
FIG. 2 is a time chart showing the basic operation of the SDRAM.
FIG. 3 is a basic operation diagram of a pipeline type SDRAM.
FIG. 4 is a diagram for explaining SDRAM timing and problems at high-speed operation;
FIG. 5 is a diagram showing a basic configuration of a semiconductor device of the present invention in which a timing signal supplied to an output circuit is synchronized with an external clock signal.
6 is a diagram for explaining a problem in the basic configuration of FIG. 5;
7 is a diagram showing a configuration of a semiconductor device of the present invention in which the basic configuration of FIG. 5 is further improved.
FIG. 8 is an operation diagram of the SDRAM of the embodiment.
FIG. 9 is a diagram showing a configuration of a portion related to output timing control of the SDRAM of the first embodiment.
FIG. 10 is a diagram showing the configuration and operation of the delay circuit of the first embodiment.
FIG. 11 is a diagram illustrating a configuration of a delay control circuit according to the first embodiment;
FIG. 12 is a time chart showing the operation of the delay control circuit of the first embodiment.
FIG. 13 is a diagram illustrating a change in an output signal of the delay control circuit according to the first embodiment.
FIG. 14 is a diagram illustrating another example of a delay control circuit.
FIG. 15 is a diagram illustrating a configuration of a phase comparison unit of the phase comparison circuit according to the first embodiment;
FIG. 16 is a time chart showing the operation of the phase comparison unit of the phase comparison circuit of the first embodiment;
FIG. 17 is a diagram illustrating a configuration of an amplifier circuit section of the phase comparison circuit according to the first embodiment;
FIG. 18 is a time chart showing the operation of the JK flip-flop in the amplifier circuit section of the phase comparison circuit of the first embodiment.
FIG. 19 is a time chart showing the count-up operation of the amplifier circuit section of the phase comparison circuit according to the first embodiment;
FIG. 20 is a time chart illustrating the count maintaining operation of the amplifier circuit unit of the phase comparison circuit according to the first embodiment;
FIG. 21 is a time chart showing the countdown operation of the amplifier circuit section of the phase comparison circuit according to the first embodiment;
FIG. 22 is a diagram illustrating a configuration of an output circuit according to the first embodiment;
FIG. 23 is a diagram illustrating a configuration of a dummy output circuit according to the first embodiment;
FIG. 24 is a time chart illustrating the operation of the dummy output circuit according to the first embodiment;
FIG. 25 is a diagram illustrating a configuration of a dummy output circuit according to a second embodiment;
FIG. 26 is a diagram illustrating a configuration of a dummy output circuit according to a third embodiment;
FIG. 27 is a diagram illustrating a configuration of a dummy output circuit according to a fourth embodiment;
FIG. 28 is a diagram showing a configuration of a portion related to output timing control of the SDRAM of the fifth embodiment.
FIG. 29 is a diagram showing a configuration of a phase comparison circuit of an SDRAM of a fifth embodiment.
FIG. 30 is a diagram illustrating a configuration of a dummy output circuit according to a fifth embodiment;
FIG. 31 is a time chart showing the operation in the fifth embodiment.
FIG. 32 is a diagram for explaining the generation of an error due to a change in the characteristics of a regular route and a dummy route.
FIG. 33 is a diagram showing a configuration of a portion related to output timing control of the SDRAM of the sixth embodiment.
FIG. 34 is a diagram showing a configuration of a dummy output circuit according to a sixth embodiment.
FIG. 35 is a time chart showing the operation of the dummy output circuit in the sixth embodiment.
FIG. 36 is a diagram showing a configuration of an output circuit according to a sixth embodiment.
FIG. 37 is a time chart showing the operation of the output circuit in the sixth embodiment.
FIG. 38 is a diagram illustrating a configuration of a switching circuit according to a sixth embodiment.
FIG. 39 is a diagram showing a configuration of a portion related to output timing control of the SDRAM of the seventh embodiment.
FIG. 40 is a diagram illustrating a configuration example of a delay circuit and a delay control circuit of the receiving-side semiconductor device according to the seventh embodiment.
FIG. 41 is a diagram illustrating a configuration of a ½ phase shift circuit according to a seventh embodiment.
FIG. 42 is a diagram illustrating a configuration of a phase determination circuit according to a seventh embodiment.
FIG. 43 is a diagram illustrating a phase determination operation in the seventh embodiment.
FIG. 44 is a diagram for explaining a phase determination operation in the seventh embodiment;
FIG. 45 is a diagram for explaining a phase determination operation in the seventh embodiment;
FIG. 46 is a truth table of the phase determination operation in the seventh embodiment.
47 is a diagram showing a configuration of a portion related to output timing control of the SDRAM of the eighth embodiment; FIG.
FIG. 48 is a diagram showing a configuration of a portion related to output timing control of the SDRAM of the ninth embodiment.
FIG. 49 is a diagram illustrating a configuration of a phase determination circuit according to a ninth embodiment.
FIG. 50 is a diagram for explaining a phase determination operation in the ninth embodiment.
FIG. 51 is a truth table of the phase determination operation in the ninth embodiment.
FIG. 52 is a diagram illustrating a configuration of a delay control circuit according to a ninth embodiment.
FIG. 53 is a diagram showing a configuration of a portion related to output timing control of the SDRAM of the tenth embodiment.
FIG. 54 is a diagram illustrating a phase determination operation in the tenth embodiment.
FIG. 55 is a diagram showing a configuration of a portion related to output timing control of the SDRAM of the eleventh embodiment.
FIG. 56 is a diagram showing an arrangement of a clock input circuit, an output timing control circuit, a clock distribution circuit, and an output circuit in the SDRAM of the twelfth embodiment.
FIG. 57 is a diagram showing output timing in a conventional semiconductor device.
FIG. 58 is a diagram showing output timing in the semiconductor device of the present invention.
FIG. 59 is a diagram showing an element arrangement and signal wirings in a semiconductor device system according to a thirteenth embodiment.
FIG. 60 is a time chart showing signal waveforms in the thirteenth embodiment.
FIG. 61 is a diagram showing element arrangement and signal wirings in a semiconductor device system according to a fourteenth embodiment.
FIG. 62 is a diagram illustrating a clock timing adjustment system in a controller according to a fourteenth embodiment.
FIG. 63 is a diagram showing an element arrangement and signal wirings in a semiconductor device system according to a fifteenth embodiment.
FIG. 64 is a diagram showing a clock timing adjustment system in the controller of the fifteenth embodiment.
FIG. 65 is a diagram showing an element arrangement and signal wirings in the semiconductor device system according to the sixteenth embodiment.
FIG. 66 is a diagram illustrating a clock timing adjustment system in a controller according to a sixteenth embodiment;
[Explanation of symbols]
11 ... External signal input terminal
12 ... Signal output terminal
13 ... Input circuit
14 ... Output circuit
20, 30 ... Output timing control circuit
21, 31 ... delay circuit
22, 32 ... Phase comparison circuit
23, 33 ... Delay control circuit
34 ... Dummy input circuit
35 ... Dummy output circuit

Claims (14)

A clock input circuit for receiving an external clock;
A phase comparison circuit having one input coupled to the clock input circuit for comparing signals at the one input and the other input;
An input connected to the clock input circuit, delaying the input by a delay time corresponding to the output of the phase comparison circuit, and outputting a data output timing signal having a predetermined phase with respect to the external clock A real delay circuit;
A dummy delay circuit having an input coupled to the clock input circuit, delaying the input by a delay time corresponding to the output of the phase comparison circuit, and supplying the output to the other input of the phase comparison circuit;
A data output circuit for outputting data according to the data output timing signal ;
A dummy output circuit that is provided in series between the other input of the dummy delay circuit and the phase comparison circuit and generates a first propagation delay time equivalent to the propagation delay time in the data output circuit, and the clock input circuit A dummy clock input circuit for generating a second propagation delay time equivalent to the propagation delay time in FIG.
A semiconductor device comprising: The semiconductor device according to claim 1,
The semiconductor device is a semiconductor device which is a synchronous semiconductor memory. The semiconductor device according to claim 1,
The real delay circuit and the dummy delay circuit are semiconductor devices each including a plurality of delay units connected in series. The semiconductor device according to claim 1,
The input terminal is connected to the clock input circuit, the output terminal is connected to one input of the dummy delay circuit and the phase comparison circuit, and the frequency of the reference clock output from the clock input circuit is divided by 1 / N. A semiconductor device further comprising a peripheral (N: integer). The semiconductor device according to claim 1,
The semiconductor device in which the delay time in both the actual delay circuit and the dummy delay circuit is controlled in common according to the output of the phase comparison circuit. The semiconductor device according to claim 1 ,
A semiconductor device further comprising a dummy load circuit connected to the dummy output circuit and driven by the dummy output circuit. The semiconductor device according to claim 6 ,
A semiconductor device in which a load value in the dummy load circuit changes according to a switching signal. The semiconductor device according to claim 1 ,
The power supply of the data output circuit and the dummy output circuit is a semiconductor device independent of the internal power supply of the semiconductor device. The semiconductor device according to claim 1 ,
The data output circuit and the dummy output circuit are semiconductor devices in which drive characteristics change according to a mode signal. The semiconductor device according to claim 1,
A dummy signal line is further provided between the dummy delay circuit and the other input of the phase comparison circuit, and the dummy signal line is equivalent to a delay time in a signal line between the actual delay circuit and the data output circuit. Semiconductor device having a long line delay time. The semiconductor device according to claim 1 ,
The actual delay circuit includes first and second actual delay circuits that output first and second actual data output timing signals as the data output timing signal, respectively.
The dummy delay circuit includes first and second dummy delay circuits that output first and second dummy clocks to the dummy data output circuit,
When the data is high, the data output circuit outputs the data according to the first actual data output timing signal, and the dummy output circuit operates according to the first dummy clock,
When the data is low, the data output circuit outputs the data in accordance with the second actual data output timing signal, and the dummy output circuit operates in accordance with the second dummy clock. The semiconductor device according to claim 11 , wherein
A first delay control circuit for controlling the delay time in the first real delay circuit and the first dummy delay circuit according to a first output signal from the phase comparison circuit;
A semiconductor device comprising: a second delay control circuit that controls the delay time in the second actual delay circuit and the second dummy delay circuit in accordance with a second output signal from the phase comparison circuit. The semiconductor device according to claim 12 ,
The phase comparison circuit is a semiconductor device that outputs one of the first and second output signals according to the data. The semiconductor device according to claim 1 ,
The size of the dummy output circuit is a semiconductor device smaller than the size of the data output circuit.

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