Abstract:
A data arrangement control signal generation circuit for use in a semiconductor memory device includes a plurality of data arrangement control signal generation units connected in series, each for selectively generating a data arrangement control signal according to a column address strobe (CAS) latency.

Description:
This application claims priority from Korean Patent Application No. 10-2004-0087324, filed Oct. 29, 2004. 
   FIELD OF INVENTION 
   The present invention relates to a semiconductor memory device; and, more particularly, to a semiconductor memory device for reducing power consumption. 
   DESCRIPTION OF PRIOR ART 
   In prior art, a semiconductor memory device employs 2-bit pre-fetch scheme; but 4-bit pre-fetch scheme is considered. Here, the 2-bit pre-fetch is to read two data with one read command through two different buses at a time and output the two data at a rising edge and a falling edge of a clock, respectively. 
     FIG. 1  is a block diagram showing a pipe latch in a semiconductor memory device in prior art. 
   The exemplified semiconductor memory device that performs the conventional 4-bit pre-fetch loads 4 serial data inputs on 4 global input/output lines (GIO) with one read command. That is, a data corresponding to a first address is loaded on an even global input/output line GIO_EV 0 , a data corresponding to a second address is loaded on an odd global input/output line GIO_OD 0 , a data corresponding to a third address is loaded on an even global input/output line GIO_EV 1 , and a data corresponding to a fourth address address  3  is loaded on an odd global input/output line GIO_ 0 D 1 . Here, rdo/fdo are data output lines for outputting data corresponding to the rising edge and falling edge. 
   The pipe latch  120  in the conventional semiconductor memory device includes 4 pipe latches, and receives data that is carried on an output line Mxoutb of an external multiplexer  110  when a pipe latch-in signal PIN&lt; 0 : 3 &gt; becomes a logic low level “L”, which controls whether data applied to the pipe latch  120  will be received or not. 
     FIG. 2  is a block diagram showing input system of signals that are required for arrangement in a pipe latch shown in  FIG. 1 . 
   That is, through the pipe latch, the data that is loaded on the output line Mxoutb of the multiplexer  110  passes through 4 times of arrangement. At the first step, that data is loaded on one of the 4 pipe latches depending on the pipe latch-in signal PIN&lt; 0 : 3 &gt;, then arranged depending on a data arrangement control signal isoseb 0 _d 0  at the second step, and then arranged depending on an odd data control signal isoseb 1 _rd for arranging odd data in response to a start address and an even data control signal isoseb 1 _fd for arranging even data in response to the start address at the third step. At the fourth step, data that is stored at the pipe latch is loaded on the rising edge output line rdo and the falling edge output line fdo depending on an output control signal fpout, fpout for outputting data that is stored at the pipe latches. 
   Here, the data arrangement control signal isoseb 0 _do is a control signal for arranging the data that is applied to the pipe latch  121  on the output line of the multiplexer  110  based on whether the start address is odd or even. 
   On the other hand, when data is read, in order to make the period from the read command to data output being different depending on user request, the data arrangement control signal soseb needs to contain CAS latency information. For this end, there are generated all kinds of data arrangement control signals for supporting a DDR SDRAM in prior art. That is, in prior art, as shown as the timing diagram for data arrangement control signal generation in  FIG. 3 , all kinds of data arrangement control signals such as soseb 00 , soseb 05 , soseb 10 , soseb 15 , soseb 20 , soseb 25 , soseb 30  are generated. 
     FIG. 4  is a circuit diagram for data arrangement control signal generation in prior art. 
   The data arrangement control signal generating circuit in prior art generates the data arrangement control signal soseb 00  by logically combining a CASP (Column Address Strobe Pulse) signal (CAS Pulse that is a pulse signal enabled at the instance when a read or write command is applied) and an address signal ADD 0 . Further, the data arrangement control signals soseb 05 , soseb 10 , soseb 15 , soseb 20 , soseb 25 , soseb 30  are generated, by subsequently delaying the data arrangement control signal soseb 00  using alternately a rising clock and a falling clock from a delay locked loop (DLL) clock. 
   The following Table 1 shows correspondence between the CLs and the data arrangement control signals. 
   
     
       
             
             
             
           
         
             
                 
               TABLE 1 
             
             
                 
                 
             
             
                 
               CL (CAS Latency) 
               soseb 
             
             
                 
                 
             
           
           
             
                 
               1.5 
               soseb05 
             
             
                 
               2.0 
               soseb10 
             
             
                 
               2.5 
               soseb15 
             
             
                 
               3.0 
               soseb20 
             
             
                 
               3.5 
               soseb25 
             
             
                 
               4.0 
               soseb30 
             
             
                 
                 
             
           
        
       
     
   
   With a circuit for selecting a data arrangement control signal as shown in  FIG. 5 , all the data arrangement control signals generated as above are inputted and one data output arrangement control signal corresponding to the set CL is outputted. In other words, the data arrangement control signal that is outputted from the circuit for data arrangement control signal selection is used as the data arrangement control signal isoseb 0 _do in  FIG. 2 . 
   However, for example, when CL is 2, only data arrangement control signals soseb 00 , soseb 05  and soseb 10  are needed but the remaining data arrangement control signals are not necessary. As a result, the conventional data arrangement control signal generating circuit unnecessarily consumes current because it generates all kinds of data arrangement control signals. 
   SUMMARY OF INVENTION 
   It is, therefore, an object of the present invention to provide a data arrangement control signal generation circuit for generating only the required data arrangement control signals according to a predetermined CAS Latency and a method thereof. 
   In accordance with an aspect of the present invention, there is provided a data arrangement control signal generation circuit for use in a semiconductor memory device including: a plurality of data arrangement control signal generation units connected in series, each for selectively generating a data arrangement control signal according to a column address strobe (CAS) latency. 
   In accordance with another aspect of the present invention, there is provided a data arrangement control signal generation method for generating data arrangement control signals that are used for arranging data signals that are inputted to pipe latches in a semiconductor memory device, the method including the steps of: (a) outputting a first data arrangement control signal by logically combining a CASP signal that is enabled with an external read command, and a predetermined address signal; (b) transferring the first data arrangement control signal that is inputted under control of a rising clock that is outputted from a delay locked loop, as a second data arrangement control signal; and (c) controlling transfer of the second data arrangement control signal by using a first CAS latency signal that is generated with set CAS latency information, and the rising clock. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects and features of the present invention will become apparent from the following description of preferred embodiments taken in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a block diagram showing a pipe latch in a semiconductor memory device in prior art; 
       FIG. 2  is a block diagram showing input system of signals that are required for arrangement in a pipe latch shown in  FIG. 1 ; 
       FIG. 3  is a timing diagram for SOSEB signal generation in prior art; 
       FIG. 4  is a circuit diagram for SOSEB signal generation in prior art; 
       FIG. 5  is a circuit diagram for SOSEB signal selection in prior art; 
       FIG. 6  is a circuit diagram for SOSEB signal generation in accordance with the first embodiment of the present invention; and 
       FIG. 7  is a circuit diagram for SOSEB signal generation in accordance with the second embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF INVENTION 
   Hereinafter, a data arrangement control signal generation circuit in accordance with the present invention will be described in detail referring to the accompanying drawings. 
     FIG. 6  is a circuit diagram showing a data arrangement control signal generation circuit in accordance with a first embodiment of the present invention. 
   According to the first embodiment of the present invention, the data arrangement control signal generation circuit includes a first to a seventh data arrangement control signal generation units  610 ,  620 ,  630 ,  640 ,  650 ,  660 , and  670 , serially coupled, for generating a first to a seventh data arrangement control signals soseb 00  to soseb 30 . Each of the data arrangement control signal generation units  610  to  670  is switched by using CL information to prevent the data arrangement control signal from being unnecessarily generated. Particularly, each data arrangement control signal generation unit uses, as a control signal, a smaller CL than the CL corresponding to the data arrangement control signal that is outputted from the each of the data arrangement control signal generation units  610 ,  620 ,  630 ,  640 ,  650 ,  660 , and  670 . 
   More particularly, the first data arrangement control signal generation unit  610  outputs a first data arrangement control signal soseb 00  by logically combining a CASP signal that is enabled by an external read command, and a predetermined address signal. 
   The second data arrangement control signal generation unit  620  receives and switches the first data arrangement control signal soseb 00  through a first transfer gate  621  that is controlled with a rising clock that is outputted from a delay locked loop (DLL) to output the second data arrangement control signal soseb 05 . 
   The third data arrangement control signal generation unit  630  outputs the third data arrangement control signal soseb 1 O by receiving and switching the second data arrangement control signal sosebO 5  and a disable signal DIS DLL through a second transfer gate  631  that is controlled with a CL 15  and the rising clock RCLK_DLLZ. That is, when the CL is set as CL=1.5 in the semiconductor memory device, the second transfer gate  631  is turned off by the CL 15  so that the third data arrangement control signal generation unit  630  does not output the third data arrangement control signal soseb 1 O. 
   The fourth data arrangement control signal generation unit  640  receives and switches the third data arrangement control signal soseb 10  through a third transfer gate  641  that is controlled with the CL 15 , CL 2  and a falling clock FCLK_DLLZ to output the fourth data arrangement control signal soseb 15 . That is, when the CL is set as CL=2.0 in the semiconductor memory device, the third transfer gate  641  is turned off by the CL 152 Z for a logic NOR operations to be performed to the CL 15  and the CL 2  so that the fourth data arrangement control signal generating unit  640  does not output the fourth data arrangement control signal soseb 15 . 
   The fifth data arrangement control signal generation unit  650  receives and switches the fourth data arrangement control signal soseb 15  through a fourth transfer gate  651  that is controlled with the CL 15 , CL 2 , CL 25  and the rising clock RCLK_DLLZ to output the fifth data arrangement control signal soseb 20 . 
   The sixth data arrangement control signal generation unit  660  receives and switches the fifth data arrangement control signal soseb 20  through a fifth transfer gate  661  that is controlled with the CL 15 , CL 2 , CL 25 , CL 3  and the falling clock FCLK_DLLZ to output the sixth data arrangement control signal soseb 25 . 
   The seventh data arrangement control signal generation unit  670  receives and switches the sixth data arrangement control signal soseb 25  through a sixth transfer gate  671  that is controlled with the CL 15 , CL 2 , CL 25 , CL 3 , CL 35  and the falling clock RCLK_DLLZ. 
   According to the operation as described above, only the data arrangement control signals that are required can be generated by using the CLs that are set in a mode register set (MRS) in the semiconductor memory device. For example, when CL=3, the first to fifth data arrangement control signals are used while the sixth and seventh signals are not used. Accordingly, there&#39;s no need to generate the sixth and seventh data arrangement control signals. 
     FIG. 7  is a circuit diagram showing a data arrangement control signal generation circuit in accordance with a second embodiment of the present invention, which is similar to the first embodiment as shown in  FIG. 6  except that generation of the control signals that are applied to the respective transfer gates that are included in the fourth to seventh data arrangement control signal generating units. 
   For example, the fourth data arrangement control signal generation unit  740  receives and switches the third data arrangement control signal soseb 10  through a third transfer gate  741  that is controlled with the CL 2  and the falling clock FCLK_DLLZ to output the fourth data arrangement control signal soseb 15 . That is, when the CL is set as CL=2.0 in the semiconductor memory device, the third transfer gate  741  is turned off by the CL 2  so that the fourth data arrangement control signal generation unit  740  does not generate the fourth data arrangement control signal soseb 15 . At this point, the transfer gates in the fifth to seventh data arrangement control signal generation units are turned on under control of the clock that is outputted from the DLL but outputs only the previously inputted signal because the third data arrangement control signal soseb 10  is not transferred since the third transfer gate  741  is turned off. 
   As described above, the present invention can prevent or reduce unnecessary current consumption by generating only the data arrangement control signals required when data is read. 
   The present application contains subject matter related to Korean patent application No. 2004-87324, filed in the Korean Patent Office on Oct. 29, 2004, the entire contents of which being incorporated herein by reference. 
   While the present invention has been described with respect to the particular embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the spirit and scope of the invention as defined in the following claims.