Patent Publication Number: US-8976615-B2

Title: Semiconductor memory device capable of performing refresh operation without auto refresh command

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority under 35 U.S.C. §119 to Korean Patent Application No. 10-2012-0102936 filed on Sep. 17, 2012, the disclosure of which is hereby incorporated by reference in its entirety. 
     BACKGROUND 
     1. Field 
     Example embodiments of the inventive concepts relate to a memory device, and particularly to a semiconductor memory device and a memory system including the same. 
     2. Description of Related Art 
     Semiconductor memory devices may be classified into volatile memory devices and nonvolatile memory devices. In a volatile memory device such as a dynamic random access memory (DRAM), it is required to perform refresh operation at a predetermined period to retain data stored in a memory cell. 
     SUMMARY 
     Example embodiments of the inventive concepts provide a semiconductor memory device capable of performing refresh without using an auto refresh command. 
     Example embodiments of the inventive concepts also provide a memory system including the semiconductor memory device. 
     Example embodiments of the inventive concepts also provide a method of controlling a semiconductor memory device capable of performing refresh without using an auto refresh command. 
     The technical objectives of example embodiments of the inventive concepts are not limited to the above disclosure; other objectives may become apparent to those of ordinary skill in the art based on the following descriptions. 
     In accordance with example embodiments of the inventive concepts, a semiconductor memory device includes an internal address generating circuit, an internal command generating circuit and a memory cell array. 
     The internal address generating circuit is configured to parse an external address and control timing of the external address to generate an internal address. The internal command generating circuit is configured to control timing of auto refresh based on the external address and an external command and control timing of the external command to generate an internal command. The memory cell array includes at least one memory bank group, and each of the memory bank group includes a plurality of memory banks and operates in response to the internal address and the internal command. When a read command or a write command is input, in case that a part of memory bank(s) of a first memory bank group perform(s) a read operation or a write operation, the rest of the memory bank(s) of the first memory bank group may perform in a refresh operation. 
     In an embodiment, the internal address may have an address structure in which a row address and a column address are integrated. 
     In an embodiment, the memory bank(s) that perform(s) a read operation or a write operation may automatically perform an active operation, a read/write operation and a pre-charge operation when a read command or a write command is input. 
     In an embodiment, the semiconductor memory device may perform the active operation and the pre-charge operation without using an active command and a pre-charge command. 
     In an embodiment, the semiconductor memory device may perform the refresh operation without using an auto refresh command. 
     In an embodiment, a second memory bank group of the memory cell array may independently operate from the first memory bank group. 
     In an embodiment, when the first memory bank group is activated and the second memory bank group is inactivated, memory banks included in the second memory bank group may automatically perform refresh. 
     In an embodiment, the semiconductor memory device may have a data input/output (IO) structure with a long bust length. 
     In an embodiment, the semiconductor memory device may further include an input/output (IO) sense amplifier and an IO circuit. The input/input (IO) sense amplifier is configured to amplify data output from the memory cell array to generate a first data, and transfer input data to the memory cell array. The IO circuit is configured to determine an output order of the first data, perform a parallel-serial conversion to generate an output data, and buffer the input data to provide the buffered data to the IO sense amplifier. 
     In accordance with another aspect of example embodiments of the inventive concepts, a method of controlling a semiconductor memory device may include performing a data input/output operation on a first memory bank included in a first memory bank group; performing a refresh operation on a second memory bank included in the first memory bank group; performing a refresh operation on the first memory bank included in the first memory bank group; and performing a data input/output operation on the second memory bank included in the first memory bank group. 
     In an embodiment, the method of controlling a semiconductor memory device may further include performing a refresh operation on memory banks included in a second memory bank group. 
     In an embodiment, the method may perform the refresh operation without using an auto refresh command. 
     In an embodiment, the performing the data input/output operation on the first memory bank included in the first memory bank group may perform at the same time as the performing the refresh operation on the second memory bank included in the first memory bank group. 
     In an embodiment, the performing the refresh operation on the first memory bank included in the first memory bank group may perform at the same time as the performing the data input/output operation on the second memory bank included in the first memory bank group. 
     According to at least one example embodiment of the inventive concepts, a semiconductor memory device includes an internal address generating circuit configured to analyze an external address and to control timing of the external address to generate an internal address; an internal command generating circuit configured to control timing of an auto refresh operation based on the external address and an external command and to control timing of the external command to generate an internal command; and a memory cell array including one or more memory bank groups, each of the one or more memory bank groups including a plurality of memory banks and operating in response to the internal address and the internal command, wherein, when a read command or a write command is input, if a first portion of the plurality of memory banks of a first memory bank group from among the one or more memory bank groups performs a read operation or a write operation, a second portion of the plurality of memory banks of the first memory bank group performs a refresh operation, the first portion including one or more of the plurality of memory banks of the first memory bank group, the second portion including the one or more of the plurality of memory banks of the first memory bank group which are not included in the first portion. 
     The internal address may include an address structure in which a row address and a column address are integrated. 
     The semiconductor memory device may be configured such that, when the read command or write command is input, the one or more memory banks of the first portion of the plurality of memory banks perform an active operation, a read/write operation and a pre-charge operation when a read command or a write command is input. 
     The semiconductor memory device may be configured to perform the active operation and the pre-charge operation without using an active command and a pre-charge command. 
     The semiconductor memory device may be configured to perform the refresh operation without using an externally received auto refresh command. 
     The second memory bank group of the memory cell array may be configured to operate independently from the first memory bank group. 
     The semiconductor memory device may be configured such that when the first memory bank group is activated and the second memory bank group is inactivated, memory banks included in the second memory bank group perform a refresh operation. 
     The semiconductor memory device may be configured to have a data input/output (IO) structure with a long burst length. 
     The semiconductor memory device may further include an input/output (IO) sense amplifier configured to amplify data output from the memory cell array to generate first data, and transfer input data to the memory cell array; and an IO circuit configured to determine an output order of the first data, perform a parallel-serial conversion to generate an output data, and buffer the input data to provide the buffered data to the IO sense amplifier. 
     According to example embodiments of the inventive concepts, a method of controlling a semiconductor memory device includes performing a data input/output operation on a first memory bank included in a first memory bank group; performing a first refresh operation on a second memory bank included in the first memory bank group; performing a second refresh operation on the first memory bank included in the first memory bank group; and performing a data input/output operation on the second memory bank included in the first memory bank group. 
     The method may further include performing a third refresh operation on memory banks included in a second memory bank group. 
     The method may further include controlling a timing of the first refresh operation and a timing of the second refresh operation based on a read command or a write command. 
     The refresh operation may be performed without using an external auto refresh command. 
     The data input/output operation performed on the first memory bank included in the first memory bank group may be performed at the same time as the first refresh operation. 
     The second refresh operation may be performed at the same time as the data input/output operation performed on the second memory bank included in the first memory bank group. 
     According to example embodiments of the inventive concepts, a semiconductor memory device may include a memory cell array including one or more memory bank groups, each of the one or more memory bank groups including a plurality of memory banks; and an internal command generating circuit configured to receive an external command which does not include a refresh command and configured to control refresh operations of the one or more memory bank groups based on the external command. 
     The semiconductor device may further include an internal address generating circuit configured to analyze an external address and to control timing of the external address to generate an internal address, wherein the internal command generating circuit is configured to control timing of the refresh operations based on the external address and the external command. 
     The internal command generating circuit may be configured such that when the external command corresponds to a read command or a write command, based on the external command, the internal command generating circuit controls a first portion of the plurality of memory banks of a first one of the one or more memory bank groups to perform a read operation or a write operation, and the internal command generating circuit controls a second portion of the plurality of memory banks of a first one of the one or more memory bank groups to perform a refresh operation, the first portion including one or more of the plurality of memory banks of the first memory bank group, the second portion including the one or more of the plurality of memory banks of the first memory bank group which are not included in the first portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of example embodiments will become more apparent by describing in detail example embodiments with reference to the attached drawings. The accompanying drawings are intended to depict example embodiments and should not be interpreted to limit the intended scope of the claims. The accompanying drawings are not to be considered as drawn to scale unless explicitly noted. 
         FIG. 1  is a block diagram illustrating a semiconductor memory device in accordance with example embodiments of the inventive concepts; 
         FIG. 2  is a flowchart illustrating a method of controlling the semiconductor memory device in accordance with example embodiments of the inventive concepts; 
         FIG. 3  is a diagram illustrating an operation of the semiconductor memory device performing a burst read operation in accordance with example embodiments of the inventive concepts; 
         FIG. 4  is a diagram illustrating a method of generating an address of the semiconductor memory device in accordance with example embodiments of the inventive concepts; 
         FIG. 5  is a plan view illustrating an example of a layout structure of the semiconductor memory device of  FIG. 1  in accordance with example embodiments of the inventive concepts; 
         FIGS. 6 to 8  are diagrams illustrating memory modules including the semiconductor memory device in accordance with example embodiments of the inventive concepts; 
         FIG. 9  is a schematic perspective view illustrating an example of a stacked semiconductor device including the semiconductor memory device in accordance with example embodiments of the inventive concepts; 
         FIGS. 10 to 13  are block diagrams illustrating memory systems including the semiconductor memory device in accordance with Example embodiments of the inventive concepts; 
         FIG. 14  is a block diagram illustrating an example of a memory system including the semiconductor memory device and an optical link in accordance with example embodiments of the inventive concepts; and 
         FIG. 15  is a block diagram illustrating an example of an electronic system including the semiconductor memory device in accordance with example embodiments of the inventive concepts. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Various embodiments will now be described more fully with reference to the accompanying drawings in which some embodiments are shown. These inventive concepts may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure is thorough and complete and fully conveys example embodiments of the inventive concepts to those skilled in the art. In the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. 
     It will be understood that when an element or layer is referred to as being “on,” “connected to” or “coupled to” another element or layer, it can be directly on, connected or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numerals refer to like elements throughout. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. 
     It will be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or section from another region, layer or section. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of example embodiments of the inventive concepts. 
     Spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element&#39;s or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. 
     The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments of the inventive concepts. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
     Embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures). As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, embodiments should not be construed as limited to the particular shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an implanted region illustrated as a rectangle will, typically, have rounded or curved features and/or a gradient of implant concentration at its edges rather than a binary change from implanted to non-implanted region. Likewise, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation takes place. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of example embodiments of the inventive concepts. 
     Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments of the inventive concepts belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
     Hereinafter, preferred example embodiments of the inventive concepts will be described with reference to the accompanying drawings. 
       FIG. 1  is a circuit diagram illustrating a semiconductor memory device  100  in accordance with example embodiments of the inventive concepts. 
     Referring to  FIG. 1 , the semiconductor memory device  100  may include an internal address generating circuit  110 , an internal command generating circuit  120 , a memory cell array  130 , an input/output (I/O) sense amplifier  140  and an input/output (I/O) circuit  150 . 
     The internal address generating circuit  110  parses an external address ADDR and control timing of the external address ADDR to generate an internal address. The internal command generating circuit  120  controls timing of an auto refresh operation based on the external address ADDR and an external command CMD and control timing of the external command CMD to generate the internal command. The memory cell array  130  includes at least one memory bank group, each of the one or more memory bank groups includes a plurality of memory banks and operates in response to the internal address and the internal command. 
     The internal address generating circuit  110  may include an address parser  112  that parses the external address ADDR and an address timing controller  114  that controls timing of the external address ADDR to generate the internal address. The internal command generating circuit  120  may include a command timing controller  122  that controls timing of the external command CMD and an auto refresh timer  124  that controls an auto refresh timing based on the external address ADDR and the external command CMD. 
     The internal command generating circuit  120  may control the timing of the command so that a first memory bank group GROUP1 and a second memory bank group GROUP2 in the memory cell array  130  operate independently. For example, when the first memory bank group GROUP1 performs a read operation, if only a read command RD is input, the semiconductor memory device  100  may perform active operation ACT, perform n times a burst read operation on the first memory bank group GROUP1, and perform in a pre-charge operation. The active operation ACT may, for example, activate one or more memory banks preparing them for at least one of data read and write operations. Similarly, when the first memory bank group GROUP1 performs a write operation, if only a write command WR is input, the semiconductor memory device  100  may perform active operation ACT, perform n times a burst write operation on the first memory bank group GROUP1, and perform a pre-charge operation. 
     In case a read command or a write command is input, when a part of memory banks of a first memory bank group GROUP1 perform a read operation or a write operation, the rest of the memory banks of the first memory bank group GROUP1 may perform a refresh operation, for example in response to signals received from the auto refresh timer  124 , without the need to receive an exterior auto refresh command from outside memory device  100 . 
     Further, when the first memory bank group GROUP1 is activated and the second memory bank group GROUP2 is inactivated, memory banks included in the second memory bank group GROUP2 may automatically perform refresh, for example in response to signals received from the auto refresh timer  124 . Further, while the first memory bank group GROUP1 performs a read operation, the second memory bank group GROUP2 may perform a read operation or a refresh operation. 
     The I/O sense amplifier  140  amplifies data output from the memory cell array  130  to generate a first data, and transfers an input data DIN to the memory cell array  130 . The I/O circuit  150  determines an output order of the first data, perform a parallel-serial conversion to generate an output data DOUT, and buffer the input data DIN to provide the buffered data to the IO sense amplifier  140 . 
     The semiconductor memory device of  FIG. 1  may be a data memory for storing only data except for a program. 
       FIG. 2  is a flowchart illustrating a method of controlling the semiconductor memory device in accordance with example embodiments of the inventive concepts. 
     Referring to  FIG. 2 , the method of controlling a semiconductor memory device in accordance with example embodiments of the inventive concepts may include the following operations. 
     1) performing a data input/output operation on a first memory bank included in a first memory bank group (S 1 ). 
     2) performing a refresh operation on a second memory bank included in the first memory bank group (S 2 ). 
     3) performing a refresh operation on the first memory bank included in the first memory bank group (S 3 ). 
     4) performing a data input/output operation on the second memory bank included in the first memory bank group (S 4 ). 
     5) performing a refresh operation on memory banks included in a second memory bank group (S 5 ). 
     In  FIG. 2 , operations S 1  and S 2  may be executed at the same time, and operations S 3  and S 4  may be executed at the same time. For example, while an input/output operation on the first memory bank included in the first memory bank group is performed, a refresh operation on the second memory bank included in the first memory bank group may be performed. Further, while a refresh operation on the first memory bank included in the first memory bank group is performed, a data input/output operation on the second memory bank included in the first memory bank group may be performed. 
     As illustrated in  FIG. 2 , the second memory bank group may independently operate from the first memory bank group, and the second memory bank group may perform refresh operation when the second memory bank group is not activated. Further, when the second memory bank group is activated, the second memory bank group may perform a data input/output operation. 
       FIG. 3  is a diagram illustrating an operation of the semiconductor memory device performing a burst read operation in accordance with example embodiments of the inventive concepts. The burst read operation is an operation mode in which two or more data are read or written at one time when one read command or one write command is input. 
     In  FIG. 3 , while a first memory bank BANK A included in a memory bank group performs an active operation  11 , a second memory bank BANK B included in the memory bank group may perform a refresh operation. When a read command is input, the first memory bank BANK A may automatically perform the active operation  11 , a read operation  12 , a pre-charge operation  13  and the refresh operation  14 , for example in response to signals received from the internal command generating circuit  120 . During the read operation  12 , data stored in the first memory bank BANK A are read according to a burst length of the semiconductor memory device. Similarly, when the read command is input, the second memory bank BANK B may also automatically perform the active operation  16 , a read operation  17 , a pre-charge operation  18  and the refresh operation  15 , for example in response to signals received from internal command generating circuit. 
     Accordingly, the semiconductor memory device according to embodiment of the example embodiments of the inventive concepts may perform a refresh operation even without receiving a refresh command from the exterior. 
       FIG. 4  is a diagram illustrating a method of generating an address, for example an internal address, of the semiconductor memory device in accordance with example embodiments of the inventive concepts.  FIG. 4  illustrates the method of generating an address of the semiconductor memory device when the burst length BL is 128. The address illustrated in  FIG. 4  includes two portions: New Address and don&#39;t care bits. The New Address portion has an integrated structure of a row address ROW ADDRESS and part of a column address COLUMN ADDRESS, and lower seven bits BIT6:BIT0 of the column address are set to a don&#39;t care condition because the burst length is 128. The New Address may be, for example, an internal address. 
       FIG. 5  is a plan view illustrating an example of a layout structure of the semiconductor memory device of  FIG. 1  in accordance with example embodiments of the inventive concepts. 
     Referring to  FIG. 5 , a semiconductor memory device  200  may include four memory bank groups BANK GROUP1 to BANK GROUP4. Each of the memory bank groups BANK GROUP1 to BANK GROUP4 may include two memory banks. The memory bank group BANK GROUP1 includes memory banks BANK A and BANK B, the memory bank group BANK GROUP2 includes memory banks BANK C and BANK D, the memory bank group BANK GROUP3 includes memory banks BANK E and BANK F, and the memory bank group BANK GROUP4 includes memory banks BANK G and BANK H. Further, pads PAD for communicating with the exterior are disposed at the edge and a peripheral region  250  of the middle portion of the semiconductor memory device  200 . 
     As described above, when the memory bank BANK A included in the memory bank group BANK GROUP1 performs a data input/output operation in a read mode or a write mode, the memory bank BANK B may perform a refresh operation. Similarly, when the memory bank BANK C included in the memory bank group BANK GROUP2 performs the data input/output operation in the read mode or the write mode, the memory bank BANK D may perform the refresh operation, when the memory bank BANK E included in the memory bank group BANK GROUP3 performs the data input/output operation in the read mode or the write mode, the memory bank BANK F may perform the refresh operation, and when the memory bank BANK G included in the memory bank group BANK GROUP4 performs the data input/output operation in the read mode or the write mode, the memory bank BANK H may perform the refresh operation. 
     Although not shown in the drawings, the number of memory bank groups of the semiconductor memory device may not only be 4 but also 8 or more, and each memory bank group may include 2 or more memory banks. 
       FIGS. 6 to 8  are diagrams illustrating memory modules including semiconductor memory devices in accordance with example embodiments of the inventive concepts. Referring to  FIG. 6 , the memory module  300  may include a printed circuit board (PCB)  310 , a plurality of memory chips  320 , and a connector  330 . The plurality of memory chips  320  may be bonded to top and bottom surfaces of the PCB  310 . The connector  330  may be electrically connected to the plurality of memory chips  320  through conductive lines (not shown). Also, the connector  330  may be connected to a slot of an external host. 
     Referring to  FIG. 7 , the memory module  400  may include a PCB  410 , a plurality of memory chips  440 , a connector  430 , and a plurality of buffers  420 . Each of the plurality of buffers  420  may be disposed between the memory chips  420  and the connector  430 . 
     The memory chips  440  and the buffers  420  may be provided on top and bottom surfaces of the PCB  410 . The memory chips  440  and the buffers  420  formed on the top and bottom surfaces of the PCB  410  may be connected through a plurality of via holes. 
     Referring to  FIG. 8 , the memory module  500  may include a PCB  510 , a plurality of memory chips  520 , a connector  530 , a plurality of buffers  540 , and a controller  550 . 
     The memory chips  520  and the buffers  540  may be provided on top and bottom surfaces of the PCB  510 . The memory chips  520  and the buffers  540  formed on the top and bottom surfaces of the PCB  510  may be connected through a plurality of via holes. 
     In  FIGS. 6 to 8 , the memory chips may include the semiconductor memory devices in accordance with example embodiments of the inventive concepts. Therefore, the memory chips may perform a refresh operation without an exterior auto refresh command, for example in the manner discussed above with reference to  FIGS. 1-5 . 
       FIG. 9  is a schematic perspective diagram illustrating an example of a stacked semiconductor device  600  including a semiconductor memory device in accordance with example embodiments of the inventive concepts. 
     Referring to  FIG. 9 , the stacked semiconductor device  600  may include an interface chip  610 , and memory chips  620 ,  630 ,  640  and  650  which are electrically connected through through-silicon vias  660 . Although the through-silicon vias  660  disposed in two rows are shown in  FIG. 9 , the stacked semiconductor device  600  may include any number of through-silicon vias. 
     The memory chips  620 ,  630 ,  640  and  650  included in the stacked semiconductor device  600  may include the semiconductor memory device in accordance with the Example embodiments of the inventive concepts. Therefore, the memory chips  620 ,  630 ,  640  and  650  may perform a refresh operation without the exterior auto refresh command, for example in the manner discussed above with reference to  FIGS. 1-5 . 
     The interface chip  610  may perform interfacing between the memory chips  620 ,  630 ,  640  and  650  and the external devices. 
       FIGS. 10 to 13  are block diagrams illustrating examples of memory systems including a semiconductor memory device in accordance with example embodiments of the inventive concepts. 
     Referring to  FIG. 10 , the memory system  700  may include a host  710  and a data memory device  720 . 
     The host  710  may generate an address signal ADD and a command CMD, and provide the address signal ADD and the command CMD to the data memory device  720  through buses. Data DQ may be transmitted from the host  710  to the data memory device  720  through the buses, or transmitted from the data memory device  720  to the host  710  through the buses. 
     The data memory device  720  may include semiconductor memory devices in accordance with example embodiments of the inventive concepts. Therefore, the data memory device  720  may perform a refresh operation without the exterior auto refresh command, for example in the manner discussed above with reference to  FIGS. 1-5 . 
     Referring to  FIG. 11 , the memory system  800  may include a host  810  and a data memory device  820 . In the memory system  800  of  FIG. 11 , the command CMD and an address ADD are integrated to form a packetized signal C/A, differently from the memory system  700  of  FIG. 10 . 
     Referring to  FIG. 12 , the memory system  850  may include a central processing unit (CPU)  852 , a DRAM  853 , a data memory device  854 , an external storage device  855  and an I/O device  856 . 
     The DRAM  853  may communicate with the CPU  852  through a first bus BUS — 1, the data memory device  854  may communicate with the CPU  852  through a second bus BUS — 2, the external storage device  855  may communicate with the CPU  852  through a third bus BUS — 3, and the I/O device  856  may communicate with the CPU  852  through a fourth bus BUS — 4. The data memory device  854  is mainly used to store data, and may include semiconductor memory devices according to example embodiments of the inventive concepts. Therefore, the data memory device  854  may perform a refresh operation without the exterior auto refresh command, for example in the manner discussed above with reference to  FIGS. 1-5 . The data memory device  854  may include a DRAM, and have a long burst length BL and perform a burst operation. 
     Referring to  FIG. 13 , the memory system  900  may be a MemCache system that includes a CPU  910 , a DRAM  853 , a normal registered dual-in-line memory modules (RDIMM)  921  and  922 , a dual-in-line memory modules (DIMM)  923  to  929 . 
     In  FIG. 13 , the normal RDIMM  921  and  922  may be used to store a program and data, and the DIMM  923  to  929  may be used to store data. Each of the DIMM  923  to  929  may include semiconductor memory devices according to example embodiments of the inventive concepts. Therefore, the semiconductor memory devices included in the DIMM  923  to  929  may perform a refresh operation without the exterior auto refresh command, for example in the manner discussed above with reference to  FIGS. 1-5 . The semiconductor memory devices included in the DIMM  923  to  929  may include a DRAM, and have a long burst length BL and perform a burst operation. 
       FIG. 14  is a block diagram illustrating an example of a memory system  1000  including a semiconductor memory device and an optical link according to example embodiments of the inventive concepts. 
     Referring to  FIG. 14 , the memory system  1000  may include a controller  1020 , a data memory device  1030 , and a plurality of optical links  1010   a  and  1010   b  configured to interconnect the controller  1020  and the data memory device  1030 . The controller  1020  may include a control unit  1021 , a first transmitter  1022 , and a first receiver  1023 . The control unit  1021  may transmit a control signal SN 1  to the first transmitter  1022 . 
     The first transmitter  1022  may include a first optical modulator  1022 _ 1 , which may convert the control signal SN 1 , which is an electric signal, into a first optical transmission signal OPT 1 , and transmit the first optical transmission signal OPT 1  to the optical link  1010   a.    
     The first receiver  1023  may include a first optical demodulator  1023 _ 1 , which may convert a second optical receiving signal OPT 2 ′ received from the optical link  1010   b  into a data signal SN 2 , which is an electric signal, and transmit the data signal SN 2  to the control unit  1021 . 
     The data memory device  1030  may include a second receiver  1031 , a memory cell array  1032 , and a second transmitter  1033 . The second receiver  1031  may include a second optical modulator  1031 _ 1 , which may convert a first optical receiving signal OPT 1 ′ received from the optical link  1010   a  into the control signal SN 1 , which is the electric signal, and transmit the control signal SN 1  to the memory cell array  1032 . 
     In the memory cell array  1032 , data may be written under the control of the control signal SN 1 , or the data signal SN 2  output from the memory cell array  1032  may be transmitted to the second transmitter  1033 . 
     The second transmitter  1033  may include a second optical modulator  1033 _ 1 , which may convert the data signal SN 2 , which is the electric signal, into a second optical data signal OPT 2 , and transmit the second optical data signal OPT 2  to the optical link  1010   b.    
     The data memory device  1030  may include the semiconductor memory device according to example embodiments of the inventive concepts. Therefore, the data memory device  1030  may perform a refresh operation without the exterior auto refresh command, for example in the manner discussed above with reference to  FIGS. 1-5 . Further, the data memory device  1030  may include a DRAM, and have a long burst length BL and perform a burst operation. 
       FIG. 15  is a block diagram illustrating an example of an electronic system  2000  including a semiconductor memory device in accordance with example embodiments of the inventive concepts. 
     Referring to  FIG. 15 , the electronic system  2000  in accordance with example embodiments of the inventive concepts may include a controller  2010 , an input and output device  2020 , a memory device  2030 , an interface  2040 , a data memory device  2050  and a bus  2060 . The memory device  2030  may be generally a semiconductor memory device for storing a program and data. The data memory device  2050  may include the semiconductor memory device in accordance with example embodiments of the inventive concepts. Therefore, the data memory device  2050  may perform a refresh operation without the exterior auto refresh command, for example in the manner discussed above with reference to  FIGS. 1-5 . Further, the data memory device  2050  may include a DRAM, and have a long burst length and perform a burst operation. The bus  2060  may function to provide a path in that data is mutually transferred among the controller  2010 , the input and output device  2020 , the memory device  2030 , the data memory device  2050  and the interface  2040 . 
     The controller  2010  may include any one of logic devices that can perform functions of at least one of a microprocessor, a digital signal processer, and a microcontroller, or functions similar to those. The input and output device  2020  may include at least one selected from a key pad, a key board, and a display device. The memory device  2030  may function to store data and/or instructions performed by the controller  2010 . 
     The memory device  2030  may include a volatile memory chip such as a dynamic random access memory (DRAM) and a static random access memory (SRAM), a non-volatile memory chip such as a flash memory, a phase change memory, a magnetic random access memory (MRAM), or a resistive random access memory (RRAM), or a combination of thereof. 
     The interface  2040  may function to transmit/receive data to/from a communication network. The interface  2040  can include an antenna, wired or wireless transceivers or the like to transmit and receive data by wires or wirelessly. In addition, the interface  2040  may include optical fibers to transmit and receive data through the optical fibers. The electronic system  2000  may be further provided with an application chipset, a camera image processor, and an input/output (I/O) device. 
     The electronic system  2000  may be implemented as a mobile system, personal computer, an industrial computer, or a logic system that may perform various functions. For example, the mobile system may be any one of a personal digital assistant (PDA), a portable computer, a web tablet, a mobile phone, a wireless phone, a laptop computer, a memory card, a digital music system, and an information transmitting/receiving system. If the electronic system  2000  is an apparatus that can perform wireless communication, the electronic system  2000  may be used in a communication system such as a Code Division multiple Access (CDMA), a Global System for Mobile communication (GSM), a North American Digital Cellular (NADC), an Enhanced-Time Division Multiple Access (E-TDMA), a Wideband Code Division Multiple Access (WCDMA), or a CDMA 2000. 
     In the semiconductor memory device according to example embodiments of the inventive concepts, when a read command or a write command is input, in case that a first memory bank included in a memory bank group of a memory cell array perform an input/output operation, a second memory bank of the memory bank group may perform a refresh operation. On the contrary, when the first memory bank of the memory bank group perform a refresh operation, a second memory bank of the memory bank group may perform an input/output operation. Therefore, the semiconductor memory device according to example embodiments of the inventive concepts may perform refresh operation without the exterior auto refresh command. Therefore, the semiconductor memory device according to example embodiments of the inventive concepts may perform refresh without using an exterior auto refresh command. Thus, in the semiconductor memory device according to example embodiments of the inventive concepts, addressing is easy, a whole data bandwidth can be used, and latency may not vary. Accordingly, the semiconductor memory device according to example embodiments of the inventive concepts may be suitable for a system having a data input/output structure of long burst length, and also suitable for storing data. 
     Example embodiments of the inventive concepts may be applied to a semiconductor device and, particularly to a DRAM and a memory system including the DRAM. 
     The foregoing is illustrative of embodiments and is not to be construed as limiting thereof. Example embodiments of the inventive concepts having thus been described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the intended spirit and scope of example embodiments, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function, and not only structural equivalents but also equivalent structures.