Abstract:
A semiconductor memory device is capable of resolving a problem of operational efficiency difference that can occur due to a loading difference on a supplying line while receiving a driving voltage of a unit bit line sense amplifier supplied from a certain part. The memory device includes a plurality of unit bit line sense amplifiers in a BLSA region, a pull-up power line and a pull-down power line used as power lines of the plurality of unit bit line sense amplifiers, a plurality of normal drivers connected to the pull-up power line at regular intervals in the BLSA region, and a plurality of over drivers connected to the pull-up power line at regular intervals in the BLSA region.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to semiconductor design technologies, and more particularly, to a bit line sense amplifier array for use-in a semiconductor memory device.  
       DESCRIPTION OF RELATED ART  
       [0002]     In a semiconductor memory device, there is a current trend to reduce power supply voltage due to continuous scaling down of line width and cell size. Hence, a need has existed for design technology to meet the performance required for low voltage environments.  
         [0003]     Most of semiconductor memory devices incorporate in a chip an internal voltage generation circuit that accepts an external voltage (power supply voltage) and generates an internal voltage. The memory devices allow the internal voltage generation circuits themselves to supply voltages required for operating circuits within the chip. Among them, in a memory device using a bit line sense amplifier, such as a Dynamic Random Access Memory (DRAM), a core voltage VCORE is employed to sense cell data.  
         [0004]     As the core voltage that is used for the DRAM operating voltage becomes low, there may be difficulty in amplifying a plurality of cell data for a short time.  
         [0005]     To solve such a problem, a bit line sense amplifier over driving method has been adopted for driving a pull-up power line of a bit line sense amplifier with a voltage (generally, power supply voltage VDD) higher than a core voltage VCORE for a prescribed time at an initial operation of the bit line sense amplifier, that is, after charge sharing between a memory cell and a bit line.  
         [0006]     Hereinafter, a conventional semiconductor memory device adopting such an over driving method will be described.  
         [0007]      FIG. 1  is a plan view of a conventional semiconductor memory device employing an over driving method.  
         [0008]     Referring to  FIG. 1 , the conventional semiconductor memory device is divided into a cell area and a sub-hall area among many areas. The cell area is typically a cell array including a Word Line (WL) and a Bit Line (BL). And, the sub-hall area is typically a bit line sense amplifier driver that drives a bit line sense amplifier array having a Sub WL Driver (SWD) for driving the WL and a plurality of unit bit line sense amplifiers for sensing and amplifying data carried on the BL, and pull-up and pull-down power lines of the bit line sense amplifiers.  
         [0009]      FIG. 2  is a circuit diagram of the bit line sense amplifier array depicted in  FIG. 1 .  
         [0010]     Referring to  FIG. 2 , the bit line sense amplifier array is provided with a plurality of unit bit line sense amplifiers  201  and  203 . In fact, there are a plurality of unit bit line sense amplifiers, but only two unit bit sense amplifiers are illustrated for convenience of explanation. In addition, bit line precharge portions  205  and  207  are further arranged to correspond to the unit bit line sense amplifiers  201  and  203  and precharge bit lines.  
         [0011]     Further, in order to control the bit line sense amplifier array, there are prepared in the sub-hall area a normal driver  213 , an over driver  211  and a pull-down driver  215  for driving power lines RTO and SB of the unit bit line sense amplifiers  201  and  203  by using the core voltage VCORE (normal driving voltage), the power supply voltage VDD (over driving voltage) and a ground voltage VSS. In  FIG. 2 , reference numeral  209  denotes a power line precharge portion for precharging the power lines RTO and SB of the unit bit line sense amplifiers  201  and  203 .  
         [0012]     More specifically, the normal driver  213  is driven by a normal driving signal SAP 2 , the over driver  211  is driven by an over driving signal SAP 1 , and the pull-down driver  215  is driven by a pull-down driving signal SAN.  
         [0013]     The unit bit line sense amplifiers  201  and  203  perform sensing operations by commonly using the pull-up power line RTO. These amplifiers conduct the over driving operation during a certain initial interval of a sensing operation interval and thereafter the normal driving operation, thereby improving sensing efficiency.  
         [0014]     In this process, however, the device for controlling the over driving operation is provided in the sub-hall area and shares its output (the normal driving voltage or over driving voltage). Therefore, the unit bit line sense amplifiers, which are relatively far from the sub-hall area having the over driver  211  and the normal driver  213 , perform the over driving operation and normal driving operation only with a voltage decreased by loading of their power lines. Thus, there may be differences between sensing speeds and sensing efficiencies.  
         [0015]     In addition, since the common node pull-up power line RTO is a sharing node between the plurality of unit bit line sense amplifiers  201  and  203  and thus weak in a mesh shape, there is a voltage drop resulting from power consumption in connecting the pull-up power line RTO and the power supply voltage VDD through the over driver  211  that generally utilizes a PMOS transistor for low power use.  
       SUMMARY OF THE INVENTION  
       [0016]     It is, therefore, an object of the present invention to provide a semiconductor memory device which receives a driving voltage of unit bit line sense amplifier supplied from any part therein but is capable of resolving an operational efficiency difference that occurs from a loading difference on a supply line.  
         [0017]     Another object of the present invention is to provide a semiconductor memory device allowing a plurality of unit bit line sense amplifiers to have the same over driving operation efficiency and normal driving operation efficiency.  
         [0018]     Still another object of the present invention is to provide a semiconductor memory device capable of solving a voltage drop problem by pull-up power lines (over driver and normal driver) that are weak in a mesh shape.  
         [0019]     In accordance with an aspect of the present invention, there is provided a semiconductor memory device, including a plurality of unit bit line sense amplifiers in a BLSA region, a pull-up power line and a pull-down power line used as power lines of the plurality of unit bit line sense amplifiers, a plurality of normal drivers connected to the pull-up power line at regular intervals in the BLSA region, and a plurality of over drivers connected to the pull-up power line at regular intervals in the BLSA region.  
         [0020]     In accordance with a further aspect of the present invention, there is provided a semiconductor memory device, including a cell region including a plurality of unit cell, a BLSA region including a plurality of bit line sense amplifiers, and a sub region including plural driving means, wherein the BLSA region includes a plurality of normal drivers for supplying a first operation voltage to the plurality of bit line sense amplifiers and a plurality of over drivers for supplying a second operation voltage to the plurality of bit line sense amplifiers. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0021]     The above and other objects and features of the instant invention will become apparent from the following description of preferred embodiments taken in conjunction with the accompanying drawings, in which:  
         [0022]      FIG. 1  is a plan view of a conventional semiconductor memory device;  
         [0023]      FIG. 2  is a circuit diagram of the bit line sense amplifier array shown in  FIG. 1 ;  
         [0024]      FIG. 3  is diagram of a bit line sense amplifier array in accordance with a preferred embodiment of the present invention;  
         [0025]      FIG. 4  is a detailed circuit diagram of the bit line sense amplifier array shown in  FIG. 3 ;  
         [0026]      FIG. 5  is a diagram of a circuit that implements the over drivers and the normal drivers implemented with PMOS transistors in  FIG. 4  with NMOS transistors; and  
         [0027]      FIGS. 6A and 6B  are diagrams of circuits that have the power line precharge portion in the X-hall area. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0028]     Hereinafter, preferred embodiments of the present invention will be set forth in detail with reference to the accompanying drawings to the extent that the invention can be readily carried out by those in the art to which the invention pertains.  
         [0029]      FIG. 3  is a diagram of a bit line sense amplifier array in accordance with a preferred embodiment of the present invention.  
         [0030]     Referring to  FIG. 3 , the bit line sense amplifier array  301  includes a plurality of unit bit line sense amplifiers  309  and  310 , a plurality of over drivers  303  and  305 , a plurality of normal drivers  304  and  306 , and a plurality of pull-down drivers  307  and  308  that are configured to correspond to the over drivers  303  and  305  and the normal drivers  304  and  306 . In fact, there are provided a plurality (or N-number) of unit bit sense amplifiers, but only the two bit line sense amplifiers prepared at both ends are illustrated for convenience of explanation. The location and number of each of the over drivers  303  and  305 , the normal drivers  304  and  306 , and the pull-down drivers  307  and  308  may be arranged to correspond to those of the unit bit line sense amplifiers  309  and  310 . That is, provided in the first unit bit line sense amplifier  309  are the first over driver  303  for over driving operation, the first normal driver  304  for normal driving operation, and the first pull-down driver  307  that are configured to correspond to the first over driver  303  and the first normal driver  304 .  
         [0031]     Further, the first over driver  303 , the first normal driver  304  and the first pull-down driver  307  may be arranged individually in the first unit bit line sense amplifier  309 . They may be also partially arranged within a range for which an efficiency difference does not occur due to loading difference of power line in transfer of over driving voltage (power supply voltage) and normal driving voltage (core voltage) for over driving and normal driving operations at far distance from the over driver  303  and the normal driver  304 .  
         [0032]     The normal drivers  304  and  306  are driven by a normal driving signal, the over drivers  303  and  305  are driven by an over driving signal, and the pull-down drivers  307  and  308  are driven by a pull-down driving signal.  
         [0033]     In order to control the bit line sense amplifier array  301  as above, there is provided in a sub-hall area  302  a power line precharge portion  311  for precharging a pull-up power line and a pull-down power line which are power lines of the array  301 .  
         [0034]     The following is a detailed explanation of the concept of the present invention as discussed above.  
         [0035]      FIG. 4  is a detailed circuit diagram of the bit line sense amplifier array shown in  FIG. 3 .  
         [0036]     With reference to  FIG. 4 , the bit line sense amplifier array is composed of a plurality of unit bit line sense amplifiers  401  and  403 , a plurality of over drivers  411   a  and  411   b,  a plurality of normal drivers  413   a  and  413   b,  and a plurality of pull-down drivers  415   a  and  415   b.  In addition, bit line precharge portions  405  and  407  are further arranged to correspond to the unit bit line sense amplifiers  401  and  403  and to precharge bit lines.  
         [0037]     As in  FIG. 3 , the location and number of each of the over drivers  411   a  and  411   b,  the normal drivers  413   a  and  413   b,  and the pull-down drivers  415   a  and  415   b  may be arranged to correspond to those of the unit bit line senses amplifiers  401  and  403 . Further, the over driver  411   a,  the normal driver  413   a  and the pull-down driver  415   a  may be provided individually in the unit bit line sense amplifier  401 . They may be also partially provided within the range that an efficiency difference does not occur due to loading difference of power line in transfer of over driving voltage (power supply voltage) and normal driving voltage (core voltage) for over driving and normal driving operations at far distance from the over driver  411   a  and the normal driver  413   a.    
         [0038]     To control the bit line sense amplifier array as above, there is prepared in the sub-hall area a power line precharge portion  409  for precharging power lines RTO and SB of the unit bit line sense amplifiers  401  and  403 .  
         [0039]     The normal drivers  413   a  and  413   b  are driven by a normal driving signal SAP 2 , the over drivers  411   a  and  411   b  are driven by an over driving signal SAP 1 , and the pull-down drivers  415   a  and  415   b  are driven by a pull-down driving signal SAN.  
         [0040]     Further, each of the over drivers  411   a  and  411   b  and the normal drivers  413   a  and  413   b  may be implemented with a PMOS transistor, and each of the pull-down drivers  415   a  and  415   b  may be implemented with an NMOS transistor. This is made by considering the characteristics between a gate input and a threshold voltage of each transistor.  
         [0041]     In the configuration, the present invention is provided with all or part of the over drivers  411   a  and  411   b,  the normal drivers  413   a  and  413   b  and the pull-down drivers  415   a  and  415   b  to correspond to the location and number of the unit bit line sense amplifiers  401  and  403 , while the prior art has the single over driver on one side of the unit bit line sense amplifiers  401  and  403 .  
         [0042]     In succession, an operation of the bit line sense amplifier array will be described below in detail.  
         [0043]     Data is first carried in the bit lines when they share charge with the memory cell, and the unit bit line sense amplifiers  401  and  403  are operated to amplify the data. At this time, the amplification operation of the unit bit line sense amplifiers  401  and  403  is made in such a way that the over driving signal SAP 1  is activated for over driving operation during an initial operation interval to drive the over drivers  411   a  and  411   b  and the normal driving signal SAP 2  is activated for normal driving operation during the subsequent intervals to drive the normal drivers  413   a  and  413   b.    
         [0044]     Further, the present invention can prevent a malfunctioning of the unit bit line sense amplifiers  401  and  403  since it includes the plurality of over drivers  411   a  and  411   b  and normal drivers  413   a  and  413   b  even when any of the over drivers  411   a  and  411   b  and any of the normal drivers  413   a  and  413   b  are not operated by issuance of any problem therein.  
         [0045]     Also, the present invention solves the existing voltage drop problem that can occur due to a weakness of the pull-up power line RTO driven by a single power source, that is, power supply voltage VDD, in the mesh shape. This is accomplished by allowing the pull-up power line RTO to use a plurality of power supply voltages by the plurality of the over drivers  411   a  and  411   b.  The normal drivers  413   a  and  413   b  are used in the same manner.  
         [0046]     The present invention is not limited to the embodiment as described above and the accompanying drawings and it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the technical aspect of the invention.  
         [0047]     For instance, it should be noted that the logic gates and transistors illustrated in the preferred embodiment as mentioned above may be implemented with different gate types and arrangements based on polarities of input and output signals used therein.  
         [0048]     Further, although the present invention is illustrated with respect to the case where the over drivers  411   a  and  411   b  and the normal drivers  413   a  and  413   b  are implemented with PMOS transistors, and the pull-down drivers  415   a  and  415   b  that are configured to correspond to the over drivers  411   a  and  411   b  and the normal drivers  413   a  and  413   b  are implemented with NMOS transistors in the above embodiment, this illustration is but one implementation example.  
         [0049]     Referring to  FIG. 5 , there is shown an example that implements the over drivers  501   a  and  501   b  and the normal drivers  503   a  and  503   b  implemented with PMOS transistors in  FIG. 4  with NMOS transistors.  
         [0050]     As such, in case where the over drivers  501   a  and  501   b  and the normal drivers  503   a  and  503   b  are implemented with NMOS transistors, the over drivers  501   a  and  501   b  should be driven by a higher voltage than the power supply voltage VDD by at least a threshold voltage and the normal drivers  503   a  and  503   b  should be driven by a higher voltage than the core voltage VCORE by at least a threshold voltage.  
         [0051]     As mentioned above, when the NMOS transistors are used, the power consumption of the semiconductor memory device is increased. In general, however, the use of the NMOS transistors can decrease the size of the semiconductor memory device because they are implemented by an area smaller than that of PMOS transistors. The result is obtained under the assumption that the PMOS transistors in which electrons are minority carriers have a small number of electrons existing per unit area compared to the NMOS transistors and thus acquire a same driving current.  
         [0052]      FIGS. 6A and 6B  are circuit diagrams showing examples that have the power line precharge portion in an X-hall area.  
         [0053]     The X-hall area herein is an area that corresponds to a row address pass and has an X decoder and a main word line driver, wherein one X-hall area is arranged per bank.  
         [0054]     That is, by arranging the power line precharge portion for precharging the power line of the unit bit line sense amplifier in the X-hall area as in  FIGS. 6A and 6B , it is possible to precharge the power lines of the plurality of unit bit line sense amplifiers in which one power line precharge portion is contained in one bank.  
         [0055]     Accordingly, a space restriction problem can be resolved by arranging one power line precharge portion per unit bit line sense amplifier.  
         [0056]     As set forth above, the present invention allows the unit bit line sense amplifiers to perform stable over driving and normal driving operations by preventing occurrence of over driving operation efficiency difference and normal driving operation efficiency difference therebetween, and also can improve the speed of the semiconductor memory device.  
         [0057]     Further, the present invention can prevent a malfunctioning of the unit bit line sense amplifiers since it includes the plurality of over drivers and normal drivers, even when any of the over drivers and any of the normal drivers are not operated.  
         [0058]     Moreover, the present invention can solve the voltage drop problem that occurs due to the pull-up power line that is weak in a mesh shape, thereby achieving reduction in power consumption.  
         [0059]     The present invention can accomplish reduction in area and power of the semiconductor memory device by implementing the over drivers and the normal drivers with PMOS or NMOS transistors.  
         [0060]     The present application contains subject matter related to the Korean patent applications Nos. KR 10-2005-0090856 and KR 10-2006-0049138, filed in the Korean Patent Office on Sep. 28, 2005 and on May 31, 2006, respectively, the entire contents of which being incorporated herein by references.  
         [0061]     While the present invention has been described with respect to certain specific 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.