Abstract:
The present invention relates to a column redundancy circuit for a semiconductor memory which can facilitate a high integration semiconductor circuit whose memory array is divided into a plurality of array units to be properly operated at a high frequency. The plurality of array units in the memory array include a plurality of normal memory cells and a plurality of redundancy memory cells. The redundancy data stored in the redundancy memory cells are outputted to a first main amplifier, and the normal data stored in the normal memory cells are outputted to a second main amplifier. A column redundancy unit outputs a redundancy enable signal according to a column address, a row address and a fuse short state. According to the logical state of the redundancy enable signal, the switch unit selects the redundancy data from the first main amplifier or the normal data from the second amplifier, and outputs it to a data output buffer.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a column redundancy circuit for a semiconductor memory, and in particular to a column redundancy circuit for a semiconductor memory which can facilitate a high integration semiconductor circuit whose memory array is divided into a plurality of array units to be properly operated at a high frequency, by selecting and outputting one of a normal data and a redundancy data which are outputted from the memory array, according to a row address and a column address. 
     2. Description of the Background Art 
     A column redundancy circuit using a column address and a redundancy circuit by inputs and outputs have been known as conventional column redundancy circuits. 
     FIG. 1 is a block diagram illustrating the conventional column redundancy circuit using the column address. 
     A clock buffer  1  buffers an external clock signal EX_CLK, and outputs it to a pulse width control unit  5 . An address buffer  2  buffers an external address EX_ADD, and outputs it to a column redundancy unit  4  and a column predecoder  6 . In a burst mode, an address counter  3  counts the buffered external address EX_ADD, and outputs an internal address IN_ADD to the column redundancy unit  4  and the column predecoder  6 . The column redundancy unit  4  determines whether to repair each memory array unit according to the external address EX_ADD and the internal address IN_ADD to be inputted to the column redundancy unit  4 , and outputs corresponding redundancy information RE_INF. 
     The pulse width control unit  5  serves to output to the column predecoder  6  the internal clock signal IN_CLK for determining a pulse width of a column selecting signal according to the buffered external clock signal EX_CLK, and to output to a column decoder  7  a redundancy clock signal CLK_RE_INF having the redundancy information RE_INF. 
     The column predecoder  6  enables a normal address path in a non-redundancy mode where a repair operation is not performed. To the contrary, the column predecoder  6  disables the normal address path in a redundancy mode where the repair operation is carried out, predecodes a column address Y_ADD from the address buffer  2 , and outputs it to the column decoder  7 . A pulse width of the predecoded column address Y_ADD is determined by the external clock signal EX_CLK. 
     The column decoder  7  determines whether to repair according to the redundancy clock signal CLK_RE_INF, and outputs a normal column selecting signal NYS or a redundancy column selecting signal RYS to a memory array  8 . That is, the column decoder  7  outputs the normal column selecting signal NYS in the non-redundancy mode, and outputs the redundancy column selecting signal RYS in the redundancy mode. Here, the normal column selecting signal NYS and the redundancy column selecting signal RYS are signals for selecting a sense amplifier (not shown) in the memory array  8 . 
     The memory array  8  consists of a plurality of normal memory cells and a plurality of redundancy memory cells. When the column decoder  7  outputs the normal column selecting signal NYS, the data stored in the normal memory cells of the memory array are read. In case the column decoder  7  outputs the redundancy column selecting signal RYS, the data stored in the redundancy memory cells of the memory array  8  are read. The data which have been read are inputted to a main amplifier  9  via an input/output line LIOT/B, amplified and outputted to an output buffer (not shown). 
     FIGS.  2   a  and  2   b  are timing views of the circuit in FIG.  1 . FIG.  2   a  is a timing view in the non-redundancy mode, and FIG.  2   b  is a timing view in the redundancy mode. As shown therein, in a state where the external clock signal EX_CLK is inputted, if a column address strobe signal CAS is inputted, the external address EX_ADD and the internal address IN_ADD are transited. When a first predetermined time t 1  lapses after the internal address IN_ADD is transited, the redundancy information RE_INF is at a high level, and the redundancy clock signal IN_CLK is also at a high level. As shown in FIG.  2   a , what the redundancy clock signal IN_CLK is at a high level implies that the column redundancy circuit is operated in the non-redundancy mode. In FIG.  2   b , what the redundancy clock signal IN_CLK is at a high level means that the column redundancy circuit is operated in the redundancy mode. 
     When a second predetermined time t 2  lapses after the first predetermined time t 1 , the normal column selecting signal NYS is enabled in the normal mode, as shown in FIG.  2   a , and the redundancy column selecting signal RYS is enabled in the redundancy mode, as depicted in FIG.  2   b.    
     The second predetermined time t 2  is a time taken to determine whether the column predecoder  6  and the column decoder  7  operate the column redundancy circuit in the normal mode or the redundancy mode, according to whether to repair, and is identical in the normal mode and the redundancy mode. 
     The second predetermined time t 2  is clearly longer than when the normal column selecting signal NYS is outputted without determining whether to repair. As the second predetermined time t 2  becomes longer, a whole processing speed of the column redundancy circuit is delayed. 
     In order to overcome such a disadvantage, there is provided the redundancy circuit by inputs and outputs. 
     FIG. 3 is a block diagram illustrating the conventional redundancy circuit by inputs and outputs. As shown therein, the clock buffer  1 , the address buffer  2  and the address counter  3  are identical in constitution and operation to those in FIG. 1. A pulse width control unit  31  outputs to a column predecoder  32  an internal clock signal IN_CLK for determining a pulse width of a column selecting signal according to a buffered external clock signal EX_CLK. An externally-inputted column address Y_ADD is inputted to a column decoder  33  via the address buffer  2  and the column predecoder  32 . The column decoder  33  outputs a column selecting signal YS to the memory array  34 . Here, the column address Y_ADD and the column selecting signal YS do not relate to a repair operation. The memory array  34  includes normal memory cells and redundancy memory cells. Each array is not divided into a plurality of array units, differently from the memory array  8  as illustrated in FIG.  1 . The data stored in the normal array cells are inputted to a main amplifier  35  through a normal input/output line NLIOT/B, and the data stored in the redundancy memory cells are inputted to the main amplifier  35  via a redundancy input/output line RLIOT/B. 
     The column redundancy unit  36  determines whether to repair the normal input/output line NLIOT/B and the redundancy input/output line RLIOT/B, and outputs redundancy information RE_INF to the main amplifier  35 . According to the redundancy information RE_INF, the main amplifier  35  amplifies and outputs one of the data inputted to the normal input/output line NLIOT/B and the redundancy input/output line RLIOT/B. 
     As described above, in the circuit as shown in FIG. 3, when the column selecting signal YS (identical to the normal column selecting signal NYS as shown in FIG. 1) is outputted to the memory array  34 , whether to repair is not determined, differently from the circuit as shown in FIG.  1 . Accordingly, an extra time to determine whether to repair is not necessary. As a result, the circuit in FIG. 3 is faster in operation than the circuit in FIG.  1 . However, the memory array is not divided, and thus redundancy efficiency is reduced. In addition, as the memory array is divided into a plurality of array units, and thus the number of the array units is increased, a load of the redundancy input/output line RLIOT/B is also increased. Accordingly, in order to employ such a circuit, the number of the array units must be limited. Thus, it is not suitable for a high integration circuit where the memory array is divided into many array units. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to provide a column redundancy circuit for a semiconductor memory which can improve an operational speed of a high integration semiconductor circuit whose memory array is divided into a plurality of memory array units. 
     In order to achieve the above-described object of the present invention, there is provided a column redundancy circuit for a semiconductor memory including: a memory array consisting of a plurality of array units respectively having a plurality of normal memory cells and a plurality of redundancy memory cells, each array unit outputting a normal data stored in the normal memory cell, and outputting a redundancy data stored in the redundancy memory cell; a first main amplifier amplifying the redundancy data; a second main amplifier amplifying the normal data; a column redundancy unit outputting a redundancy enable signal according to a column address, a row address and a fuse short state; and a switch unit selecting and outputting one of the redundancy data amplified in the first main amplifier or the normal data amplified in the second main amplifier. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will become better understood with reference to the accompanying drawings which are given only by way of illustration and thus are not limitative of the present invention, wherein: 
     FIG. 1 is a block diagram illustrating a conventional column redundancy circuit employing a column address of a semiconductor memory; 
     FIGS.  2   a  and  2   b  are timing views of the circuit in FIG. 1, wherein: 
     FIG.  2   a  is a timing view in a non-redundancy mode; and 
     FIG.  2   b  is a timing view in a redundancy mode; 
     FIG. 3 is a block diagram illustrating a conventional redundancy circuit by inputs and outputs of the semiconductor memory; 
     FIG. 4 is a block diagram illustrating a column redundancy circuit employing a column address of a semiconductor memory in accordance with a preferable embodiment of the present invention; 
     FIG. 5 is a detailed structure view illustrating a memory array, first and second main amplifiers and a switch unit in the configuration of FIG. 4; 
     FIG. 6 is a detailed circuit view illustrating a column redundancy unit in the configuration of FIG. 4; and 
     FIGS.  7   a  and  7   b  are timing views of the circuit in FIG. 4, wherein: 
     FIG.  7   a  is a timing view in a non-redundancy mode; and 
     FIG.  7   b  is a timing view in a redundancy mode. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A column redundancy circuit for a semiconductor memory in accordance with the present invention will now be described with reference to the accompanying drawings. 
     FIG. 4 is a block diagram illustrating the column redundancy circuit using a column address of the semiconductor memory in accordance with a preferable embodiment of the present invention. A clock buffer  1 , an address buffer  2  and an address counter  3  as shown in FIG. 4 are identical in constitution and operation to those as shown in FIG. 1, and thus explanation thereof is omitted. 
     A pulse width control unit  41  outputs an internal clock signal IN_CLK for controlling a pulse width of a column selecting signal to a column predecoder  42  and a column decoder  43  according to an external clock signal EX_CLK buffered in the clock buffer  1 . A column decoder  43  receives a predecoded column address and the internal clock signal IN_CLK, and outputs a normal column selecting signal NYS and a redundancy column selecting signal RYS to a memory array  44 , regardless of whether to repair. 
     The memory array  44  includes a plurality of normal memory cells and a plurality of redundancy memory cells. In more detail, referring to FIG. 5, the memory array  44  consists of a plurality of array units  441 - 446 . Each array unit  441 - 446  includes the plurality of normal memory cells and the plurality of redundancy memory cells (not shown). In addition, each array unit  441 - 446  is connected to local normal input/output lines LIO_N and local redundancy input/output lines LIO_R. The plurality of normal input/output lines LIO_N are connected to a global normal input/output line GIO_N, and the plurality of local redundancy input/output line LIO_R are connected to a global redundancy input/output line GIO_R. 
     The redundancy data stored in the redundancy memory cells by the redundancy column selecting signal RYS from the column decoder  43  are outputted to a first main amplifier  46  through the local redundancy input/output line LIO/R and the global redundancy input/output line GIO_R. The normal data stored in the normal memory cells by the normal column selecting signal NYS from the column decoder  43  are outputted to a second main amplifier  47  through the local redundancy input/output line LIO/N and the global redundancy input/output line GIO_N. 
     The first main amplifier  46  amplifies the inputted redundancy data, and outputs it to a switch unit  48 , and the second main amplifier  47  amplifies the inputted normal data, and outputs it to the switch unit  48 . The first main amplifier  46  includes four amp units MR 1 -MR 4  which are connected to the global redundancy input/output line GIO_R, respectively. The second main amplifier  47  includes four amp units MN 1 -MN 4  which are connected to the global normal input/output line GIO_N. 
     A column redundancy unit  45  receives the external address and the internal address, determines whether to repair, and outputs a redundancy enable signal EN_RE to the switch unit  48 . In more detail, referring to FIG. 6, the column redundancy unit  45  includes a plurality of enable units  450 - 457  outputting a column address true signal Y_ADDT or a column address bar signal Y_ADDB according to row addresses X_ADD 0 , X_ADD 1  and fuse states F 0 , F 1 ; and a combination unit  460  combining signals outputted from the plurality of enable units  450 - 457 , and outputting the redundancy enable signal EN_RE to the switch unit  48 . 
     The number of the plurality of enable units  450 - 457  is identical to that of the column addresses. A first enable unit  450  includes: a NAND gate N 61  receiving a read/write enable signal R/W at its one-side input terminal; a plurality of fuses F 0 , F 1 ; a plurality of switching transistors N 1 , N 2  having their gate connected to receive row addresses X_ADD 0 , X_ADD 1 , and being connected to the other input terminal of the NAND gate N 61  through the fuses F 0 , F 1 ; and two transmission gates T 1 , T 2 . On the other hand, FIG. 6 illustrates two fuses F 0 , F 1  and two switching transistors N 1 , N 2  for convenience. However, the entire number thereof is identical to the number of the row addresses. 
     The two transmission gates T 1 , T 2  are turned on/off according to a level of an output signal from the NAND gate N 61  and a level of the other side input terminal thereof. A first column address true signal Y_ADD 0 T is passed through the first transmission gate T 1 , and a first column address bar signal Y_ADD 0 B is passed through the second transmission gate T 2 . The first transmission gate T 1  and the second transmission gate T 2  have a complementary relationship. That is, when the first column address true signal Y_ADD 0 T is passed, the first column address bar signal Y_ADD 0 B is interrupted. Also, in case the first column address bar signal Y_ADD 0 B is passed, the first column address true signal Y_ADD 0 T is interrupted. The other enable units  451 - 457  are identical in constitution to the first enable unit  450 . However, each enable unit  451 - 457  outputs different address signals. For instance, the second enable unit  451  selectively outputs a second column address true signal Y_ADD 1 T or a second column address bar signal Y_ADD 1 B. 
     The operation of the first enable unit  450  will now be explained. It is presumed that the read/write enable signal R/W is enabled, that is the input terminal at the one side of the first NAND gate N 61  is at a high level. 
     The plurality of row addresses X_ADD 0 , X_ADD 1  which are inputted from the address buffer  2  are sequentially coded. After a first row address X_ADD 0  is coded, a second row address X_ADD 1  is coded. In case the first row address X_ADD 0  is coded, the first switching transistor N 1  is turned on. In this state, if the first fuse F 0  is disconnected, the terminal at the other side of the first NAND gate N 61  is at a high level. To the contrary, if the first fuse F 0  is connected, the terminal at the other side of the first NAND gate N 61  is at a low level. 
     In the case that the first fuse F 0  is disconnected, namely when it is presumed that the terminal at the other side of the NAND gate N 61  is at a high level, the NAND gate N 61  outputs a low-level signal. As a result, the first transmission gate T 1  is turned on, and thus the column address true signal Y_ADD 0 T is passed therethrough. To the contrary, when the first fuse F 0  is not disconnected, namely when the terminal at the other side of the NAND gate NAND 61  is at a low level, the first transmission gate T 1  is turned off, the second transmission gate T 2  is turned on, and thus the column address bar signal Y_ADD 0 B is passed therethrough. 
     As described above, the first enable unit  450  outputs the first column address true signal Y_ADD 0 T or the first column address bar signal Y_ADD 0 B according to whether the fuse is connected or disconnected. 
     In addition, the second enable unit  451  outputs the second column address true signal Y_ADD 1 T or the second column address bar signal Y_ADD 1 B according to a fuse (not shown) is connected or disconnected. 
     The eight enable units  450 - 457  respectively selectively output the first to eighth column address true signals Y_ADD 0 T or the first to eighth column address bar signals Y_ADD 0 B according to the first address signal X_ADD 0  to be coded. 
     When the column address true signals Y_ADD 0 T-Y_ADD 7 T or the column address bar signals Y_ADD 0 B-Y_ADD 7 B outputted from the plurality of enable units  450 - 457  are all at a high level, the combination unit  460  outputs the redundancy enable signal EN_RE having a high level to the switch unit  46 . For this, the combination unit  460  includes: NAND gates N 62 , N 63 , N 64  NANDing a predetermined number of output signals among the output signals from the enable units  450 - 457 , respectively; a NOR gate NOR 6  NORing output signals from the NAND gates N 62 , N 63 , N 64 ; and two inverters I 61 , I 62  buffering a level of the output signal from the NOR gate NOR 6 , and outputting the redundancy enable signal EN_RE. 
     The signals outputted from the first to third enable units  450 - 452  are NANDed in the second NAND gate N 62 . The signals outputted from the fourth to sixth enable units  453 - 455  are NANDed in the third NAND gate N 63 , and the signals outputted from the seventh and eight enable units  456 ,  457  are NANDed in the fourth NAND gate N 64 . On the other hand, according to the present invention, the address signals respectively outputted from the eight enable units  450 - 457  are NANDED in the three NAND gates N 62 -N 64 . However, the number of the NAND gates may be changed, if necessary. 
     The signals outputted from the second to fourth NAND gates N 62 -N 64  are combined in the NOR gate NOR 6 , and the levels thereof are converted in the two inverters I 61 , I 62 . Accordingly, the signals are outputted to the switch unit  48  as the redundancy enable signal EN_RE. As described above, the combination unit  460  outputs the redundancy enable signal EN_RE at a high level when the eight address signals are all at a high level, and outputs the redundancy enable signal EN_RE at a low level when any of the eight address signals is at a low level. 
     The switch unit  48  is enabled by the read/write enable signal R/W, and outputs the redundancy data amplified in the first main amplifier  46  to a data output buffer  49 , or outputs the normal data amplified in the second main amplifier  47  to the data output buffer  49 , according to the redundancy enable signal EN_RE. For this, as depicted in FIG. 5, the switch unit  48  includes: a buffer unit  470  having a NAND gate N 7 , a NOR gate NOR 7  and four inverters I 71 -I 74 , and outputting a redundancy switching signal ENR and a normal switching signal ENN; a plurality of redundancy switches SWR 1 -SWR 4 ; and a plurality of normal switches SWN 1 -SWN 4 . 
     The plurality of redundancy switches SWR 1 -SWR 4  are connected to the four amp units MR 1 -MR 4  of the first main amplifier  46 , switched by the redundancy switching signal ENR, and thus output the normal data amplified in the four amp units MR 1 -MR 4  to the data output buffer  49 . The plurality of normal switches SWN 1 -SWN 4  are connected to the four amp units MN 1 -MN 4  of the second main amplifier  47 , switched by the normal switching signal ENN, and thus output the redundancy data amplified in the four amp units MN 1 -MN 4  to the data output buffer  49 . 
     The read/write enable signal R/W and the redundancy enable signal EN_RE from the column redundancy unit  45  are NANDed in the NAND gate N 7  of the buffer unit  470 . The NANDed signal is buffered in the first and second inverters I 71 , I 72 , and outputted as the redundancy switching signal ENR. In addition, the read/write enable signal R/W is inverted in the third inverter I 73 , and NORed with the redundancy enable signal EN_RE in the NOR gate NOR 7 . The output signal from the NOR gate NOR 7  is inverted in the fourth inverter I 74 , and outputted as the normal switching signal ENN. 
     When the redundancy enable signal EN_RE is at a low level, the redundancy switching signal ENR becomes a high level, thereby electrically connecting the plurality of redundancy switches SWR 1 -SWR 4 . Accordingly, the redundancy data from the first main amplifier  46  is outputted to the data output buffer  49 . The normal switching signal ENN becomes a low level, and thus the plurality of normal switches SWN 1 -SWN 4  are interrupted. As a result, the normal data from the second main amplifier  47  is not transmitted to the data output buffer  49 . To the contrary, when the redundancy enable signal EN_RE is at a high level, the plurality of normal switches SWN 1 -SWN 4  are electrically connected, thereby transmitting the normal data to the data output buffer  49 . 
     FIGS.  7   a  and  7   b  are timing views of the circuit in FIG.  4 . FIG.  7   a  is a timing view in a non-redundancy mode, and FIG.  7   b  is a timing view in a redundancy mode. Referring to FIGS.  7   a  and  7   b , the points that the external address EX_ADD and the internal address IN_ADD are transited are identical as shown in FIGS.  2   a  and  2   b . However, referring to FIGS.  2   a  and  2   b , the redundancy clock signal IN_CLK becomes a high level when a first predetermined time t 1  lapses after the internal address IN_ADD is transited. According to the preferable embodiment of the present invention, as depicted in FIGS.  7   a  and  7   b , the redundancy clock signal IN_CLK becomes a high level as soon as the internal address IN_ADD is transited. In the conventional art, the normal column selecting signal NYS and the redundancy column selecting signal RYS are outputted when the first predetermined time t 1  and the second predetermined time t 2  lapse after the internal address IN_ADD is transited. However, in accordance with the preferable embodiment of the present invention, the normal column selecting signal NYS and the redundancy column selecting signal RYS are outputted when the second predetermined time t 2  lapses after the internal address IN_ADD is transited. Accordingly, the present invention reduces by the time from an internal address transition point to an output point of the redundancy clock signal having the redundancy information (the first predetermined time t 1 ). 
     As discussed earlier, the column redundancy circuit in accordance with the present invention can improve speed by switching the data outputted from the memory array according to the redundancy information. In addition, in the normal mode, the normal data outputted from the memory array is amplified in the main amplifier, and in the redundancy mode, the redundancy data outputted from the memory array is amplified in the main amplifier. As a result, the present invention can be applied even when a load of the input/output line is high. Furthermore, the present invention can be also applied to a high integration semiconductor memory circuit. 
     As the present invention may be embodied in several forms without departing from the spirit or essential characteristics thereof, it should also be understood that the above-described embodiment is not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be construed broadly within its spirit and scope as defined in the appended claims, and therefore all changes and modifications that fall within the meets and bounds of the claims, or equivalences of such meets and bounds are therefore intended to be embraced by the appended claims.