Abstract:
A data output circuit includes a plurality of registers and a plurality of register output selection switches that are respectively connected to the plurality of registers. Pairs of the plurality of register output selection switches are connected by respective common active regions. A first data group selection switch is connected to the common active regions of a first set of the plurality of register output selection switches. A second data group selection switch is connected to the common active regions of a second subset of the plurality of register output selection switches. An output driver is connected to the first and second data group selection switches.

Description:
RELATED APPLICATION 
   This application claims the benefit of Korean Patent Application No. 2002-45287, filed Jul. 31, 2002, the disclosure of which is hereby incorporated herein by reference. 
   FIELD OF THE INVENTION 
   The present invention relates to integrated circuit memory devices, and, more particularly, to data output circuits for synchronous integrated circuit memory devices. 
   BACKGROUND OF THE INVENTION 
   In conventional integrated circuit memory devices, various kinds of pipeline structures have been used to increase the speed in a column output path. One example of such a pipeline structure is a wave pipeline structure in which a plurality of registers is used. The wave pipeline structure has a relatively simple circuit construction and operates at relatively high speed. As a result, wave pipeline structures are often used in synchronous integrated circuit memory devices. 
     FIG. 1  is a block diagram that illustrates a data output path in a conventional synchronous integrated circuit memory device and also illustrates a column output path in a read operation mode. Referring now to  FIG. 1 , a read command is input to the synchronous integrated circuit memory device. Next, memory cell data, which is respectively output through bit line sense amplifiers  2 ,  3 ,  4 ,  5 , is provided to a corresponding local input/output line (LI 0 i: i ranging from 1 to 3) through each corresponding column selection transistor M 1 –M 4  that respectively respond to column selection signals CSL 0 –CSL 3  applied from a column address decoder (not shown). input/output sense amplifiers  6 ,  7 ,  8 ,  9  are respectively connected to the local input/output lines L 100 –L 103  and are configured to amplify data provided to the local input/output lines L 100 –L 103  and apply the amplified data to a multiplexer  10  connected to a global input/output line. 
   The multiplexer  10  multiplexes the data output from the input/output sense amplifiers  6 ,  7 ,  8 ,  9 , and applies the data to a data output multiplexer  100 . The data is transferred from the multiplexer  10  through one switch selected among a plurality of data line switches SF 1 –SF 16  within the data output multiplexer  100 . The data line switches SF 1 –SF 16  are activated in response to a data line selection signal applied through data line selection signal lines DL 0 –DL 3  and apply output data from the multiplexer  10  to a corresponding register. The output data respectively stored at the first through nth registers  101 – 116  are provided to input terminals of a plurality of register output selection switches S 1 –S 16 . When one of the register output selection switches S 1 –S 16  is switched on by a switching selection signal, the data is provided onto a multiplexing output line. 
   The switching selection signals (CDQ 0 _F-CDQ 7 _F, CDQ 0 _S-CDQ 7 _S) are provided to the register output selection switches S 1 –S 16  according to the timing diagram of  FIG. 2 . The switching selection signals (CDQ 0 _F-CDQ 7 _F) are generated in response to a first edge (a rising edge or a falling edge) of a clock signal CLK shown in  FIG. 2 . The switching selection signals (CDQ 0 _S-CDQ 7 _S) are generated in response to a second edge (a falling edge or a rising edge) of the clock CLK.  FIG. 2  further illustrates a data output operation of the integrated circuit memory device of  FIG. 1 . Data (DOFi, DOSi) respectively representing the data on two multiplexing output lines are individually applied to input terminals of first and second data group selection switches SW 1 , SW 2 . When one of the first and second data group selection switches SW 1 , SW 2  is switched on in response to group selection output switching signals (CLKDQ_F, CLKDQ_S) that are applied complementarily to one another, output data DOUT, which is synchronized to a clock, is output through an output pin PD 1  connected to an output terminal of an output driver  30  as shown in  FIG. 2 . 
   As described above with respect to  FIGS. 1 and 2 , a function of the data output multiplexer  100  is to provide a double data rate DDB output operation. The data output circuit comprises the data output multiplexer  100  together with the first and second data group selection switches SW 1 , SW 2  and the output driver  30 . The data output multiplexer  100  is used to ensure a high-speed data output operation of about 500 MHz to reduce data skew and junction loading and/or wiring loading. 
   A conventional double data rate data output multiplexer  100  may have a wave pipeline structure as discussed above, but there is room for improvement in the art. Referring now to  FIG. 3 , switches S 1 –S 4  are connected to the multiplexing output line DOFi. Each of the switches S 1 –S 4  may comprise a CMOS transmission gate, but is illustrated herein as one MOS transistor for convenience.  FIG. 3  also illustrates various signal lines coupled to the gate G, source S and drain D regions. As shown in  FIG. 3 , the multiplexing output line DOFi has four junction portions. Thus, the multiplexing output line DOFi within the data output multiplexer  100  of  FIG. 1  has eight junction portions (eight switches S 1  through S 8 ). Because the junction loading on the multiplexing output lines DOFi and DOSi is relatively large, a data output time may be delayed. 
     FIG. 4  schematically shows lengths of wire lines (L 1 , L 2 , L 3 , and L 4 ) that are disposed before/after the plurality of register output selection switches S 1 –S 8  and the multiplexing output line L 3 . Referring now to  FIG. 4 , a length (D 2   a ) of the wire line L 2  is longer than a length (D 1   a ) of the wire line L 1 , and a length (D 3   a ) of the wire line L 3  is also relatively long. In general, if a length of the wire line L 2 , which is made of metal, is relatively long, then a wire loading is concentrated onto a multiplexing output node and a data output may be delayed. 
     FIG. 5  shows a disposition relation between the plurality of register output selection switches S 1 –S 16  and the first and second data group selection switches SW 1 , SW 2 . Wiring lengths of the multiplexing output lines DOFi, DOSi are different from each other. That is to say, a data output path PA 1  passing through a first register  101 , a data output path PA 2  passing through an eighth register  108 , and a data output path PA 3  passing through an nth register  116 , are all different from one another. Thus, data skew may occur. 
     FIGS. 6 and 7  respectively show a connection relation of the overlap prevention control signal lines CL 1 –CL 5  for respectively providing complementary switching selection signals, which are applied to the register output selection switches S 1 –S 16 . For example, when the switch S 1  of  FIG. 6  is switched on, the switch S 16  is switched off, and when the switch S 2  is switched on, the switch S 15  is switched off so as to prevent an overlap of data. If switch S 1  is switched on by a high signal, a low signal inverted from the high signal is applied to the switch S 16 . The low signal functions as an overlap prevention control signal. 
   As shown in  FIG. 6 , a considerable difference in length exists between the overlap prevention control signal line CL 1  and the overlap prevention control signal line CL 3 . Further, as shown in  FIG. 7 , only the overlap prevention control signal line CL 1  is longer than other overlap prevention control signal lines CL 2 , CL 3 , CL 4 , CL 5 . Therefore, if the overlap prevention control signal lines have different lengths, a path difference may cause a multiplexing overlap of output data. 
   SUMMARY OF THE INVENTION 
   In accordance with some embodiments of the present invention, a data output circuit comprises a plurality of registers and a plurality of register output selection switches that are respectively connected to the plurality of registers. Pairs of the plurality of register output selection switches are connected by respective common active regions. A first data group selection switch is connected to the common active regions of a first set of the plurality of register output selection switches. A second data group selection switch is connected to the common active regions of a second subset of the plurality of register output selection switches. An output driver is connected to the first and second data group selection switches. 
   In other embodiments, the plurality of register output selection switches comprises a plurality of CMOS transmission gates, respectively. 
   In further embodiments, a data output circuit comprises a plurality of registers and a plurality of register output selection switches that are respectively connected to the plurality of registers via a plurality of first wires having first lengths. A data group selection switch is connected to the plurality of register output selection switches by a plurality of second wires having second lengths that are shorter than the first lengths. An output driver is connected to the data group selection switch. 
   In still further embodiments, a data output circuit comprises a plurality of registers and a plurality of register output selection switches respectively connected to the plurality of registers. A first data group selection switch is connected to a first subset of the plurality of register output selection switches via a first line having a first length. A second data group selection switch that is connected to a second subset of the plurality of register output selection switches via a second line having a second length that is approximately equal to the first length. An output driver is connected to the first and second data group selection switches. 
   In still further embodiments, a data output circuit comprises a plurality of registers and a plurality of register output selection switches respectively connected to the plurality of registers and arranged in a circular configuration. Respective ones of a plurality of overlap prevention control signal lines are connected to pairs of the plurality of register output selection switches. A data group selection switch is connected to the plurality of register output selection switches. An output driver is connected to the data group selection switch. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other features of the present invention will be more readily understood from the following detailed description of specific embodiments thereof when read in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a block diagram that illustrates a data output circuit in a conventional synchronous integrated circuit memory device; 
       FIG. 2  is a timing diagram of a data output operation of the data output circuit of  FIG. 1 ; 
       FIG. 3  is a schematic that illustrates register output selection switches of  FIG. 1 ; 
       FIG. 4  is schematic that illustrates register output selection switches and a data group selection switch of  FIG. 1 ; 
       FIG. 5  is a schematic that illustrates the wiring of the register output selection switches and data group selection switches of  FIG. 1 ; 
       FIGS. 6 and 7  are schematics that illustrate overlap prevention control signal lines for the data output circuit of  FIG. 1 ; 
       FIGS. 8 and 9  are schematics that illustrate register output selection switches for a data output circuit in accordance with some embodiments of the present invention; 
       FIG. 10  is a schematic that illustrates the wiring of register output selection switches and a data group selection switch in accordance with some embodiments of the present invention; 
       FIG. 11  is a schematic that illustrates the wiring of register output selection switches and data group selection switches in accordance with some embodiments of the present invention; and 
       FIGS. 12 and 13  are schematics that illustrate overlap prevention control signal lines for a data output circuit in accordance with some embodiments of the present invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit the invention to the particular forms disclosed, but on the contrary, the invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the claims. Like numbers refer to like elements throughout the description of the figures. It will also be understood that when an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly connected” or “directly coupled” to another element, there are no intervening elements present. 
   In accordance with various embodiments of the present invention, a data output circuit for use in a synchronous integrated circuit memory device having a wave pipeline data output multiplexer structure will now be described. 
   Referring now to  FIGS. 8 and 9 , a connection configuration between a multiplexing output line DOFi and switches S 1 –S 4  of the plurality of register output selection switches S 1 –S 16 , which may reduce junction loading is illustrated. As shown in  FIG. 8 , active regions S for mutually adjacent register output selection switches S 1 , S 2  are formed in common. Therefore, the multiplexing output line DOFi shown in  FIG. 8  has two junction portions. The multiplexing output line DOFi within the data output multiplexer  100  of  FIG. 1  would have four junction portions because of the eight switches S 1  through S 8 . Thus, the junction loading on the multiplexing output lines DOFi, DOSi may be reduced by half. 
     FIG. 9  shows that a drain terminal D is coupled to a voltage source VDD or a ground voltage VSS, a source terminal is used in common, and output data from a register and a switching selection signal CDQX_F are AND-gated and applied to a gate terminal G. Again, the multiplexing output line DOFi shown in  FIG. 8  has two junction portions. Thus, the junction loading on the multiplexing output lines DOFi, DOSi may be reduced by half. In accordance with some embodiments of the present invention, the register output selection switches may comprise CMOS transmission gates, respectively. 
   That is, when the output part active regions S for mutually adjacent register output selection switches S 1 , S 2  are formed in common, the output terminals for two register output selection switches are connected to the multiplexing output line through a single line. Thus, the junction loading of the multiplexing output line that is connected in common with lines connected with the output terminals of the register output selection switches is reduced. 
     FIG. 10  illustrates a disposition of the wire lines to reduce wire loading in accordance with some embodiments of the present invention. Referring now to  FIG. 10 , wires having lengths L 11 , L 22 , L 33 , and L 44  are disposed before/after a plurality of register output selection switches S 1 –S 8 . A length D 2  of the wire line L 22  is shorter than a length D 1  of the wire line L 11 , and a length D 3  of the wire line L 33  is relatively short compared to the length L 11 . Therefore, when the length of the wire line L 22  and L 33  is shorter than the length of wire line L 11 , wire loading at the multiplexing output node may be reduced and data output delay may also be reduced. Note that the distance between the plurality of register output selection switches S 1  through S 8  is presumed to be significantly less than the length of the wires L 11 , L 22 , L 33 , and L 44 . 
   Thus, in accordance with some embodiments of the present invention, the lengths of lines connected to output terminals of the register output selection switches are shorter than the lengths of lines connected to input terminals of the register output selection switches. As a result, wire loading of the multiplexing output line, which is coupled in common with the lines that are connected to the output terminals of the register output selection switches within the data output multiplexer, may be reduced. 
     FIG. 11  illustrates a disposition of the wire lines to reduce skew between output data in accordance with some embodiments of the present invention. As shown in  FIG. 11 , the wiring lengths of the multiplexing output lines DOFi, DOSi are equal and all of the data output path PA 11  passing through a first register  101 , the data output path PA 22  passing through an eighth register  108 , and a data output path PA 33  passing through an nth register  116  are equal in the length. Thus, the first and second data group selection switches SW 1 , SW 2  are disposed near a center of the lines connected to the output terminals of the register output selection switches. The lengths of the first and second multiplexing output lines, which connect the register output selection switches S 1  through S 16  with the first and second data group selection switches SW 1  and SW 2 , are almost the same. As a result, skew between output data respectively output through the lines that are connected to the output terminals of the register output selection switches within the data output multiplexer may be reduced. 
     FIGS. 12 and 13  illustrate a disposition of the register output selection switches S 1  through S 16  to reduce multiplexing overlap of output data in accordance with some embodiments of the present invention. Referring now to  FIG. 12 , the register output selection switches S 1 –S 16  are disposed in a wrap-around configuration. Referring now to  FIG. 13 , most of the overlap prevention control signal lines are individually connected between switches having one switch therebetween. As a result, lengths of the control signal lines are about equal so as to prevent a multiplexing overlap of data. In  FIG. 13 , for example, when switch S 1  is switched on, switch S 16  is switched off, and when switch S 16  is switched on, switch S 8  is switched off As shown in  FIG. 13 , lengths of all wires except the overlap prevention control signal lines CL 8  and CL 16  are about the same. 
   By arranging the register output selection switches in a wrap-around configuration, most of the overlap prevention control signal lines connect two of the switches with one switch in between. As a result, most of the overlap prevention control signal lines have about the same wiring length. As a result, a skew between output data individually output through lines that are connected to the output terminals of the register output selection switches within the data output multiplexer may be reduced, and a path difference between various ones of the overlap prevention control signal lines may be reduced so as to avoid a multiplexing overlap of the output data. 
   Thus, in accordance with various embodiments of the present invention, junction loading, wire loading, data skew, and data overlap may be reduced. As a result, a data output circuit in an integrated circuit memory device may operate at higher speeds. 
   In concluding the detailed description, it should be noted that many variations and modifications can be made to the preferred embodiments without substantially departing from the principles of the present invention. All such variations and modifications are intended to be included herein within the scope of the present invention, as set forth in the following claims.