Abstract:
Provided is directed to a negative word line driver, including: a block select address generation unit for generating first and second block select addresses having a block information according to an active signal; a row decoder controller for generating a control signal to disable a word line; a main word line driver for accessing a main word line by being driven in response to a signal coding the first block select address and the control signal; and a phi X driver for accessing a sub word line by being driven in response to a signal coding the second block select address and the control signal wloff.

Description:
This application relies for priority upon Korean Patent Application No. 2003-0091647 filed on Dec. 15, 2003, the contents of which are herein incorporated by reference in their entirety. 
   BACKGROUND 
   1. Field of the Invention 
   The present invention relates to a semiconductor memory device, and more particularly to, a negative word line driver in a semiconductor memory device. 
   2. Discussion of Related Art 
   The negative word line driver supplies VPP to a word line when enabling the word line, while supplying a voltage (hereinafter, denoted with VBBW) lower than VSS to a word line when disabling the word line. 
   As using this negative word line driving method, a refresh characteristic is improved as well as other AC parameters are. Especially, it increases a refresh time and decreases a VPP burden while using a low Vcc. Moreover, the negative word line driving method is employed in order to improve a write recovery time TWR. 
   It will be described about a negative word line driving method of conventional art in  FIG. 1  with reference to  FIGS. 1 to 4 . 
   Referring to  FIG. 1 , a block select address Bax having a block information is generated from a select address generation unit  10  according to an active signal. As a main word line driver  40  is driven by block select addresses Bax 3 – 12 , a main word line mwl is selected. On the other hand, a phi X driver  30  is driven by block select addresses Bax 0 ,  1 ,  2 , and a sub word line driver  50  is driven by outputs fx, fxb of the phi X driver  30 , to select a sub word line swl. 
   A row decoder controller  20  generates a precharge signal Xpcg for disabling a word line. The precharge signal Xpcg controls the phi X driver  30  and the main word line  40 . That is, enabling a word line is performed in response to the block select address Bax, while disabling a word line is performed in response to the precharge signal Xpcg. 
     FIG. 2  is a detailed circuit diagram illustrating a row decoder controller of  FIG. 1 . 
   A NAND gate G 1  combines a reverse signal of a signal R 2 ACB deciding a precharging timing and a block select enable signal BS, and then the output signal of the NAND gate G 1  passes through inverters I 1  to I 3 . Accordingly, an output of the inverter I 3  becomes the precharge signal Xpcg. 
     FIG. 3  is a detailed circuit diagram illustrating a main word line driver of  FIG. 1 . 
   Signals Bax 34 &lt; 0 : 3 &gt; which have predecoded a block select address Bax 34  are applied to gates of NMOS transistors Q 1 , Q 2 , Q 3 , Q 4  and each source of the NMOS transistors Q 1 , Q 2 , Q 3 , Q 4  is connected to a common node com. 
   One of signals Bax 56 &lt; 0 : 3 &gt; which have predecoded a block select address Bax 56  is applied to a gate of NMOS transistor Q 9  and one of signals Bax 78 &lt; 0 : 3 &gt; which have predecoded a block select address Bax 78  is applied to a gate of NMOS transistor Q 10 . As a result, the NMOS transistors Q 9 , Q 10  are turned on or off thereto. In condition that the NMOS transistors Q 9 , Q 10  are turned on, When the NMOS transistor Q 1  is turned on according to the predecoded signal Bax 34 &lt; 0 &gt;, a potential of node N 1  becomes VBBW level. As the same to it, when the NMOS transistor Q 2  is turned on according to the predecoded signal Bax 34 &lt; 1 &gt;, a potential of node N 2  becomes VBBW level. When the NMOS transistor Q 3  is turned on according to the predecoded signal Bax 34 &lt; 2 &gt;, a potential of node N 3  becomes VBBW level. Additionally, when the NMOS transistor Q 4  is turned on according to the predecoded signal Bax 34 &lt; 3 &gt;, a potential of node N 4  becomes VBBW level. 
   On the other hand, when the precharge signal Xpcg is enabled, a signal predecoding a block select address is disabled, which results in that the NMOS transistors Q 1  to Q 4  are turned off and PMOS transistors Q 5 , Q 6 , Q 7 , Q 8  are turned on. Accordingly, the nodes N 1 , N 2 , N 3 , N 4  become high level. 
   The level of node N 1  is shifted to VPP or VBBW level according to a low level shifter  40   a , the level of node N 2  is shifted to VPP or VBBW level according to a low level shifter  40   b , and the level of node N 3  is shifted to VPP or VBBW level according to a low level shifter  40   c . Furthermore, the level of node N 4  is shifted to VPP or VBBW level according to a low level shifter  40   d.    
   Each output of each low level shifter  40   a    40   d  is inverted by corresponding inverter I 4  to I 7 . A first main word line mwl&lt; 0 &gt; is driven or precharged in response to an output of the inverter I 4 . A second main word line mwl&lt; 1 &gt; is driven or precharged in response to an output of the inverter  15 . A third main word line mwl&lt; 2 &gt; is driven or precharged in response to an output of the inverter  16 . A fourth main word line mwl&lt; 3 &gt; is driven or precharged in response to an output of the inverter I 7 . 
     FIG. 4  is a detailed circuit diagram illustrating the level shifter of  FIG. 3 . 
   Because a PMOS transistor Q 13  is turned on, when an input signal IN, namely, each node N 1  to N 4  of  FIG. 3 , is high level, a PMOS transistor Q 11  and a NMOS transistor Q 15  are turned on. As a result, the level shifter of  FIG. 4  outputs VBBW. On the other hand, when the input signal IN is low level, a NMOS transistor Q 14  and a PMOS transistor Q 12  are turned on. As a result, the level shifter of  FIG. 4  outputs VPP. 
   In the aforementioned conventional art, in order to precharge each main word line, that is, to become VBBW level, level shifters are connected to each main word line as shown in  FIG. 3 . 
   For instance, when each memory block uses 512 numbers of word lines and a phi X driver is coded by 4:1, 128 numbers of main word lines are required, and thus 128 numbers of level shifters should be connected to each main word line. Although the phi X driver is coded by 8:1, 64 numbers of main word lines are required, and thus the number of level shifters also needs as same as the number of main word lines. 
   Therefore, it causes problems that a chip size is increased and a signal for precharing a word line is delayed. 
   SUMMARY OF THE INVENTION 
   The present invention is directed to provide a negative word line driver capable of solving the aforementioned problems. 
   Another object of the present invention is provide a negative word line driver capable of enabling or disabling main word lines without connecting level shifters with main word lines. 
   One aspect of the present invention is to provide a negative word line driver, including: a block select address generation unit for generating first and second block select addresses Bax having a block information according to an active signal; a row decoder controller for generating a control signal for disabling a word line; a main word line driver for accessing a main word line by being driven in response to a signal coding the first block select address and the control signal; and a phi X driver for accessing a sub word line by being driven in response to a signal coding the second block select address and the control signal. 
   Another aspect of the present invention is to provided a negative word line driver, including: a block select address generation unit for generating first and second block select addresses Bax having a block information according to an active signal; a row decoder controller for generating a control signal to disable a word line; a main word line driver for making a main word line low level according to a signal coding the first block select address, and also making the main word line high level according to the control signal; and a phi X driver for accessing a sub word line by being driven in response to a signal coding the second block select address and the control signal. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete understanding of the present invention may be had by reference to the following description when taken in conjunction with the accompanying drawings in which: 
       FIG. 1  is a block diagram illustrating a negative word line driver of the conventional art; 
       FIG. 2  is a detailed circuit diagram illustrating a row decoder controller of  FIG. 1 ; 
       FIG. 3  is a detailed circuit diagram illustrating a main word line driver of  FIG. 1 ; 
       FIG. 4  is a detailed circuit diagram illustrating a level shifter of  FIG. 3 ; 
       FIG. 5  is a block diagram illustrating a negative word line driver in accordance with the present invention; 
       FIG. 6  is a detailed circuit diagram illustrating a row decoder controller of  FIG. 5 ; 
       FIG. 7  is a detailed circuit diagram illustrating a level shifter of  FIG. 5 ; 
       FIG. 8  is a detailed circuit diagram illustrating a main word line driver of  FIG. 5 ; and 
       FIG. 9  is a timing diagram illustrating an operation of a negative word line driver in accordance with the present invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Hereinafter, it will be described about embodiments of the present invention with reference to the accompanying drawings in detail. 
     FIG. 5  is a block diagram illustrating a negative word line driver in accordance with the present invention. 
   Referring to  FIG. 5 , a block select address Bax having a block information is generated from a block select address generation unit  100  according to an active signal. A row decoder controller  200  generates a control signal wloff for disabling a word line. A main word line driver  400  is driven by block select addresses Bax 3 – 12  and the control signal wloff and thus a main word line mwl is accessed. On the other hand, a phi X driver  300  is driven by block select address Bax 0 ,  1 ,  2  and the control signal wloff, and a sub word line driver  500  is driven by outputs fx, fxb of the phi X driver. Accordingly, a sub word line swl is accessed. 
   That is, enabling a word line is performed according to the block select address Bax, while disabling a word line is performed according to the control signal wloff. 
     FIG. 6  is a detailed circuit diagram illustrating a row decoder controller of  FIG. 5 . 
   A NAND gate G 2  combines a reverse signal of a signal R 2 ACB deciding a precharging timing and a block select enable signal BS. An output level of the NAND gate G 2  is shifted by a low level shifter  500   a . An output of the level shifter  500   a  passes through inverters I 8  to I 9 . An output of an inverter I 9  becomes the control signal wloff. As shown in  FIG. 6 , when the block select enable signal BS is high level and the signal R 2 ACB deciding the precharing timing is low level, the control signal wloff falls down to low level. 
     FIG. 7  is a detailed circuit diagram illustrating the level shifter of  FIG. 6 . 
   When the input signal IN is high level, a PMOS transistor Q 17  is turned on according to an output of an inverter I 10 , and thus a NMOS transistor Q 18  is turned on. As a result of this, the level shifter of  FIG. 7  outputs VPP. On the other hand, when the input signal IN is low level, a PMOS transistor Q 16  is turned on, and thus a NMOS transistor Q 19  is turned on. As a result of this, the level shifter of  FIG. 7  outputs VBBW. 
     FIG. 8  is a detailed circuit diagram illustrating a main word line driver of  FIG. 5 . 
   When the control signal wloff from a row decoder controller  200  is high level, NMOS transistors Q 34 , Q 36 , Q 38 , Q 40  and each PMOS transistor Q 26 , Q 28 , Q 30 , Q 32  in pairs of cross-coupled PMOS transistors P 1  to P 4  are turned on. Therefore, nodes N 9 , N 10 , N 11 , N 12  become VBBW level and thus each output of inverters I 10  to I 13  becomes high level (VPP level). Accordingly, first to fourth main word lines mwl&lt; 0 &gt; to mwl&lt; 3 &gt; are enabled to VPP level. When the first to fourth main word lines mwl&lt; 0 &gt; to mwl&lt; 3 &gt; are enabled to VPP level, each NMOS transistors Q 35 , Q 37 , Q 39 , Q 41  is turned on and thus VBBW level of each node N 9 , N 12  is latched thereto. 
   The signals Bax 34 &lt; 0 : 3 &gt; which have predecoded a block select address Bax 34  are respectively applied to NMOS transistors Q 20 , Q 21 , Q 22 , Q 23 . And each source of NMOS transistors Q 20  to Q 23  is connected to a common node com. 
   Moreover, one of signals Bax 56 &lt; 0 : 3 &gt; which have predecoded a block select address Bax 56  is applied to a gate of a NMOS transistor Q 24  and one of signals Bax 78 &lt; 0 : 3 &gt; which have predecoded a block select address Bax 78  is applied to a gate of a NMOS transistor Q 25 . As a result, the NMOS transistors Q 24 , Q 25  are turned on or off thereto. 
   In condition that the NMOS transistors Q 24 , Q 25  are turned on, when the NMOS transistor Q 20  is turned on according to the predecoded signal Bax 34 &lt; 0 &gt;, a potential of node N 5  becomes VBBW level, which leads the PMOS transistor Q 27  to be turned on. Therefore, a potential of node N 9  is transited from VBBW level to VPP level. As the same to it, when the NMOS transistor Q 21  is turned on according to the predecoded signal Bax 34 &lt; 1 &gt;, a potential of node N 6  becomes VBBW level, which leads the PMOS transistor Q 29  to be turned on. Therefore, a potential of node N 10  is transited from VBBW level to VPP level. When the NMOS transistor Q 22  is turned on according to the predecoded signal Bax 34 &lt; 2 &gt;, a potential of node N 7  becomes VBBW level and thus the PMOS transistor Q 31  is turned on. Accordingly, a potential of node N 11  is transited from VBBW level to VPP level. When the NMOS transistor Q 23  is turned on according to the predecoded signal Bax 34 &lt; 3 &gt;, a potential of node N 8  becomes VBBW level and thus the PMOS transistor Q 33  is turned on. Accordingly, a potential of node N 12  is transited from VBBW level to VPP level. 
   As a potential of each node N 9  to N 12  is inverted by inverters  10  to  113 , each word line mwl&lt; 0 &gt; to mwl&lt; 3 &gt; becomes VBBW level. 
   It will be described about the present invention with reference to  FIG. 9  as follows. 
   When the block select enable signal BS is high level and the signal R 2 ACB deciding the precharging timing is low level, the control signal wloff becomes low level. For instance, when the signals Bax 34 &lt; 0 &gt;, Bax 56 , Bax 78  coding the block select address are high level, the first main word line is disabled to low level VBBW. 
   Contrarily, when the block select enable signal BS is low level and the signal R 2 ACB deciding the precharging timing is high level, the control signal wloff becomes high level. For instance, the signals Bax 34 &lt; 0 &gt;, Bax 56 , Bax 78  coding the block select address are low level, the first main word line is enabled to high level VPP. 
   As described earlier, the present invention can remarkably reduce a chip size by remarkably reducing the number of level shifters. Furthermore, a delay path can be reduced by shifting level in a main word line driver at the same time. 
   Although the present invention has been described in connection with the embodiment of the present invention illustrated in the accompanying drawings, it is not limited thereto. It will be apparent to those skilled in the art that various substitutions, modifications and changes may be made thereto without departing from the scope and spirit of the invention.