Abstract:
There is provided a pulse generator capable of generating a pulse with a reduced number of transistors that toggle in response to a clock signal, thereby reducing power consumption. The pulse generator includes a plurality of unit cells, wherein an nth unit cell (n is a natural number more than 2) generates a pulse in response to a divided-by-N clock signal (N is a natural number), a signal output from an (n−1) th  unit cell and a signal output from an (n+1 ) th  unit cell. The n th  unit cell is reset or generates the pulse whose width is equivalent to the width of the clock signal, according to the logic level of the signal output from the n+1 th  unit cell.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    1. Technical Field  
           [0002]    The present invention relates to a pulse generator, and more particularly, to a latch-based pulse generator, which is used in an active matrix type thin film transistor liquid crystal display (TFT-LCD) driver.  
           [0003]    2. Discussion of the Related Art  
           [0004]    [0004]FIG. 1 is a circuit diagram of a common pulse generator  100 . Referring to FIG. 1, the pulse generator  100  includes inverters  120  and  140 , a flip-flop  110 , and a NAND gate  130 . As shown in FIG. 1, the inverters  120  and  140  (i.e., complementary metal oxide semiconductor (CMOS) inverters) include positive channel metal oxide semiconductor (PMOS) and negative channel metal oxide semiconductor (NMOS) transistors. The NAND gate  130  also includes two PMOS and NMOS transistors.  
           [0005]    The flip-flop  110  latches data DIN input to an input terminal D and outputs the result of the latching to an output terminal Q in response to a clock signal CLK input to a clock terminal CK and a complementary clock signal CLKB input to a complementary clock terminal CKB. The flip-flop  110  is reset in response to a falling edge of a reset signal RSB input to a reset terminal RB.  
           [0006]    [0006]FIG. 2 is a circuit diagram of the flip-flip  110  shown in FIG. 1. Referring to FIG. 2, the flip-flop  110  includes PMOS transistors  1101 ,  1105 ,  1113 , and  1117 , NMOS transistors  1103 ,  1107 ,  1111 , and  1115 , two inverters  1119  and  1123 , and two NAND gates  1109  and  1121 .  
           [0007]    Referring to FIGS. 1 and 2, the transistors  1101 ,  1107 ,  1111 , and  1117 , the inverter  120 , and the NAND gate  130  toggle in response to the clock signal CLK, and the transistors  1103 ,  1105 ,  1113 , and  1115  toggle in response to the complementary clock signal CLKB.  
           [0008]    [0008]FIG. 3 is a circuit diagram of a pulse generator  300  that sequentially latches n data. The pulse generator  300  includes first through n th  pulse generators  100 _ 1 ,  100 _ 2  . . .  100 _n. The structure of each of the first through n th  pulse generators  100 _ 1 ,  100 _ 2  . . .  100 _n is the same or similar to that of the pulse generator  100  of FIG. 1.  
           [0009]    The pulse generator  100 _ 1  receives and latches an input signal DIN in response to a clock signal CLK and outputs two output signals DOUT 1  and L_CLK 1 . The output signal DOUT 1  is input to an input terminal DIN 2  of a second pulse generator  100 _ 2  and the other output signal L_CLK 1  is used as a pulse for latching data.  
           [0010]    The second pulse generator  100 _ 2  receives and latches the output signal DOUT 1  in response to an inverted clock signal CLKB and outputs two output signals DOUT 2  and L_CLK 2 . The output signal DOUT 2  is input to an input terminal of a third pulse generator, and the output signal L_CLK 2  is used as a pulse for latching data.  
           [0011]    In the pulse generator  300 , the first through n th  pulse generators  100 _ 1 ,  100 _ 2  . . .  100  _n, are connected in series and generate pulses L_CLK 1 , L_CLK 2  . . . L_CLKn, respectively, in response to clock signals CLK and CLKB. Thus, the pulses L_CLK 1 , L_CLK 2  . . . L_CLKn, which are used to latch related data, are sequentially generated.  
           [0012]    For instance, when latching 128 bits of data, a minimum of 128 input clock signals CLK or CLKB are required. In doing so, each of the pulse generators  100 _ 1 ,  100 _ 2  . . .  100 _n, which include the transistors  1101 ,  1103 ,  1105 ,  1107 ,  1111 ,  1113 ,  1115 , and  1117 , toggle the clock signals CLK and CLKB. Therefore, the output of one pulse generator (e.g., the pulse generator  100 _n) toggles a minimum of 127 times to generate a pulse L_CLKn, resulting in excess power consumption.  
         SUMMARY OF THE INVENTION  
         [0013]    The present invention provides a pulse generator capable of generating a pulse with a reduced number of transistors that toggle in response to a clock signal, thereby reducing power consumption.  
           [0014]    According to an aspect of the present invention, there is provided a pulse generator comprising a plurality of unit cells, wherein an n th  unit cell (n is a natural number more than 2) generates a pulse in response to a divided-by-N clock signal (N is a natural number), a signal output from an (n−1) th  unit cell and a signal output from an (n+1) th  unit cell.  
           [0015]    The n th  unit cell is reset or generates the pulse whose width is equivalent to the width of the clock signal, based on the logic level of the signal output from the (n+1) th  unit cell. The phases of the signal output from the (n−1) th  unit cell and the signal output from the (n+1) th  unit cell are changed with a time difference.  
           [0016]    The n th  unit cell comprises a first NAND gate that NANDs the signal output from the (n−1) th  unit cell and the signal output from the (n+1) th  unit cell, a first inverter that inverts a signal output from the first NAND gate, a second NAND gate that NANDs the divided-by-N clock signal and a signal output from the first inverter, a second inverter that inverts a signal output from the second NAND gate and outputs the pulse as an inverted signal, and a latch that latches a reset signal and the signal output from the second NAND gate.  
           [0017]    The second NAND gate comprises first and second PMOS transistors, and first and second NMOS transistors, wherein the divided-by-N clock signal is input to a gate of the first PMOS transistor and a gate of the first NMOS transistor, and a signal output from the first inverter is input to a gate of the second PMOS transistor and a gate of the second NMOS transistor.  
           [0018]    According to another aspect of the present invention, there is provided a pulse generator comprising a plurality of unit cells, wherein a divided-by-N clock signal (N is a natural number), a signal output from the second output terminal of an n−1 th  unit cell (n is a natural number more than 2), and a signal output from a third output terminal of an n+1 th  unit cell are input to a first input terminal, a second input terminal, and a third input terminal of an n th  unit cell of the plurality of unit cells, respectively, wherein the n th  unit cell outputs a pulse whose width is equivalent to the width of the divided-by-N clock signal to a first output terminal of the n th  unit cell in response to the signals that are input to the first, second and third input terminals of the n th  unit cell.  
           [0019]    The n th  unit cell is reset or outputs the pulse whose width is equivalent to the width of the divided-by-N clock signal to the first output terminal of the n th  unit cell, based on the logic level of the signal output from the third output terminal of the (n+1) th  unit cell. The phases of the signal output from the second output terminal of the n−1 th  unit cell and the signal output from the third output terminal of the n+1 th  unit cell are changed with a time difference.  
           [0020]    The n th  unit cell comprises a first NAND gate that NANDs the signal which is output from the n−1 th  unit cell and input to the second input terminal of the n th  unit cell, and the signal which is output from the n+1 th  unit cell and input to the third input terminal of the n th  unit cell; a first inverter that inverts a signal output from the first NAND gate; a second NAND gate that NANDs the divided-by-N clock signal input to the first input terminal of the n th  unit cell and a signal output from the first inverter; a second inverter that inverts a signal output from the second NAND gate and outputs an inverted signal as the output signal of the n th  unit cell; and a latch that latches a reset signal, and a signal output from the second NAND gate.  
           [0021]    The n th  unit cell comprises a first NAND gate that NANDs the signal which is output from the n−1 th  unit cell and input via the second input terminal of the n th  unit cell, and the signal which is output from the n+1 th  unit cell and input via the third input terminal of the n th  unit cell; a first inverter that inverts a signal output from the first NAND gate; a second NAND gate that NANDs the divided-by-N clock signal input via the first input terminal of the n th  unit cell and a signal output from the first inverter; a second inverter that inverts a signal output from the second NAND gate and outputs an inverted signal as an output signal of the n th  unit cell; a first transmission circuit that responds to the signal output from the second NAND gate and the signal output from the second inverter; a second transmission circuit that responds to the signal output from the second NAND gate and the signal output from the second inverter; a third NAND gate that NANDs a reset signal and a signal output from a shared node and outputs the result of NAND to the third output terminal of the n th  unit cell; and a third inverter that inverts the signal output from the third NAND gate and outputs an inverted signal to the second output terminal of the n th  unit cell.  
           [0022]    According to yet another aspect of the present invention, there is provided a pulse generator comprising a first NAND gate that NANDs a first input signal and a second input signal; a first inverter that inverts a signal output from the first NAND gate; a second NAND gate that NANDs a divided-by-N clock signal and a signal output from the first inverter; a second inverter that inverts a signal output from the second NAND gate; and a latch that latches a reset signal and the signal output from the second NAND gate. The second inverter generates a pulse corresponding to the divided-by-N clock signal in response to the second input signal.  
           [0023]    According to still another aspect of the present invention, there is provided a pulse generator comprising a first NAND gate that NANDs a first input signal and a second input signal input to a second input terminal; a first inverter that inverts a signal output from the first NAND gate; a second NAND gate that NANDs a divided-by-N clock signal input to a first input terminal and a signal output from the first inverter; a second inverter; a first transmission circuit that responds to a signal output from the second NAND gate and a signal output from the second inverter; a second transmission circuit that responds to the signal output from the second NAND gate and the signal output from the second inverter; a third NAND gate that NANDs a reset signal and a signal output from the shared node and outputs the result of NAND to a third output terminal; and a third inverter. The second inverter generates a pulse whose width is equivalent to the width of the divided-by-N clock signal in response to the second input signal. In addition, the phases of the first and second input signals are changed.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]    The above aspects of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings, in which:  
         [0025]    [0025]FIG. 1 is a circuit diagram of a conventional flip-flop-based pulse generator;  
         [0026]    [0026]FIG. 2 is a circuit diagram of a flip-flop shown in FIG. 1;  
         [0027]    [0027]FIG. 3 is a circuit diagram of a conventional pulse generator capable of sequentially latching n data;  
         [0028]    [0028]FIG. 4 is a circuit diagram of a latch-based pulse generator according to an exemplary embodiment of the present invention;  
         [0029]    [0029]FIG. 5 is a circuit diagram of a latch-based pulse generator according to another exemplary embodiment of the present invention;  
         [0030]    [0030]FIG. 6 is a circuit diagram of a clock signal generating circuit;  
         [0031]    [0031]FIG. 7 is a circuit diagram of the NAND gates shown in FIGS.  4  and/or  5 ;  
         [0032]    [0032]FIG. 8 is a circuit diagram of a pulse generator capable of sequentially latching n data; and  
         [0033]    [0033]FIG. 9 is a timing diagram illustrating the operation of the pulse generator shown in FIG. 8. 
     
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0034]    [0034]FIG. 4 is a circuit diagram of a latch-based pulse generator  400  according to an exemplary embodiment of the present invention. Referring to FIG. 4, the pulse generator  400  includes first, second and third input terminals  481 ,  482 ,  483  and first, second and third output terminals  491 ,  492 ,  493 .  
         [0035]    A first NAND gate  401  receives and NANDs an input signal SFT_IN input to the second input terminal  482  and an input signal SFTR_IN input via the third input terminal  483 , and outputs the result of the NAND operation to a first inverter  403 .  
         [0036]    The level of the input signal SFTR_IN input to the third input terminal  483  is changed from a logic high level to a logic low level over a predetermined length of time after the level of the input signal SFT_IN input to the second input terminal  482  is changed from a logic low level to a logic high level.  
         [0037]    The first inverter  403  receives and inverts the signal output from the first NAND gate  401  and outputs an inverted signal enb to a second NAND gate  405 .  
         [0038]    The second NAND gate  405  receives and NANDs a divided-by-N clock signal CLK 2 _EO (where N is 2) input to the first input terminal  481  and the inverted signal enb output from the first inverter  403 , and outputs the result of the NAND operation to a second inverter  409  and a NAND gate  411   a  of a latch  411 .  
         [0039]    The second inverter  409  receives and inverts the signal output from the second NAND gate  405  and outputs an output signal LAT_PUL to the first output terminal  491 . The output signal LAT_PUL is a pulse for latching data.  
         [0040]    The latch  411  comprises two NAND gates  411   a  and  411   b . The NAND gates  411   a  and  411   b  receive and latch a reset signal SYRB input via a fourth input terminal  484  and the signal output from the second NAND gate  405  as a set signal, respectively. The latch  411  may be an R-S latch.  
         [0041]    A third inverter  413  receives and inverts a signal output from the NAND gate  411   a  and outputs an output signal SFTR to the third output terminal  493 . A fourth inverter  415  receives and inverts a signal output from the NAND gate  411   b  and outputs an output signal SFT_OUT to the second output terminal  492 .  
         [0042]    The latch-based pulse generator  400  is reset according to the logic level of the signal SFTR_IN input to the third input terminal  483 , or receives the divided-by-2 clock signal CLK 2 _EO via the first input terminal  481  and outputs it as an output signal LAT_PUL to the first output terminal  491 . The latch-based pulse generator  400  is also reset in response to the reset signal SYRB.  
         [0043]    [0043]FIG. 5 is a circuit diagram of a latch-based pulse generator  500  according to another exemplary embodiment of the present invention. Referring to FIG. 5, the pulse generator  500  includes first, second and third input terminals  581 ,  582 ,  583  and first, second and third output terminals  591 ,  592 ,  593 .  
         [0044]    A first NAND gate  501  receives and NANDs an input signal SFT_IN from the second input terminal  582  and an input signal SFTR_IN from the third input terminal  583 , and outputs the result of the NAND operation to a first inverter  503 .  
         [0045]    The level of the input signal SFTR_IN input to the third input terminal  583  is changed from a logic high level to a logic low level over a predetermined length of time after the level of the input signal SFT_IN input to the second input terminal  582  is changed from a logic low level to a logic high level.  
         [0046]    The first inverter  503  receives and inverts a signal output from a first NAND gate  501  and outputs an inverted signal enb to a second NAND gate  505  and a second transmission circuit  517 .  
         [0047]    The second NAND gate  505  receives and NANDs a divided-by-2 clock signal CLK 2 _EO input via the first input terminal  581  and the enb signal output from the first inverter  503 , and outputs the result of the NAND operation to a second inverter  509 , a first transmission circuit  511 , and the second transmission circuit  517 .  
         [0048]    The first transmission circuit  511  is connected between a shared node  515  and the second output terminal  592 , and switches on or off between the shared node  515  and the second output terminal  592  in response to the signal output from an output terminal  507  of the second NAND gate  505  and a signal output from the second inverter  509 .  
         [0049]    The first transmission circuit  511  includes a negative channel metal oxide semiconductor (NMOS) transistor  511   a  and a positive channel metal oxide semiconductor (PMOS) transistor  511   b . The NMOS transistor  511   a  and the PMOS transistor  511   b  are connected between the shared node  515  and the second output terminal  592 . The signal output from the output terminal  507  of the second NAND gate  505  is input to the gate of the NMOS transistor  511   a . The signal output from the second inverter  509  is input to the gate of the PMOS transistor  511   b.    
         [0050]    The second transmission circuit  517  is connected between the shared node  515  and the output terminal of the first inverter  503  and switches on or off between the shared node  515  and the output terminal of the first inverter  503  in response to the signal from the second NAND gate  505  and the signal output from the second inverter  509 .  
         [0051]    The second transmission circuit  517  includes an NMOS transistor  517   b  and a PMOS transistor  517   a . Both the PMOS transistor  517   a  and the NMOS transistor  517   b  are connected between the shared node  515  and the output terminal of the first inverter  503 . The signal output from the output terminal  507  of the second NAND gate  505  is input to the gate of the PMOS transistor  517   a . A signal output from the second inverter  509  is input to the gate of the NMOS transistor  517   b.    
         [0052]    The second inverter  509  receives and inverts the signal output from the second NAND gate  505  and outputs an output signal LAT_PUL to the first output terminal  591 . The output signal LAT_PUL is a pulse for latching data.  
         [0053]    A third NAND gate  521  receives and NANDs a reset signal SYRB input via a fourth input terminal  584  and the signal output from the shared node  515 , and outputs a signal SFTR as the result of the NAND operation to the third output terminal  593  and a third inverter  523 .  
         [0054]    The third inverter  523  receives and inverts the signal output from the third NAND gate  521  and outputs an inverted signal SFT_OUT to the second output terminal  592  and the first transmission circuit  511 .  
         [0055]    [0055]FIG. 6 is a circuit diagram of a clock signal generating circuit  600 . Referring to FIG. 6, the clock signal generating circuit  600 , which generates a divided-by-2 clock signal, includes a flip-flop  610 , a first NOR gate  630 , and a second NOR gate  650 .  
         [0056]    A clock signal CLK is input to a clock terminal CK of the flip-flop  610 , an inverted clock signal CLKB is input to an inverted clock terminal CKB of the flip-flop  610 , and a signal output from an inverted output terminal QB of the flip-flop  610  is input to an input terminal D of the flip-flop  610 . The clock signal CLK and the inverted clock signal CLKB are complementary to each other, and an output signal CLK 2  and an inverted output signal CLK 2 B are complementary to each other.  
         [0057]    The first NOR gate  630  receives and NORs the clock signal CLK and the output signal CLK 2  output from the flip-flop  610 , and outputs a signal CLK 2 _ODD as the result of the NOR operation. The output signal CLK 2  output from the flip-flop  610  is a divided-by-2 signal of the clock signal CLK.  
         [0058]    The second NOR gate  650  receives and NORs the clock signal CLK and the inverted output signal CLK 2 B output from the flip-flop  610 , and outputs a signal CLK 2 _EVEN as the result of the NOR operation. The inverted output signal CLK 2 B is a divided-by-2 signal of the inverted clock signal CLKB. The flip-flop  610  is reset in response to a falling edge of a reset signal RESETB.  
         [0059]    The waveforms of the signal CLK 2 _ODD output from the first NOR gate  630  and the signal CLK 2 _EVEN output from the second NOR gate  650  are illustrated in FIG. 9. The divided-by-2 clock signals CLK 2 _EO shown in FIGS. 4 and 5 are equivalent or similar to the signal CLK 2 _ODD output from the first NOR gate  630  or the signal CLK 2 _EVEN output from the second NOR gate  650 . Thus, the signal CLK 2 _ODD is a divided-by-2 odd-numbered clock signal and the signal CLK 2 _EVEN is a divided-by-2 even-numbered clock signal.  
         [0060]    [0060]FIG. 7 is a circuit diagram of the NAND gates  405 ,  505  shown in FIGS. 4 and 5. Referring to FIG. 7, a first PMOS transistor  4051  and a second PMOS transistor  4053  are connected in parallel between a power supply voltage VDD and the output terminals  407 ,  507  of FIGS. 4 and 5 of the second NAND gates  405 ,  505 . A first NMOS transistor  4055  and a second NMOS transistor  4057  are connected in series between the output terminals  407 ,  507  of the second NAND gates  405 ,  505  and a ground voltage VSS.  
         [0061]    The divided-by-2 clock signal CLK 2 _EO is input to the gate of the first PMOS transistor  4051  and the gate of the first NMOS transistor  4055 . A signal enb output from the first inverters  403 ,  503  of FIGS. 4 and 5 is input to the gate of the second PMOS transistor  4053  and the gate of the second NMOS transistor  4057 .  
         [0062]    Because the divided-by-2 clock signal CLK 2 _EO is input to the gate of the first PMOS transistor  4051  and the gate of the first NMOS transistor  4055 , only the first PMOS transistor  4051  and the first NMOS transistor  4055  toggle in response to the divided-by-2 clock signal CLK 2 _EO.  
         [0063]    On the other hand, in the conventional pulse generator  100  shown in FIGS. 1 and 2, the transistors  1101 ,  1103 ,  1105 ,  1107 ,  1111 ,  1113 ,  1115 , and  1117 , the transistors of the inverter  120 , and the transistors of the NAND gate  130  all toggle in response to the clock signal CLK. Therefore, the power consumed by the pulse generators  400 ,  500  of FIGS. 4 and 5 with the NAND gates  405 ,  505 , shown in FIG. 7 is significantly smaller than the power consumed by the pulse generator  100  shown in FIG. 1.  
         [0064]    [0064]FIG. 8 is a circuit diagram of a pulse generator  800  capable of sequentially latching n data. Referring to FIG. 8, the pulse generator  800  includes a first dummy unit cell  810 , a pulse generator set  830 , and a second dummy unit cell  850 .  
         [0065]    The pulse generator set  830  includes n unit cells  830 _ 1 ,  830 _ 2  . . .  830 _n. Each of the n unit cells  830 _ 1 ,  830 _ 2  . . .  830 _n has the same or similar construction and function as the pulse generator  400 ,  500  of FIGS. 4 and 5. The n th  unit cell  830 _ 1  outputs the divided-by-2 odd-numbered clock signal CLK 2 _ODD as an output signal LAT-PUL 1  in response to the divided-by-2 odd-numbered clock signal CLK 2 _ODD, an output signal SFT_OUT 0  output from the (n−1) th  (i.e., first dummy) unit cell  810 , and an output signal SFTR 2  output from the n+1 th  unit cell  830 _ 2 .  
         [0066]    More specifically, the n th  unit cell  830 _ 1  is reset in response to the logic level of the signal SFTR 2  output from the (n+1) th  unit cell  830 _ 2 , or outputs an output signal LAT_PUL as a pulse whose width is equivalent to the width of the divided-by-2 odd-numbered clock signal CLK 2 _ODD. The pulse LAT_PUL is used to latch data input to a source data line of for example, an active matrix type thin film transistor liquid crystal display (TFT_LCD) driver.  
         [0067]    Thus, when the inverted output signal enb output from the first inverters  403 ,  503  of FIGS. 4 and 5 is at a logic low level, the pulse generators  400 ,  500  output a deactivated output signal LAT_PUL, i.e., LAT_PUL is at a logic low level, irrespective of the level of the divided-by-2 clock signal CLK 2 _EO. However, when the output signal enb output from the first inverters  403 ,  503  is at a logic high level, the pulse generators  400 ,  500  output as the output signal LAT_PUL a pulse whose width is equivalent to the width of the clock signal CLK 2 _EO.  
         [0068]    In the unit cell  830 _ 1 , the divided-by-2 clock signal CLK 2 _ODD is input to its first input terminal, a signal SFT_OUT 0  output from a second output terminal of the first dummy unit cell  810  is input to its second input terminal, and a signal SFTR 2  output from a third output terminal of the unit cell  830 _ 2  is input to its third input terminal.  
         [0069]    In the n th  unit cell  803 _n, the divided-by-2 odd-numbered clock signal CLK 2 _ODD is input to its first input terminal, a signal output from a second output terminal of the (n−1) th  unit cell is input to its second input terminal, and a signal SFTRD 2  output from a third output terminal of the second dummy unit cell  850  is input to its third input terminal. A signal LAT_PULn output from a first output terminal of the n th  unit cell  830 _n is used as a signal for latching n th  data.  
         [0070]    [0070]FIG. 9 is a timing diagram illustrating the operation of the pulse generator  800 , shown in FIG. 8. The operation of the pulse generator  800  will be described in detail with reference to FIGS.  4 - 9 .  
         [0071]    First, a case where 128 data bits are sequentially latched is explained. The clock signal generating circuit  600  of FIG. 6 alternately generates the divided-by-2 odd-numbered clock signal CLK 2 _ODD and the divided-by-2 even-numbered clock signal CLK 2 _EVEN in response to the clock signal CLK and the inverted clock signal CLKB.  
         [0072]    The first dummy unit cell  810  outputs an activated signal SFT_OUT 0  as an input signal SFT_IN 1  to the unit cell  830 _ 1  when the start signal START input as an input signal SFT_IN 0  to the second input terminal of the first dummy unit cell  810  is activated and an activated signal SFTR 1  output from a third output terminal of the activated unit cell  830 _ 1  is input as an input signal SFTR_IND 1  to the third input terminal of the first dummy unit cell  810 .  
         [0073]    The unit cell  830 _ 1  generates the pulse LAT_PUL 1  whose width is equivalent to the width of the divided-by-2 odd-numbered clock signal CLK 2 _ODD in response to the activated input signal SFT_IN 1  and the output signal SFTR 2  output from the unit cell  830 _ 2 , and outputs an activated output signal SFT_OUT 1  and the deactivated output signal SFTR 1 , respectively. Accordingly, the first dummy unit cell  810  is reset in response to the deactivated output signal SFTR 1 .  
         [0074]    The activated signal SFT_OUT 1  output from the unit cell  830 _ 1  is input as an input signal SFT_IN 2  to the unit cell  830 _ 2 . The unit cell  830 _ 2  generates a pulse LAT_PUL 2  whose width is equivalent to the width of a divided-by-2 even-numbered clock signal CLK 2 _EVEN in response to the activated input signal SFT_IN 2  and an activated output signal SFTR 3  output from a third unit cell, and activates and outputs an activated output signal SFT_OUT 2  and the deactivated output signal SFTR 2 . The unit cell  830 _ 1  is reset in response to the deactivated output signal SFTR 2 .  
         [0075]    The above operations of the pulse generator  800  are repeated until 128 source data bits are latched. Therefore, 128 pulses are sequentially generated by each of 128 unit cells  830 _ 1 ,  830 _ 2  . . .  830 _n.  
         [0076]    While this invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents.