Abstract:
A high voltage generation circuit comprises a first boosting unit, a second boosting unit, a delay circuit which delays the output of the first boosting unit as applied the second boosting unit, a pre-charge unit, and switch units which connect respective nodes in response to control signals. A voltage supply circuit is also provided that converts an externally supplied power source voltage (VCC) to a predetermined pre-charge voltage (VPP 2 ).

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to a semiconductor device, and more particularly, to a semiconductor device having a high voltage generator with a short pumping operation time and improved efficiency in current usage. A claim of priority is made to Korean Patent Application No. 03-78641 filed on Nov. 7, 2003 in the Korean Intellectual Property Office, the disclosure of which is hereby incorporated by reference in its entirety. 
   2. Description of the Related Art 
   It is quite common for a semiconductor device to use a relatively higher voltage to drive some circuits as compared with other circuits internal to the device. For example, a semiconductor memory device will often use a voltage to drive word lines that is higher than a normally provided external voltage. The term “external” generally refers to a voltage provided by a circuit outside the semiconductor device itself, as compared with “internal” voltages which are generated by circuits within the semiconductor device. Thus, where a relatively higher voltage is required, the semiconductor device typically includes a high voltage generation circuit that converts the external voltage supplied to the semiconductor device into a signal suitable for use by high voltage circuits and components. In conventional semiconductor devices, a pumping circuit is generally used as a high voltage generation circuit. 
   In situations where a host system runs off of ordinary batteries, similarly constructed, high voltage generation circuits are typically required to internally generate voltages exceeding the nominal output of the batteries. 
   Recent host system evolutions have consistently seen power source voltages decreased. As a result, the externally provided power source voltages applied to semiconductor memory devices within the host systems has also been decreasing. While some accommodation to lower externally supplied voltages has been made within the design of semiconductor memory devices, the amount by which the internally required high voltages can be reduced is proportionally much less than the amount by which the external power source voltage has been reduced. Accordingly, it is increasingly difficult to generate the required high voltages with semiconductor memory devices using conventional high voltage generators. 
   In addition to the problem of unmet overall demand for high voltages, the relative pumping efficiency of high voltage generators is also becoming a problem. That is, as externally supplied voltages have decreases, the pumping efficiency of conventional circuits generating high voltages has markedly dropped. 
   Further problems arise from the decrease in externally supplied voltages. Fir example, conventional high voltage generation circuits typically require the use of one or more pumping circuits that use capacitors. When the externally supplied voltage is significantly lower than a desired high voltage, it is not uncommon to see three or more boosting stages used to develop the high voltage. Unfortunately, the time required to fully pre-charge the capacitors in each of these boosting stages increases proportionally, and as a result, the time for one operation increases to the point where the entire boosting timing becomes unacceptably long. 
   SUMMARY OF THE INVENTION 
   The present invention provides a high voltage generation circuit which efficiently generates a high voltage output for subsequent used within a semiconductor memory device. 
   The present invention further provides a high voltage generation circuit having a reduced pre-charge time for boosting units used to develop the high voltage output. 
   Accordingly, in one aspect, the present invention provides a high voltage generation circuit generating a high voltage output (VPP). The circuit comprises a first node receiving an driving signal defined by a power source voltage (VCC), a first boosting unit connected between the first node and a second node, wherein the first boosting unit changes the electrical potential of the first node in response to the driving signal, and pre-charges the second node with a pre-charge voltage (VPP 2 ) in response to a pre-charge signal, a second boosting unit connected between a third node and a fourth node, wherein the second boosting unit changes the electrical potential of the third node in response to the driving signal, and pre-charges the fourth node with the pre-charge voltage (VPP 2 ) in response to the pre-charge signal, a delay circuit connected between first and third nodes and delaying an output from the first boosting unit to the second boosting unit, a pre-charge circuit pre-charging the second and fourth nodes with the pre-charge voltage (VPP 2 ) in response to the pre-charge signal, a first switch response to a transfer signal connecting the second and fourth nodes, and a second switch response to a transmission signal outputting the high voltage output (VPP) from the fourth node. 
   In another aspect, the present invention provides a high voltage generation circuit generating a high voltage output (VPP) comprising; a pre-charge voltage supply circuit generating a pre-charge voltage (VPP 2 ) in response to an externally provided power source voltage (VCC), a first node receiving the pre-charge voltage (VPP 2 ), a first pumping capacitor connected between the first node and a second node, wherein the first pumping capacitor changes the electrical potential of the first node and pre-charges the second node in response to the pre-charge voltage (VPP 2 ), a second pumping capacitor connected between a third node and a fourth node, wherein the second pumping capacitor changes the electrical potential of the third node and pre-charges the fourth node in response to the pre-charge voltage (VPP 2 ), a delay circuit connected between first and third nodes and delaying an output from the first pumping capacitor to the second pumping capacitor, a pre-charge circuit pre-charging the second and fourth nodes with the pre-charge voltage (VPP 2 ) in response to a pre-charge signal, a first switch response to a transfer signal connecting the second and fourth nodes, and a second switch response to a transmission signal outputting the high voltage output from the fourth node. 
   In yet another aspect, the present invention provides a high voltage generation circuit generating a high voltage output (VPP), comprising; a level converter receiving a power source voltage varying between a VCC voltage level and a ground voltage level, and generating a driving signal having an upper voltage level of VPP 2 , where VPP 2  is higher than VCC, and a lower voltage level of VBB, where VBB is lower than ground voltage, a first node receiving the drive signal, a first boosting unit connecting the first node and a second node, wherein the first boosting unit drives the electrical potential of the first node between VPP 2  and VBB in response to driving signal, and pre-charging the second node to VPP 2 , a second boosting unit connected between a third node and a fourth node, wherein the second boosting unit drives the electric potential of the third node in response to the driving signal, and pre-charges the fourth node to VPP 2 , a delay circuit connected between first and third nodes and delaying an the output from the first boosting unit as applied to the second boosting unit, a pre-charge circuit pre-charging the second and fourth nodes to VPP 2 , a first switch, response to a transfer signal, connecting the second and fourth nodes, and a second switch, response to a transmission signal, outputting the high voltage output from the fourth node. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above objects and other advantages of the present invention will become more readily apparent upon a review of the description of certain presently preferred embodiments that follow. This description is made in reference to the attached drawings in which: 
       FIGS. 1   a  through  1   c  are diagrams showing the operation of a prior art triple pumping circuit; 
       FIG. 2   a  is a diagram showing a pumping circuit using the external supply voltage (VCC) as the pre-charge voltage of a pumping capacitor; 
       FIG. 2   b  is a timing diagram of the operation of the circuit shown in  FIG. 2   a;    
       FIG. 3   a  is a diagram of a high voltage generation circuit according to a preferred embodiment of the present invention; 
       FIG. 3   b  is a timing diagram of the operation of the high voltage generation circuit shown in  FIG. 3   a;    
       FIG. 4   a  is a diagram of a high voltage generation circuit according to another preferred embodiment of the present invention; 
       FIG. 4   b  is a timing diagram of the operation of the high voltage generation circuit shown in  FIG. 4   a;    
       FIG. 5   a  is a diagram of a high voltage generation circuit according to still another preferred embodiment of the present invention; and 
       FIG. 5   b  is a timing diagram of the operation of the high voltage generation circuit shown in  FIG. 5   a.    
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1   a,  four capacitors (C 1  through C 4 ) are pre-charged from an external power source voltage (VCC). Then, a first switch (SW 1 ) and a second switch (SW 2 ) are turned on, and by driving C 1  and C 2  with the power source voltage (VCC), a first pumping operation is performed. As a result, the electrical charge from C 1  is provided to C 4  and the charge from C 2  is provided to C 3 . Accordingly, a voltage level is developed on C 3  and C 4  that is equal to VCC+0.5 VCC. 
   Referring now to  FIG. 1   b,  first switch (SW 1 ) and second switch (SW 2 ) are turned off, and a third switch (SW 3 ) is turned on. Thereafter, by driving C 3  with the power source voltage (VCC), a second pumping operation is performed. As a result of this second pumping operation, C 3  develops a voltage level equal to VCC+1.5 VCC, and thereafter the charge stored on C 3  is provided to C 4 , such that a voltage equilibrium is maintained. Accordingly, a voltage of 2 VCC is developed on C 3  and C 4 . 
   Referring now to  FIG. 1   c,  a third pumping operation if performed in which C 4  is driven with the power source voltage (VCC) until a voltage developed on C 4  becomes equal to 3 VCC. Then, if the first through third switch (SW 1  through SW 3 ) are turned off and a fourth switch (SW 4 ) is turned on, the voltage stored in C 4  is discharged to an external load. In theory, the voltage developed on C 4  in  FIG. 1   c  should rise to 3 VCC, or an intended high voltage VPP. However, the voltage actually developed on C 4  is closer to about 2.5 VCC. 
   Referring again to the triple pumping circuit shown in  FIGS. 1   a  through  1   c,  in order to generate a high voltage on a one time basis, three separate pumping operations are required, thereby increasing the time required to accomplish the entire pumping operation. In addition, after the high voltage generator concludes each pumping operation, the pumping capacitors must be pre-charged from the external supply voltage. This requirement allows charge stored on C 3  or C 4  is be discharged to the external supply voltage and the efficiency of overall current usage is degraded accordingly. 
   For example, if we assume an external supply voltage (VCC) of 2V and a desired high voltage (VPP) of 4.5V, it takes three separate pumping operations to develop a VPP voltage of 4.5V. In addition, even when the voltage of the pumping driver is reduced to 0V during the pre-charge operation, the voltage of the VPP is 2.5V and therefore 0.5V is wasted. 
     FIG. 2   a  is a circuit diagram showing one embodiment of a pumping circuit that uses an external supply voltage (VCC) as a pre-charge voltage for one or more pumping capacitor(s). 
   Referring to  FIG. 2   a,  a pumping circuit  200  according to one embodiment of the present invention comprises a first boosting unit  202 , a second boosting unit  204 , a pre-charge circuit  206 , a delay circuit  208 , and a transmission circuit  210 . 
   A first pulse (P 1 ), or driving signal, shown here as a square wave signal applied to a first node (NO 1 ), swings between the power supply voltage (VCC) and ground. A second pulse (P 2 ), or transfer signal, is used as a transfer pulse and is applied to pumping circuit  200  between a second node (NO 2 ) and a fourth node (NO 4 ). A third pulse (P 3 ), or transmission signal, is used as a transfer pulse and is applied to between a fourth node (NO 4 ) and an output terminal. A fourth pulse (P 4 ), or pre-charge signal, is used a pre-charge pulse to pre-charge capacitors C 1  and C 2  in the first and second boosting units to the levels of second node (NO 2 ) and fourth node (NO 4 ), respectively, as raised to said levels by power source voltage (VCC). 
   A delay circuit  208  is disposed between the first boosting unit  202  and the second boosting unit  204  to transfer the voltage developed on C 1  to C 2 . Pre-charge circuit  206  is connected to the second and fourth nodes (NO 2  and NO 4 ). Transmission circuit  210  transfers the voltage of the fourth node (NO 4 ) to the outside. 
     FIG. 2   b  is a timing diagram illustrating the operation of the pumping circuit shown in  FIG. 2   a.    
   Referring to  FIGS. 2   a  and  2   b,  C 1  and C 2  are first pre-charged by power source voltage (VCC) when the fourth pulse (P 4 ) is at a “high” logic level so that the voltage at second node (NO 2 ) and fourth node (NO 4 ) rise to VCC. 
   If the fourth pulse (P 4 ) goes a “low” logic level and the first pulse (P 1 ) and the second pulse (P 2 ) go high, the voltage at the node (NO 1 ) becomes VCC. Second node (NO 2 ) is connected to fourth node (NO 4 ), and the voltage at both of these nodes rises to become VCC+0.5 VCC. 
   When the first pulse (P 1 ) is subsequently transferred to third node (NO 3 ) through delay circuit  208 , second pulse (P 2 ) goes low. At this time, second and fourth nodes are disconnected from each other and the voltage at third node (NO 3 ) becomes VCC. Accordingly, the voltage at fourth node (NO 4 ) becomes 1.5 VCC+VCC. If the third pulse (P 3 ) goes high, the voltage at fourth node (NO 4 ) becomes equal to VPP under the influence of an external capacitor and this voltage is provided through transmission circuit  210  to an external load or signal line. 
   If first pulse (P 1 ) goes low, the voltage at first node (NO 1 ) falls to 0V and respective voltages at the second through fourth nodes also fall to this level. Thereafter, fourth pulse (P 4 ) goes high and pre-charges capacitors C 1  and C 2 . 
   If the pumping circuit shown in  FIG. 2   a  is used, a high voltage output is generated by twice pumping through delay circuit  208 , thus reducing the time required to pre-charge capacitors C 1  and C 2 , as compared with the conventional triple pumping scheme explained with reference to the circuit shown in  FIG. 1 . Accordingly, the time required for a single operation of the high voltage generator is greatly reduced, as compared with the conventional approach. 
   However, if through this operation, the double pumping scheme is performed by using an external power source voltage (VCC) as the pre-charge voltage for pumping capacitors C 1  and C 2 , the maximum amount of electrical charge that can be stored by C 1  and C 2  is limited by VCC. In addition, when capacitor C 1  is pre-charged, if the voltage at fourth node (NO 4 ) is higher than VCC even though the voltage at third node (NO 3 ) becomes 0V. That is, when the generated output voltage (VPP) is much higher than the pre-charge voltage (VCC), some portion of the charge stored on capacitor C 2  is discharged to VCC. Thus, the amount of power wasted by the pumping circuit is unacceptable. 
     FIG. 3   a  is a diagram of a high voltage generation circuit according to a preferred embodiment of the present invention. 
   Referring to  FIG. 3   a,  a high voltage generation circuit  300  according to another embodiment of the present invention comprises a VPP 2  supply circuit  301 , a first boosting unit  302 , a second boosting unit  304 , a pre-charge circuit  306 , a delay circuit  308 , and a transmission circuit  310 . These circuit components are similar to their counterparts described above in relation to  FIG. 2A . However, the pre-charge voltage provided to pre-charge circuit  306  is not equal to the power source voltage (VCC), but is equal to a pre-charge voltage VPP 2  having a voltage value higher than that of power source voltage (VCC). 
   VPP 2  supply circuit  301  may take the form of any circuit capable of providing a stable VPP 2  voltage, which is used whenever high voltage generation circuit  300  is in operation. 
     FIG. 3   b  is a timing diagram illustrating the operation of the high voltage generation circuit shown in  FIG. 3   a.    
   Referring to  FIGS. 3   a  and  3   b,  when fourth pulse (P 4 ) first goes high, second node (NO 2 ) and fourth node (NO 4 ) are pre-charged by pre-charge voltage (VPP 2 ) provided by VPP 2  supply circuit  301 . 
   If the fourth pulse (P 4 ) goes low and the first pulse (P 1 ) and second pulse (P 2 ) both go high, the voltage at first node (NO 1 ) becomes VCC. The second node (NO 2 ) is connected to fourth node (NO 4 ) such that the voltages developed on second and fourth nodes becomes VPP 2 +0.5 VCC. 
   When first pulse (P 1 ) is subsequently transferred through delay circuit  308  to third node (NO 3 ), the second pulse (P 2 ) goes low. At this time, second node and fourth node are disconnected from each other and the voltage at third node (NO 3 ) becomes equal to VCC. Accordingly, the voltage at fourth node (NO 4 ) becomes 1.5 VCC+VPP 2 . If the third pulse (P 3 ) goes high, the voltage at fourth node (NO 4 ) becomes VPP under the influence of an external capacitor and this voltage is provided through transmission circuit  310  to an external load or signal line. 
   The process by which the high voltage (VPP) is generated in the high voltage generation circuit of  FIG. 3   a  is highly efficient when compared to the high voltage generation process in the high voltage generation circuit  200  of FIG.  2 . Accordingly, with a shorter pumping timing, the high voltage (VPP) can be efficiently generated even with a reduced power source voltage (VCC) derived from a host system. 
   If the first pulse (P 1 ) goes low, the voltage at first node (NO 1 ) also becomes 0V and the voltage at the second through fourth nodes becomes VCC. Then, finally, the fourth pulse (P 4 ) goes high, and pumping capacitors C 1  and C 2  are pre-charged with the pre-charge voltage VPP 2 . 
   The high voltage generation circuit shown in  FIG. 3   a  does not need multiple pumping step operations such that the time required to generate a desired high voltage output can be further reduced. Also, since pumping capacitors C 1  and C 2  are pre-charged not just with power source voltage (VCC) but with pre-charge voltage VPP 2 , which is higher than the power source voltage, the amount of charge that can be stored in the pumping capacitors is increased. Thus, the high voltage output voltage (VPP) generated can be increased and the efficiency of the high voltage generator increases. 
   In addition, when the second pumping capacitor C 2  is pre-charged, even though the voltage at third node (NO 3 ) becomes 0V, the voltage at fourth node (NO 4 ) becomes VPP 2  and the amount of wasted electrical charge is greatly reduced. 
   Meanwhile, by forming VPP 2  supply circuit  301  separately from high voltage generation circuit  300 , the time needed to pump a high voltage generation circuit with pre-charge voltage VPP 2 , to pump again with VPP, and to pre-charge again can be significantly reduced, and the amount of wasted current can be reduced. In addition, by forming VPP 2  supply circuit  301  separately from the high voltage generation circuit  300 , the pre-charge voltage VPP 2  that is needed whenever the high voltage generation circuit  300  performs a pumping operation can be stably provided. 
     FIG. 4   a  is a diagram of a high voltage generation circuit according to yet another preferred embodiment of the present invention. 
   The high voltage generation circuit  400  shown in  FIG. 4   a  is characterized, by way of comparison to  FIG. 3   a,  in that it further comprises a level converter  402  for converting the power source voltage (VCC) to the pre-charge voltage VPP 2 . 
   The high voltage generation circuit  400  uses the pre-charge voltage (VPP 2 ) to pre-charge pumping capacitors C 1  and C 2  through the level converter  402 . In addition, VPP 2  is used as a high power source of a driver driving the pumping capacitors C 1  and C 2 . Also, in this case, in order to reduce VPP 2  charge consumption in the high voltage generation circuit  400 , VPP 2  is only used in the driver end to drive the pumping operation of capacitors C 1  and C 2 , and to achieve this level converter  402  converts VCC to VPP 2 . 
     FIG. 4   b  is a timing diagram of the operation of the high voltage generation circuit shown in  FIG. 4   a.    
   Referring to  FIGS. 4   a  and  4   b,  when fourth pulse (P 4 ) first goes high, the voltages at second node (NO 2 ) and fourth node (NO 4 ) are pre-charged with the pre-charge voltage (VPP 2 ) provided by VPP 2  supply circuit  301 . 
   If the fourth pulse (P 4 ) then goes low and the first pulse (P 1 ) and second pulse (P 2 ) go high, the voltage at first node (NO 1 ) becomes VPP 2 . The second node (NO 2 ) is connected to the fourth node (NO 4 ) and the voltage of the second node and fourth node becomes 1.5 VPP 2 . 
   When the first pulse (P 1 ) is subsequently transferred through delay circuit  408  to third node (NO 3 ), the second pulse (P 2 ) goes low. At this time, the second node and fourth node are disconnected and third node (NO 3 ) becomes VPP 2 . Accordingly, the voltage at fourth node (NO 4 ) becomes 2.5 VPP 2 . If the third pulse (P 3 ) goes high, fourth node (NO 4 ) becomes VPP under the influence of an external capacitor and this voltage is provided through transmission circuit  210  (as shown in of  FIG. 2 ) to an external load or signal line. 
   The high voltage output (VPP) which is generated at this time is a high efficiency voltage improved by 2.5 (VPP 2 −VCC) level over the high voltage generated in the high voltage generation circuit  200  of  FIG. 2 . Accordingly, with a shorter pumping time, the high voltage output (VPP) can be generated from a reduced power source voltage (VCC) supplied by a host system. 
   If the first pulse (P 1 ) then goes low, first node (NO 1 ) falls to 0V and the voltage at the second through fourth nodes falls by VCC. Then, finally, the fourth pulse (P 4 ) goes high, and C 1  and C 2  are pre-charged with the pre-charge voltage VPP 2 . 
     FIG. 5   a  is a diagram of a high voltage generation circuit according to still another preferred embodiment of the present invention. 
   The high voltage generation circuit  500  shown in  FIG. 5   a  is characterized, by way of comparison to  FIG. 3   a,  in that it further comprises a level converter  502 , which converts the power source voltage level (VCC) to a pre-charge voltage VPP 2 , and the ground voltage level (0V) to a negative voltage (VBB) lower than the ground voltage. In addition, the high voltage generation circuit  500  further comprises a low voltage (VBB) generation circuit  504  which provides an electrical charge resulting from a low voltage signal equal to or less than 0V whenever the high voltage generation circuit  500  operates. 
   Through the level converter  502 , high voltage generation circuit  500  uses VBB, which is lower than 0V, as a low voltage source of a driver driving pumping capacitors C 1  and C 2 , and uses pre-charge voltage VPP 2  as a high voltage source such that the dynamic range of the driving voltage is increased. Also in high voltage generation circuit  500 , the second node (NO 2 ) and fourth node (NO 4 ) are designed to be pre-charged by the pre-charge voltage (VPP 2 ) from the VPP 2  supply circuit  301 . 
   In  FIG. 5   a,  the VPP 2  supply circuit  301  and the VBB supply circuit  504  are needed to continuously provide VPP 2  and VBB to be used in the high voltage generation circuit  500 . 
     FIG. 5   b  is a timing diagram illustrating the operation of the high voltage generation circuit shown in  FIG. 5   a.    
   Referring to  FIGS. 5   a  and  5   b,  when the fourth pulse (P 4 ) first goes high, C 1  and C 2  are pre-charged with the pre-charge voltage (VPP 2 ) provided by VPP 2  supply circuit  301  so that voltage levels at second node (NO 2 ) and fourth node (NO 4 ) rise to VCC. When the fourth pulse (P 4 ) goes low, the pre-charging operation stops. 
   If the first pulse (P 1 ) goes low, the first node (NO 1 ) and third node (NO 3 ) are driven to VBB. If the first pulse (P 1 ) and second pulse (P 2 ) go high, the first node (NO 1 ) is driven VPP 2 . The second node (NO 2 ) is connected to fourth node (NO 4 ) and the voltage at both the second and fourth nodes becomes 1.5 VPP 2 −VBB. 
   When the first pulse (P 1 ) is subsequently transferred through delay circuit  208  to the third node (NO 3 ), the second pulse (P 2 ) goes low. At this time, the second node (NO 2 ) and fourth node (NO 4 ) are disconnected and third node (NO 3 ) is driven from VBB to VPP 2 . Accordingly, fourth node (NO 4 ) becomes 2.5 VPP 2 −2 VBB. If the third pulse (P 3 ) goes high, the fourth node (NO 4 ) becomes VPP under the influence of an external capacitor and this voltage is provided through transmission circuit  210  to an external load or signal line. 
   If the first pulse (P 1 ) goes low, the voltage at first node (NO 1 ) also becomes 0V and the voltage at second through fourth nodes is also lowered by VCC. Then, finally, the fourth pulse (P 4 ) goes high, such that C 1  and C 2  are pre-charged with the pre-charge voltage VPP 2 . 
   The high voltage output (VPP) generated at this time is a high efficiency voltage improved by {2.5 (VPP 2 −VCC)−2VBB} over the high voltage generated in the high voltage generation circuit  200  of  FIG. 2 . Accordingly, with a shorter pumping time, the high voltage output (VPP) can be generated from a reduced power source voltage (VCC) supplied by a host system. 
   Several presently embodiments have been explained above with reference to the accompanying drawings. However, the present invention is not limited to the preferred embodiment described above, and those of ordinary skill in the art will understand that variations and modifications to the foregoing fall within the scope of the present invention as particularly defined by the following claims. 
   The high voltage generation circuit according to the present invention does not need multiple pumping operations to produce a desired high voltage output. Thus, the desired high voltage output is more quickly developed. In addition, pumping capacitors C 1  and C 2  are pre-charged not with the power source voltage (VCC), but with a pre-charge voltage VPP 2 , which is higher than the power source voltage such that the amount of charge that can be stored in the pumping capacitors increases. Thus, the generated high voltage (VPP) can be increased and the efficiency of the high voltage generator increases. 
   Further, when the second pumping capacitor (C 2 ) is pre-charged, even though the voltage at third node (NO 3 ) becomes 0V, the voltage at fourth node (NO 4 ) becomes VPP 2 , and therefore the amount of wasted electrical charge is reduced. 
   Also, by using the VBB and VPP 2  voltage levels to drive pumping capacitors, the amount of electrical charge stored in the capacitors increases such that the high voltage output (VPP) finally generated is increased and can be generated efficiently. 
   Meanwhile, by forming the VPP 2  supply circuit separately from the high voltage generation circuit, the time required to pump a high voltage generation circuit with pre-charge voltage VPP 2 , to pump again with VPP voltage, and to pre-charge this again can be reduced and the amount of wasted current can be reduced. In addition, by forming the VPP 2  supply circuit and VBB generation circuit separately from the high voltage generation circuit, VPP 2  current and VBB current that are needed whenever the high voltage generation circuit  300  performs a pumping operation can be stably provided.