Abstract:
A method of providing multiple voltage outputs includes receiving an input signal from a multifunctional pump. The method also includes sending a first output signal based on the input signal using a first switch and sending a second output signal based on the input signal using a second switch and a transistor.

Description:
TECHNICAL FIELD 
   This invention relates to providing regulated voltages to an external circuit. 
   BACKGROUND 
   A voltage pump is used to provide voltage to an external circuit. Voltage pumps have a single function, such as a read pump, a program/erase pump or a standby pump. The read pump provides a required voltage to the external circuit so that data can be read. A program/erase pump provides the required voltage to store or to erase data. A standby pump maintains a minimum voltage until other commands (e.g., program/erase, read) are received. 

   
     DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram of a multifunctional pump system. 
       FIG. 2  is a circuit diagram of a multifunctional pump. 
       FIG. 3  is a higher level circuit diagram schematic of a voltage regulation switch. 
       FIG. 4  is a circuit level diagram of another embodiment of the voltage regulation switch. 
   

   DESCRIPTION 
   Referring to  FIG. 1 , a multifunctional pump system  10  includes a multifunctional pump  20  and a regulation switch  70 . Multifunctional pump  20  functions as a program/erase pump, a standby pump, and a read pump. When multifunctional pump  20  functions as a program/erase pump, the multifunctional pump is in a program mode or in an erase mode. When multifunctional pump  20  functions as a standby pump, pump  20  is in a standby mode. When multifunctional pump  20  functions as a read pump, pump  20  is in a read mode. 
   As described in more detail below, multifunctional pump  20  receives an input signal, IN 1 , and if enabled by one, two or three enabling signals, E 1 , E 2 , and E 3  (FIG.  2 ), the pump produces a corresponding output voltage, IN 2 , which represents a read pump, standby pump or a program/erase pump depending on the enabling signals received. 
   For multifunctional pump system  10  to function properly, the system provides multiple outputs and multiple voltage levels to satisfy requirements of an external circuit (not shown). For example, when multifunctional pump  20  is in the program mode, multifunctional pump  20  slews from a read level voltage (e.g., 5 volts (V)) to a program level voltage (e.g., 7 V) and back down to a verify level voltage (e.g., 5 V); and system  10  provides an output corresponding to these voltage changes. Another output is required from system  10  that provides a constant voltage (e.g., 5 V). Thus, system  10  provides both a variable voltage level signal and a constant voltage. 
   In order to meet these requirements in a multifunctional pump system  10 , a regulation switch  70  is added to regulate an output, IN 2 , of multifunctional pump  20  and to produce two outputs. Multifunctional pump  20  supplies IN 2 , as input to regulation switch  70  and the regulation switch produces a first output signal, O 1 , and second output signal, O 2 . First output signal, O 1 , is the program/erase pump voltage and second output voltage, O 2 , is a standby/read voltage. 
   Referring to  FIG. 2 , multifunctional pump  20  includes a comparator  12 , an oscillator  14 , clock drivers (e.g., first clock driver  16   a , second clock driver  16   b , third clock driver  16   c , fourth clock driver  16   d , and fifth clock driver  16   e ), arrays (e.g., first array  18   a , second array  18   b , third array  18   c , fourth array  18   d , and fifth array  18   e ), and a feedback network  22 . Each array is a circuit array that includes switches, capacitors, and transistors configured similar to any standard voltage pump configuration. Comparator  12  receives input, IN 1 , and compares IN 1  to a feedback signal F 1 . If feedback signal F 1  is less than input signal IN 1 , then comparator  12  turns-on oscillator  14 . Oscillator  14  then supplies an oscillating signal to each of the clock drivers  16   a-e . When activated, each of the clock drivers  16   a-e  supply a signal to a corresponding array  18   a-e . The output from each array  18   a-e  are connected to a node  24  so that an output signal, IN 2 , is measured from node  24 . In this embodiment, oscillator  14  is a four phase clock. 
   Enable signals (e.g., first enable signal E 1 , second enable E 2 , and third enable signal E 3 ) activate corresponding clock drivers to place multifunctional pump  20  in different modes. For instance, multifunctional pump  20  is in the standby mode when first enable signal, E 1 , enables clock driver  16   a  and turns-on first array  18   a . Multifunctional pump  20  is in the read mode if first array  18   a  is already turned-on and second enable signal, E 2 , enables second clock driver  16   b  to turn-on second array  18   b . Multifunctional pump  20  is in the program mode, if first array  18   a  and second array  18   b  are already turned-on and third enable signal, E 3 , enables third clock driver  16   a , fourth clock driver  16   b , fifth clock driver  16   e  simultaneously to correspondingly activate third array  18   c , fourth array  18   d , and fifth array  18   e.    
   Feedback circuit  22  connects to node  24  and supplies feedback signal, F 1 , from arrays  18   a-e  to comparator  12 . In this embodiment, feedback circuit  22  is made of resistive elements. In other embodiments, feedback circuit  22  can have resistive elements that include transistors configured as a voltage divider. 
   In single function pumps, a standby pump uses one array, a read pump uses two arrays, and a program/erase pump uses five arrays. In this embodiment, multifunctional pump  20  uses only five arrays. Multifunctional pump  20  saves approximately 45% of the die size area than if there were three separate pumps. For instance, the read pump occupies about 0.164 square millimeters (mm), a standby pump occupies 0.109 square mm, and a program pump occupies 0.329 square mm. By combining all three functions and using only five arrays, multifunctional pump  20  occupies only 0.329 square mm which is equal to the size of a program pump. 
   In this embodiment, during standby mode and read mode, IN 2  is equal to 4.8 V. During program mode IN 2  is equal to 7.0 V and during erase mode, IN 2  is equal to 5.0 V. 
   Regulation switch  70  as shown in  FIG. 3  includes a comparator  40 , a first transistor  42  (e.g., p-channel metal oxide semiconductor), a first switch  44 , and a second switch  46 . Comparator  40  receives a feedback voltage, F 2 , and compares it to a reference voltage, R 1 , when enabled by a fourth enable signal, E 4 . Feedback voltage F 2 , connects a transistor source  45  to comparator  40 . If F 2  is less than R 1 , comparator  40  regulates a gate  43  of first transistor  42 . First transistor  42  acts as a series regulation switch. Thus, transistor  42  is turned-on when the voltage of transistor gate  43  drops below a threshold voltage, V T , of transistor  42 . However, as the voltage increases from comparator  40  to transistor gate  43 , the first transistor  42  gradually turns-off so that the transistor is off when the voltage at transistor gate  43  is greater than IN 2 −V T . For example, when IN 2 =4.8 V and V T =0.7 V, transistor  42  turns off at gate voltages greater than 4.1 volts. 
   In this embodiment, first switch  44  is a back-to-back switch which includes logic circuits (e.g., AND gates) and a complimentary metal oxide semiconductor transistor. Second switch  46  includes a p-channel metal oxide semiconductor transistor. 
   Referring to  FIG. 4 , in other embodiments, regulation switch  70  includes a set of additional switches (a third switch  58 , a fourth switch  64 , a fifth switch  56 , a sixth switch  62 , and a seventh switch  60 ) and a feedback system  66 . 
   Multifunctional pump  20  is turned-off when first switch  46 , second switch  44 , third switch  58  and fourth switch  64  are open or off and fifth switch  56 , sixth switch  62  and seventh switch  60  are closed or on. With fifth switch closed and third switch open, first transistor  42  is off since the transistor gate is tied to the transistor drain. When multifunctional pump  20  is turned off, first output signal, O 1 , and second output signal, O 2 , are both equal to a constant voltage, V CC . The following table summarizes, the switch and signals in the no pump mode: 
   
     
       
             
             
             
           
         
             
                 
                 
             
           
           
             
                 
               Switch 1 
               Off 
             
             
                 
               Switch 2 
               Off 
             
             
                 
               Switch 3 
               Off 
             
             
                 
               Switch 4 
               Off 
             
             
                 
               Switch 5 
               On 
             
             
                 
               Switch 6 
               On 
             
             
                 
               Switch 7 
               On 
             
             
                 
               Enable signal, E 4   
               X 
             
             
                 
               First output signal, O 1   
               V CC   
             
             
                 
               Second output signal, O 2   
               V CC   
             
             
                 
                 
             
           
        
       
     
   
   In the standby mode and read modes, first switch  46  and third switch  58  are closed and the remaining switches are open. Fourth enable signal, E 4 , disables comparator  40 . When the third switch  58  is on, output  41  of comparator  40  is shorted to ground and when fifth switch  56  is opened transistor  40  is fully-on. Therefore, second output signal O 2  is equal to 4.8 V and output signal O 1 , with seventh switch  60  closed, is equal to V CC . The following table summarizes, the switch and signals in the standby/read mode: 
   
     
       
             
             
             
           
         
             
                 
                 
             
           
           
             
                 
               Switch 1 
               On 
             
             
                 
               Switch 2 
               Off 
             
             
                 
               Switch 3 
               On 
             
             
                 
               Switch 4 
               Off 
             
             
                 
               Switch 5 
               Off 
             
             
                 
               Switch 6 
               Off 
             
             
                 
               Switch 7 
               Off 
             
             
                 
               Enable signal, E 4   
               Low 
             
             
                 
               First output signal, O 1   
               V CC   
             
             
                 
               Second output signal, O 2   
               4.8 V 
             
             
                 
                 
             
           
        
       
     
   
   During a program/erase mode first switch  46 , second switch  44  and fourth switch  64  are closed and the remaining switches are open. Fourth enable signal E 4  is high and activates comparator  40 . Thus, output voltage O 1  is directly connected to IN 2  and is equal to either 5 V or 7 V and O 2  is equal to a constant voltage of 4.7 V. The following table summarizes, the switch and signals in the program/erase mode: 
   
     
       
             
             
             
           
         
             
                 
                 
             
           
           
             
                 
               Switch 1 
               On 
             
             
                 
               Switch 2 
               On 
             
             
                 
               Switch 3 
               Off 
             
             
                 
               Switch 4 
               On 
             
             
                 
               Switch 5 
               Off 
             
             
                 
               Switch 6 
               Off 
             
             
                 
               Switch 7 
               Off 
             
             
                 
               Enable signal, E 4   
               High 
             
             
                 
               First output signal, O 1   
               7.0 V/5.0 V 
             
             
                 
               Second output signal, O 2   
               4.7 V 
             
             
                 
                 
             
           
        
       
     
   
   A feedback circuit  66  includes a second transistor  48 , a third transistor  50 , a fourth transistor  52  and a fifth transistor  54 . Each transistor gate is tied to the transistor drain so that feedback circuit  66  is a voltage divider. The voltage divider allows for feedback voltage F 2  to be a lower voltage than the IN 2 . However, the amount of transistors in feedback circuit  66  is dependent on the reference voltage R 1  chosen. In this embodiment, the reference voltage is 1.33 V so that there are four transistors used in feedback circuit  66 . 
   The invention is not limited to the specific embodiments described herein. For example, multifunctional pump system  10  could be designed for other voltages level outputs. 
   Other embodiments not described herein are also within the scope of the following claims.