Abstract:
The present invention provides a reference voltage signal generator capable of generating a constant reference voltage signal regardless of temperature variation by compensating a voltage signal change due to temperature variation. The reference voltage signal generator includes: a voltage signal generating unit receiving a power supply voltage signal and generating a first voltage signal; a regulation sense amplifier generating a regulation voltage signal by regulating the first voltage signal according to the variation of the power supply voltage signal; and a voltage distributing unit including a variable resistor for compensating a voltage signal variation according to a change in temperature, wherein the voltage distributing unit distributes the regulation voltage signal and outputs a feedback voltage signal dependent on temperature to the regulation sense amplifier, and a reference voltage signal independent of the temperature.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a reference voltage signal generator, and more particularly, to a reference voltage signal generator capable of generating a constant reference voltage signal regardless of a temperature change by effectively compensating voltage variation due to a change in the temperature. 
     DESCRIPTION OF THE PRIOR ART 
     A reference voltage signal generator is a device that generates a voltage signal used as a reference voltage signal of memory devices, e.g., flash memory devices adopting various levels of voltage signals generated from one power supply voltage signal. 
     Generally, the reference voltage signal generator must generate constant reference voltage signals even if the output voltage signal of the power supply varies. 
     Referring to FIG. 1, a conventional reference voltage signal generator comprises a first voltage signal generating unit  110 , a regulation sense amplifier  120 , a voltage distributing unit  130  and a second voltage signal generating unit  140 . The first voltage signal generating unit  110  receives a power supply voltage signal in response to an enable signal En and generates a first voltage signal V 11  of a predetermined value. 
     The regulation sense amplifier  120  receives the first voltage signal V 11  from the first voltage signal generating unit  110  in response to the enable signal En and generates a regulated voltage signal Vr to the voltage distributing unit  130 . Furthermore, the regulation sense amplifier  120  also receives a feedback voltage signal Vfb from the voltage distributing unit  130  and generates the constant regulation voltage signal Vr independently of any change in the voltage signal level of the power supply. 
     The second voltage signal generating unit  140 , which has the same configuration as that of the first voltage signal generating unit  110 , receives the constant regulation voltage signal Vr and generates a reference voltage signal Vref which is stable and constant. In FIG. 1, the numeral references ‘I 100 ’ and ‘S 100 ’ are an inverter and a switching element, respectively. 
     Although the conventional reference voltage signal generator can generates a constant reference voltage signal Vref independently of any change in the voltage signal variation of the power supply, the constant reference voltage signal Vref may be changed by effect of a change of temperature. 
     That is, resistors R 11  and R 12  of the voltage distributing unit  130  do not reflect the temperature change, therefore it is difficult to compensate the voltage signal variation due to the change in temperature. 
     SUMMARY OF THE INVENTION 
     It is, therefore, an object of the present invention to provide a reference voltage signal generator capable of generating a constant reference voltage signal regardless of a change in temperature, by compensating voltage signal change due to the temperature variation. 
     It is, therefore, another object of the present invention to provide a reference voltage signal generator comprising a variable resistor for compensating the voltage signal variation according to a change in temperature, in order to produce a constant reference voltage signal, even if the temperature changes. 
     In accordance with another aspect of the present invention, there is provided a reference voltage signal generating device comprising: a voltage signal generating unit receiving a power supply voltage signal and generating a first voltage signal; a regulation sense amplifier generating a regulation voltage signal by regulating the first voltage signal according to the variation of the power supply voltage signal; and a voltage distributing unit including a variable resistor for compensating a voltage signal variation according to a change in temperature, wherein the voltage distributing unit distributes the regulation voltage signal and outputs a feedback voltage signal dependent on a temperature to the regulation sense amplifier, and a reference voltage signal independent of the temperature. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects and features of the present invention will become apparent from the following description of the preferred embodiments given in conjunction with the accompanying drawings, in which: 
     FIG. 1 is a circuit diagram showing a configuration of the conventional reference voltage signal generator; 
     FIG. 2 is a circuit diagram showing a configuration of a reference voltage signal generator according to the present invention; 
     FIG. 3 is a circuit diagram showing a configuration of a voltage signal generating unit of the reference voltage signal generator shown in FIG. 2; 
     FIG. 4 is a circuit diagram showing configuration of a regulation sense amplifier of the reference voltage signal generator shown in FIG. 2; 
     FIG. 5A is a graph showing resistor temperature coefficients of normal resistors and a variable resistor for compensating voltage signal variation according a change in temperature; and 
     FIG. 5B is a graph showing temperature dependencies of a voltage signal outputted from the voltage signal generating unit and a feedback voltage signal outputted from the voltage distributing unit. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, a reference voltage signal generator according to embodiments of the present invention will be described in detail referring to the accompanying drawings. 
     Referring to FIG. 2, a reference voltage signal generator, in accordance with the present invention, comprises a voltage signal generating unit  210 , a regulation sense amplifier  220  and a voltage distributing unit  230 . 
     The voltage signal generating unit  210  receives a power supply voltage signal Vsource in response to an enable signal En and outputs a first voltage signal V 21  to the regulation sense amplifier  220 . The regulation sense amplifier  220  receives the first voltage signal V 21  from the voltage signal generating unit  210  in response to the enable signal En and a feedback voltage signal Vfb, varying with temperature, from the voltage distributing unit  230 , and the regulation sense amplifier  220  generates a constant regulation voltage signal Vref independently of any change in the voltage signal level of the power supply. The voltage distributing unit  230  comprises two output terminals OUT 1  and OUT 2 , three normal resistors R 21 , R 23  and R 24  and a variable resistor R 22  for compensating voltage signal variation according to a change in temperature. The voltage distributing unit  230  receives the regulation voltage signal Vr from the regulation sense amplifier  220  and outputs the feedback voltage signal Vfb, varying according to a change in temperature, to a first output terminal OUT 1  connected to the regulation sense amplifier  220 , and the voltage distributing unit  230  also outputs a reference voltage signal Vref to a second output terminal OUT 2 . 
     The reference voltage signal generator of the present invention will be explained in detail, referring to FIGS. 2 to  4 . 
     FIG. 3 is a circuit diagram showing the configuration of the voltage signal generating unit  210  in FIG.  2 . 
     The voltage signal generating unit  210  comprises an electric current mirror including four switching elements(from S 21  to S 24 ), a switching element S 25 , and two resistors R 25  and R 26 . That is, the voltage signal generating unit  210  comprises the current mirror comprising the switching elements S 21  and S 22  receiving the power supply voltage signal Vsource, respectively, the switching element S 23  connected between the switching element S 21  and the ground GND, and the switching element S 24  connected to the switching element S 23 . The switching element S 21  is a PMOS transistor, and the switching element S 22  is a diode-connected PMOS transistor. The switching element S 23  is an NMOS transistor, and the switching element S 23  is a diode-connected NMOS transistor. Also, gates of the switching element S 21  and S 22  are connected to each other and are applied the voltage signal on node N 21  which is a connecting point of the switching elements S 22  and S 24 . Gates of the switching element S 23  and the switching element S 24  are connected to each other and are applied the potential on node N 21  which is a connecting point of the switching elements S 22  and S 24 . 
     Also, the voltage signal generating unit  210  further comprises the switching element S 25 , resistors R 25  and R 26 . The switching element S 25  is a PMOS transistor connected to the switching element S 22  and an output terminal OUT 3  from which the regulation voltage signal Vr is outputted, the potential at node N 21  is applied to the gate of the switching element S 25 . The resistor R 25  is connected between the switching element  24  and the ground GND, and the resistor R 26  is connected between the output terminal OUT 3  and the ground GND and is connected in parallel with the resistor R 25 . 
     Referring to FIG. 4, the regulation sense amplifier  220  comprises a switching element S 26  operating in response to the enable signal En and receiving the power supply voltage signal Vsource, a current mirror including switching elements S 27  and S 28 , a switching element S 29  connected to the seventh switching element S 27  and receiving signals from the voltage signal generating unit  210 , a switching element S 30  connected the switching elements S 28  and S 29 , a switching element S 32  connected to the common node of the switching elements S 29  and S 30  and the ground GND, a switching element S 31  connected to the switching element S 26  and the output terminal OUT 4 , a switching element S 33  connected to the switching element S 27 , a switching element S 34  connected to the switching element S 33  and the ground GND, a switching element S 35  connected to the switching element S 31  and the ground GND, and a switching element S 36  connected to the output terminal OUT 4  and the ground GND. In FIG. 4, the numerical reference ‘I 20 ’ denotes an inverter. 
     The switching element S 26  is a PMOS transistor that operates in response to the enable signal En, and the switching element S 27  is a diode-connected PMOS transistor, and the switching element S 28  is a PMOS transistor of which gate is connected to the gate of the seventh switching element S 27 . The switching element S 29  is an NMOS transistor of which gate receives the first voltage signal V 21  from the voltage signal generating unit  210 , and the switching element S 30  is an NMOS transistor of which gate receives the feedback voltage signal Vfb from the voltage distributing unit  230 . The switching element S 31  is a PMOS transistor of which gate receives potential on node N 23 , a connecting point of the switching element S 28  and S 30 , the switching element S 33  is a diode-connected PMOS transistor, and the switching element S 34  is a diode-connected NMOS transistor. The gates of the switching elements S 33  and S 34  are connected to each other. The switching elements S 32  and S 35  are NMOS transistors of which gates receive the potential on node N 24 , a connecting point of the switching elements S 33  and S 34 . 
     The switching element S 36  is an NMOS transistor, connected to the output terminal OUT 4  and node N 25 , a connecting point of the switching elements S 31  and S 35 , and the switching element S 36  operates in response to the enable signal En. The switching element S 32 , S 34  and S 36  are connected to the ground GND with the switching element S 35 . 
     In the meantime, the threshold voltage of the switching element S 33  and S 34  are controlled in manufacturing processes in order to determine the potential on node N 24 . The switching element S 32  regulates the amount of current flowing to the switching elements S 29  and S 30  according to the electrical potential at node N 24 . 
     Also, the switching element S 35 , connected to node N 25  and the ground GND, plays a role of a load resistor according to potential at node N 24 . 
     Referring to FIG. 2, the voltage distributing unit  230  comprises a resistor R 21  connected to the output terminal OUT 1 , from which the feedback voltage signal Vfb is outputted, a resistor R 22  connected to the output terminal OUT 1  and the ground GND, a resistor R 23  connected to the output terminal of the regulation sense amplifier  220  and the second output terminal OUT 2 , from which the reference voltage signal Vref is outputted, and a resistor R 24  connected the ground and the output terminal OUT 2  shared with the resistor R 23 . 
     The resistors R 21 , R 23  and R 24  are normal resistors of which resistance values are not changed according to the change of temperature, but the resistor R 22  is a variable resistor for compensating voltage signal variation according to a change in temperature. 
     Hereinafter, the operation of the reference voltage signal generator according to the present invention will be described in detail. 
     First, the operation of the voltage signal generating unit  210  shown in FIG. 3 is the same as the following. 
     The resistance value of the resistor R 25  is regulated in order to generate the first voltage signal V 21  from the voltage signal of the power supply. 
     If the resistance value of the resistor R 25  is increased, the current flowing to the switching element S 24  is decreased, and the potential on N 21  increases. The current flowing to the output terminal of the voltage signal generating unit  210  decrease because the potential at node N 21  is not quite enough to turn-on the switching element S 25 . 
     When the current flowing to the output terminal OUT 3  decreases, the voltage drop is generated by the resistor R 26 , and the voltage across the resistor R 26  is outputted to the output terminal OUT 3 . 
     On the other hand, the potential at node N 21  is decreased in proportion to the resistance value of the resistor R 25 , and a high level of the first voltage signal V 21  is outputted to the output terminal OUT 3 . In case that the potential at node N 21  is low, the fifth switching element S 25  is partially turned-on, so that the maximum value of current can flow. Accordingly, a high voltage can be obtained from the resistor R 26  by the maximum current, and the voltage of high level is outputted to the output terminal OUT 3 . 
     As mentioned above, the first voltage signal V 21 , the voltage signal of desired value obtained by regulating the resistance value of the resistor R 25  in the voltage signal generating unit  210 , is inputted to the regulation sense amplifier  220 . 
     The value of the first voltage signal V 21  may be different from the target value, when the power supply voltage signal Vsource is high or low. The regulation sense amplifier  220  senses the power supply voltage signal Vsource and regulates the first voltage signal V 21  to a target value according as the voltage signal of the power supply is high or low. 
     Hereinafter, the operations of the regulation sense amplifier  220  and the voltage distributing unit  230  will be described in detail. 
     The regulation voltage signal Vr is determined by the comparison of the first voltage signal V 21  and the feedback voltage signal Vfb. 
     When a low enable signal En is applied, the switching element S 26  changes into turn-off state, and the output terminal OUT 4  is disconnected from the ground. If a high enable signal EN is applied, the voltage signal of the power supply is applied to the current mirrors, which are composed of the switching elements S 27  and S 28  flowing same current. The switching elements S 29  and S 30  receive the current from the switching elements S 27  and S 28 , respectively. 
     At this time, the first voltage signal V 21  is inputted from the voltage signal generating unit  210  to the gate of the switching element S 29 , and a feedback voltage signal Vfb is inputted from the voltage distributing unit  230  to the gate of the switching element S 30 . The feedback voltage signal Vfb is a voltage signal inputted to the regulation sense amplifier  220  from the voltage distributing unit  210  dividing the regulation voltage signal Vr to a predetermined voltage signal value. 
     The potential on node N 23  increases because the current flowing to the switching element S 30  is less than the current flowing to the switching elements S 29 , when the first voltage signal V 21  is higher than the feedback voltage signal Vfb. At this time, the high potential at node N 23  is applied to the gate of the switching element S 31 , the switching element S 31  changes into a nearly turn-off state, and the potential at node N 25 , namely the regulation voltage signal Vr, becomes low. 
     In contrast to this, when the first voltage signal V 21  is lower than the feedback voltage signal Vfb, the potential at node N 23  decreases because the current flowing to the switching element S 30  is greater than the current flowing to the switching element S 29 . At this time, the low potential at node N 23  is applied to the gate of the switching element S 31 , the switching element S 31  changes into the turn-on state, and the potential at the node N 25 , namely the regulation voltage signal Vr, becomes high. 
     By such a feedback operation, the regulation sense amplifier  220  regulates the first voltage signal V 21  in order to generate the regulation voltage signal Vr. 
     In the meantime, the switching elements S 32  and S 35  serve as current sinkers, which flow a constant current from the current mirror to the ground GND and from the switching element S 31  to the ground GND, respectively. The voltage signal applied to the switching elements S 32  and S 35  is controlled by the diode-connected switching elements S 33  and S 34 . If the threshold voltages of the switching elements S 33  and S 34  are equal, half of the power supply voltage signal Vsource is applied to the gates of the switching elements S 32  and S 35  because the potential on the source of the switching element S 33  is the same with the potential of the power supply voltage signal Vsource. If the threshold voltages of the switching elements S 33  and S 34  are not equal, the power supply voltage signal Vsource is divided according to the voltage distribution law shown in the following equation 1. 
     
       
           Vsource=Vtp+Vtn   Eq. 1.  
       
     
     In Eq. 1, ‘Vtp’ and ‘Vtn’ are the voltages on the sources of the switching element S 33  and S 34 , respectively. Therefore, the potential at node N 24  is constant if the power supply voltage signal Vsource is constant, and the constant potential at node  24  is applied to the gates of the switching element S 32  and S 35 , respectively. By the switching elements S 32  and S 35  flowing constant currents, the control of the regulation voltage signal Vr is performed only by the switching elements S 27 , S 28  and S 31 . 
     The regulation voltage signal Vr outputted from the regulation sense amplifier  220  is distributed by the voltage distributing unit  230  including a variable resistor R 22  for compensating voltage signal variation according to a change in temperature, and the distributed voltage is inputted to the regulation sense amplifier  220  again as the feedback voltage signal Vfb. 
     FIG. 5A is a resistor temperature coefficient graph that shows the temperature dependencies of the normal resistor R 21 , R 23  and R 24  and the variable resistor R 22  for compensating voltage signal variation according to the change of temperature. 
     Referring to  5 A, while the resistance values of normal resistors R 21 , R 23  and R 24  do not change (even if the temperatures changes), the resistance value of the variable resistor R 22  changes. 
     Accordingly, as shown in the following Eq. 2, the feedback voltage signal Vfb, obtained from the output terminal OUT  1  connected to the variable resistor R 22  increases in proportional to the resistance value of the variable resistor R 22 , namely the feedback voltage signal Vfb increases in proportional to temperature. 
     
       
           Vbf=Vr *( R 4/( R 3+ R 4))  Eq. 2.  
       
     
     Referring to FIG. 5B, when the first voltage signal V 21  inputted from the voltage signal generating unit  210  increases in response to the increase of the temperature, the feedback voltage signal Vfb, used for regulating the first voltage signal V 21 , is varied with the resistance value of the variable resistor R 22 , therefore, the constant reference voltage signal may be generated regardless of the change in temperature. 
     While the present invention has been described with respect to the particular embodiments, it will be apparent to those skilled in the art that various changes and modifications may be made without departing from the scope of the invention as defined in the following claims.