Abstract:
A reference voltage generation circuit includes a loading block suitable for generating a reference current and first and second mirroring currents obtained by mirroring the reference current based on a power source voltage, a biasing block suitable for generating a first bias voltage controlled corresponding to variations in the power source voltage and a second bias voltage controlled corresponding to variations in temperature based on the first mirroring current, a compensation block suitable for compensating for the reference current based on the first and second bias voltages, and an output load block suitable for generating a reference voltage which corresponds to the reference current based on the second mirroring current.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority under 35 U.S.C. 119(a) to Korean Patent Application No. 10-2016-0068796, filed on Jun. 2, 2016, which is incorporated herein by reference in its entirety. 
       BACKGROUND 
     1. Field 
       [0002]    Various embodiments of the present invention relate to a semiconductor design technology and, more particularly, to a reference voltage generation circuit and a method for driving the same. 
       2. Description of the Related Art 
       [0003]    In order to perform a stable operation semiconductor devices generally use a reference voltage. For example, the reference voltage may be used as a reference for generating an internal voltage and for determining logic value of signals. The reference voltage is ideally required to have a uniform voltage level regardless of variations in process, voltage and temperature (PVT) of semiconductor devices. 
         [0004]    A reference voltage is generated in a reference voltage generation circuit included in a semiconductor device, For example, the reference voltage generation circuit includes a band gap reference (BGR) circuit. However, the conventional BGR circuit has a complicated circuit structure. 
       SUMMARY 
       [0005]    Various embodiments of the present invention are directed to a reference voltage generation circuit having a simple circuit structure and can thus occupy a smaller area in a semiconductor device, The reference voltage generation circuit may generate a stable reference voltage uniform regardless of variations in process, voltage and temperature (PVT). The present invention is also directed to a method for driving the reference voltage generation circuit. 
         [0006]    In accordance with an embodiment of the present invention, a reference voltage generation circuit includes a loading block suitable for generating a reference current and first and second mirroring currents obtained by mirroring the reference current based on a power source voltage; a biasing block suitable for generating a first bias voltage controlled corresponding to variations in the power source voltage and a second bias voltage controlled corresponding to variations in temperature based on the first mirroring current; a compensation block suitable for compensating for the reference current based on the first and second bias voltages; and an output load block suitable for generating a reference voltage which corresponds to the reference current based on the second mirroring current. 
         [0007]    The loading block may include: a first loading unit coupled between a power source voltage terminal and a first reference node and suitable for generating the reference current; a second loading unit coupled between a power source voltage terminal and a first mirroring node and suitable for generating the first mirroring current; and a third loading unit coupled between the power source voltage terminal and an output node of the reference voltage and suitable for generating the second mirroring current. 
         [0008]    The first loading unit may include a first PMOS transistor having a gate coupled to the first reference node, a source coupled to the power source voltage terminal, and a drain coupled to the first reference node, and the second loading unit may include a second PMOS transistor having a gate coupled to the first reference node, a source coupled to the power source voltage terminal, and a drain coupled to the first mirroring node, and the third loading unit may include a third PMOS transistor having a gate coupled to the first reference node, a source coupled to the power source voltage terminal, and a drain coupled to the output node of the reference voltage. 
         [0009]    The first to third PMOS transistors may operate in a saturation region. 
         [0010]    The compensation block may include: a first compensation unit coupled between the first reference node and a second reference node and suitable for compensating for the reference current based on the first bias voltage during variations in the power source voltage; and a second compensation unit coupled between the second reference node and a ground voltage terminal and suitable for compensating for the reference current based on the second bias voltage during variations of temperature. 
         [0011]    The first compensation unit relay include a first NMOS transistor having a gate receiving the first bias voltage, a source coupled to the second reference node, and a drain coupled to the first reference node, and the second compensation unit may include a second NMOS transistor having a gate receiving the second bias voltage, a source coupled a ground voltage terminal, and a drain coupled to the second reference node. 
         [0012]    The first NMOS transistor may operate in a saturation region, and the second NMOS transistor may operate in a linear region. 
         [0013]    The biasing block include: a first biasing unit coupled between a second mirroring node and the ground voltage terminal and suitable for generating the first bias voltage that is lowered below a voltage loaded onto the second mirroring node; and a second biasing unit coupled between the first mirroring node and the second mirroring node and suitable for generating a voltage loaded onto the first mirroring node as the second bias voltage. 
         [0014]    The first biasing unit may include: a first resistance element coupled between the second mirroring node and a third mirroring node; and a third NMOS transistor having a gate coupled to the second mirroring node, a source coupled to the ground voltage terminal, and a drain coupled the third mirroring node. 
         [0015]    The first biasing unit may generate a voltage loaded onto the third mirroring node as the first bias voltage 
         [0016]    A size of the first NMOS transistor may be larger than a size of the third NMOS transistor. 
         [0017]    The second biasing unit may include a fourth NMOS transistor to having a gate coupled to the first mirroring node, a source coupled to the second mirroring node, and a drain coupled to the first mirroring node. 
         [0018]    The third and fourth NMOS transistors may operate in a saturation region. 
         [0019]    The output load block may include second resistance element coupled between the output node of the reference voltage and the ground voltage terminal. 
         [0020]    In accordance with another embodiment of the present invention, a method for driving a reference voltage generation circuit includes: generating a first bias voltage corresponding to variations in a power source voltage; generating a second bias voltage which is not responsive to the variations in the power source voltage; and generating a stable reference voltage regardless of the variations in the power source voltage by controlling a reference current based on the first and second bias voltages. 
         [0021]    The second bias voltage may be corresponding to variations in temperature; and generating a stable reference voltage regardless of the variations in temperature by controlling a resistance value reflected in the reference current based on the first and second bias voltages. 
         [0022]    The resistance value may be controlled based on a linear resistance characteristic. 
         [0023]    In accordance with yet another embodiment of the present invention, a method for driving a reference voltage generation circuit includes: generating a first bias voltage which is not responsive to variations in temperature; generating a second bias voltage corresponding to the variations in temperature; and generating a stable reference voltage regardless of the variations in temperature by controlling a resistance value reflected in a reference current based on the first and second bias voltages. 
         [0024]    The resistance value may be controlled based on a linear resistance characteristic. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0025]    The above and other features and advantages of the present invention will become more apparent to those skilled in the art to which the present invention belongs by describing in detail various embodiments thereof with reference to the attached drawings in which: 
           [0026]      FIG. 1  is a diagram illustrating a reference voltage generation circuit in accordance with an embodiment of the present invention. 
           [0027]      FIG. 2  is a graph illustrating temperature dependent resistance characteristics of various elements employed in the reference voltage generation circuit of  FIG. 1 . 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    Various embodiments of the present invention will be described below in more detail with reference to the accompanying drawings. These embodiments are provided so that this disclosure is thorough and complete. All “embodiments” referred to in this disclosure refer to embodiments of the inventive concept disclosed herein. The embodiments presented are merely examples and are not intended to limit the scope of the invention, 
         [0029]    Moreover, it is noted that the terminology used herein is for the purpose of describing the embodiments only and is not intended to be limiting of the invention. As used herein singular forms are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including” when used in this specification, indicate the presence of stated features, but do not preclude the presence or addition of one or more other non-stated features. As used herein, the term “and/or” indicates any and all combinations of one or more of the associated listed items. It is also noted that in this specification, “connected/coupled” refers to one component not only directly coupling another component but also indirectly coupling another component through an intermediate component. 
         [0030]    It will be understood that, although the terms “first”, “second”, “third”, and so on may be used herein to describe various elements, these elements are not limited by these terms. These terms are used to distinguish one element from another element. Thus, a first element described below could also be termed as a second or third element without departing from the spirit and scope of the present invention. 
         [0031]    The drawings are not necessarily to scale and, in some instances, proportions may have been exaggerated in order to clearly illustrate features of the embodiments. 
         [0032]    Referring now to  FIG. 1  a configuration of a reference voltage generation circuit  100  is provided, in accordance with an embodiment of the present invention. 
         [0033]    According to the embodiment of  FIG. 1 , the reference voltage generation circuit  100  may include a loading block  110 , a compensation block  120 , a biasing block  130 , and an output load block  140 . 
         [0034]    The loading block  110  may generate a reference current IREF, a first mirroring current I 1  and a second mirroring current I 2  based on a power source voltage VDD. That is, the loading block  110  may serve as a current mirroring block that mirrors the reference current IREF to generate the first mirroring current I 1  and the second mirroring current I 2 . 
         [0035]    The loading block  110  may include a first loading unit, a second loading unit, and a third loading unit. 
         [0036]    The first loading unit may be coupled between a power source voltage VDD terminal, where the power source voltage VDD is supplied, and a first reference node RN 1 . The first loading unit may generate the reference current IREF. For example, the first loading unit may include a first PMOS transistor P 1  that is diode-connected. The first PMOS transistor P 1  may have a gate coupled to the first reference node RN 1 , a source coupled to the power source voltage VDD terminal, and a drain coupled to the first reference node RN 1 . The first PMOS transistor P 1  may operate in a saturation region. 
         [0037]    The second loading unit may be coupled between the power source voltage VDD terminal and a first mirroring node MN 1 . The second loading unit may generate the first mirroring current I 1 . For example, the second loading unit may include a second PMOS transistor P 2 . The second PMOS, transistor P 2  may have a gate coupled to, the first reference node RN 1 , a source coupled to the power source voltage VDD terminal, and a drain coupled to the first mirroring node MN 1 . The second PMOS transistor P 2  may operate in a saturation region. 
         [0038]    The third loading unit may be coupled between the power source voltage VDD terminal and an output node of a reference voltage VREF. The third loading unit may generate the second mirroring current I 2 . For example, the third loading unit may include a third PMOS transistor P 3 , The third PMOS transistor P 3  may have a gate coupled to the first reference node RN 1 , a source coupled to the power source voltage VDD terminal, and a drain coupled to the output node of the reference voltage VREF. The third PMOS transistor P 3  may operate in a saturation region. 
         [0039]    The compensation block  120  may compensate for the reference current IREF based on first and second bias voltages VB 1  and VB 2 . 
         [0040]    The compensation block  120  may include a first compensation unit and a second compensation unit. 
         [0041]    The first compensation unit may be coupled between the first reference node RN 1  and a second reference node RN 2 . The first compensation unit may control the reference current IREF based on the first bias voltage VB 1 . For example the first compensation unit may include a first NMOS transistor NI, The first NMOS transistor N 1  may have a gate receiving the first bias voltage VB 1 , a source coupled to the first reference node RN 1  and a drain coupled to the second reference node RN 2 . The first NMOS transistor N 1  may operate in a saturation region. 
         [0042]    The second compensation unit may be coupled between the second reference node RN 2  and a ground voltage VSS terminal where a ground voltage VSS is suppled. The second compensation unit may control a resistance value reflected in the reference current IREF based on the second bias voltage VB 2 . For example, the second compensation unit may include a second NMOS transistor N 2 . The second NMOS transistor N 2  may have a gate receiving the second bias voltage VB 2 , a source coupled to the ground voltage VSS terminal, and a drain coupled to the second reference node RN 1   a . The second NMOS transistor N 2  may operate in a linear region. 
         [0043]    The biasing block  130  may generate the first bias voltage VB 1  controlled to correspond to variations in the power source voltage VDD and the second bias voltage VB 2  controlled to correspond to variations in temperature, based on the first mirroring current The biasing block  130  may form a first mirroring path for the first mirroring current I 1  along with the second loading unit P 2 . 
         [0044]    The biasing block  130  may include first and second biasing units. 
         [0045]    The first biasing unit may be coupled between a second mirroring node MN 2  and the ground voltage VSS terminal, The first biasing unit may generate the first bias voltage VB 1  that is dropped below a voltage loaded onto the second mirroring node MN 2 . For example, the first biasing unit may include a first resistance element (i.e., a resistor) RS and a third NMOS transistor N 3  that are coupled in series between the second mirroring node MN 2  and the ground voltage VSS terminal. The first resistance element RS may be coupled between the second mirroring node MN 2  and a third mirroring node MN 3 . The third NMOS transistor N 3  may have a gate coupled to the second mirroring node MN 2 , a source coupled to the ground voltage VSS terminal, and a drain coupled to the third mirroring node MN 3 . The third NMOS transistor N 3  may operate in a saturation region. The size (i.e., width and length) of the third NMOS transistor N 3  may be smaller than the size (i.e., width and length) of the first NMOS transistor N 1 . This is because a gate voltage of the first NMOS transistor N 1  is unconditionally lower than a gate voltage of the third NMOS transistor N 3 . Hence, for the reference current TREE and the first mirroring current to have the same value, the width and length of the third NMOS transistor N 3  are designed to be smaller than those of the first NMOS transistor. 
         [0046]    The second biasing unit may be coupled between the first mirroring node MN 1  and the second mirroring node MN 2 . The second biasing unit may supply a voltage loaded onto the first mirroring node MN 1  as the second bias voltage VB 2  to the second compensation unit. For example, the second biasing unit may include a fourth NMOS transistor N 4  that is diode-connected. The fourth NMOS transistor N 4  may have a gate coupled to the first mirroring node MN 1 , a source coupled to the second mirroring node MN 2 , and a drain coupled to the first mirroring node MN 1 . The fourth NMOS transistor N 4  may operate in a saturation region. 
         [0047]    The output load block  140  may generate the reference voltage VREF based on the second mirroring current  12 . For example, the output load block  140  may include a second resistance element (I.E., a resistor) RL. The second resistance element RL may be coupled between the output node of the reference voltage VREF and the ground voltage VSS terminal. 
         [0048]    Hereinafter, an operation of the reference voltage generation circuit  100  when the power source voltage VDD varies is described below. 
         [0049]    When the power source voltage VDD varies, the loading block  110  may generate the reference current IREF, the first mirroring current I 1  and the second mirroring current I 2  having an abnormal level. For example, when the power source voltage VDD varies, the gate-source voltages Vgs of the first to third PMOS transistors P 1  to P 3  also vary, hence the reference current IREF, the first mirroring current I 1  and the second mirroring current I 2  may increase or decrease from a normal level. 
         [0050]    The first resistance element RS and the third NMOS transistor N 3  may control the first bias voltage VB 1  based on the first mirroring current I 1 . For example when the first mirroring current I 1  varies, the first bias voltage VB 1 . generated from the third mirroring node MN 3  may vary. A variation amount of the first bias voltage VB 1  may be relatively greater than a variation amount of the voltage loaded onto the second mirroring node MN 2 . Conversely, the variation amount of the voltage loaded onto the second mirroring node MN 2  may be relatively smaller than the variation amount of the first bias voltage VB 1 . 
         [0051]    The first NMOS transistor N 1  may control the reference current IREF based on the first bias voltage VB 1 . For example, a gate-source voltage Vgs of the first NMOS transistor N 1  may be controlled by the first bias voltage VB 1 , a current amount of the reference current IREF may be controlled by the first NMOS transistor N 1 . In other words, the reference current IREF varied by variations in the power source voltage VDD may be compensated by the first NMOS transistor N 1 . 
         [0052]    As the reference current IREF is compensated as above, the first mirroring current I 1  and the second mirroring current I 2  may be compensate together, and the output load block  140  may finally generate the reference voltage VREF regardless of variations in the power source voltage VDD. 
         [0053]    The fourth NMOS transistor N 4  may keep the second bias voltage VB 2  constant based on the first mirroring current  11 . Since the second bias voltage VB 2  may correspond to the voltage loaded onto the first mirroring node MN 1 , as described above, the variation amount of the second bias voltage VB 2  may be considerably smaller than the variation amount of the first bias voltage VB 1 . In other words the variation amount of the second bias voltage VB 2  may be negligible. Accordingly, as a gate-source voltage Vgs of the second NMOS transistor N 2  remains constant, the resistance value reflected in the reference current IREF remains constant. 
         [0054]    An operation of the reference voltage generation circuit  100  when a temperature varies is described below. 
         [0055]      FIG. 2  is a graph illustrating temperature dependent resistance characteristics of some elements shown in  FIG. 1 . 
         [0056]    Referring to  FIG. 2 , resistance values of MOS transistors included in the reference voltage generation circuit  100  may vary based on temperatures. This may be related to threshold voltages filth of the MOS transistors. 
         [0057]    Particularly, a resistance value RV_N 1  of the first NMOS transistor N 1  and a resistance value RV_N 3  of the third NMOS transistor N 3  may vary based on variations in temperature. Since the size of the first NMOS transistor N 1  may be larger than the size of the third NMOS transistor N 3 , a variation amount of the temperature dependent resistance value of the first NMOS transistor N 1  may be greater than a variation amount of the temperature dependent resistance value of the third NMOS transistor N 3 . 
         [0058]    When temperature varies as above, the resistance value RV_N 1  of the first NMOS transistor N 1  may vary, hence the reference current IREF, the first mirroring current I 1  and the second mirroring current I 2  may vary together. 
         [0059]    The biasing block  130  may control the second bias voltage VB 2  based on temperatures. For example, the biasing block  130  may control the second bias voltage VB 2  based on the variation amount of the temperature dependent resistance value of the third NMOS transistor N 3  and a variation amount of a temperature dependent resistance value of the fourth NMOS transistor N 4 . A variation amount of a temperature dependent resistance value RV_RS of the first resistance element. RS may be ignored based upon the characteristics of a passive resistor. 
         [0060]    The second NMOS transistor N 2  may compensate for the resistance value RV_N 1  varied by the first NMOS transistor N 1  by controlling the resistance value reflected in the reference current IREF to based on the second bias voltage VB 2 . The resistance value may correspond to a resistance value RV_N 2  of the second NMOS transistor N 2 . For example, a gate voltage of the second NMOS transistor N 2  may be controlled based on the second bias voltage VB 2 , and the reference current IREF may be controlled based on the resistance value RV_N 2  of the second NMOS transistor N 2  operating in the linear region. In other words, the reference current IREF varied with variations in the temperature may be compensated based on a linear resistance characteristic of the second NMOS transistor N 2 . 
         [0061]    The resistance value RV_N 2  of the second NMOS transistor N 2  may be designed to be controlled in consideration of temperature dependent resistance values of elements included in the reference voltage generation circuit  100 . At any rate, the resistance value RV_N 2  of the second NMOS transistor N 2  may be designed to be controlled to correspond to a difference between the temperature dependent resistance value RV_N 1  of the first NMOS transistor N 1  and the temperature dependent resistance value RV_N 3  of the third NMOS transistor N. 
         [0062]    As the reference current IREF is compensated, the first mirroring current I 1  and the second mirroring current I 2  may be compensated together, and the output load block  140  may finally generate the reference voltage VREF regardless of variations in temperature. 
         [0063]    The resistance value RV_RS of the first resistance element RS to may have a resistance characteristic that is contrary to a resistance characteristic of the first NMOS transistor N 1 . However, the variation amount of the temperature dependent resistance value of the first resistance element RS may be insignificant as compared with the variation amount of the temperature dependent resistance value of the first NMOS transistor N 1 . In other words, the variation amount of the temperature dependent resistance value of the first resistance element RS may not compensate for the variation amount of the temperature dependent resistance value of the first NMOS transistor N 1 . 
         [0064]    In accordance with an embodiment of the present invention, the reference voltage generation circuit may occupy a smaller area because of a simple circuit structure designed with transistors and resistances. The reference voltage generation circuit may generate a stable reference voltage regardless of variations in process, voltage and temperature (PVT). 
         [0065]    While the present invention has been described with respect to specific embodiments, the embodiments are not intended to be restrictive, but rather descriptive, Further, it is noted that the present invention may be achieved in various ways through substitution, change, and modification, by those skilled in the art without departing from the spirit and/or scope of the present invention as defined by the following claims.