JP4517062B2 - Constant voltage generator - Google Patents

Description

  The present invention relates to a low output voltage constant voltage generation circuit and a constant current generation circuit suitable for a step-down DC-DC converter circuit having a low output voltage.

  Conventionally, in this type of constant voltage generation circuit, for example, Non-Patent Document 1 is known. In the constant voltage generating circuit shown in Non-Patent Document 1, a circuit configuration as shown in FIG. 2 is used, and a constant voltage is always generated regardless of variations in temperature and power supply voltage.

を得る。ただし、Ｖ_T＝ｋＴ／ｑ、このＶ_Tを熱電圧と呼んでいる。ｋ：ボルツマン定数、T：絶対温度、ｑ：単位電荷である。 In FIG. 2, the circuit constituted by the first diode 10, the second diode 20, the impedance element (R3) 30, and the operational amplifier 40 having a differential gain of A times increases in current value as the temperature rises. Generates a current with a positive temperature coefficient. If the operational amplifier 40 has a large differential gain A, the voltages at its two input terminals (+ terminal 62 and −terminal 61) match. Accordingly, when the impedance elements 300 and 320 have the same value, the currents flowing through them are also equal. Here, let this current be I _P. On the other hand, the anode / cathode junction area of the diode 20 is set to N times the anode / cathode junction area of the diode 10. At this time, the voltage across the diode 10 V _BED1, V _BED2 the voltage across the diode 20, if the voltage across v _R3 impedance element 30, than to v _R3 = V _BED1 -V _BED2 holds,
v _R3 = V _T ln (I _P / I _S ) −V _T ln (I _P / NI _S ) = V _T lnN
Because

Get. However, V _T = kT / q, and this V _T is called a thermal voltage. k: Boltzmann constant, T: absolute temperature, q: unit charge.

と表される。ここでＶ_GOは、０°Kにおけるシリコンのバンドギャップ電圧の推定値であり、Eは定数、γ＝４−ｎ、ｎは移動度の温度係数である。ここで、Ｉ_P＝ＧＴ^αと置けば、

と書ける。なお、αの値は（１）式より求まり、抵抗R３が温度係数を持たない場合には、ほぼ１である。（３）式より、Ｖ_BED1は負の温度係数を持つ電圧であることがわかる。 From equation (1), it can be seen that I _P is a current that varies in proportion to the temperature. Since the value increases as the temperature rises, the current has a positive temperature coefficient. Since this current I _P flows through the diode 10, the voltage V _{BED1 at the} terminal 62 can be determined by referring to Non-Patent Document 1.

It is expressed. Here, V _GO is an estimated value of the band gap voltage of silicon at 0 ° K, E is a constant, γ = 4-n, and n is a temperature coefficient of mobility. Here, if I _P = GT ^α ,

Can be written. Note that the value of α is obtained from equation (1), and is approximately 1 when the resistor R3 does not have a temperature coefficient. From equation (3), it can be seen that V _BED1 is a voltage having a negative temperature coefficient.

で表される電圧となる。ただし、Ｋ＝（Ｒ₁／Ｒ₃）ｌnＮである。（４）式を温度Tで微分して零とおけば、Ｖ_REFの温度係数が零となる条件が求まる。 Since I _{P in} equation (1) has a positive temperature coefficient and V _{BED1 in} equation (3) has a negative temperature coefficient, it is expected that a voltage with no temperature change can be obtained by combining the two. Is done. Actually, since the current flowing through the impedance element 300 is I _P , V _REF in FIG.

The voltage is represented by However, K = (R ₁ / R ₃ ) lnN. If the equation (4) is differentiated by the temperature T and set to zero, the condition that the temperature coefficient of V _REF becomes zero can be obtained.

より

であるから、これより、

となることがわかる。 This condition is

Than

So, from this,

It turns out that it becomes.

Equation (6) is an equation representing the temperature dependence of the V _REF voltage at which the temperature coefficient becomes zero at T = T ₀ . Now, when T = T ₀ = 25 ° C., V _T is about 26 mV. When γ = 2.8, α = 1, and V _GO = 1.205 [V], V _REF is 1.252 [ V]. When the temperature changes, V _REF changes with this value as a maximum value. As can be seen from equation (6), the term that changes in temperature is a term that includes V _T , and this value is small. Therefore, if a voltage of about 1.25 [V] is set as V _REF , this can be said to be a voltage having no temperature dependence.

In the circuit of FIG. 2, if the characteristic of the operational amplifier 40 is not affected by the fluctuation of the power supply voltage, it is considered that the value of V _REF represented by the equation (6) does not change. If the value of the differential gain A is sufficiently large, this condition is satisfied.

  From the above, it can be seen that the circuit of FIG. 2 has a function of a constant voltage generation circuit that can always supply a constant voltage value even when the temperature and the power supply voltage fluctuate.

  As a second conventional example, a circuit described in Non-Patent Document 2 is known. In this constant voltage generation circuit, a circuit configuration as shown in FIG. 3 is used, and a constant voltage is always generated regardless of variations in temperature and power supply voltage.

However, the circuit of FIG. 3 can be said to be a modification of the circuit of FIG. This is a circuit mainly used in a process using a CMOS element. The operation principle of the circuit of FIG. 3 is the same as that of FIG. I _P in FIG. 3 is the same as that represented by the above formula (1). Also, V _REF in FIG. 3 is the same as that represented by the above equation (6). If V _REF is taken out from the terminal 230 in FIG. 3, the impedance element 320 (R2) can be omitted. However, since it is useful for maintaining the symmetry and balance of the circuit, it may be left if there is a margin in the occupied area.

3, the current I _P flowing through the PMOS transistor is not subject to power supply voltage variation. This is because when the PMOS transistor operates in the saturation region, the change in the drain-source voltage does not affect the drain current value. 3, even when the voltage value of the power source and the terminal 230 due to fluctuations in the power source voltage is changed, the value of the current I _P flowing through the PMOS transistor does not change to be changed is the gate-source voltage. The gate terminal of the PMOS transistor is always controlled so that the voltage of the terminal 61 and the terminal 62 generates a matching current I _P by the operational amplifier 40. Since the voltages at the terminals 61 and 62 are determined with reference to the ground, they are irrelevant to fluctuations in the power supply voltage, and if the temperature is constant, the current _IP is constant regardless of changes in the power supply voltage.

The first difference between the circuits of FIG. 2 and FIG. 3 is that the current I _P is supplied from the operational amplifier 40 in FIG. 2 to the PMOS transistor in FIG. The current I _P flowing through the circuit may be used in other circuits, but the circuit shown in FIG. 3 is used for this purpose.

  A second difference between the circuits of FIGS. 2 and 3 is the difference in the polarity of the operational amplifier 40. In FIG. 2, the positive input terminal of the operational amplifier is connected to the anode of the diode 10, and the negative input terminal is connected to the impedance element 30 side of the diode 20 and the impedance element 30 connected in series. In contrast, in FIG. 3, the negative input terminal of the operational amplifier is connected to the anode of the diode 10, and the positive input terminal is connected to the impedance element 30 side of the diode 20 and the diode 20.

  In FIG. 2, the negative feedback signal fed back from the output terminal of the operational amplifier 40 to the negative input terminal (the feedback factor is {(R3 + Ron) / (R2 + R3 + Ron, where Ron is the equivalent resistance of the diode). )}), And a positive feedback signal fed back to the positive input terminal (feedback rate is (Ron) / (R1 + Ron)). ) Is reduced, and the configuration of the figure is selected so that the circuit operates stably. On the other hand, in FIG. 3, it operates as a common source amplifier circuit. Since the polarity of the feedback signal is inverted by the PMOS transistor, the polarity of the input terminal of the operational amplifier 40 is also inverted to stabilize the circuit operation as described above.

P.R.Gray, P.J.Hurst, S.H.Lewis, and R.G.Meyer, “Analysis and Design of Analog Integrated Circuits”, Fourth Edition, p.323, JOHN WILEY & SONS, INC., 2001. R. Gregolian and G.C.Temes, “Analog MOS Integrated Circuits for Signal Processing”, p.559, JOHN WILEY & SONS, INC., 1986.

  As described above, the circuit of FIG. 2 proposed in Non-Patent Document 1 and the circuit of FIG. 3 proposed in Non-Patent Document 2 can always generate a constant voltage even when the temperature and the power supply voltage fluctuate. Although it is possible, this voltage is about 1.25 [V]. In order to generate an always constant voltage higher or lower than this voltage, or a voltage having a positive temperature coefficient, a negative temperature coefficient, a constant current having no temperature coefficient, etc. Each needs to be created based on [V]. Therefore, each circuit is required, and all the above requirements cannot be satisfied with the same circuit configuration, so that it is not suitable for use as a common circuit block (so-called IP) corresponding to various uses.

  Therefore, in the present invention, a constant voltage higher than 1.25 [V], a constant voltage lower than a constant voltage, a voltage having a positive temperature coefficient or a negative temperature coefficient, a constant current having no temperature coefficient, etc. are generated. It is an object of the present invention to provide an identical circuit configuration that can be implemented.

  A first form of the constant voltage circuit according to the present invention includes a first current generating circuit means for generating a current having a positive temperature coefficient whose current value increases as the temperature increases, and a negative current whose current value decreases as the temperature increases. Second current generating circuit means for generating a current having a temperature coefficient and a combining circuit means for combining both currents.

  The combining circuit means is configured by connecting impedance elements having different impedances in series, supplying a current having the positive temperature coefficient and a current having a negative temperature coefficient to one impedance element, and supplying the other impedance element to the other impedance element. A current having a positive temperature coefficient or a current having a negative temperature coefficient is supplied to generate a constant voltage that does not depend on a temperature change at both ends of both impedance elements. The output voltage is set by the impedance value of the impedance element that supplies a current having a positive temperature coefficient and a current having a negative temperature coefficient and / or the impedance value of the impedance element that determines the current value of the second current generation circuit means.

  The second form of the constant voltage circuit of the present invention includes a first current generating circuit means for generating a current having a positive temperature coefficient whose current value increases as the temperature rises, and a positive current generated by the first current generating circuit means. A second current generating circuit means for generating a current having a negative temperature coefficient that decreases the current value as the temperature rises, and a combining circuit means for synthesizing both currents. Prepare.

  The synthesizing circuit means generates a constant voltage not depending on the temperature change at both ends of the impedance element by supplying the impedance element with the current having the positive temperature coefficient and the current having the negative temperature coefficient. The output voltage is set according to the impedance value of the impedance element that determines the impedance value of the impedance element and / or the current value of the second current generation circuit means.

  By appropriately selecting the impedance value of the impedance element, the temperature coefficient of the voltage across the impedance element connected in series can be made zero.

In the above constant voltage generation circuit, the circuit means for generating a current having a positive temperature coefficient is the same as the circuit of FIG. 3 introduced in Non-Patent Document 2, and this is known. The circuit of FIG. 3 is controlled by an operational amplifier so that the voltage across the first diode and the voltage across the circuit where the second diode and the first impedance element are connected in series are always equal. This circuit uses a MOS transistor as a current source. The current of the MOS transistor flows through a circuit in which the first diode, the second diode, and the first impedance element are connected in series. As a result, the current flowing through the first impedance element, in other words, the current I _{P of the} MOS transistor controlled by the operational amplifier becomes a current having a positive temperature coefficient.

  In the above constant voltage generation circuit, the circuit means for generating a current having a negative temperature coefficient is obtained by using the operational amplifier and the first transistor to obtain the voltage across the first diode or the second diode. , Applied to both ends of the second impedance element. Since the voltage across the diode has a negative temperature coefficient, when this voltage is applied across the second impedance element, the current flowing through the second impedance is changed to the first or second diode. Is obtained by dividing the voltage at both ends by the impedance value of the second impedance element, and it can be seen that this has a negative temperature coefficient.

  Therefore, when a current having a positive temperature coefficient and a current having a negative temperature coefficient created by the circuit means are added to the current combining means, the current means is always independent of changes in temperature and power supply voltage. A constant voltage can be generated.

  Further, there is provided a constant current generating circuit means that always generates a constant current regardless of changes in temperature and power supply voltage by using the above constant voltage generating circuit.

The constant current generating circuit means includes a new third impedance element connected in series to the first diode or a circuit in which the second diode and the first impedance element are connected in series. This is realized by configuring a circuit and applying the voltage across the new series circuit across the fourth impedance element. In this case, the current flowing in the new third impedance element, because it is the current I _P with a positive temperature coefficient, the opposite ends of the third impedance element appears a voltage having a positive temperature coefficient. On the other hand, the voltage at both ends of the first diode or the circuit in which the second diode and the first impedance element are connected in series has a negative temperature coefficient. The temperature coefficient of the voltage across the circuit can be set to various values such as positive, negative, or zero by adjusting the impedance value of the third impedance element.

  The voltage across the new circuit in which both are connected in series is applied across the fourth impedance element using the operational amplifier and the second transistor. Since the fourth impedance element has a temperature characteristic, its impedance value changes with temperature. By adjusting the temperature coefficient of the fourth impedance element and the impedance value of the third impedance element, the temperature coefficient of the voltage at both ends of a new circuit in which the two are connected in series is adjusted and matched. The current flowing through the fourth impedance element is constant regardless of the temperature.

  According to the present invention, the same circuit configuration does not depend on temperature and power supply voltage fluctuations, and does not depend on a constantly constant voltage higher than 1.25 [V], or always lower than a constant voltage, or fluctuations in power supply voltage. However, it is possible to generate a voltage having a positive temperature coefficient or a negative temperature coefficient, or a constant current that does not depend on variations in temperature and power supply voltage.

  Hereinafter, embodiments of the present invention will be described in detail based on examples. FIG. 1 is a circuit diagram showing an embodiment of the present invention.

In FIG. 1, a circuit means 100 for generating a current having a positive temperature coefficient includes a first diode D1 (10) having a one-fold anode-cathode junction area and a second diode-N second anode-cathode junction area. Diode D2 (20), first impedance element R _P (30), operational amplifier 40, current source I _P (41, 42, 43) controlled by operational amplifier 40, and third impedance element R _AD (300 ).

が成立する。この時、Ｉ_Pは電源電圧の影響を直接受けることはない。すなわち演算増幅器４０の差動利得Aが十分大きければ、電源電圧変動の影響が端子６１および６２に現れることはない。以上より、回路手段１００によって正の温度係数を持つ電流Ｉ_Pが発生される。さらに図１の回路の演算増幅器４０は、電流源４３を制御している。これより、電流源４３にも正の温度係数を持つ電流Ｉ_Pが発生される。 Among these, D1, D2 and R _P correspond to D1, D2 and R3 in FIGS. The role of the operational amplifier 40 in FIG. 1, similar to the role of the operational amplifier in FIG. 3, by controlling the current of the current source 41 and 42, to change the current flowing in the D1 or series connected R _P and D2 In other words, the potentials of the two input terminals 61 and 62 of the operational amplifier 40 are matched. When the potentials of the terminals 61 and 62 are equal, the same as when the equation (1) is derived,

Is established. In this case, I _P is not affected by the power supply voltage directly. That is, if the differential gain A of the operational amplifier 40 is sufficiently large, the influence of the power supply voltage fluctuation does not appear at the terminals 61 and 62. Thus, the current I _P is generated having a positive temperature coefficient by the circuit means 100. Further, the operational amplifier 40 in the circuit of FIG. 1 controls the current source 43. As a result, a current I _P having a positive temperature coefficient is also generated in the current source 43.

の電圧が発生する。ここでＶ_GOは、０°Ｋにおけるシリコンのバンドギャップ電圧の推定値であり、Ｅは定数、γ＝４−ｎ、ｎは移動度の温度係数である。 When the current shown by the equation (7) flows, both ends of the diode D1 are similar to the case of the equation (2).

Is generated. Here, V _GO is an estimated value of the band gap voltage of silicon at 0 ° K, E is a constant, γ = 4-n, and n is a temperature coefficient of mobility.

が成立する。Ｖ_BED1は負の温度係数を持つので、回路手段２００はこの負の温度係数を持つＶ_BED1を利用することにより、負の温度係数を持った電流を発生させる。 If G is set to a constant, I _P = GT ^α, just like equation (3),

Is established. Since V _BED1 has a negative temperature coefficient, the circuit means 200 generates a current having a negative temperature coefficient by using V _BED1 having the negative temperature coefficient.

と表され、負の温度係数を持つ電流が得られる。なお、Ｖ_BED1の電圧は、電源電圧の変化には依存しないので、Ｉ_Nにおいても電源電圧変動の影響はない。 The circuit means 200 includes an operational amplifier 101, a MOS transistor 102, and an impedance element R _N (103) in addition to the diode D1 (10). Operational amplifier 101 and the MOS transistor 102 serve Baffua, when differential gain B of the operational amplifier 101 is sufficiently large, the voltage across the diode D1, the voltage across the impedance element R _N coincides. Also when the input current of the operational amplifier 101 is assumed to be zero, the current flowing between the drain and source of the current I _N and MOS transistor 102 that flows through the impedance element R _N coincides. From the above,

And a current having a negative temperature coefficient is obtained. The voltage of V _BED1 does not depend on the change in the power supply voltage is not affected by fluctuations in the power source voltage even I _N.

Further, since the voltages at the 61st terminal and the 62nd terminal match, the same function can be achieved even if the voltage at the 61st terminal is used instead of the 62nd terminal which is the voltage across the diode D1 (10). . The voltage at the 61st terminal is the sum of the voltage across the first impedance element R _P of the circuit means 100 and the voltage across the diode D2 (20). Further, the circuit means 200 may be configured to apply the voltage across the diode D2 (20) across the impedance element R _N (103).

This is because the voltage across the impedance element R _P has a positive temperature coefficient, but since this value is small, the temperature coefficient of the voltage across the diode D2 (20) is approximately the temperature coefficient of the voltage across the diode D1 (10). It is because it is equal to. Therefore, by adjusting the impedance value of the impedance be configured to apply across the element R _N (103) of the voltage across the impedance element R _N (103) of the diode D2 (20), the voltage across the diode D1 (10) The same function as that applied to both ends of the impedance element R _N (103) can be achieved.

As described above, since the current I _P having a positive temperature coefficient and the current I _N having a negative temperature coefficient that do not depend on the change of the power supply voltage are obtained, the impedance element R _G1 (210) and the impedance element R _G2 are obtained. A constant voltage V _REF (240) independent of changes in temperature and power supply voltage can be generated at the output terminal 230 by means for synthesizing both currents connected in series with (220).

となる。ただし、

とした。 Voltage V _REF at the output terminal 230, current source current I _P supplied from the 43 impedance elements R _G1 (210) and R _G2 supplied to the (220), a current mirror circuit 150 a current I _N flowing through the MOS transistor 102 Is generated as a combined voltage supplied to the impedance element _RG2 as the current of the current source 152 by

It becomes. However,

It was.

が成立する温度Ｔ₀で温度係数を持たなくなる。その条件は、

であり、この時、

となることがわかる。この場合、Ｉ_PおよびＩ_N共に電源電圧変動の依存性はないので、Ｖ_REFについても電源電圧の変化による影響はない。 Just as in the discussion in equations (4) to (6), equation (11) is

At a temperature T ₀ at which The condition is

And at this time

It turns out that it becomes. In this case, both I _P and I _N have no dependency on the fluctuation of the power supply voltage, so that V _REF is not affected by the change of the power supply voltage.

(13) from the equation, V _REF in FIG. 1, the V _REF in FIG. 2 or FIG. 3, it can be seen that is multiplied by the coefficient of resistance ratio of R _G2 / R _N. Therefore, by changing the value of R _G2 as V _{REF in} FIG. 1, not only the conventional 1.25 [V], but also from 0 [V] to a value close to Vcc in the range in which the current source 43 operates normally. It can be realized. In this case, the temperature characteristic of V _REF is the same as that of the conventional FIG. 2 or FIG. 3 because the curly braces of the equation (13) coincide with those of the equation (6). The (12) conditions, at K _G, since satisfactory by varying the R _G1 or R _P, V _REF and (12) conditions, good conveniently can be controlled independently.

を満たすＫ_Gを選択することにより、２３０番端子のＶ_REFは正の温度係数を持つ電圧とすることができる。 Further, in the equation (11),

By selecting the K _G satisfying, V _REF 230 Pin may be a voltage having a positive temperature coefficient.

In the above-described example, the synthesis circuit for obtaining V _REF is a 64th terminal which is a connection end of the impedance element 210 (R _G1 ) and the impedance element 220 (R _G2 ) in the series circuit of the impedance element 210 and the impedance element 220. The negative temperature coefficient current I _N is input to the impedance element 210, and the positive temperature coefficient current _IP is input to the 230th terminal of the impedance element 210, and V _REF is obtained from the 230th terminal. It is good.

For example, instead of the series circuit of the impedance element 210 and the impedance element 220, only the impedance element 220 is used, and a negative temperature coefficient current I _N and a positive temperature coefficient current _IP are input to the 64th terminal of the impedance element 220. It is good also as a structure. According to this configuration, V _REF can be expressed by setting R _G1 to 0 in equation (11). Even in this case, it is possible to set a condition for the temperature differential coefficient to be zero. Further, it is possible to change the size of the V _REF by adjusting the resistance ratio of R _G2 / R _N.

Also, a positive temperature coefficient current _IP is input to the 64th terminal, which is the connection end of the impedance element 210 (R _G1 ) and the impedance element 220 (R _G2 ), and a negative temperature coefficient is applied to the 230th terminal of the impedance element 210. Current I _N may be input, and V _REF may be obtained from the 230th terminal. According to this configuration, V _REF can be expressed by exchanging the current I _N and the current I _{P in} Equation (11). Even in this case, it is possible to set a condition for the temperature differential coefficient to be zero. Further, if the same calculation as in the equations (11) to (13) is performed, the magnitude of V _REF can be changed by adjusting the resistance ratio of [(R _G1 + R _G2 ) / R _N ]. Recognize.

となる。ただし、

である。（１４）式でＲ_ADを調整してＫ_Cを変化させれば、Ｖ₆₅として任意の温度係数を持つ電圧を作ることが出来ることがわかる。 Further, in FIG. 1, the voltage V ₆₅ at the 65th terminal to which the diode D1 (10) and the impedance element R _AD (300) are connected in series has an arbitrary temperature coefficient that does not depend on the change of the power supply voltage. Voltage. The voltage V _BED1 across the diode D1 is given by equation (9), and the current I _P flowing through the impedance element R _AD is given by equation (7).

It becomes. However,

It is. It can be seen that a voltage having an arbitrary temperature coefficient can be made as V ₆₅ by adjusting R _AD in equation (14) and changing K _C.

と表す。ただし、βはインピーダンス素子Ｒ_Cの値の温度係数であり、Ｒ_C0はＴ=Ｔ₀における値を表している。 In Figure 1, with the operational amplifier 301 and the MOS transistor 302, the voltage V ₆₆ 66 Pin, is made to coincide with the voltage of the V _65. The impedance element R _C (303) generally has temperature characteristics.

It expresses. Here, β is a temperature coefficient of the value of the impedance element R _C , and R _C0 represents a value at T = T ₀ .

と表されるので、Ｋ_CすなわちＲ_ADを調整して、

により温度Ｔの係数を揃えれば、温度Ｔ=Ｔ₀近傍における、インピーダンス素子Ｒ_Cが持つ温度係数の影響を受けない、一定の電流Ｉ_Cを得ることが出来る。 From the above, the current flowing through the impedance element R _C , that is, the current I _{C at the} 310 terminal is

Therefore, adjust K _C , R _AD ,

If the coefficients of the temperature T are made uniform, a constant current I _C that is not affected by the temperature coefficient of the impedance element R _C in the vicinity of the temperature T = T ₀ can be obtained.

Incidentally, FIG. 1 shows the configuration of connecting the impedance element R _AD to the diode D1, the impedance element R _AD may also be configured to be connected in series to the series circuit of the diode D1 and the impedance element R _P. This equal voltage of 61 Pin and 62 Pin, since the current source 41 and the current source 42 flowing the same current I _P is also connected either to the impedance element R _AD because the same effects It is.

  As described above, according to the configuration of FIG. 1, it has a positive temperature coefficient or a negative temperature coefficient, although it does not depend on any constant voltage or power supply voltage fluctuation that does not depend on temperature and power supply voltage fluctuation. It can be seen that a constant current independent of voltage, temperature and power supply voltage fluctuations can be generated simultaneously.

  Next, the characteristics of this example will be described. The result of having simulated the structure of FIG. 1 with the circuit simulation tool is shown. Since the performance of the circuit of FIG. 1 is considered to depend greatly on the voltage gain of the operational amplifier used, the characteristic in the ideal case where the voltage gain of the operational amplifier is infinite is indicated by a dotted line, and an actual element is used. The values obtained when the operational amplifier is realized as a standard value and the characteristics in the case of 60 dB are indicated by solid lines.

FIG. 4 shows the temperature characteristics of V _REF . The voltage of V _REF is set to 0.5 V, and the temperature coefficient is set to zero at 25 ° C. Vcc at this time is 3.6V. When the temperature change is in the range of −25 ° C. to + 75 ° C., the change in V _REF is about 2.4 mV (48 ppm / ° C.) when using an ideal operational amplifier, and about when using an operational amplifier with a voltage gain of 60 dB. 3.0 mV (60 ppm / ° C.). A slight non-linearity appears in the temperature characteristic of FIG. Is that this characteristic is similar to the non-patent document 1 properties described above, (13) clear from equation, the cause of non-linearity is because there remains term V _T.

  In addition, ppm is an abbreviation for parts per million and means 1/1 million. For example, 1000 ppm / ° C. represents (1/1000) / ° C. = 0.1% / ° C.

FIG. 5 shows the power supply voltage dependency of V _REF . The graph shows a change in the V _REF voltage when the power supply voltage changes from 2.4 V to 5.5 V at 25 ° C. At this time, the change in V _REF is about 2.2 mV (0.71 mV / V) when an ideal operational amplifier is used, and about 2.0 mV (0.65 mV / V) when an operational amplifier having a voltage gain of 60 dB is used. V). In the characteristic of FIG. 5, the characteristic of Ideal and the characteristic of Gain of 60 dB both show the same change with respect to the change of the power supply voltage, and the difference in the voltage gain of the operational amplifier is the change of the power supply voltage versus the output voltage. It does not affect the characteristics. That is, it can be seen that the influence of the voltage gain of the operational amplifier does not appear.

  Note that the offset of the voltage value included in the characteristics of 60 dB is an input offset generated in the operational amplifier by finite Gain.

FIG. 6 shows the temperature characteristics of the constant current IC. The resistance has a temperature coefficient of -2,600 ppm / ° C. The current value was set to about 3 μA, and the temperature coefficient was set to zero at 25 ° C. Vcc at this time is 3.6V. In this case as well, a non-linear characteristic appears, but it is very small compared to the magnitude of the resistance temperature change. It can be seen that the temperature coefficient cancellation based on the equation (17) is effectively performed. In FIG. 6, in the temperature range of −25 ° C. to + 75 ° C., the change in I _C is about 0.0021 μA (70 ppm / ° C.) when an ideal operational amplifier is used, and when an operational amplifier with a voltage gain of 60 dB is used. However, it is almost unchanged, and is about 0.022 μA (73 ppm / ° C.).

FIG. 7 shows the power supply voltage dependence characteristics of I _C. At a temperature of 25 ° C., the power supply voltage changes from 2.4V to 5.5V. Although the change in the current value due to the change in the power supply voltage is hardly observed, the current value when the ideal operational amplifier is used is slightly different from the current value when the operational amplifier having the voltage gain of 60 dB is used (16 This is because the current value itself is determined by the voltage applied to both ends of the resistor, as shown in equation (1). This voltage is affected by the input offset generated in the operational amplifier by finite Gain.

  The characteristics shown in FIGS. 4 to 7 allow the circuit of FIG. 1 to supply an arbitrary voltage determined by the resistance ratio as a reference voltage regardless of temperature change and power supply voltage variation, and the temperature coefficient of resistance and It can be seen that a constant current determined by the resistance value can be obtained without being affected by fluctuations in the power supply voltage.

FIG. 8 shows an application example of the configuration of FIG. In FIG. 1, the voltage V _REF that does not depend on the temperature change and the power supply voltage fluctuation is generated between the terminal 230 and the ground, but in the case of FIG. 8, it is generated between the terminal 230 and Vcc. The operation of the circuit of FIG. 8 can be considered in the same manner as the circuit of FIG.

  FIG. 9 shows a specific method for constructing the diode D1 or D2 in FIG. 1 or FIG. The diode of FIG. 1 may be configured by connecting the collector and base terminals of a pnp transistor to a ground terminal, for example, as shown in FIG. Thereby, the circuit of FIG. 1 can be specifically configured on the IC. Further, the diode in FIG. 8 may be configured by connecting the collector and base terminals of the npn transistor to the Vcc terminal, as shown in FIG. 9B, for example.

The circuit of the present invention can be applied to various configurations that require a reference voltage source or a reference current source, such as a switching regulator.

It is a figure which shows the circuit structure of the constant voltage and constant current generator of the Example of this invention. It is a figure which shows the circuit structure of the constant voltage and constant current generator of a prior art example. It is a figure which shows the other structural example of the circuit of the constant voltage and constant current generator of a prior art example. It is a figure of the result of having simulated the temperature characteristic of the output voltage in the constant voltage and constant current generator of the Example of this invention. It is a figure which shows the result of having simulated the power supply voltage fluctuation characteristic of the output voltage in the constant voltage and constant current generator of the Example of this invention. It is a figure which shows the result of having simulated the temperature characteristic of the output current in the constant voltage and constant current generator of the Example of this invention. It is a figure which shows the result of having simulated the power supply voltage fluctuation characteristic of the output current in the constant voltage and constant current generator of the Example of this invention. It is a figure which shows the other Example in the constant voltage and constant current generator of this invention. In the constant voltage and constant current generator of this invention, it is the figure which showed the specific structural method of the diode used.

Explanation of symbols

1 Power supply (Vcc) terminals 10 and 20 Diode element 30 Impedance element (R _P )
40 Operational Amplifier (A)
41, 42, 43 Current source 50 controlled by operational amplifier 50 Generated current 100 having positive temperature coefficient Circuit 101 generating current having positive temperature coefficient Operational amplifier (B)
102 NMOS transistor (FIG. 1) or PMOS transistor (FIG. 8)
103 Impedance element (R _N )
150 Current mirror circuit 151, 152 Current source 200 in the current mirror circuit Circuit 210, 220 for generating a current having a negative temperature coefficient Output impedance elements (R _G1 , R _G2 )
301 Operational Amplifier (C)
302 NMOS transistor (FIG. 1) or PMOS transistor (FIG. 8)
303 Impedance element ( _RC )
V _REF (230) Output voltage (output voltage terminal)
I _C (310) Output current (output current terminal)
I _P Current having a positive temperature coefficient I _N Current having a negative temperature coefficient 61, 62, 63, 64, 65, 66 Internal terminals in the circuit

Claims (2)

First current generating circuit means for generating a current having a positive temperature coefficient whose current value increases as the temperature rises;
Second current generating circuit means for generating a current having a negative temperature coefficient in which the current value decreases as the temperature rises;
And a synthesis circuit means for synthesizing both currents,
Said combining circuit means, different impedance constituted by connecting an impedance element in series with, and supplies a current having a current and a negative temperature coefficient having the positive temperature coefficient to one of the impedance elements, the other impedance element Supply a current with a positive temperature coefficient or a current with a negative temperature coefficient to generate a constant voltage that does not depend on temperature changes at both ends of both impedance elements,
Impedance value of the impedance element for supplying a current having a current and a negative temperature coefficient having the positive temperature coefficient,
A combined impedance value of the two impedance elements,
A constant voltage generating circuit, wherein an output voltage is set by at least one impedance value of impedance values of an impedance element that determines a current value of the second current generating circuit means. The first current generating circuit means includes a differential gain amplifier, a first diode connected to the negative input terminal of the differential gain amplifier, a second diode connected to the positive input terminal of the differential gain amplifier, and And a voltage across the first diode and a voltage across the series circuit are always controlled to be equal by a differential gain amplifier so that a power supply voltage is applied to the first diode and the series circuit. It is a circuit that generates a current with a positive temperature coefficient that does not depend on
The second current generating circuit means includes a second impedance element for applying a voltage across the first diode or a voltage across a series circuit of the second diode and the first impedance element , The constant voltage generation circuit according to claim 1 , wherein the second impedance element is a circuit that generates a current having a negative temperature coefficient independent of a power supply voltage.

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