JP2011220777A - Voltage generation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a voltage generation circuit that allows voltage characteristics linearly varying with temperature to become programmable without switching the size of a diode and a resistor with an analog switch.SOLUTION: A voltage generation circuit comprises a first series circuit including a resistor R1 and a diode Q1, a second series circuit including resistors R2, R3 and a diode Q2, an operational amplifier OP for amplifying a potential difference between a common node of the resistor R1 and the diode Q1 and a common node of the resistor R2 and the resistor R3, and a current adjusting means for adjusting a value of current I1 flowing through the first series circuit and a value of current I2 flowing through the second series circuit in accordance with the output voltage of the operational amplifier OP. The current adjusting means includes a first feedback transistor group M3, a second feedback transistor group M4, a switching transistor group M1, and a switching transistor group M2.

Description

  The present invention relates to a voltage generation circuit that can change the characteristics of a voltage that varies linearly with temperature in a programmable manner.

  In a voltage generation circuit that works as a power supply circuit such as a pressure sensor, when the sensitivity of the sensor driven by the voltage generation circuit has temperature characteristics, the voltage generated in the voltage generation circuit is changed according to the temperature. It is necessary to cancel the temperature characteristic of the sensor sensitivity. For this purpose, means for performing temperature compensation of sensitivity is known. As a specific voltage generation circuit, there is one using a bandgap reference circuit (for example, see Patent Documents 1 and 2).

JP 2001-91387 A Japanese Patent No. 3233946

  However, when the band gap reference circuit as described above is incorporated in a semiconductor integrated circuit as a voltage generation circuit, the voltage generated by the band gap reference circuit can be adapted to the temperature characteristics of sensor sensitivity that varies for each sensor. In order to make it possible to adjust the temperature gradient with an external control signal, for example, as shown in FIG. 7, the size and resistance values of the transistors constituting the band gap reference circuit are not switched using an analog switch. must not.

  In FIG. 7, Q1 is a first diode using a PNP transistor, Q2 is a second diode in which K PNP transistors identical to the PNP transistor constituting the first diode Q1 are connected in parallel, OP is an operational amplifier, OUT is an output terminal, S11, S12, S13, S21, S22,..., S2K are analog switches, and R1, R2, and R3 are resistors. In this bandgap reference circuit, the resistance value of the resistor R3 is adjusted by appropriately setting the on / off of the analog switches S11, S12, S13, and the on / off of the analog switches S21, S22,. Is appropriately set, the emitter area of the second diode Q2 can be adjusted.

  However, in the analog switch as described above, unless the on-resistance is reduced as much as possible, the characteristic variation of the analog switch affects the characteristic variation of the bandgap reference circuit, and the reproducibility of the predetermined temperature characteristic is deteriorated. There's a problem. In order to avoid this, if the circuit is configured with the on-resistance of the analog switch kept low, the analog switch must be increased in size, increasing the physical circuit scale and increasing the cost. There is a problem that leads to.

  The object of the present invention is to suppress the influence on the circuit characteristics due to the on-resistance value of the analog switch as much as possible, or to change the size of the diode and the resistance that determines the circuit characteristics with an analog switch in a linear function. It is an object of the present invention to provide a voltage generation circuit that can change the characteristics of a changing voltage in a programmable manner.

To achieve the above object, the invention according to claim 1 is directed to a first series circuit in which a first resistor and a first diode are connected in series, the first diode is connected to a first power supply terminal, and a second resistor. A third resistor and a second diode connected in series, the second diode connected to the first power supply terminal, a common connection point of the first resistor and the first diode, and the second diode An operational amplifier that amplifies the potential difference at the common connection point of the two resistors and the third resistor, and adjusts the value of the first current flowing through the first series circuit according to the output voltage of the operational amplifier, and flows through the second series circuit Current adjusting means for adjusting the value of the second current, the current adjusting means comprising a plurality of feedback transistors each having a gate connected to the output terminal of the operational amplifier and a drain commonly connected. A first switch transistor group having a return transistor group and a switch transistor for connecting each feedback transistor of the first feedback transistor group between a second power supply terminal and the first resistor of the first series circuit; A second feedback transistor group including a plurality of feedback transistors whose gates are connected to the output terminal of the operational amplifier and whose drains are commonly connected, and each feedback transistor of the second feedback transistor group is connected to the second power supply terminal and the second series. And a second switch transistor group having a switch transistor connected to the second resistor of the circuit.
According to a second aspect of the present invention, in the voltage generation circuit according to the first aspect, the first feedback transistor group and the first switch transistor group, or the second feedback transistor group and the second switch transistor group are defined as 1 It is characterized in that it is replaced with one feedback transistor, or is replaced with a series circuit of one switch transistor conducted with one feedback transistor.
According to a third aspect of the present invention, in the voltage generation circuit according to the first or second aspect, the plurality of feedback transistors have different size ratios.
According to a fourth aspect of the present invention, in the voltage generating circuit according to the third aspect, the plurality of feedback transistors have binary weights set to sizes of each other.

  According to the present invention, the values of the first current and the second current can be changed without changing the size of the first and second diodes and the values of the first to third resistors for creating a voltage having a temperature coefficient by analog switching. The temperature gradient of the voltage change can be changed in a programmable manner. For this reason, it is possible to improve the productivity of a semiconductor integrated circuit in which a circuit is built and to reduce the chip cost by suppressing the circuit size.

1 is a circuit diagram of a voltage generation circuit according to a first embodiment of the present invention. FIG. 2 is an explanatory diagram of switching of a size ratio W / L of a PMOS transistor group M3 of the voltage generation circuit of FIG. It is a temperature characteristic figure of the output voltage of the voltage generation circuit of FIG. It is a circuit diagram of the voltage generation circuit of the 2nd Example of this invention. It is a circuit diagram of the voltage generation circuit of the 3rd Example of this invention. It is a circuit diagram of the voltage generation circuit of the 4th Example of this invention. It is a circuit diagram of the conventional voltage generation circuit.

<First embodiment>
FIG. 1 shows a voltage generation circuit according to a first embodiment of the present invention. Q1 is a first diode using a PNP transistor, Q2 is a second diode in which K diode connection circuits of the same PNP transistor as the PNP transistor constituting the first diode Q1 are connected in parallel, OP is an operational amplifier, and OUT is an output terminal. Further, M1 is a first switch transistor group, and is composed of m switch transistors M11 to M1m of PMOS whose sources are commonly connected to the power supply VDD and whose gates are individually connected to the control terminals C11 to C1m. M2 is a second switch transistor group, and includes n switch transistors M21 to M2n of PMOS whose sources are commonly connected to the power supply VDD and whose gates are individually connected to the control terminals C21 to C2n. M3 is a first feedback transistor group, the gate is commonly connected to the output terminal of the operational amplifier OP, the drain is commonly connected to one end of the resistor R1, and the source is individually connected to the drains of the switch transistors M11 to M1m. M feedback transistors M31 to M3m. Further, M4 is a second feedback transistor group, the gate is commonly connected to the output terminal of the operational amplifier OP, the drain is commonly connected to one end of the resistor R2 and the output terminal OUT, and the source is connected to the drains of the switch transistors M21 to M1n. It consists of n feedback transistors M41 to M4n of PMOS connected individually. m = n or m ≠ n. These switch transistor groups M1, M2 and feedback transistor groups M3, M4 constitute current control means.

  The switch transistors M11 to M1m are individually controlled to be turned on / off by a voltage applied to the control terminals C11 to C1m, and the switches M21 to M2n are individually controlled to be turned on / off by a voltage applied to the control terminals C21 to C2n.

Further, the feedback transistors M31 to M3m have a size ratio W / L (W is channel width, L is channel length) of ^2t (t = 0, 1, 2, 3,...). Binary weight is set. For example, W / L of transistor M31 is 1, W / L of transistor M32 is 2, W / L of transistor M33 is 4, W / L of transistor M34 is 8, and so on. The same applies to the feedback transistors M41 to M4n.

  Therefore, assuming that the number of transistors in the transistor groups M1 to M4 is four, for example, and the feedback transistor groups M3 and M4 are in the above relationship, the feedback transistor group M3 can be obtained by turning on only the switch transistor M11. W / L is 1, W / L of the feedback transistor group M3 is 2 if only the switch transistor M12 is turned on, W / L of the feedback transistor group M3 is 3 if the switch transistors M11 and M12 are turned on, and the switch transistor When only M13 is turned on, the W / L of the feedback transistor group M3 becomes 4,..., And as shown in FIG. 2, by inputting a 4-bit digital signal to the control terminals C11 to C14, The size ratio of the feedback transistor group M3 can be switched from the outside in 16 ways with W / L = 1 to 15. That. The same applies to the feedback transistor group M4. If the number of transistors constituting each of the switch transistor groups M1 and M2 and the feedback transistor groups M3 and M4 is further increased, the number of switching of the size ratio W / L of the feedback transistor groups M3 and M4 can be further increased.

となる。 In the band gap reference circuit of FIG. 1, the base-emitter voltage of the transistor constituting the diode Q1 is Vbe1, the base-emitter voltage of the transistor constituting the diode Q2 is Vbe2, Kb is the Boltzmann constant, and T is the absolute temperature. , Q is the electron charge, Is is the reverse saturation current of the transistor constituting the diode Q1, I1 is the current flowing through the resistor R1, and I2 is the current flowing through the resistor R2, and the diode Q2 constitutes the diode Q1 as described above. If the same transistor as the transistor is configured in parallel connection,

It becomes.

となる。ここで、

に設定すれば、すなわち、Ｖbe1＞Ｖbe2を満足するように設定すれば、出力端子ＯＵＴに現れる出力電圧Ｖoutは、

となる。 From the equations (1) and (2), the difference ΔVbe between the base and emitter voltages of the transistors constituting the diodes Q1 and Q2 is

It becomes. here,

Is set so that Vbe1> Vbe2 is satisfied, the output voltage Vout appearing at the output terminal OUT is

It becomes.

となる。ここで、Ｉ１／Ｉ２の値を変化させれば、図３に示すように、出力電圧Ｖoutの温度勾配を変化させることができる。このＩ１／Ｉ２の値の切り替えは、帰還トランジスタ群Ｍ３のサイズ比Ｗ／Ｌと帰還トランジスタ群Ｍ４のサイズ比Ｗ／Ｌの少なくとも一方を変化することにより可能となり、前記したように制御端子Ｃ１１〜Ｃ１ｍ、Ｃ２１〜Ｃ２ｎに外部から入力させる制御信号によって、広い範囲に亘って細かく切替可能となる。 Therefore, the temperature gradient of the output voltage Vout is

It becomes. Here, if the value of I1 / I2 is changed, the temperature gradient of the output voltage Vout can be changed as shown in FIG. The switching of the value of I1 / I2 is made possible by changing at least one of the size ratio W / L of the feedback transistor group M3 and the size ratio W / L of the feedback transistor group M4. By a control signal input from the outside to C1m and C21 to C2n, it becomes possible to finely switch over a wide range.

As described above, in this embodiment, the temperature gradient of the voltage change can be changed in a programmable manner by switching the size ratio of the feedback transistor without changing the size and the resistance value of the bipolar transistor by analog switching. At this time, the feedback transistor M31～M3m, a ^{2 t} relationship size ratio of M41~M4n (t = 0,1,2,3, ···) by setting the binary weights such that less control signal Many size ratios can be selected by the number of lines, and the ratio of currents I1 / I2 can be selected from many, and the number of temperature gradients that can be set increases. For example, if the number of feedback transistors in the feedback transistor groups M3 and M4 is four, 256 types of temperature gradients can be set with an 8-bit control signal. In addition, the CMOS process can be realized by using a parasitic bipolar of P substrate-well-diffusion layer.

<Second embodiment>
FIG. 4 shows a voltage generation circuit according to the second embodiment of the present invention. In this circuit, the switch transistor group M1 and the feedback transistor group M3 connected to the resistor R1 are only the transistors M11 and M31, the transistor M31 is always on, and the transistor M21 of the switch transistor group M2 is always on. It is. The rest is the same as the circuit of FIG. When configured in this way, the value of the current I2 flowing through the resistor R2 is exclusively controlled by the control signal input from the outside to the control terminals C22 to C2n, whereby the temperature gradient according to the equation (6) is determined.

  In this embodiment, only one current I2 is controlled, but as in the first embodiment, the temperature gradient of the voltage change is programmable without changing the size and resistance of the bipolar transistor by analog switching. In the CMOS process, it can be realized by using a parasitic bipolar of P substrate-well-diffusion layer.

<Third embodiment>
FIG. 5 shows a voltage generation circuit according to a third embodiment of the present invention. In this circuit, the switch transistor group M2 is deleted, the transistor M11 of the switch transistor group M1 is deleted, and the feedback transistor group M4 is only the transistor M41. The rest is the same as the circuit of FIG. In such a configuration, the value of the current I1 flowing through the resistor R1 is exclusively controlled by a control signal input from the outside to the control terminals C12 to C1m, whereby the temperature gradient according to the equation (6) is determined.

  In this embodiment, only one current I1 is controlled. However, as in the first embodiment, the temperature gradient of the voltage change is programmable without changing the size and resistance of the bipolar transistor by analog switching. In the CMOS process, it can be realized by using a parasitic bipolar of P substrate-well-diffusion layer.

<Fourth embodiment>
FIG. 6 shows a voltage generation circuit according to a fourth embodiment of the present invention. In this circuit, the diode Q1 is changed to a diode Q1 ′ constituted by an NPN transistor, the diode Q2 is changed to a diode Q2 ′ constituted by an NPN transistor, and the transistor groups M1 to M4 are changed to NMOS transistors M11 ′ to M1m ′. , M21 ′ to M2n ′, M31 ′ to M3m ′, and M41 ′ to M4n ′, which are changed to transistor groups M1 ′ to M4 ′, and operate in the same manner as the voltage generation circuit of FIG. However, the control signals input to the control terminals C11 to C1m and C21 to C2n are “1” and “0” opposite to those shown in FIG. Further, the CMOS process can be realized by using an N substrate-well-diffusion layer parasitic bipolar.

<Other examples>
In each of the above embodiments, the output terminal OUT is taken out from the common connection point between the resistor R2 and the transistor M41 or the common connection point between the resistor R2 and the transistor M41 ′. However, the output terminal OUT may be taken out from the output terminal of the operational amplifier OP. Of course it is good. Further, the plurality of feedback transistors in the feedback transistor groups M3, M4, M3 ′, and M4 ′ may have a size ratio W / L not limited to the ^2t relationship described above, but may be a 1 / ^2t relationship. . Furthermore, the relationship may be 2t or 1 / 2t. That is, if the transistors in the feedback transistor group have different weights between them without having the same size ratio W / L, the currents I1 and I2 can be finely adjusted. Can also be reduced.

Claims (4)

A first series circuit in which a first resistor and a first diode are connected in series, and the first diode is connected to a first power supply terminal;
A second series circuit in which a second resistor, a third resistor, and a second diode are sequentially connected in series, and the second diode is connected to the first power supply terminal;
An operational amplifier for amplifying a potential difference between a common connection point of the first resistor and the first diode and a common connection point of the second resistor and the third resistor;
Current adjusting means for adjusting the value of the first current flowing through the first series circuit according to the output voltage of the operational amplifier and adjusting the value of the second current flowing through the second series circuit;
The current adjusting means includes: a first feedback transistor group including a plurality of feedback transistors whose gates are connected to the output terminal of the operational amplifier and whose drains are commonly connected; and each feedback transistor of the first feedback transistor group is connected to a second power supply terminal. Switch transistor group having a switch transistor for connection between the first series circuit and the first resistor, and a plurality of feedback transistors having a gate connected to the output terminal of the operational amplifier and a drain connected in common A second feedback transistor group, and a switch transistor for connecting each feedback transistor of the second feedback transistor group between the second power supply terminal and the second resistor of the second series circuit. A voltage generation circuit comprising a switch transistor group. The voltage generation circuit according to claim 1,
The first feedback transistor group and the first switch transistor group, or the second feedback transistor group and the second switch transistor group are replaced with one feedback transistor, or one conductive transistor is connected to one feedback transistor. A voltage generation circuit characterized by being replaced with a series circuit of switch transistors. The voltage generation circuit according to claim 1 or 2,
The voltage generating circuit, wherein the plurality of feedback transistors have different size ratios. The voltage generation circuit according to claim 3, wherein
The voltage generating circuit, wherein the plurality of feedback transistors have binary weights set to sizes of each other.

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