CN102809979B - Third-order compensation band-gap reference voltage source - Google Patents

Abstract

The invention discloses a third-order compensation band-gap reference voltage source, which comprises a first PMOS (p-channel metal oxide semiconductor) tube, a first triode, a second triode, a third triode, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor and a first amplifier. The reference voltage source disclosed by the invention provides a simple third-order compensation way, the current of the fourth resistor is PTAT (proportional to absolute temperature) current, and the voltage drop of the fourth resistor is increased along with the rising of the temperature, so that the current of the sixth resistor is also increased along with the rising of the temperature, the current of the fifth resistor is the sum of the current of the fourth resistor and the current of the sixth resistor, thus being equivalent to that the resistance of the fifth resistor is increased along with the rising of the temperature, i.e. the second-order item and the third-order item of VBE are compensated in such way, a conventional band-gap reference total framework does not need to be changed for the compensation way, a design process is simplified, and the cost is saved.

Description

A third-order compensated bandgap reference voltage source

technical field

The invention belongs to the technical field of power supplies, and in particular relates to the design of a bandgap reference voltage source.

Background technique

High-precision voltage sources are widely used in integrated circuits and are an indispensable part of many analog and hybrid circuits, such as analog-to-digital converters (ADC), switching power supply technology (DC-DC), low-dropout linear regulators (LDO). In these circuits, the voltage source is used as a benchmark for comparison, and its accuracy directly affects the accuracy and performance of the entire circuit.

Among many circuits that generate reference voltages, the bandgap reference has the advantages of small temperature coefficient, high power supply rejection ratio, high precision, and compatibility with CMOS technology. The voltages are summed to obtain an output voltage with a small temperature coefficient. The traditional bandgap reference source is shown in Figure 1. It consists of three field effect transistors M ₁ , M ₂ , and M ₃ , and three triodes Q ₁ , Q ₂ , and Q ₃ (where the ratio of the emitter area of Q ₂ to Q ₁ is N), composed of two resistors R ₁ , R ₂ and an operational amplifier A ₁ , the operational amplifier makes the drain voltages of M ₁ and M ₂ tubes equal through feedback, so the voltage on the resistor R ₁ is:

V _R1 =V _BE1 -V _BE2 =V _T lnN=I _C R ₁

In the above formula, V _T is the thermal voltage, which is:

${\mathrm{<span\; class="notranslate">\; V</span>}}_{\mathrm{<span\; class="notranslate">\; T</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; KT</span>}}{\mathrm{<span\; class="notranslate">\; q</span>}}$

K is the thermodynamic constant, T is the absolute temperature, and q is the electronic charge.

so:

${\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; KT</span>}}{\mathrm{<span\; class="notranslate">\; QUR</span>}}$

The output voltage:

V _OUT =I _C R ₂ +V _BE3

The value of _IC is proportional to temperature, called PTAT (Proporational To Absolute Temperature) current, which has a positive temperature coefficient. Multiplying _IC and R ₂ gives a voltage proportional to temperature, which is used to compensate the voltage proportional to temperature A primary term of the voltage V _BE with a negative temperature coefficient to achieve a low temperature coefficient of the final output voltage, where V _BE represents the voltage difference between the emitter and base of the triode.

In fact, V _BE not only has a negative first-order term, but also a negative high-order term, and the reference source in Figure 1 only considers its first-order term, so as the temperature rises, the final output temperature coefficient changes from positive to negative. of.

Based on the above reasons, many secondary or high-order compensation structures have been proposed, and relatively good results have been achieved. However, these compensation structures are relatively complicated, and not only need to add a lot of components such as resistors and transistors on the basis of traditional bandgap reference sources , but also need to make some changes to the basic framework shown in Figure 1, increasing the difficulty and cost of circuit design.

Contents of the invention

The object of the present invention is to solve the problem of complex structure of the existing bandgap reference source, and propose a third-order compensated bandgap reference voltage source.

The technical solution of the present invention is: a third-order compensated bandgap reference voltage source, comprising: a first PMOS transistor, a first transistor, a second transistor, a third transistor, a first resistor, a second resistor , the third resistor, the fourth resistor, the fifth resistor, the sixth resistor, the seventh resistor and the first amplifier, wherein the source of the first PMOS transistor is connected to the external power supply, the gate is connected to the output terminal of the first amplifier, and the drain Connect the first terminal of the first resistor, the first terminal of the second resistor, the first terminal of the seventh resistor and the collector of the third transistor; the collector of the first transistor is connected to the second terminal of the first resistor , the collector of the second transistor is connected to the second terminal of the second resistor, and the base of the first transistor is connected to the base of the second transistor and the second terminal of the seventh resistor as the reference voltage source The output terminal of the second triode is connected to the first terminal of the third resistor, the emitter of the first triode is connected to the other end of the third resistor and the first terminal of the fourth resistor is connected to the first terminal of the fourth resistor. The second terminal is connected to the first terminal of the fifth resistor, the second terminal of the fifth resistor is connected to the ground potential, the positive input terminal of the first amplifier is connected to the collector of the second triode, and the negative input terminal is connected to the collector of a triode The base of the third triode is connected to the emitter of the first triode, the emitter is connected to the first terminal of the sixth resistor, and the second terminal of the sixth resistor is connected to the first terminal of the fifth resistor.

Beneficial effects of the present invention: the third-order compensation bandgap reference voltage source of the present invention provides a simple third-order compensation method, the current of the fourth resistor is PTAT current, so the voltage drop on the fourth resistor will increase with temperature increases, so that the current of the sixth resistor also increases with the increase of temperature, and the current of the fifth resistor is the sum of the current of the fourth resistor and the current of the sixth resistor, which is equivalent to the fifth resistor The resistance value increases with the increase of temperature, that is, the second-order and third-order terms of V _BE are compensated in this way. This compensation method does not need to change the overall framework of the traditional bandgap reference, which simplifies the design process. Cost savings.

Description of drawings

FIG. 1 is a schematic diagram of an existing traditional bandgap reference.

Fig. 2 is a schematic diagram of the structural framework of the bandgap reference of the present invention.

FIG. 3 is a schematic diagram of an embodiment of a bandgap reference with a start-up circuit according to the present invention.

FIG. 4 is a schematic diagram of the variation of the output reference voltage of the bandgap reference source with temperature in an embodiment of the present invention.

FIG. 5 is a schematic diagram of the power supply rejection ratio of the output voltage of the bandgap reference source in an embodiment of the present invention.

Detailed ways

Further description will be given below in conjunction with the accompanying drawings and specific embodiments.

The bandgap reference source presented in the present invention realizes the third-order compensation in a very simple way, and only needs to slightly change the structure of the traditional bandgap reference source, and only needs to add a few components, which is simple to implement, but can realize Better compensation effect. In order to make the purpose, technical solution and advantages of the present invention relative to other reference voltages clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

Fig. 2 is a structural schematic diagram of the reference of the present invention, specifically including a bandgap reference part and a compensation part, wherein the bandgap reference part includes a first PMOS M ₁ , a first triode Q ₁ , a second triode Q ₂ , a A resistor R ₁ , a second resistor R ₂ , a third resistor R ₃ , a fourth resistor R ₄ , a fifth resistor R ₅ and an operational amplifier. The source and substrate of M ₁ are connected to the power supply VDD, the gate is connected to the output of the operational amplifier, the drain is connected to one end of R ₁ and R ₂ , the collector of QN ₁ is connected to the other end of R ₁ , and the collector of Q ₂ is connected to R The other end of ₂ , the base of Q ₁ is connected to the base of Q ₂ , the emitter of Q ₂ is connected to one end of resistor R ₃ , the emitter of Q ₁ is connected to the other end of R ₃ and one end of R ₄ , and the other end of R ₄ One end is connected to one end of _R5 , the other end of _R5 is grounded, the positive input terminal of the operational amplifier is connected to the collector of _Q2 , and the negative input terminal is connected to the collector of _Q1 .

The compensation part includes the third transistor Q ₃ , the sixth resistor R ₆ , and the seventh resistor R ₇ , the collector of Q ₃ is connected to the drain of M ₁ , the base is connected to the emitter of Q ₁ , and the emitter node R ₆ One end, the other end of _R6 is connected to the intersection of _R4 and _R5 , one end of _R7 is connected to the drain end of _M1 , and the other end is connected to the base of _Q1 .

The specific compensation principle is: the current flowing through R ₄ increases linearly with the increase of temperature, that is, the PTAT current, then the voltage on R ₄ will also increase with the increase of current, and as the voltage on R ₄ increases Increase, the current flowing through _Q3 will also increase, so that the current flowing through _R5 is greater than that flowing through _R4 , which is equivalent to the value of _R5 increasing as the temperature rises. It can be seen that in this way, the negative higher-order terms in V _BE are compensated, that is, the third-order compensation can be realized in a very simple way.

R ₇ provides base bias current for Q ₁ and Q ₂ , Q ₃ and R ₆ form the compensation body, Q ₃ is in the cut-off state when the temperature is very low, so it is the same as the traditional bandgap reference sum, as the temperature increases As the voltage rises, the voltage on _R4 gradually increases, and the current flowing through _Q3 also gradually increases:

Current flowing through _R5 :

${\mathrm{<span\; class="notranslate">\; I</span>}}_{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}$

An increase in I _Q3 increases I _R5 , so the actual effective value of R ₅ R ₅ (EFFECT) becomes:

${\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; EFFECT</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; I</span>}}_{{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 3</span>}}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}}{{\mathrm{<span\; class="notranslate">\; I</span>}}_{{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 4</span>}}}}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; R</span>}}_{\mathrm{<span\; class="notranslate">\; 5</span>}}$

The output voltage:

V _REF =V _BE +I _PTAT ×R ₅ (EFFECT)

By increasing R ₅ (EFFECT) to compensate the negative second-order and third-order items in V _BE , the third-order compensation is realized by only using two resistors and one transistor, which is more efficient than other compensation methods Simple.

The bandgap reference source here also includes a start-up circuit, and the start-up output end of the start-up circuit is connected with the output end of the reference voltage source.

Figure 3 shows a schematic diagram of an embodiment of a bandgap reference source with a startup circuit, the startup circuit part includes a second PMOS transistor M ₂ , a third PMOS transistor M ₃ , a first NMOS transistor M ₄ , and a second NMOS transistor M ₅ , the third NMOS transistor M ₆ , the fourth NMOS transistor M ₇ , the fourth triode Q ₄ , the eighth resistor R ₈ , and the ninth resistor R ₉ , wherein the source of the second PMOS transistor M ₂ is connected to the external power supply VDD , gate and drain are connected to the collector of the fourth triode _Q4 , the source and substrate of the third PMOS transistor _M3 are connected to the external power supply VDD, and the gate is connected to the collector and drain of the fourth triode _Q4 The pole is connected to the drain of the first NMOS transistor _M4 , the gate of _M4 is connected to the drain, the source and the substrate are grounded, the gate of _M5 is connected to the gate of _M4 , the source and the substrate are grounded, and the drain The pole is connected to the gate of _M6 , the source of _M6 is connected to the gate of _Q4 and used as the start-up output terminal of the start-up circuit, the drain of _M6 is connected to the source of _M7 , the substrate is grounded, and the _M7 The gate and drain of _R9 are connected to the external power supply VDD, the substrate is grounded, the first terminal of R9 is connected to the external power supply VDD, and the second terminal is connected to the drain of the second NMOS transistor _M5 ; the emitter of the fourth triode _Q4 Connect to the first terminal of _R8 , and the other end of _R8 is grounded.

When the start-up circuit is powered on, _M6 and _M7 provide current for the entire circuit, so that the entire circuit will not work in a zero state; after the reference voltage is established, the current generated by the reference provides a bias for the operational amplifier (Figure 3 In I _BIAS ), the existence of R ₉ makes M ₇ cut off after the reference voltage is established, and the startup circuit is turned off, which no longer affects the work of the reference.

Fig. 4 is a schematic diagram of the variation of the output reference voltage with temperature. In the range of -60 to 120 degrees, the maximum variation of the reference voltage is 0.67 millivolts, which is about 3.2ppm. Compared with the more than ten ppm of the general benchmark, there has been a great improvement, and only a few components have been added, that is, the third-order compensation has been realized in a simple way.

Figure 5 is a schematic diagram of the power supply rejection ratio of the output voltage. When the frequency is 1k, the power supply rejection ratio is 63db, which is higher than the traditional bandgap reference source.

Those skilled in the art will appreciate that the embodiments described here are to help readers understand the principles of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific modifications and combinations based on the technical revelations disclosed in the present invention without departing from the essence of the present invention, and these modifications and combinations are still within the protection scope of the present invention.

Claims (1)

1. A third-order compensated bandgap reference voltage source, comprising: a first PMOS transistor, a first transistor, a second transistor, a third transistor, a first resistor, a second resistor, a third resistor, the fourth resistor, the fifth resistor, the sixth resistor, the seventh resistor and the first amplifier, in, The source of the first PMOS transistor is connected to the external power supply, the gate is connected to the output terminal of the first amplifier, and the drain is connected to the first terminal of the first resistor, the first terminal of the second resistor, the first terminal of the seventh resistor and the third The collector of the triode; the collector of the first triode is connected to the second terminal of the first resistor, the collector of the second triode is connected to the second terminal of the second resistor, and the base of the first triode is connected to The base of the second triode and the second terminal of the seventh resistor serve as the output terminal of the reference voltage source, the emitter of the second triode is connected to the first terminal of the third resistor, and the first terminal of the first triode The emitter is connected to the other end of the third resistor and connected to the first terminal of the fourth resistor, the second terminal of the fourth resistor is connected to the first terminal of the fifth resistor, the second terminal of the fifth resistor is connected to the ground potential, and the first amplifier The positive input terminal of the second transistor is connected to the collector of the second transistor, and the negative input terminal is connected to the collector of the first transistor; the base of the third transistor is connected to the emitter of the first transistor, and the emitter is connected to the first transistor of the sixth resistor. One terminal, the second terminal of the sixth resistor is connected to the first terminal of the fifth resistor; The third-order compensated bandgap reference voltage source also includes a startup circuit, and the startup output terminal of the startup circuit is connected to the output terminal of the reference voltage source; The startup circuit includes a second PMOS transistor, a third PMOS transistor, a first NMOS transistor, a second NMOS transistor, a third NMOS transistor, a fourth NMOS transistor, a fourth triode, an eighth resistor, and a ninth resistor, in, The source of the second PMOS transistor is connected to the external power supply, the gate and the drain are connected to the collector of the fourth triode; the source and substrate of the third PMOS transistor are connected to the external power supply, and the gate is connected to the collector of the fourth triode. The electrode and the drain are connected to the drain of the first NMOS transistor; the gate of the first NMOS transistor is connected to the drain, and the source and the substrate are grounded; the gate of the second NMOS transistor is connected to the gate of the first NMOS transistor _M4 , The source and the substrate are grounded, and the drain is connected to the gate of the third NMOS transistor; the source of the third NMOS transistor is connected to the gate of the fourth transistor and used as the output terminal of the start-up circuit, and the third NMOS transistor The drain of the fourth NMOS tube is connected to the source and the substrate is grounded; the gate and drain of the fourth NMOS tube are connected to the external power supply, the substrate is grounded, the first terminal of the ninth resistor is connected to the external power supply, and the second terminal is connected to the second terminal of the ninth resistor. The drain of the second NMOS transistor; the emitter of the fourth transistor is connected to the first terminal of the eighth resistor, and the other end of the eighth resistor is grounded.

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