High-precision bandgap reference circuit

Abstract

The present invention discloses a high-precision bandgap reference circuit, comprising: a bandgap circuit, which adopts a cascode current mirror structure to generate a positive temperature coefficient current and a negative temperature coefficient voltage; a negative temperature coefficient current extraction circuit, which extracts the negative temperature coefficient voltage generated by the bandgap circuit and generates a negative temperature coefficient current; a current compensation circuit, which receives the current I0 output by the negative temperature coefficient current extraction circuit and the positive temperature coefficient current I generated by the bandgap circuit. IN , and output current with positive temperature coefficient I IN Second-order related compensation current I out The present invention not only retains the advantages of the traditional Bandgap voltage reference such as simple structure and strong process compatibility, but also achieves the goals of low output voltage temperature coefficient and low power consumption.

Description

Technical Field

[0001] The present invention relates to the technical field of power supply, and in particular to a high-precision bandgap reference circuit. Background Art

[0002] Bandgap reference circuits are essential components of analog integrated circuits. Their function is to provide other integrated circuits with a reference source that is independent of process and power supply, exhibits low temperature drift, and has a high power supply rejection ratio. Therefore, the performance of this reference source determines the performance of other circuits. The accuracy of the bandgap voltage reference largely determines the accuracy and performance of the entire circuit.

[0003] The accuracy of the bandgap voltage reference is largely determined by the temperature coefficient. The current bandgap structures include traditional bandgap, second-order temperature compensated bandgap, precise temperature compensated bandgap, and piecewise linear compensated bandgap.

[0004] The traditional bandgap is currently the most widely used bandgap structure. Its advantages include simplicity, low power consumption, strong process compatibility, ease of implementation, and low cost. Traditional bandgap uses first-order temperature compensation, resulting in a temperature coefficient of approximately 40ppm / °C to 50ppm / °C. While this structure is simple and power-efficient, its temperature coefficient is too high for a high-precision voltage reference.

[0005] Using high-precision bandgap temperature compensation, the temperature coefficient can reach 5ppm / ℃-20ppm / ℃, but it has disadvantages such as high price, complex structure, poor process compatibility, and high power consumption. Summary of the Invention

[0006] The present invention provides a high-precision bandgap reference circuit, which has the advantages of retaining the advantages of a traditional Bandgap voltage reference such as a simple structure and strong process compatibility, while achieving the goals of a low output voltage temperature coefficient and low power consumption.

[0007] The above-mentioned object of the present invention is achieved by the following technical solution, a high-precision bandgap reference circuit, characterized in that it includes:

[0008] The bandgap circuit uses a cascode current mirror structure to generate a positive temperature coefficient current I IN and negative temperature coefficient voltage;

[0009] The negative temperature coefficient current extraction circuit extracts the negative temperature coefficient voltage generated by the bandgap circuit to generate a negative temperature coefficient current, and uses the MOS tube to combine the negative temperature coefficient current generated by the current extraction circuit and the positive temperature coefficient current I obtained by the Bandgap circuit.IN Resultant current I0;

[0010] The current compensation circuit receives the current I0 output by the negative temperature coefficient current extraction circuit and the positive temperature coefficient current I generated by the bandgap circuit. IN , and output current with positive temperature coefficient I IN Second-order related compensation current I out , compensation current I out After passing through the poly resistor, it is combined with the voltage division of the current I0 in the poly resistor to obtain the reference voltage.

[0011] The present invention is further configured such that the negative temperature coefficient current extraction circuit includes a transistor Q1 and a first operational amplifier for extracting the negative temperature coefficient voltage generated by the bandgap circuit and generating a negative temperature coefficient current, which is compared with the positive temperature coefficient current I obtained by the bandgap circuit. IN The current Iztat is synthesized by the MOS tubes M5 and M6 and output to the current compensation circuit as the current I0.

[0012] The present invention is further configured such that the current compensation circuit includes MOS transistors T1, T2, T3, T4, and T5, wherein the MOS transistors T1 and T2 are connected in series, the MOS transistors T3 and T4 are connected in series, the gates of the MOS transistors T4 and T5 are connected to form a current mirror, the gate and drain of the MOS transistor T1 are connected, the gate and drain of the MOS transistor T2 are connected, the gates of the MOS transistors T1 and T3 are connected, the gate and drain of the MOS transistor T4 are connected, the drain of the MOS transistor T3 is connected to the power supply VDD, and the sources of the MOS transistors T2, T4, and T5 are grounded; current I0 is connected to the gates of the MOS transistors T1 and T3, and current 2I is connected to the gate of the MOS transistor T5. IN , the current I0 and the current I are connected to the drain of MOS tube T5. IN .

[0013] The present invention is further configured such that the MOS tube in the current compensation circuit is selected to have a MOS tube width-to-length ratio that results in a low output voltage temperature coefficient.

[0014] The present invention is further configured such that the operational amplifiers in the bandgap circuit and the negative temperature coefficient current extraction circuit are subthreshold operational amplifiers.

[0015] In summary, the beneficial effects of the present invention are:

[0016] 1. The op amps used in the traditional bandgap voltage reference and negative temperature coefficient current extraction circuits have been upgraded to subthreshold op amps, which reduces power consumption to a certain extent.

[0017] 2. By adjusting the device parameters in modules such as current compensation, that is, adjusting the width-to-length ratio of the MOS tube, the output voltage temperature coefficient can be reduced;

[0018] 3. The bandgap core circuit adopts cascode current mirror structure, which greatly improves the low-frequency power supply rejection ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a schematic diagram of the principle structure of an embodiment of the present invention;

[0020] Figure 2 is a circuit diagram of an embodiment of the present invention;

[0021] Figure 3 is a circuit schematic diagram of a second-order current compensation circuit in an embodiment of the present invention;

[0022] Figure 4 is a circuit schematic diagram of a subthreshold operational amplifier in an embodiment of the present invention;

[0023] Figure 5 is a current compensation principle diagram in an embodiment of the present invention, wherein: Figure 5 (1) is the waveform of the second-order compensation current, Figure 5 (2) is the waveform of the compensated output voltage, Figure 5 (3) is the uncompensated output voltage waveform. Figure 5 (4) is the output voltage waveform after compensation. DETAILED DESCRIPTION

[0024] The specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0025] Embodiment: A high-precision bandgap reference circuit, such as Figure 1 As shown, it includes a bandgap circuit, a negative temperature coefficient current extraction circuit and a current compensation circuit.

[0026] The bandgap circuit is a traditional bandgap voltage reference circuit that uses a cascode current mirror structure to generate a positive temperature coefficient current I IN and negative temperature coefficient voltage;

[0027] The negative temperature coefficient current extraction circuit extracts the negative temperature coefficient voltage generated by the bandgap circuit to generate a negative temperature coefficient current, and uses the MOS tube to combine the negative temperature coefficient current generated by the current extraction circuit and the positive temperature coefficient current I obtained by the Bandgap circuit. IN The resultant current I0; Figure 2 As shown, the negative temperature coefficient current extraction circuit includes a transistor Q1 and a first operational amplifier for extracting the negative temperature coefficient voltage generated by the bandgap circuit and generating a negative temperature coefficient current, which is compared with the positive temperature coefficient current I obtained by the Bandgap circuit. INThe current Iztat is synthesized by the MOS tubes M5 and M6 and output to the current compensation circuit as the current I0.

[0028] The current compensation circuit receives the current I0 output by the negative temperature coefficient current extraction circuit and the positive temperature coefficient current I generated by the bandgap circuit. IN , and output current with positive temperature coefficient I IN Second-order related compensation current I out , compensation current I out After passing through the poly resistor, the reference voltage is obtained by combining the current I0 with the voltage divider in the poly resistor. Figure 3 As shown, the current compensation circuit includes MOS transistors T1, T2, T3, T4, and T5, wherein the MOS transistors T1 and T2 are connected in series, the MOS transistors T3 and T4 are connected in series, the gates of the MOS transistors T4 and T5 are connected to form a current mirror, the gate and drain of the MOS transistor T1 are connected, the gate and drain of the MOS transistor T2 are connected, the gates of the MOS transistors T1 and T3 are connected, the gate and drain of the MOS transistor T4 are connected, the drain of the MOS transistor T3 is connected to the power supply VDD, and the sources of the MOS transistors T2, T4, and T5 are grounded; the current I0 is connected to the gates of the MOS transistors T1 and T3, and the current 2I is connected to the gate of the MOS transistor T5. IN , the current I0 and the current I are connected to the drain of MOS tube T5. IN .

[0029] Figure 3 In the equation: VGS(T1)+VGS(T2)=VGS(T3)+VGS(T5), the current flowing through T3 is the current flowing through T5 minus 2I. IN , let the current flowing through T3 be I b , the current flowing through T5 is I x .

[0030] but

[0031] And because I x =I IN +I0+I out (2)

[0032] I b =I x -2I IN (3)

[0033] Substituting (2) and (3) into (1), we can finally deduce That is, the output voltage and PTAT 2 Related, it is a second-order compensation circuit.

[0034] The MOS tube in the current compensation circuit is selected to have a width-to-length ratio that makes the output voltage temperature coefficient low. Specifically, the width-to-length ratio of the MOS tube is selected through experiments to have a set that can make the output voltage temperature coefficient low.

[0035] like Figure 4 As shown, the operational amplifiers in the bandgap circuit and the negative temperature coefficient current extraction circuit are subthreshold operational amplifiers.

[0036] These improvements not only retain the advantages of the traditional Bandgap voltage reference such as simple structure and strong process compatibility, but also achieve the goal of low output voltage temperature coefficient and reduced power consumption.

[0037] like Figure 5 As shown, the second-order compensation current and the compensated output voltage generated by the current compensation circuit (the compensation current i out The waveform of the poly resistance voltage is as follows Figure 5 (1) and (2) show that the uncompensated output voltage of the circuit (with I0 input) has the following waveform: Figure 5 As shown in (3), the output voltage waveform after circuit compensation is as follows Figure 5 (4) As shown. Compared with existing technical solutions, the main advantages of this invention are high precision, reduced power consumption, and strong process compatibility. The temperature drift can reach 2ppm / ℃ within the range of -40-125℃; power consumption is greatly reduced due to the use of subthreshold operational amplifiers; and the PSRR at low frequencies can reach 60dB.

[0038] The above description is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the creative concept of the present invention, which all fall within the scope of protection of the present invention.

Claims

1. High-precision bandgap reference circuit, characterized in that, include: The bandgap circuit uses a cascode current mirror structure to generate a positive temperature coefficient current I IN and negative temperature coefficient voltage; The negative temperature coefficient current extraction circuit extracts the negative temperature coefficient voltage generated by the bandgap circuit to generate a negative temperature coefficient current, and uses the MOS tube to combine the negative temperature coefficient current generated by the current extraction circuit and the positive temperature coefficient current I obtained by the Bandgap circuit. IN Resultant current I0; And a current compensation circuit, which receives the current I0 output by the negative temperature coefficient current extraction circuit and the positive temperature coefficient current I generated by the bandgap circuit IN , and outputs a current with a positive temperature coefficient I IN Second-order related compensation current I out , compensation current I out After passing through the poly resistor, it is combined with the voltage division of the current I0 in the poly resistor to obtain the reference voltage; The current compensation circuit includes MOS transistors T1, T2, T3, T4, and T5, wherein the MOS transistors T1 and T2 are connected in series, the MOS transistors T3 and T4 are connected in series, the gates of the MOS transistors T4 and T5 are connected to form a current mirror, the gate and drain of the MOS transistor T1 are connected, the gate and drain of the MOS transistor T2 are connected, the gates of the MOS transistors T1 and T3 are connected, the gate and drain of the MOS transistor T4 are connected, the drain of the MOS transistor T3 is connected to the power supply VDD, and the sources of the MOS transistors T2, T4, and T5 are grounded; current I0 is connected to the gates of the MOS transistors T1 and T3, and current 2I is connected to the gate of the MOS transistor T5. IN , the current I0 and the current I are connected to the drain of MOS tube T5. IN .

2. The high-precision bandgap reference circuit according to claim 1, wherein: The negative temperature coefficient current extraction circuit includes a transistor Q1 and a first operational amplifier for extracting the negative temperature coefficient voltage generated by the bandgap circuit and generating a negative temperature coefficient current, which is compared with the positive temperature coefficient current I obtained by the bandgap circuit. IN The current Iztat is synthesized by the MOS tubes M5 and M6 and output to the current compensation circuit as the current I0.

3. The high-precision bandgap reference circuit according to claim 1, wherein: The MOS tube in the current compensation circuit is selected to have a width-to-length ratio that enables a low output voltage temperature coefficient.

4. The high-precision bandgap reference circuit according to claim 2, wherein: The op amp used in the bandgap circuit and the negative temperature coefficient current extraction circuit is a subthreshold op amp.

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