A bandgap reference circuit with high power supply rejection ratio with second order temperature compensation

Abstract

The application discloses a kind of band gap reference circuit with high power supply rejection ratio with second-order temperature compensation in the technical field of semiconductor circuit, including starting circuit for providing a bias current when circuit starts, avoid the stable operating point that the positive and negative feedback branch current of operational amplifier circuit input end is all 0 when circuit works;Operational amplifier circuit is used for clamping, using its virtual short characteristics makes the voltage of two input terminals of operational amplifier approximately equal;Second-order temperature compensation circuit is used for compensating the linear and nonlinear term in base-emitter voltage of bipolar transistor, reduce the temperature drift of band gap reference circuit;Reference voltage output circuit is used for outputting reference voltage, providing stable and accurate reference voltage source, while participating in the starting current control generated by starting circuit goes to.The application is innovative and efficient, can provide stable and small temperature drift reference voltage, and also make it have larger voltage input range, high power supply rejection ratio and reliable starting circuit.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor circuit technology, specifically a bandgap reference circuit with high power supply rejection ratio and second-order temperature compensation. Background Technology

[0002] A bandgap reference circuit is a circuit used to generate a stable reference voltage. This circuit uses an internal mechanism to weighted summation of voltages with positive and negative temperature coefficients, making the temperature coefficient of the output voltage close to zero, thus outputting a stable voltage almost unaffected by temperature changes. An example is the base-emitter voltage Vo of a bipolar transistor. BE It is negatively correlated with temperature, exhibiting a negative temperature coefficient, while the thermal voltage V T It has a positive temperature coefficient. By canceling the two out in a certain proportion, a voltage with a near-zero temperature coefficient can be obtained.

[0003] Traditional bandgap reference circuits use first-order low-temperature compensation, that is, only the V of the transistor is compensated. BE Compensation is performed on the linear portion of the transistor. This compensation was generally sufficient for older chips operating in less complex environments, but it leads to significant temperature drift in applications with high temperature requirements. This necessitates improving the temperature characteristics of the reference power supply. Due to the transistor's V... BE The relationship with temperature is not linear; it contains nonlinear terms. Therefore, if second-order temperature compensation is applied to these nonlinear terms, the temperature characteristics of the reference power supply can be further improved.

[0004] Therefore, it is necessary to propose a bandgap reference circuit with high power supply rejection ratio that has second-order temperature compensation and can provide second-order low-temperature compensation for the bandgap reference circuit and output a sufficiently stable voltage. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a bandgap reference circuit with high power supply rejection ratio and second-order temperature compensation. In addition to providing a stable voltage reference with a certain degree of absolute accuracy and a small temperature drift coefficient, it also provides a large input voltage range, a high power supply rejection ratio, and a reliable startup circuit.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A bandgap reference circuit with high power supply rejection ratio and second-order temperature compensation is characterized by comprising a startup circuit, an operational amplifier circuit, a second-order temperature compensation circuit, and a reference voltage output circuit.

[0008] The startup circuit is electrically connected to the operational amplifier circuit. The startup circuit is used to provide a bias current when the circuit starts up, so as to avoid the circuit working at the stable operating point where the positive and negative feedback branch currents at the input of the operational amplifier circuit are both 0, and help the circuit smoothly enter the normal working state.

[0009] The operational amplifier circuit is electrically connected to the second-order temperature compensation circuit and the second current mirror circuit. The operational amplifier circuit is used to clamp the voltage, and its virtual short characteristic is used to make the voltages at the two input terminals of the operational amplifier approximately equal.

[0010] The second-order temperature compensation circuit is electrically connected to the reference voltage output circuit. It is used to compensate for the linear and nonlinear terms in the base-emitter voltage of the bipolar transistor, reduce the temperature drift of the bandgap reference circuit, and improve the accuracy of the reference voltage.

[0011] The output terminal of the reference voltage output circuit is VBG. The output terminal VBG is used to output the reference voltage, providing a stable and accurate reference voltage source, and at the same time, it participates in controlling the flow direction of the starting current generated by the starting circuit.

[0012] The basic principle of the scheme is as follows: the startup circuit consists of MP0-MP8, MN0, MN1, MN8, R0, and C0; the operational amplifier circuit consists of MP9-MP8. 16 The circuit consists of MN2-MN7 and C1; the second-order temperature compensation circuit is composed of MP. 17 -MP 25 The circuit consists of R1-R5 and Q0-Q2; the output reference voltage circuit is composed of MP. 26 -MP 28 It consists of R6 and C2.

[0013] The beneficial effects of the basic scheme are: 1. By introducing a second-order temperature compensation circuit, the bandgap reference circuit of the present invention can output a reference voltage with minimal temperature drift in an operating environment of -40℃ to 125℃, so that the reference voltage can maintain high stability and accuracy at the operating temperature.

[0014] 2. The operational amplifier circuit is designed not only to clamp the input signal, but also to achieve a high power supply rejection ratio (PSRR) by adjusting the appropriate gain and bandwidth. This means the circuit can suppress power supply voltage fluctuations. This helps reduce the impact of power supply voltage fluctuations on the reference voltage, thereby improving the stability and reliability of the entire circuit.

[0015] 3. The circuit structure of this invention allows it to operate over a wide range of input voltages, which is of great significance for power supply adaptability in different application scenarios. At the same time, the circuit can maintain stable performance even in environments where the input voltage is not very stable.

[0016] 4. The design of the startup circuit ensures that the circuit will not operate at the stable operating point where the current in the positive and negative feedback branches is zero. This is crucial to preventing the circuit from getting stuck or malfunctioning during operation.

[0017] 5. By comprehensively applying first-order and second-order temperature compensation techniques, the bandgap reference circuit of this invention can provide a reference voltage with high accuracy and low temperature drift. This is a significant advantage for electronic systems requiring high accuracy and low temperature drift.

[0018] Furthermore, the startup circuit also includes a startup current generation circuit and a first current mirror circuit. The startup current generation circuit is used to receive changes in the enable signal to generate a startup current, and to control the direction of the startup current flow through the reference voltage output from the reference voltage output circuit. The first current mirror circuit is used to proportionally replicate the startup current input to the operational amplifier circuit.

[0019] The beneficial effects of the basic scheme are: the startup current generation circuit includes PMOS transistors MP0-MP5 connected in series with their gates controlled by the enable signal PD, and R0 connected in series with the drain of MP5; and NMOS transistors MN0 and MN2 connected in series with their gates controlled by the output signal VBG. O The source is connected in series with R0; the first current mirror circuit includes MN1, whose gate is electrically connected to the source of MN0; MP7, whose gate is electrically connected to the PD signal; MP7, whose drain is electrically connected to the source of MN1; MP6, which is connected in series with the source of MP7; MP8, whose gate is electrically connected to the gate of MP6; and MP9 and MP8, whose source and drain are connected in series. 10 in parallel.

[0020] 1. In the startup current generation circuit, PMOS transistors MP0-MP5 are connected in a diode configuration. Multiple PMOS transistors enable them to quickly respond to the enable signal PD and toggle, thus accelerating the circuit's startup process. When MP0-MP5 are turned on by the enable signal, a voltage difference is generated across R0, which in turn generates a startup current. This fast-response mechanism is particularly important for applications requiring rapid startup.

[0021] 2. If the circuit is not operating at the point where the current in the positive and negative feedback branches is 0, then VBG will output normally. If it is, after the circuit starts working, VBG will rise from a low level to the designed output voltage, which is approximately 1.2V in this bandgap design, greater than the threshold voltage V of MN0. TN In both scenarios, MN0 will eventually conduct. At this point, the starting current will flow directly to ground through MN0 and no longer through MN1. The starting circuit will no longer affect subsequent circuits. If the set VBG is less than V... TN Then the startup circuit needs to be adjusted accordingly, such as by using a resistor divider at the output to generate a voltage that is higher than the V of the NMOS transistor in the technology library used.TN A higher voltage can be used to replace the control signal VBG, or the startup circuit can be replaced. This mechanism ensures that the startup circuit, after completing its work, will not affect the operation of subsequent circuits, thus protecting the normal operation of the subsequent circuits.

[0022] 3. The first current mirror circuit can mirror the startup current and input it into the operational amplifier circuit. This current mirroring mechanism ensures that the operational amplifier circuit receives a current proportional to the startup current that is sufficient to enable the subsequent circuits to operate normally, thereby improving the reliability of the circuit operation.

[0023] 4. Since a voltage difference will always be generated across R0 after the startup circuit is turned on, resulting in a continuous startup current, the current mirror circuit can be used to proportionally replicate the current. This allows R0 to be increased to reduce the startup current, and then a sufficient current to power subsequent circuits can be replicated. When the replication circuit is turned off, it will not increase power consumption excessively. This is a significant advantage for low-power applications.

[0024] Furthermore, a capacitor C0 is connected in parallel to the gate NM0, which is controlled by the output signal VBG.

[0025] The beneficial effect of the basic scheme is that the source and drain of MN0 are connected in parallel with capacitor C0, which avoids the circuit from suddenly starting up and V BG During normal output, this can cause transient oscillations or even jumps in the circuit.

[0026] Furthermore, the operational amplifier circuit uses PMOS as the Cascode structure operational amplifier for the input differential pair.

[0027] The advantages of the basic scheme are: the operational amplifier circuit includes MP9 and MP4 connected in parallel with the MOSFET MP8. 10 MP9 gate and MP 11 The gate electrical connection, MP9 and MP 11 The sources of MP are all electrically connected to the input voltage VDD. 11 Drain and MP 12 Source-to-line, MP 12 Gate and MP 10 Gate electrical connection, MP 10 The drains are connected in series with MN2 and MN3. The gates of MN2 and MN3 are both electrically connected to their own sources. The drain of MN3 is electrically connected to the drain of MN5 and to GND. MP 12 The drains of MP are respectively electrically connected 13 and MP 14 The source, MP 13 The gate receives input signals IN1 and MP. 14 The gate of MN5 receives the input signal IN2, and the source of MN5 is connected in series with MN4 and MP.15 And MN5 and MN7, MN4 and MN6, MP 15 and MP 16 The gates of MN7 and MN5 are electrically connected, and the drains of MN7 and MN6 are electrically connected. 16 Series, MP 16 The source and MP 15 Source electrical connection, MP 13 The drain of MP is electrically connected to the drain of MN4. 14 The drain of MN3 is electrically connected to the drain of MN6, the source of MN3 is electrically connected to the gate of MN5, the source of MN2 is electrically connected to the gate of MN4, and MP... 15 The drain and MP 15 The gate electrical connection.

[0028] 1. This structure effectively increases the output impedance of the circuit by adding an extra transistor stage. Increased output impedance means the circuit is less sensitive to power supply voltage fluctuations, thereby improving the power supply rejection ratio.

[0029] 2. Using a Cascode structure can improve the DC matching of the circuit, which helps to reduce noise and interference caused by circuit mismatch.

[0030] 3. The cascading of transistors in the Cascode structure can reduce the impact of power supply voltage fluctuations on the core circuit. Through proper circuit design, power supply noise can be effectively attenuated during transmission.

[0031] 4. Employing a PMOS input differential pair reduces 1 / f noise and is suitable for low input common-mode conditions. This Cascode amplifier features a wide common-mode input range and a large output voltage swing.

[0032] Furthermore, a capacitor C1 is connected in parallel at the output of the operational amplifier circuit.

[0033] The beneficial effect of the basic scheme is that a capacitor C1 is connected in parallel between the source of MN6 and the drain of MN7.

[0034] The main function of capacitor C1 is to provide phase compensation for the output. Additionally, when the operational amplifier operates at high frequencies, the effects of internal parasitic capacitance and inductance may cause oscillations or instability. The parallel capacitor C1 provides an additional phase lag, thus offsetting the phase lead caused by parasitic elements, making the overall phase response of the circuit flatter and contributing to improved circuit stability.

[0035] 2. Phase margin is an important indicator of circuit stability. It represents the phase difference between the input and output signals before the circuit reaches a critical stable state. Phase compensation through a parallel capacitor C1 can increase the phase margin of the circuit, moving the circuit further away from the oscillation point, thereby improving the circuit's anti-interference capability and stability.

[0036] 3. The frequency response of an operational amplifier is often affected by its internal parasitic elements, leading to decreased high-frequency gain and phase distortion. A parallel capacitor C1 can form a high-frequency bypass path, allowing high-frequency signals to pass more through the capacitor rather than the operational amplifier's internal parasitic elements, thereby improving the circuit's high-frequency response and phase characteristics.

[0037] Furthermore, during second-order temperature compensation, the base-emitter voltage V of bipolar transistors Q0 and Q2 in the second-order temperature compensation circuit... BE0 and V BE2 The expressions are as follows:

[0038] V BE0 =V G0 -β0K0-(η-α0)V T lnK0

[0039] V BEh =V Gh -β h K h -(η-α h V T lnK h

[0040] In the formula, V G β is the bandgap voltage of silicon at absolute temperature; V is the voltage across the bandgap of silicon. G The remainder after subtracting the base-emitter voltage at the reference temperature; K is the ratio of the absolute temperature to the reference temperature; η is a process-dependent constant; α is a quantity related to the current flowing through the transistor. When the current flowing through the transistor is proportional to the temperature, α is 1; when the current flowing through the transistor is not related to the temperature, α is 0. Here, α0 is 1 and α2 is 0; V T This is thermal voltage.

[0041] The beneficial effect of the basic scheme is that the second-order temperature compensation circuit includes a series-connected MOSFET MP. 17 MP 18 and MP 19 MP 17 MP 18 and MP 19 The gates of MP are respectively 20 MP 21 and MP 22 The gate electrical connection, MP 17 The source and MP20 The source electrode is electrically connected and connected to MP 16 The source electrical connection, MP 17 The gate of MP9 is electrically connected to the gate of MP9. 18 The gate and MP 10 The gate electrical connection, MP 19 The source and MP 10 The gate electrical connection, MP 19 The drain of Q0 is electrically connected to the emitter of the bipolar transistor Q0. The base of Q0 is electrically connected to the base of Q1 and to the collectors of both Q0 and Q1. The emitter and collector of Q0 are connected in parallel with resistor R1. The emitter of Q1 is connected in parallel with resistor R2. R2 and the collectors of Q1 are connected in parallel with resistor R3. 22 The drain of Q1 is electrically connected to R2, and R1 and R2 have the same resistance. The collector of Q1 is electrically connected to the collector and base of Q2. The emitter of Q2 is electrically connected to R5 and R4. R5 is connected to MP. 22 The drain connection, R4 and MP 19 The drain terminals are connected, and R4 and R5 have the same resistance value.

[0042] Given the base-emitter voltage V of a bipolar transistor BE The relationship with temperature is as follows:

[0043]

[0044] In the formula, V G Here, η is the bandgap voltage of silicon at absolute temperature, T is the absolute temperature, T0 is the reference temperature, η is the process-dependent constant, α is the temperature index of the collector, and V is the reference temperature. T This is the thermal voltage. Where [(V G -V BE (T0))](T / T0) is a linear term, (η-α)V T ln(T / T0) is a nonlinear term.

[0045] When performing second-order temperature compensation, the base-emitter voltage V of bipolar transistors Q0 and Q2 is... BE0 and V BE2 The expressions are as follows:

[0046] V BE0 =V G0 -β0K0-(η-α0)V T lnK0

[0047] V BEh =V Gh -β h K h -(η-α h V T lnK h

[0048] In the formula, V G β is the bandgap voltage of silicon at absolute temperature; V is the voltage across the bandgap of silicon. G The remainder after subtracting the base-emitter voltage at the reference temperature; K is the ratio of the absolute temperature to the reference temperature; η is a process-dependent constant; α is a quantity related to the current flowing through the transistor. When the current flowing through the transistor is proportional to the temperature, α is 1; when the current flowing through the transistor is not related to the temperature, α is 0. Here, α0 is 1 and α2 is 0; V T This is the thermal voltage. When Q0 = Q2, then ΔV BE0,2 =V BE0 -V BE2 =V T lnK+δ, where δ is a residual that has almost no effect on the nonlinear term in the base-emitter voltage versus temperature relationship of a bipolar transistor and can be discarded. At this point,

[0049]

[0050] In the formula, I4 is the current flowing through R4. If it is used to cancel the nonlinear term in the formula, then:

[0051]

[0052] Since a current proportional to temperature flows through transistor Q0, α0 is 1. Let R4 = R5, then R5 = R4 = R1 / (η-1).

[0053] 1. Through a carefully designed second-order temperature compensation circuit, the temperature coefficient of the bandgap reference circuit can be further reduced. This means that the reference voltage remains highly stable under various temperature variations, thereby improving the circuit's temperature stability. This is crucial for analog circuits requiring high-precision voltage references, as it ensures the circuit functions correctly under diverse environmental conditions.

[0054] 2. The second-order temperature compensation circuit compensates for the bipolar transistor V. BE The nonlinear component that varies with temperature significantly improves the stability of the reference voltage. This stability is crucial for key functions in analog circuits, such as signal processing and data conversion, because it reduces errors and drift caused by temperature variations.

[0055] 3. In second-order temperature compensation circuits, the required resistance value can be determined relatively accurately and quickly by roughly calculating the resistance ratio using formulas (e.g., R4 = R1 / (η-1)), thus achieving precise compensation for nonlinear terms. This flexibility allows circuit designers to select appropriate resistance values ​​to optimize circuit performance based on different application scenarios and performance requirements.

[0056] Furthermore, a second current mirror circuit is connected between the reference voltage output circuit and the second-order temperature compensation circuit. The second current mirror circuit is used to mirror and replicate the MP in the second-order temperature compensation circuit proportionally. 23 -MP 25 The current in the branch.

[0057] The beneficial effect of the basic scheme is that the reference voltage output circuit includes a series-connected MOSFET MP. 25 MP 24 and MP 23 MP 25 MP 24 and MP 23 The gates of MP are respectively 28 MP 27 and MP 26 The gate electrical connection, MP 28 MP 27 and MP 26 Also connected in series, MP 26 The source and MP 23 The source electrode is electrically connected and connected to MP 20 The source electrical connection, MP 25 The drain of Q2 is electrically connected to the emitter of Q2, MP 28 The drain of MN8 is electrically connected to R6, R6 is connected in parallel with the source and drain of MN8, the drain of MN8 is electrically connected to the collector of Q2, the gate of MN8 is controlled by the enable signal PD, and the source of MN8 outputs the VBG voltage. 24 The gate and MP 18 The gate electrical connection, MP 23 The gate and MP 17 The gate electrical connection. MP9-MP 12 MP 17 MP 18 MP 20 MP 21 MP 23 MP 24 MP 26 MP 27 Together they form the second current mirror circuit.

[0058] 1. The current mirror circuit itself has the ability to replicate current with high precision. By mirroring the current I3 of the second-order temperature compensation circuit in the same proportion, it can ensure that the current in the reference voltage output circuit has the same accuracy and stability as the second-order temperature compensation circuit. This helps to reduce errors and fluctuations in current during transmission, thereby improving the performance and stability of the entire circuit.

[0059] 2. By using a current mirror circuit to mirror the current proportionally, the design of the reference voltage output circuit can be simplified. No additional current regulator or complex circuit structure is needed to achieve accurate current replication and regulation, thus reducing the complexity and cost of circuit design.

[0060] 3. Because the current mirror circuit has a flexible current replication ratio and wide applicability, the current in the reference voltage output circuit can be easily adjusted to meet different application requirements.

[0061] Furthermore, a capacitor C2 is connected in parallel at the output terminal of the reference voltage output circuit.

[0062] The beneficial effect of the basic scheme is that resistor R6 and capacitor C2 are connected in parallel.

[0063] The main function of capacitor C2 is to output a transiently stable reference voltage VBG. 1. Capacitor C2 has the ability to charge and discharge. When the voltage in the circuit changes transiently, capacitor C2 can absorb or release charge, thereby slowing down the sudden change speed and overshoot amplitude of voltage VBG, making the output of reference voltage VBG more stable.

[0064] 2. During transient processes such as circuit startup or load changes, the presence of capacitor C2 can significantly reduce the fluctuation of the reference voltage VBG, ensuring that the circuit can still output a stable voltage under these conditions.

[0065] 3. At low frequencies, capacitor C2 has a high impedance, essentially acting as an open circuit and not affecting the circuit's power supply rejection performance. However, at high frequencies, the capacitor's impedance is lower, and when connected in parallel with a resistor, it reduces the equivalent impedance, thereby improving power supply rejection performance in the high-frequency range. Thus, even under high-frequency operating conditions, the bandgap reference circuit can maintain a high power supply rejection ratio. Capacitor C2 can also be used for zero-point adjustment and phase compensation to ensure circuit stability and performance.

[0066] Furthermore, the structure of the second current mirror circuit, which serves as the current source for the operational amplifier circuit, the second-order temperature compensation circuit, and the reference voltage output circuit, is a Cascode structure made with PMOS transistors.

[0067] The beneficial effect of the basic scheme is that, in order to further improve the power supply rejection ratio of the bandgap circuit, we make the structure of the second current mirror circuit, which serves as the current source for the operational amplifier circuit, the second-order temperature compensation circuit, and the reference voltage output circuit, a Cascode structure using PMOS transistors, i.e., adding MP... 10 MP 12 MP 18 MP 21 MP 24 MP 27Meanwhile, to reduce circuit turn-off power consumption, enable control was introduced into branches that control the generation and flow of circuit current, specifically through MP0-MP5, MP7, and MP... 19 MP 22 MP 25 MP 28 The control is achieved by turning MN8 on and off.

[0068] 1. A Cascode current source using a PMOS transistor can more effectively suppress the impact of power supply voltage fluctuations on the circuit output, thus ensuring a stable output voltage under various power supply voltage conditions. The introduction of the PMOS transistor Cascode structure gives the current source section of the circuit higher stability and anti-interference capability. This helps reduce the impact of power supply voltage fluctuations on the reference voltage output circuit, thereby improving the power supply rejection ratio of the entire bandgap circuit.

[0069] 2. Introducing enable control into branches that can generate current and influence its direction allows for precise control of the circuit current. When the circuit is not in operation, enabling control can shut down branches that generate current and influence its direction, thereby reducing the circuit's shutdown power consumption. The introduction of enable control allows the circuit to quickly enter a low-power state when not in use. This helps extend battery life and reduce the overall energy consumption of the system.

[0070] 3. By improving the power supply rejection ratio and reducing turn-off power consumption, this design significantly improves the overall performance of the bandgap circuit. This allows the circuit to exhibit better stability and energy efficiency in various applications. The Cascode structure of the PMOS transistor and the introduction of enable control enhance the circuit's anti-interference capability and stability. This helps reduce the risk of circuit failure and improve system reliability. At the same time, by reducing unnecessary power consumption, it reduces energy waste caused by the circuit during standby.

[0071] Furthermore, the number of transistors in bipolar transistor Q1 is N times the number of transistors of the same type in bipolar transistor Q0, and the number of bipolar transistors Q2 is the same as that in bipolar transistor Q0.

[0072] The advantage of this basic approach is that transistors of the same size also exhibit similar thermal effects. Therefore, the performance of individual transistors of the same type is likely to change similarly with temperature variations, which helps the circuit maintain stable performance over a wide temperature range. Attached Figure Description

[0073] Figure 1 This is a schematic diagram of a bandgap reference circuit with high power supply rejection ratio and second-order temperature compensation in an embodiment of the present invention.

[0074] Figure 2This is a schematic diagram of the startup circuit of a bandgap reference circuit with high power supply rejection ratio and second-order temperature compensation in an embodiment of the present invention.

[0075] Figure 3 This is a circuit diagram of a bandgap reference circuit with high power supply rejection ratio and second-order temperature compensation in an embodiment of the present invention.

[0076] The reference numerals in the accompanying drawings include: 1. Start-up circuit; 2. Operational amplifier circuit; 3. Second-order temperature compensation circuit; 4. Reference voltage output circuit; 5. First current mirror circuit; 6. Second current mirror circuit. Detailed Implementation

[0077] The following detailed description illustrates the specific implementation method:

[0078] Example

[0079] The basics are as follows: Figure 1 , Figure 2 and Figure 3 As shown: A bandgap reference circuit with high power supply rejection ratio and second-order temperature compensation includes a startup circuit 1, an operational amplifier circuit 2, a second-order temperature compensation circuit 3, a reference voltage output circuit 4, a first current mirror circuit 5, and a second current mirror circuit 6.

[0080] The startup circuit 1 is electrically connected to the operational amplifier circuit 2. The startup circuit 1 is used to provide a bias current when the circuit starts up, so as to avoid the circuit working at the stable operating point where the positive and negative feedback branch currents at the input terminal of the operational amplifier circuit are both 0, and help the circuit smoothly enter the normal working state. The startup circuit 1 also includes a startup current generation circuit and a first current mirror circuit 5. The startup current generation circuit is used to receive the enable signal change to generate a startup current, and controls the direction of the startup current flow through the reference voltage output from the reference voltage output circuit 4. The first current mirror circuit 5 is used to proportionally replicate the startup current input to the operational amplifier circuit 2. The gate NM0 controlled by the output signal VBG is connected in parallel with a capacitor C0.

[0081] Operational amplifier circuit 2 is electrically connected to second-order temperature compensation circuit 3 and second current mirror circuit 6. Operational amplifier circuit 2 is used to clamp voltage and utilize its virtual short characteristic to make the voltages at the two input terminals of the operational amplifier approximately equal. Operational amplifier circuit 2 uses PMOS as the Cascode structure operational amplifier for the input differential pair. A capacitor C1 is connected in parallel at the output terminal of operational amplifier circuit 2.

[0082] The second-order temperature compensation circuit 3 is electrically connected to the reference voltage output circuit 4. It is used to compensate for the linear and nonlinear terms in the base-emitter voltage of the bipolar transistor, reducing the temperature drift of the bandgap reference circuit and improving the accuracy of the reference voltage. The number of transistors in bipolar transistor Q1 is N times the number of transistors of the same type in bipolar transistor Q0. The number of bipolar transistors Q2 is the same as that in bipolar transistor Q0. When performing second-order temperature compensation, the V0 of bipolar transistors Q0 and Q2... BE0 and V BE2 The expressions are as follows:

[0083] V BE0 =V G0 -β0K0-(η-α0)V T lnK0

[0084] V BEh =V Gh -β h K h -(η-α h V T lnK h

[0085] In the formula, V G β is the bandgap voltage of silicon at absolute temperature; V is the voltage across the bandgap of silicon. G The remainder after subtracting the base-emitter voltage at the reference temperature; K is the ratio of the absolute temperature to the reference temperature; η is a process-dependent constant; α is a quantity related to the current flowing through the transistor. When the current flowing through the transistor is proportional to the temperature, α is 1; when the current flowing through the transistor is not related to the temperature, α is 0. Here, α0 is 1 and α2 is 0; V T This is thermal voltage.

[0086] The reference voltage output circuit 4 outputs a VBG terminal, which is used to output a reference voltage, providing a stable and accurate reference voltage source. It also participates in controlling the flow of the starting current generated by the starting circuit. A second current mirror circuit 6 is connected between the reference voltage output circuit 4 and the second-order temperature compensation circuit 3. The second current mirror circuit 6 is used to mirror and replicate the MP signal in the second-order temperature compensation circuit 3 proportionally. 23 -MP 25 The current in the branch is such that a capacitor C2 is connected in parallel to the output terminal of the reference voltage output circuit 4.

[0087] The specific implementation process is as follows: Start-up circuit 1 consists of MP0-MP8, MN0, MN1, MN8, R0, and C0; operational amplifier circuit 2 consists of MP9-MP8... 16 The circuit consists of MN2-MN7 and C1; the second-order temperature compensation circuit 3 is composed of MP. 17 -MP 25The circuit consists of R1-R5 and Q0-Q2; the output reference voltage circuit 4 is composed of MP. 26 -MP 28 It consists of R6 and C2.

[0088] The startup current generation circuit includes PMOS transistors MP0-MP5 connected in series with their gates controlled by the enable signal PD, and R0 connected in series with the drain of MP5; and NMOS transistors MN0 and MN2 connected in series with their gates controlled by the output signal VBG. O The source is connected in series with R0; the first current mirror circuit 5 includes MN1, whose gate is electrically connected to the source of MN0; MP7, whose gate is electrically connected to the PD signal; MP7, whose drain is electrically connected to the source of MN1; MP6, which is connected in series with the source of MP7; MP8, whose gate is electrically connected to the gate of MP6; and MP9 and MP8, whose source and drain are connected in series. 10 In parallel, the source and drain of MN0 are connected in parallel with capacitor C0.

[0089] Operational amplifier circuit 2 includes MP9 and MP4 connected in parallel with MOSFET MP8. 10 MP9 gate and MP 11 The gate electrical connection, MP9 and MP 11 The sources of MP are all electrically connected to the input voltage VDD. 11 Drain and MP 12 Source-to-line, MP 12 Gate and MP 10 Gate electrical connection, MP 10 The drains are connected in series with MN2 and MN3. The gates of MN2 and MN3 are both electrically connected to their own sources. The drain of MN3 is electrically connected to the drain of MN5 and to GND. MP 12 The drains of MP are respectively electrically connected 13 and MP 14 The source, MP 13 The gate receives input signals IN1 and MP. 14 The gate of MN5 receives the input signal IN2, and the source of MN5 is connected in series with MN4 and MP. 15 And MN5 and MN7, MN4 and MN6, MP 15 and MP 16 The gates of MN7 and MN5 are electrically connected, and the drains of MN7 and MN6 are electrically connected. 16 Series, MP 16 The source and MP 15 Source electrical connection, MP 13 The drain of MP is electrically connected to the drain of MN4. 14 The drain of MN3 is electrically connected to the drain of MN6, the source of MN3 is electrically connected to the gate of MN5, the source of MN2 is electrically connected to the gate of MN4, and MP... 15The drain and MP 15 The gate of MN6 is electrically connected, and the source of MN6 and the drain of MN7 are connected in parallel with capacitor C1.

[0090] The second-order temperature compensation circuit 3 includes a series-connected MOSFET MP 17 MP 18 and MP 19 MP 17 MP 18 and MP 19 The gates of MP are respectively 20 MP 21 and MP 22 The gate electrical connection, MP 17 The source and MP 20 The source electrode is electrically connected and connected to MP 16 The source electrical connection, MP 17 The gate of MP9 is electrically connected to the gate of MP9. 18 The gate and MP 10 The gate electrical connection, MP 19 The source and MP 10 The gate electrical connection, MP 19 The drain of Q0 is electrically connected to the emitter of the bipolar transistor Q0. The base of Q0 is electrically connected to the base of Q1 and to the collectors of both Q0 and Q1. The emitter and collector of Q0 are connected in parallel with resistor R1. The emitter of Q1 is connected in parallel with resistor R2. R2 and the collectors of Q1 are connected in parallel with resistor R3. 22 The drain of Q1 is electrically connected to R2, and R1 and R2 have the same resistance. The collector of Q1 is electrically connected to the collector and base of Q2. The emitter of Q2 is electrically connected to R5 and R4. R5 is connected to MP. 22 The drain connection, R4 and MP 19 The drain terminals are connected, and R4 and R5 have the same resistance value.

[0091] The reference voltage output circuit 4 includes a series-connected MOSFET MP 25 MP 24 and MP 23 MP 25 MP 24 and MP 23 The gates of MP are respectively 28 MP 27 and MP 26 The gate electrical connection, MP 28 MP 27 and MP 26 Also connected in series, MP 26 The source and MP 23 The source electrode is electrically connected and connected to MP 20 The source electrical connection, MP 25The drain of Q2 is electrically connected to the emitter of Q2, MP 28 The drain of MN8 is electrically connected to R6, R6 is connected in parallel with the source and drain of MN8, the drain of MN8 is electrically connected to the collector of Q2, the gate of MN8 is controlled by the enable signal PD, and the source of MN8 outputs the VBG voltage. 24 The gate and MP 18 The gate electrical connection, MP 23 The gate and MP 17 The gate electrical connection. MP9-MP 12 MP 17 MP 18 MP 20 MP 21 MP 23 MP 24 MP 26 MP 27 Together they form the second current mirror circuit 6, with resistor R6 and capacitor C2 connected in parallel.

[0092] When the enable signal PD just jumps from high to low, VBG is 0, MN0 is off, and MP0-MP5 are on. They will generate current with the branch R0, and this current will be mirrored to MP8 through MP6, causing MP9 and MP5 to conduct. 10 The current in branches MN2 and MN3 is not zero at this moment, thus preventing the bandgap circuit from entering a steady state where all currents in the positive and negative feedback loops are zero. After the circuit starts normally, VBG rises to the set voltage. The bandgap voltage is 1.2V, which is greater than the threshold voltage V of MN0. TN This will cause it to conduct, at which point the current will no longer flow through MN1, and the starting circuit 1 will no longer affect the subsequent circuits. If the set VBG is less than V TN Then the startup circuit needs to be adjusted accordingly, such as by using a resistor divider at the output to generate a voltage that is higher than the V of the NMOS transistor under the current technology. TN A higher voltage can replace VBG, or the startup circuit 1 can be replaced. The purpose of C0 is to prevent transient oscillations or even jumps in the circuit when the circuit starts suddenly or when VBG is outputting normally.

[0093] Operational amplifier circuit 2 is a cascode operational amplifier with PMOS as the input differential pair. Using PMOS as the input differential pair reduces 1 / f noise and is suitable for low input common-mode conditions. This folded cascode amplifier has a wide common-mode input range and a large output voltage swing. C1 is used for output phase compensation.

[0094] Given the base-emitter voltage V of a bipolar transistor BE The relationship with temperature is as follows:

[0095]

[0096] In the formula: V G Here, η is the bandgap voltage of silicon at absolute temperature, T is the absolute temperature, T0 is the reference temperature, η is the process-dependent constant, α is the temperature index of the collector, and V is the reference temperature. T This is the thermal voltage. Where [(V G -V BE (T0))](T / T0) is a linear term, (η-α)V T ln(T / T0) is a nonlinear term.

[0097] When performing first-order linear temperature compensation, if the quantity of Q1 is N times that of Q0, then the difference in ΔV between them is... BE0,1 =V T Let lnN be the current flowing through resistor R2, and let I1 be the current. Then the current I1 = ΔV BE0,1 / R2=V T Let lnN / R2 be the current, and let it be a current with a positive temperature coefficient. Let R1 = R3, and let the current flowing through resistor R1 be I2, then I2 = ΔV BE0 / R1, and it is a negative temperature coefficient current. By adjusting the ratio of R1 to R2, I1 and I2 can cancel each other out, thus eliminating the linear term in formula (1).

[0098] For ease of expression, when performing second-order temperature compensation, we will use V G -V BE Let the value of (T0) be β, and the value of T / T0 be K. At this point, the current flowing through Q0 is proportional to the temperature, and α0 is 1; the current flowing through Q2 is almost independent of the temperature, and α2 is 0. Then the base-emitter voltage V of Q0 and Q2... BE The expressions are as follows:

[0099] V BE0 =VG0-β0K0-(η-α0)V T lnK0 (2)

[0100] V BEh =V Gh -β h K h -(η-α h V T lnK h (3)

[0101] When Q0 = Q2, then ΔV BE0,2 =V BE0 -V BE2 =V TlnK+δ, where δ is a residual, has almost no effect on the nonlinear term in the base-emitter voltage versus temperature relationship of a bipolar transistor, and can be discarded. At this point...

[0102]

[0103] In the formula, I4 is the current flowing through R4. If it is used to cancel the nonlinear term in the formula, then:

[0104]

[0105] Since a current proportional to temperature flows through transistor Q0, α0 is 1. Let R4 = R5, then R5 = R4 = R1 / (η-1).

[0106] Reference voltage output circuit 4 uses a proportional mirror MP 23 -MP 25 The current in the branch is then related to the current flowing through MP. 26 -MP 28 The currents in the branches are equal, let it be I3, then I3 = I1 + I2 + I4, finally obtaining VBG = I3 × R6. The function of C2 is to output a transiently stable VBG. In order to further improve the power supply rejection ratio of the bandgap circuit, the structure of the second current mirror circuit, which serves as the current source for the operational amplifier circuit, the second-order temperature compensation circuit, and the reference voltage output circuit, is a Cascode structure using PMOS transistors, that is, MP is added. 10 MP 12 MP 18 MP 21 MP 24 MP 27 To reduce circuit turn-off power consumption, enable control is introduced in each branch that can generate its own current, enabling precise control of the circuit current. When the circuit is not in operation, the enable control can shut down branches that generate current and influence its direction, thereby reducing turn-off power consumption. The introduction of enable control allows the circuit to quickly enter a low-power state when not in use. This helps extend battery life and reduce overall system energy consumption.

[0107] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0108] The above descriptions are merely embodiments of the present invention. Commonly known structures and characteristics are not described in detail here. Those skilled in the art are aware of all common technical knowledge in the field prior to the application date or priority date, are aware of all existing technologies in that field, and have the ability to apply conventional experimental methods prior to that date. Those skilled in the art can, under the guidance of this application, improve and implement this solution in combination with their own capabilities. Some typical known structures or methods should not be obstacles for those skilled in the art to implement this application. It should be noted that those skilled in the art can make several modifications and improvements without departing from the structure of the present invention. These should also be considered within the scope of protection of the present invention, and will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. A bandgap reference circuit with high power supply rejection ratio and second-order temperature compensation, characterized in that: It includes a startup circuit (1), an operational amplifier circuit (2), a second-order temperature compensation circuit (3), and a reference voltage output circuit (4); The startup circuit (1) is electrically connected to the operational amplifier circuit (2). The startup circuit (1) is used to provide a bias current when the circuit starts up, so as to avoid the circuit working at the stable operating point where the positive and negative feedback branch currents at the input terminal of the operational amplifier circuit are both 0, and help the circuit smoothly enter the normal working state. The operational amplifier circuit (2) is electrically connected to the second-order temperature compensation circuit (3) and the second current mirror circuit (6). The operational amplifier circuit (2) is used to clamp the voltage and utilize its virtual short characteristic to make the voltages at the two input terminals of the operational amplifier approximately equal. The second-order temperature compensation circuit (3) is electrically connected to the reference voltage output circuit (4) to compensate for the linear and nonlinear terms in the base-emitter voltage of the bipolar transistor, reduce the temperature drift of the bandgap reference circuit, and improve the accuracy of the reference voltage. The output terminal of the reference voltage output circuit (4) is VBG. The output terminal VBG is used to output the reference voltage, providing a stable and accurate reference voltage source, and at the same time participating in controlling the flow direction of the starting current generated by the starting circuit.

2. The bandgap reference circuit with high power supply rejection ratio and second-order temperature compensation according to claim 1, characterized in that: The startup circuit (1) includes a startup current generation circuit and a first current mirror circuit (5). The startup current generation circuit is used to receive the change of the enable signal to generate a startup current and control the direction of the startup current flow through the reference voltage output from the reference voltage output circuit (4). The first current mirror circuit (5) is used to proportionally replicate the startup current input to the operational amplifier circuit (2).

3. The high power supply rejection ratio bandgap reference circuit with second-order temperature compensation according to claim 2, characterized in that: A capacitor C0 is connected in parallel to the gate NM0, which is controlled by the output signal VBG.

4. The high power supply rejection ratio bandgap reference circuit with second-order temperature compensation according to claim 3, characterized in that: The operational amplifier circuit (2) uses PMOS as the Cascode structure operational amplifier for the input differential pair.

5. The high power supply rejection ratio bandgap reference circuit with second-order temperature compensation according to claim 4, characterized in that: The operational amplifier circuit (2) has a capacitor C1 connected in parallel at the output terminal.

6. The bandgap reference circuit with high power supply rejection ratio and second-order temperature compensation according to claim 5, characterized in that: In the second-order temperature compensation circuit (3), the base-emitter voltage V of bipolar transistors Q0 and Q2 is measured during second-order temperature compensation. BE0 and V BE2 The expressions are as follows: V BE0 =V G0 -β0K0-(η-α0)V T lnK0 V BE2 =V G2 -β2K2-(η-α2)V T lnK2 In the formula, V G β is the bandgap voltage of silicon at absolute temperature; V is the voltage across the bandgap of silicon. G The remainder after subtracting the base-emitter voltage at the reference temperature; K is the ratio of the absolute temperature to the reference temperature; η is a process-dependent constant; α is a quantity related to the current flowing through the transistor. When the current flowing through the transistor is proportional to temperature, α is 1; when the current flowing through the transistor is not temperature-dependent, α is 0. Here, α0 is 1 and α2 is 0; V T This is thermal voltage.

7. The bandgap reference circuit with high power supply rejection ratio and second-order temperature compensation according to claim 6, characterized in that: A second current mirror circuit (6) is connected between the reference voltage output circuit (4) and the second-order temperature compensation circuit (3). The second current mirror circuit (6) is used to mirror and replicate the MP in the second-order temperature compensation circuit (3) in the same proportion. 23 -MP 25 The current in the branch.

8. The bandgap reference circuit with high power supply rejection ratio and second-order temperature compensation according to claim 7, characterized in that: The reference voltage output circuit (4) has a capacitor C2 connected in parallel at its output terminal.

9. The bandgap reference circuit with high power supply rejection ratio and second-order temperature compensation according to claim 8, characterized in that: The second current mirror circuit (6), which serves as the current source for the operational amplifier circuit (2), the second-order temperature compensation circuit (3), and the reference voltage output circuit (4), is a Cascode structure made using PMOS transistors.

10. The bandgap reference circuit with high power supply rejection ratio and second-order temperature compensation according to claim 9, characterized in that: The number of transistors in bipolar transistor Q1 is N times the number of transistors of the same type in bipolar transistor Q0, and the number of transistors in bipolar transistor Q2 is the same as that in bipolar transistor Q0.

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