CN118885045A - A wide input range two-stage high power supply rejection ratio bandgap reference circuit - Google Patents

Abstract

The invention discloses a wide input range two-stage high power supply rejection ratio band gap reference circuit, which is used for obtaining accurate band gap reference voltage. The first stage pre-step-down circuit reduces a wide range of input voltages as the second stage bandgap reference core circuit supply voltage. The second stage band gap reference core circuit constructs band gap reference voltages through multiple branches, and band gap reference voltages with different sizes are obtained through a resistor voltage divider. The circuit has a wide range of input voltages and a high power supply ripple rejection ratio. The circuit can be used as a band gap reference voltage module in an analog chip and an analog-to-digital conversion chip.

Description

A wide input range two-stage high power supply rejection ratio bandgap reference circuit

Technical Field

The invention belongs to the technical field of electronic power and relates to the design of a two-stage bandgap reference circuit with a wide input voltage range and a high power supply rejection ratio.

Background Art

Bandgap reference circuit is one of the most basic and core circuits in analog circuits and mixed signal circuits. The overall circuit structure of the chip depends on the various indicators given by the bandgap reference voltage, which plays a decisive role in the circuit performance and normal operation.

The core indicators of the bandgap reference circuit are low temperature coefficient, wide temperature range, wide input range, low power consumption and high power supply rejection ratio. For previous designs, most of them only focused on one aspect. It is difficult to achieve high power supply rejection ratio and low temperature coefficient while achieving a wide input range. Due to the large input range of the power supply voltage, the problem of whether the circuit can work properly is also introduced. With the continuous development of the integrated circuit industry, circuits that can be compatible with multiple indicators are favored by the industry.

Summary of the invention

In order to overcome the output instability problem caused by a wide input voltage range, the present invention adopts a two-stage bandgap reference circuit, the first-stage bandgap reference uses a high-voltage device for pre-stepping down, thereby obtaining a relatively rough reference voltage source, and then the first-stage reference is used as a voltage source to power the second-stage reference voltage, thereby obtaining an accurate reference voltage source. The two-stage bandgap reference circuit used in the present invention can obtain a larger power supply rejection ratio.

The technical solution adopted by the present invention to solve its technical problem is:

The two-stage bandgap reference circuit with wide input voltage range and high power supply rejection ratio mainly consists of three circuit modules: one is a first-stage pre-step-down module, the second is a second-stage bandgap reference core circuit module, and the third is a second-stage startup detection module.

The pre-step-down module is the first stage of the bandgap reference circuit. It uses a high-voltage MOS tube to isolate the bandgap reference core and output a relatively rough bandgap reference voltage source to power the second stage. The pre-step-down module can greatly suppress power supply ripple.

The bandgap reference core circuit can generate an accurate reference voltage that is almost independent of temperature. Since the output voltage of the first-stage pre-step-down module is low, each branch can carry fewer transistors. A four-branch structure is used to improve the output voltage stability, and a low-voltage cascode current mirror structure is used to further increase the working range of the transistor. A larger resistor is used to provide the starting current for the bandgap reference. After the startup is successful, the startup current is turned off by the post-stage detection module.

The second-stage startup detection module compares the voltages at two points on the two branches of the low-voltage cascode current mirror structure, and determines whether the startup is successful through the differential input operational amplifier and the common source amplifier, and turns off the startup current after the startup is successful. The circuit also has a hysteresis effect to avoid frequent switching of the startup circuit caused by ripple.

The output reference voltage is a positive temperature coefficient voltage related to the resistance ratio and the base-emitter voltage of the transistor with a negative temperature coefficient. By changing the resistance ratio, a bandgap reference voltage with a zero temperature coefficient at room temperature is obtained. The first-level bandgap reference voltage is about 2.5V, and the second-level bandgap reference voltage is about 1.22V.

The beneficial effects of the present invention are that the present invention has a wide input range to meet different working environments; has good temperature characteristics and can work in a wide temperature range; at the same time, has low power consumption and improves the working life of the chip; has a high power supply ripple suppression ratio and can improve the system's anti-interference ability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an overall circuit diagram of the present invention.

FIG2 is a specific circuit diagram of the pre-step-down module of the present invention;

FIG3 is a specific circuit diagram of the second stage of the bandgap reference of the present invention;

FIG4 is a specific circuit diagram of the second-stage startup detection module of the present invention;

FIG5 is a simulation diagram of the first-stage temperature characteristic curve of the present invention;

FIG6 is a simulation diagram of the second-stage temperature characteristic curve of the present invention;

FIG. 7 is a simulation curve diagram of the output PSRR of the present invention.

DETAILED DESCRIPTION

The present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments.

The specific circuit structure of the first-stage pre-step-down module of the present invention is shown in Figure 2. In the pre-step-down module, R0 provides the starting current for the right bandgap reference, and M0 is the adjustment tube. The size ratio of Q3 and Q1 is N; the branch current where Q1 is located is independent of the input voltage within the normal working range of the transistor, and is proportional to the ambient temperature and inversely proportional to the resistance of R2. The voltage drop of the current flowing through R1 plus the base-emitter voltage of Q1 and Q2 is the output voltage of the first-stage pre-step-down module. This voltage is approximately independent of the input voltage and the external temperature.

The present invention proposes a design of a two-stage bandgap reference circuit with a wide input voltage range and a high power supply rejection ratio, and the overall framework structure is shown in Figure 1. The wide range input voltage is reduced by a first-stage pre-step-down circuit as the power supply voltage of the second-stage bandgap reference core circuit. The circuit has a high power supply ripple rejection ratio. It is described separately by dividing it into a first-stage pre-step-down module, a second-stage bandgap reference core circuit, and a startup detection module.

The structure of the second-stage bandgap reference core circuit of the present invention is shown in FIG3. In the circuit, EN_DET is the start-up circuit enable signal. When starting, M3 is turned on, and R3 provides the start-up current for the right path. The current is copied through M5 and M6; at the moment of starting, the source voltage of M6 is grounded, and the drain voltage of M6 is pulled down to provide bias for the gate of M7; it is copied through the current mirror of M9, M10, M11, and M12 to provide bias for the gate of M8, and the current mirror bias is established. M18 and M19 are turned on to raise the base voltage of Q4 and Q8, and the core circuit triodes are all turned on, and the circuit startup is completed. After the circuit is started, M3 is turned off, and the start-up current is turned off. The size ratio of Q5 to Q6 is M. After the circuit is stable, the current flowing through R4, R6, R8, and R10 is equal, and the current can be solved by constructing an equation; the output voltage of the second-stage bandgap reference circuit is obtained by superimposing the base voltage of Q4 with the voltage drop at R11. This voltage is approximately independent of the external temperature. IOUT is a proportional copy of the branch current and can be used as a current source for subsequent circuits. RES_DIV is a resistor divider that divides VREF into reference voltages of different sizes for subsequent circuits.

The structure of the second-stage startup current detection circuit of the present invention is shown in FIG4. The current sources IOUT1 and IOUT2 are the current proportional copies of the reference core circuit branch currents, which are the current biases of this circuit. VP and VN are the two-point voltages on the two branches where the low-voltage cascode current mirror structure is located. When starting, M30 is turned off, EN_DET outputs a low level, M3 is turned on, and a startup current is generated. After the second-stage core circuit is started, M30 is turned on, the EN_DET output flips, M3 is turned off, and the startup current is closed.

Figure 5 shows the temperature characteristic curve of the output voltage of the first-stage bandgap voltage of the present invention under different input voltages. In the operating temperature range of -55 degrees Celsius to 125 degrees Celsius, the overall curve is parabolic. The output voltage changes less with temperature, and the temperature drift coefficient of the first-stage output voltage is 55ppm/℃ under 12V input voltage.

Figure 6 shows the temperature characteristic curve of the output voltage of the second-stage bandgap reference core circuit of the present invention. In the operating temperature range of -55 degrees Celsius to 125 degrees Celsius, the whole circuit is parabolic and reaches a zero temperature coefficient near room temperature. The output voltage changes less with temperature, and the temperature drift coefficient of the second-stage output voltage is 17ppm/℃.

FIG7 is a PSRR simulation curve of the present invention. Under PVT simulation, the lowest value of PSRR at low frequency is -81dB. PSRR increases with increasing frequency. The overall bandgap reference circuit has a high PSRR and is insensitive to input voltage changes. It can work normally within the input voltage range and meet the system's demand for power supply voltage.

Claims (5)

1. A wide input range two-stage high power supply rejection ratio bandgap reference circuit, including a bandgap reference establishment circuit and a resistor divider. The characteristics are: adopting a two-stage bandgap reference structure, eliminating the operational amplifier in the bandgap reference core circuit, reducing the influence of the power supply voltage on the output, while maintaining a high power supply rejection ratio, and adopting a shutoff startup circuit to further reduce the circuit static power consumption. 2. A wide input range two-stage high power supply rejection ratio bandgap reference circuit according to claim 1, characterized in that the first stage pre-step-down circuit uses a resistor and a high-voltage PMOS to start the circuit, has a simple structure, and can complete self-starting at the moment the circuit is powered on. The high-voltage PMOS isolates the power supply from the bandgap reference core circuit and suppresses power supply ripple changes. 3. A wide input range two-stage high power supply rejection ratio bandgap reference circuit according to claim 1, characterized in that the output voltage is constructed by superimposing multiple branch currents, thereby further reducing the influence of power supply ripple on the output voltage. 4. A wide input range two-stage high power supply rejection ratio bandgap reference circuit according to claim 1, characterized in that the second-stage startup detection circuit compares the branch voltage of the second-stage core circuit and promptly shuts down the startup circuit after the startup is completed to reduce circuit power consumption. The hysteresis effect avoids frequent switching of the second-stage startup circuit. 5. A wide input range two-stage high power supply rejection ratio bandgap reference circuit according to claim 1, characterized in that the established bandgap reference voltage is divided by a resistor divider to obtain bandgap reference voltages of different sizes for use by subsequent circuits.