A variable output range fully differential high voltage driver applied to an accelerometer

Abstract

The application belongs to the technical field of integrated circuit design, and relates to a variable output range full differential high voltage driver applied to an accelerometer. The application introduces a programmable control high voltage output charge pump to generate a variable high voltage output for the full differential high voltage driver on the basis of a conventional fixed range output full differential high voltage driver; and utilizes a variable resistor to sample the output voltage of the full differential high voltage driver and a stable common mode voltage in a normal voltage circuit part of the accelerometer to compare and realize the purpose of stabilizing the common mode output voltage of the high voltage driver. Because the output of the charge pump often has a large ripple and is greatly affected by power supply fluctuation, directly sampling half of the output voltage of the charge pump as the common mode reference voltage of the high voltage driver is easy to make the common mode feedback inaccurate; by adopting the architecture of the full differential operational amplifier combining the floating current source and the AB class output to increase the power supply rejection ratio, improve the power utilization rate and reduce the static power consumption of the high voltage driver.

Description

Technical Field

[0001] This invention belongs to the field of integrated circuit design technology, and particularly relates to a fully differential high-voltage driver with variable output range for use in accelerometers. Background Technology

[0002] With the development of accelerometers, high linearity, high accuracy, and low power consumption have become the development direction and challenges. Existing MEMS accelerometer readout circuits mainly fall into two categories: open-loop and closed-loop. Open-loop accelerometer interface circuits are simple in structure and have low power consumption, but suffer from small range and poor linearity. Closed-loop accelerometer interface circuits often require feedback control of the MEMS mechanical meter head, and high-voltage feedback is currently the primary feedback method because it can improve the feedback sensitivity and overall output linearity of the MEMS accelerometer. Furthermore, while single-ended detection accelerometer interface circuits are simple in structure, have lower power consumption, and smaller chip area, they suffer from severe zero-point offset and relatively high noise. Fully differential detection and feedback methods offer numerous advantages, such as reducing common-mode noise and improving power supply rejection ratio. Therefore, high-performance accelerometer interface circuits often employ fully differential high-voltage detection and feedback methods.

[0003] Currently used fully differential feedback high-voltage drivers primarily achieve a fixed high-voltage output range. While this provides good feedback control for MEMS meters with a fixed acceleration detection sensitivity, it is ineffective for MEMS meters with low acceleration detection sensitivity. The CV conversion output voltage is too low, and a fixed-range high-voltage driver cannot effectively control the meter, resulting in insufficient electrostatic feedback and difficulty in controlling the meter. Similarly, for MEMS meters with high acceleration detection sensitivity, a fixed-range driver limits the accelerometer's range, easily leading to output saturation. Therefore, fixed-range drivers lack adaptability, preventing the accelerometer interface circuit from achieving optimal feedback control for different MEMS meters. Thus, employing feedback drivers with different high-voltage output ranges for different MEMS mechanical meters is crucial for improving the adaptability and practicality of the accelerometer interface circuit. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a fully differential high-voltage driver with a variable output range for accelerometers. This fully differential high-voltage driver can output different high-voltage feedback drive output ranges for different MEMS accelerometer heads, improving the adaptability and practicality of the accelerometer interface circuit.

[0005] This invention, based on a traditional fixed-range output fully differential high-voltage driver, introduces a programmable high-voltage output charge pump to generate a variable high-voltage output to power the fully differential high-voltage driver. Furthermore, a variable resistor is used to sample the output voltage of the fully differential high-voltage driver and compare it with the stable common-mode voltage of the constant-voltage circuit in the accelerometer to stabilize the common-mode output voltage of the high-voltage driver. Because the charge pump output often has significant ripple and is greatly affected by power supply fluctuations, directly sampling half of the charge pump's output voltage as the common-mode reference voltage of the high-voltage driver can easily lead to inaccurate common-mode feedback. In addition, by employing a fully differential operational amplifier architecture combining a floating current source and Class AB output, the power supply rejection ratio is increased, power utilization is improved, and the static power consumption of the high-voltage driver is reduced.

[0006] The technical solution of this invention:

[0007] A fully differential high-voltage driver with variable output range for use in accelerometers, comprising:

[0008] (1) Output voltage detection module, used to sample the output voltage of the fully differential operational amplifier at different ratios;

[0009] (2) Fully differential main operational amplifier with a floating current source and AB class output combined architecture, used to drive MEMS mechanical meter head;

[0010] (3) Common-mode feedback auxiliary operational amplifier, with gain and bandwidth similar to that of fully differential main operational amplifier;

[0011] (4) A programmable charge pump that can be programmed to output different voltages.

[0012] Furthermore, the output voltage detection module includes two fixed resistors Rs, two fixed capacitors C, and a variable resistor Rx; the two fixed resistors Rs and two fixed capacitors C are connected in parallel to form two RC parallel circuits; the positive terminals of the two RC parallel circuits are respectively connected to the two outputs of the fully differential main operational amplifier, and their negative terminals are connected to and connected to the positive terminal of the variable resistor Rx; the variable resistor Rx is one or more variable resistors, its positive terminal is connected to the negative terminal of the two RC parallel circuits, and its negative terminal is grounded; the fully differential main operational amplifier has its input connected to the output of the accelerometer's correction network, and its output connected to the drive terminal of the MEMS mechanical meter; the common-mode feedback auxiliary operational amplifier has its negative input connected to the negative terminal of the two RC parallel circuits, its positive input connected to the constant voltage reference VCM, and its output connected to the common-mode feedback input terminal of the fully differential main operational amplifier; the output of the programmable charge pump is connected to the power supply terminal of the fully differential main operational amplifier.

[0013] Compared with the prior art, the present invention has the following beneficial effects:

[0014] (1) Using the stable common-mode level of the constant voltage circuit in the fully differential accelerometer as the common-mode reference voltage of the high voltage driver allows the constant voltage and high voltage parts of the accelerometer to be better integrated, simplifying the circuit.

[0015] (2) It enables high voltage feedback of different ranges for different MEMS accelerometer heads, improving the adaptability of the high voltage driver. Attached Figure Description

[0016] Figure 1 This is a structural diagram of a traditional closed-loop capacitive accelerometer system.

[0017] Figure 2 This is a circuit diagram of an accelerometer containing a fully differential high-voltage driver with a variable output range, according to the present invention.

[0018] Figure 3 This is a circuit architecture diagram of a fully differential high-voltage driver with a variable output range for accelerometers according to the present invention. Detailed Implementation

[0019] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and technical solutions.

[0020] like Figure 1 The diagram shows the structure of a traditional closed-loop capacitive accelerometer system, including a MEMS mechanical sensor, a CV conversion circuit, a calibration network, a high-voltage driver, an ambient pressure power supply reference, and a charge pump. The CV conversion circuit and calibration network operate at ambient pressure, while the high-voltage driver operates at high pressure. Figure 2 This invention provides an accelerometer circuit structure diagram with a fully differential high-voltage driver that includes a variable output range. It abandons the practice of sampling half of the high voltage output from the charge pump as the common-mode reference voltage of the fully differential high-voltage driver. Instead, it directly uses the reference voltage of the constant voltage section of the circuit as the reference voltage of the high-voltage driver. Then, it samples the output voltage of the fully differential high-voltage driver through a variable resistor and compares the output high voltage with the constant voltage reference VCM at a certain ratio to complete the common-mode feedback and achieve the purpose of stabilizing the common-mode of the fully differential high-voltage drive. Figure 3 This invention provides a circuit architecture diagram of a fully differential high-voltage driver with a variable output range, which includes a fully differential main operational amplifier, a resistor Rs and a capacitor C of the output voltage detection module, a variable resistor or variable resistor array Rx, a common-mode feedback auxiliary operational amplifier, and a charge pump. The variable resistor or variable resistor array Rx and the charge pump are controlled by a digital unit.

[0021] How the circuit works:

[0022] First, a programmable charge pump controlled by a digital unit generates a high-voltage VCP for the high-voltage driver. Then, an output voltage detection module detects and outputs the common-mode level of the main operational amplifier's output. The output of the output voltage detection module is fed back to the fully differential main operational amplifier via an auxiliary operational amplifier to stabilize the common-mode voltage of the fully differential high-voltage driver. This achieves a stable output by sampling the output voltage of the fully differential high-voltage driver at a certain ratio and comparing it with a constant voltage reference VCM. The variable high-voltage power supply output achieved by programming and controlling the charge pump with a digital unit, and the sampling of the fully differential high-voltage driver's output voltage at different ratios by the output voltage detection module controlled by the digital unit, can be combined to further optimize the structure of the fully differential high-voltage driver with a variable output range.

Claims

1. A fully differential high-voltage driver with variable output range for use in accelerometers, characterized in that, The fully differential high-voltage driver includes: The output voltage detection module is used to sample the output voltage of the fully differential operational amplifier at different ratios. The fully differential main operational amplifier features a combined architecture of floating current source and Class AB output, used to drive MEMS mechanical meters. The common-mode feedback auxiliary operational amplifier has a gain and bandwidth similar to that of the fully differential main operational amplifier; A programmable charge pump that can be programmed to output different voltages; The output voltage detection module includes two fixed resistors Rs, two fixed capacitors C, and a variable resistor Rx. The two fixed resistors Rs and two fixed capacitors C are connected in parallel to form two RC parallel circuits. The positive terminals of the two RC parallel circuits are connected to the two outputs of the fully differential main operational amplifier, and their negative terminals are connected to and connected to the positive terminal of the variable resistor Rx. The variable resistor Rx is one or more variable resistors, and its positive terminal is connected to the negative terminal of the two RC parallel circuits, and its negative terminal is grounded. The fully differential main operational amplifier has its input connected to the output of the accelerometer's correction network, and its output connected to the drive terminal of the MEMS mechanical meter. The common-mode feedback auxiliary operational amplifier has its negative input connected to the negative terminal of the two RC parallel circuits, its positive input connected to the constant voltage reference VCM, and its output connected to the common-mode feedback input terminal of the fully differential main operational amplifier. The output of the programmable charge pump is connected to the power supply terminal of the fully differential main operational amplifier.

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