A High Precision Fully Differential Capacitance-Voltage Conversion Circuit System

Abstract

The invention relates to the field of MEMS (Micro Electro Mechanical System) inertial devices, in particular to a high-accuracy fully differential capacitance-voltage conversion circuit system. The high-accuracy fully differential capacitance-voltage conversion circuit system comprises a driving signal generation part, a fully differential charge amplifier and capacitance compensation arrays. A whole conversion circuit and a sensor sensitive structure still adopt an output mode in single-ended connection, and a fully differential circuit structure is realized through time division multiplexing; a circuit adopts a switch capacitance structure for removing the influence of parasitic capacitance, main signal channels adopt a correlated double sampling technology for removing low-frequency noise and detuning, the capacitance compensation array is capable of correcting the detuning and non-linearity of the sensor sensitive structure. According to the high-accuracy fully differential capacitance-voltage conversion circuit system disclosed by the invention, the influence of the parasitic capacitance can be effectively inhibited, common-mode interference generated by switch charge injection and substrate noise can be reduced, harmonic distortion of the circuit is reduced, the linearity of an accelerometer system is increased, and zero drift is inhibited.

Description

technical field [0001] The invention relates to the field of MEMS inertial devices, in particular to a high-precision fully differential capacitance-voltage conversion circuit system. Background technique [0002] Acceleration sensors can convert weak acceleration physical signals into electrical signals that can be detected. High-precision acceleration sensors are widely used in earthquake detection, automotive safety, aerospace, space microgravity measurement and other measurement fields that require high precision. People began to study the structure and manufacturing technology of the acceleration sensor very early. With the development and popularization of MEMS technology in recent years, the integration of microelectronics technology and mechanical engineering makes the acceleration sensor no matter in structure or performance. There have been great improvements and improvements. Capacitive acceleration sensor is currently the most researched type of acceleration sen...

AI Technical Summary

Problems solved by technology

And the sensitive structure of the sensor is a three-terminal device, that is, two fixed electrodes and the middle movable electrode as the output. Therefore, the single-ended detection method is generally used to process the output signal. Its advantages are simple structure, less control clocks, and easy feedback. , the disadvantage is that the zero drift is relatively serious, and the noise of the driving signal has a serious impact on the output

By applying a driving signal on the middle movable electrode, the two fixed electrodes are used as the output of the sensitive structure to realize a fully differential detection circuit structure, which can reduce the common mode interference caused by switch charge injection and substrate noise, and reduce harmonic distortion. However, there is a major problem with this structure: when the driving signal changes, the input common mode of the operational amplifier will change, which will affect the output signal and cannot be detected with high precision.

[0004] At present, by adding a reference capacitor in the circuit, a full-bridge structure can be realized, and the drive voltage opposite to the sensitive capacitor is connected to the common terminal of the reference capacitor, so that the interference of the drive signal to the common mode cancels each other out, but this method requires a reference capacitor Accurate matching with the sensitive capacitor leads to an increase in power consumption and area of ​​the overall system; and the inconsistency between the temperature coefficient of the sensitive capacitor and the temperature coefficient of the reference capacitor will lead to deviations at different temperatures

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