Capacitive sensor interface circuit with high-precision input common-mode control

Abstract

The invention discloses a capacitive sensor interface circuit, which is characterized in that an MEMS (Micro Electro Mechanical System) mechanical sensing element converts an external acceleration signal into an MEMS mechanical capacitance variable quantity to generate a sensor charge signal A and a sensor charge signal B; the input common-mode control unit is used for absorbing common-mode components of sensor charge signals, differential-mode components of the input common-mode control unit are transmitted to the capacitance-voltage conversion module for signal amplification, and capacitance-voltage conversion is achieved. The input common-mode control unit comprises active common-mode feedback control and passive common-mode control, and an active common-mode feedback control module of the input common-mode control unit comprises a feedback control loop, a level shifting network and a sampling and holding network; the feedback control loop is used for sampling the residual common-mode component and adjusting the common-mode absorption amount according to sampling; the level shift network is used for improving the output swing of the operational amplifier in the feedback control loop and reducing the gain error of the operational amplifier; the sampling and holding network can eliminate the offset voltage of the operational amplifier A2 and improve the gain precision of the operational amplifier at the same time.

Description

technical field [0001] The invention relates to the technical field of capacitive sensors, in particular to a MicroElectro Mechanical System (MEMS) capacitive accelerometer interface circuit. Background technique [0002] MEMS capacitive sensors are widely used in inertial sensors, pressure sensors, IoT microphones and other fields. The readout circuit is the bottleneck of the entire circuit system performance of the MEMS sensor. The differential sensing structure is widely used in readout circuits because of its many important advantages, including improved power supply rejection and first-order rejection of common-mode errors. However, fully differential amplifiers operate on a large input common-mode signal. Since the MEMS sensor and the total capacitance form a capacitive voltage divider, the drive signal will be attenuated at the amplifier input. Therefore, a capacitor-to-voltage converter without an input common-mode feedback control circuit would need to tolerate i...

AI Technical Summary

Problems solved by technology

Another big disadvantage of capacitor-to-voltage converters without input common-mode feedback control circuits is that the common-mode step at the input of the amplifier reduces the effective amplitude of the excitation voltage, which degrades the sensitivity of the sensor

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