Fully Differential Capacitive Sensor Readout Circuit Design And Realization Of CMOS

MEMS accelerometer with variety of superior performance has been widely used in military and commercial equipment, which includes IC MEMS sensor and readout circuit. In recent years, due to its high accuracy, high stability in the precision instrument Detection special applications. MEMS acceleration sensor, also known as micro-accelerometers, there are a variety of structures piezoresistive and capacitive etc. By contrast may know, capacitive micro machined accelerometers have the best performance, while the differential capacitance variation detection readout circuit technology is very mature. Capacitance readout circuit can be divided into about three types: continuous voltage readout, continuous current sense and fully differential switched capacitor readout circuit.Full-chip readout system uses a fully differential capacitance detection circuit, the paper work including: 1, here we mainly analyzes the structure and design concept of the pre-charge of the operational amplifier, switched-capacitor low-pass filter and output buffers; 2, external auxiliary circuit design includes bandgap voltage, a bandgap current component modules, 8bits compensation capacitor array and programmable clock; 3, The sense amplifier adopt Chopper stabilization technique to eliminate the noise and offset voltage. This paper conducted the derivation of its main operational principle and the calculating formula, and also listed out effect factor of sense amplifier’s linearity. The low noise requirement is also the key part of entire chip system design, such as the noise of reference voltage may transmitter to the output of system, therefore the reference basis for low noise performance is very important.This design followed standard integrated circuit design process, finished pre and post simulation under various process corners changes, also the work of taping out, packaging and testing. The testing mainly focus on indicators of test reference voltage, the linearity of read out amplifier circuit and so on. Test results show that the performance indicators are able to meet the design requirements.