一种微电容式传感器检测电路的分析与改进

Analysis and Improvement of an Interface Circuit of Capacitive Sensors

介绍了一种本实验室开发的集成传感器,它实现了敏感电容和接口电路在一块芯片上的集成。重点分析了它的接口电路,基于施密特触发器构建,实现敏感电容值以及参考电容值与频率值的转换,通过对两频率求差来抑制各种共模干扰。对样片进行了测试,输出频率与理论值有较大的偏差。通过分析,给出了测试结果发生偏差的原因。最后,给该电路设计了启动电路,改进了CMOS开关控制电路,重新对电路的结构进行了设计,实现了与实验室新一代传感器的集成。

A new integrated capacitive sensor is introduced briefly. The sensitive capacitance and the interface are integrated into one chip. The interface circuit, which is based on the Schmitt trigger, works as a capacitor-frequency converter. A differential frequency circuit is designed following the oscillator. It can reduce the common-mode distribution. The output frequency displays a large difference from theoretic calculation during testing. The reason for the difference is analyzed. Circuit schematic and parameters are redesigned to realize the integration with a new sensor designed in our laboratory.