利用差频电路实现微电容式传感器检测电路的温漂抑制

Difference Frequency Circuit Used to Achieve Temperature Drift Suppression of Interface Circuit in Micro-capacitive Sensors

介绍了一种本实验室开发的CMOS工艺的电容式传感器的接口电路。重点分析了基于施密特触发器的张弛振荡器接口电路,实现了敏感电容以及参考电容与频率的转换。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,输出频率与理论值基本一致。最后对该电路进行了温漂特性的仿真和测试,验证了差频电路可以将电源波动和温度的影响完全抑制在精度的允许范围内。

In this paper, CMOS-process interface circuit of micro-capacitive sensor is introduced. The relaxation oscillator which is based on the Schmitt trigger is analyzed in detail. Using it the conversion from sensitive capacitance, reference capacitance to frequency is achieved. All kinds of common-mode interference are suppressed through the difference of two frequencies. The measured results show that the output frequency is consistent with the theoretical value. Finally, the temperature drift of the circuit was simulated and tested to verify that the difference frequency circuit can completely suppress the effect of the power supply fluctuations and hold the temperature within the accuracy limits.