Difference Frequency Circuit Used to Achieve Temperature Drift Suppression of Interface Circuit in Micro-capacitive Sensors
Xiaodong Huang · Electronic Engineer · 2008
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.