Integrated accelerometer with capacitance to digital interface circuit design based on monolithic 0.18μm CMOS MEMS technology

A monolithic accelerometer with integrated capacitance to digital readout circuit implemented in mixed-signal MEMS process is proposed to demonstrate sensor-to-bit integration. The sensing range is from -5g to 5g and the variation of the capacitance is from 441.2fF to 470fF. The sensitivity of the accelerometer is 2.88fF/g. The capacitance value of the sensing range is readout by the capacitance to digital circuit to readout. The capacitance to time circuit of the sensitivity is 6.94us/pF which is equivalent to 20ns/1bit. The digital output can be obtained without analog to digital module, and thus with power saving advantage, the output signal can be directly interface to digital signal process.