A novel MASH 2-1 sigma-delta A/D converter with high-to-low conversion for closed-loop MEMS accelerometer interface
In this paper, an A/D converter offering the high-to-low level shifter function applied to the high range digital closed-loop MEMS accelerometer interface is presented. In the interface circuit, the analog front-end circuit works in the high-voltage domain and the digital back-end circuit works in the low-voltage domain, however, the cascade MASH 2-1 sigma-delta ADC just can achieve high-voltage signal converting to low-voltage signal without introducing additional high-to-low transition module. The level shifter is mainly realized by the first integrator by means of using switched-capacitor charge transfer principle. The cascade MASH 2-1 sigma-delta ADC performs a maximum signal-to-noise-plus-distortion ratio (S/(N+D)) rms/rms of 113.6 dB with 200 Hz bandwidth and sampling clock of 100-kHz. The interface was designed in TSMC 0.35 um CMOS process and was sent to the foundry to prototype.