A High-efficiency Incremental Zoom SAR ΣΔ Capacitance-to-Digital Converter

This paper proposes a high resolution incremental single-ended incremental zoom-in capacitance-to-digital converter (CDC). The ADC is designed in a SMIC 180nm CMOS process with a zoom-in SAR. The oversampling rate of the sigma-delta modulator is reduced to 64 by a zoom-in 8 bit SAR. The CDC, at 3.2 kS/s, achieves a resolution of 14.81 bits, while dissipating 2.525 mW from a 1.8V supply. The capacitance measure range of CDC is up to 20pF, finally, achieving an figure of merit (FOM) of 27.4pJ/conv-step.