A 46-nF/10-MΩ Range 114-aF/0.37-Ω Resolution Parasitic-and Temperature-Insensitive Reconfigurable RC-to-Digital Converter in 0.18-μm CMOS

Abstract

This paper presents a 46 nF/10 M Ω-range, digital-intensive, reconfigurable RC-to-digital converter (R2CDC) that can readout multiple C and R sensors in a time-interleaved fashion. Ratio-metric conversion using swing-boosted period-modulation (SB-PM) front-end by the R2CDC results in 114 aFrms/0.37 Ω rms resolutions and a worst-case temperature-drift of 64.2 ppm/°C over-40 to 125°C. Femto-farad capacitances can be sensed with a relative code-deviation less than 0.16 % even when parasitics vary 30 times the baseline. Implemented in a 0.18 μ m standard CMOS process, the R2CDC consumes 140 μ A from a 1 V supply, occupying an active area of 0.175 μm 2. © 2004-2012 IEEE.