A 46-nF/10-M omega Range 114-aF/0.37-omega Resolution Parasitic- and Temperature-Insensitive Reconfigurable RC-to-Digital Converter in 0.18-mu m CMOS

Abstract

This paper presents a 46 nF/10 M omega-range, digital-intensive, reconfigurable RC-to-digital converter ((RCDC)-C-2) 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 (RCDC)-C-2 results in 114 aFrms/0.37 omega rms resolutions and a worst-case temperature-drift of 64.2 ppm/degrees C over -40 to 125 degrees 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 mu m standard CMOS process, the (RCDC)-C-2 consumes 140 mu A from a 1 V supply, occupying an active area of 0.175 mu m(2).