A 46-nF/10-MΩ Range 114-aF/0.37-Ω Resolution Parasitic- and Temperature-Insensitive Reconfigurable RC-to-Digital Converter in 0.18-<i>μ</i>m CMOS
Arup K. George, Wooyoon Shim, Jaeha Kung, Ji-Hoon Kim, Minkyu Je, Junghyup Lee
Abstract
This paper presents a 46 nF/10 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\text{M}\Omega $ </tex-math></inline-formula> -range, digital-intensive, reconfigurable RC-to-digital converter (R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> CDC) 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 R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> CDC results in 114 aF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> / <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.37 \Omega _{\text {rms}}$ </tex-math></inline-formula> 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.18 ~\mu \text{m}$ </tex-math></inline-formula> standard CMOS process, the R <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> CDC consumes 140 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{A}$ </tex-math></inline-formula> from a 1 V supply, occupying an active area of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.175 ~\mu \text{m} ^{\mathrm{ 2}}$ </tex-math></inline-formula> .