A 0.1-nW–1-$\mu$ W Energy-Efficient All-Dynamic Versatile Capacitance-to-Digital Converter

Abstract

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Power-Efficiency Evolution of Capacitive Sensor Interfaces

“…As a switched capacitor feedback digital-to-analog converter (DAC) is typically used in a SAR ADC, the SAR approach can be conveniently used for capacitance sensing. By taking advantage of the great energy efficiency of the SAR approach, SAR-based capacitive sensor interfaces [6,7,33,34] also achieve excellent energy efficiency amongst other capacitive sensor interface architectures. In general, SAR-based capacitive sensor interfaces can be divided into two categories: 1) direct SAR capacitive sensor interfaces and 2) capacitive sensor interfaces, which include a capacitance to voltage front-end (CVFE) and a SAR ADC.…”

“…However, an OTA is needed for charge transfer. The fully dynamic architecture proposed in [34] avoids using power-hungry amplifiers, as shown in Fig. 10.…”

“…A small CDAC is not only beneficial in minimizing the SAR ADC energy consumption, but it also helps to reduce signal attenuation caused by the charge sharing between the capacitive bridge and CDAC. As shown in [34], the total DAC capacitance is only 300 fF with 250 aF unit capacitors to save ADC energy while achieving sufficiently low kT/C noise and sufficient linearity. The asynchronous dynamic logic in [37] is used to minimize the number of logic gates, which helps to reduce both active and leakage power.…”

“…10. Capacitive sensor interface architecture that includes a capacitive bridge CVFE, a SAR ADC [34], and its operation waveforms. switch, the preserved charge will slowly decline over time, which will cause errors in measurements with charge reuse.…”

A Time-Based Electronic Front-End for a Capacitive Particle Matter Detector

“…The electronic front-end therefore plays a fundamental role because it defines the ultimate resolution limit, power consumption, and area occupation of the overall sensor. Given the importance and widespread diffusion of integrated capacitive sensors, it is quite understandable that many different electronic interface topologies have been presented in literature, such as capacitance-to-voltage (C2V) [ 1 , 2 , 3 , 4 , 5 , 10 , 13 , 14 , 15 , 16 , 17 , 18 ], charge based capacitance measurement (CBCM) [ 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 ], capacitance-to-current (C2I) [ 28 , 29 , 30 ], capacitance-to-time (C2T) [ 31 , 32 , 33 , 34 , 35 ], and capacitance to digital (C2D) [ 36 , 37 , 38 , 39 , 40 , 41 , 42 ]. Each method presents very different features in terms of resolution, area occupation, circuit, complexity, measuring range, and measuring time.…”