A Fully Dynamic Event-Driven Capacitive Sensor Interface Circuits Based on Self-Reconfigurable SAR Capacitance-to-Digital Conversion for High-Density Robotic Tactile Sensing

Abstract

Covering robots entirely with electronic skins (e-skins) has been a long-term aspiration. However, the number and density of the tactile sensors are limited by factors such as routing complexity, signal latency, and power consumption. Inspired by neural signal processing, we present a multichannel capacitive interface circuits that read out the sparse tactile signals in an event-driven (ED) manner. A self-reconfigurable successive-approximation-register capacitance-to-digital converter (SR SAR CDC) is proposed to reduce power consumption in passive-sampling (PS) mode and to achieve high resolution in noise-shaping (NS) mode. To support parallel recording in NS data converters, we propose a 2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{{N}}$</tex-math> </inline-formula> oversampling-rate (2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{{N}}$</tex-math> </inline-formula> -OSR) code division multiplexing (CDM) technique. Besides, an ED inter-integrated circuit (ED-I2C) protocol is proposed to reduce communication data burden and routing complexity. Fabricated in 55-nm CMOS technology, the multichannel capacitive sensor interface occupies a chip area of 2.244 mm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\textrm{2}}$</tex-math> </inline-formula> . At a frame rate of 3.47 kHz, this work achieves a measured single-channel signal-to-noise-ratio (SNR) of 51 dB and a power consumption of 7.2 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> W/Ch in NS mode. The stand-by power can be further reduced to 1.6 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu$</tex-math> </inline-formula> W/Ch in PS mode. The ED sensing protocol significantly reduces the data burden for processing and communication, supporting a high-density integration of 4.8 sensors/cm <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$^{\textrm{2}}$</tex-math> </inline-formula> and 16 sensors/wire.