A Flexible Low-Power 130 nm CMOS Read-Out Circuit With Tunable Sensitivity for Commercial Robotic Resistive Pressure Sensors

Abstract

This paper presents a flexible and low-power ReadOut Circuit (ROC) with tunable sensitivity, designed to interface a wide range of commercial resistive pressure sensors for robotic applications. The ROC provides contact detection, monitoring small capacitance variations at low pressure (<;100 mbar), and encodes pressure measurement on 8 bit, evaluating resistive variations. Two all-digital circuits implement the conversion of the input resistance and capacitance-to-frequency, exploiting an on-chip ring oscillator as timing reference. A 130 nm RFCMOS prototype (with an active area of 428 × 159 μm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> ) has a power consumption of 27.2 μW, for VDD 1 V. Using digital control inputs, the ROC allows a wide range tuning of measurement sensitivity (6.7-46.4 mbar/LSB) and adjustable acquisition time (226.6-461.7 μs and 648-890 μs, for contact detection and pressure evaluation, respectively). The read-out time of ~1 ms is compatible with human response after touch.