A Low-Noise and Monolithic Array Tactile Sensor Based on Incremental Delta-Sigma Analog-to-Digital Converters

Abstract

A low-noise and monolithic array tactile sensor, in which a tactile sensing unit, a low-noise analog front end (AFE), and a high-resolution delta-sigma analog-to-digital converter (ΔΣ ADC) are fully integrated, is presented in this paper. In this proposed system, compared with a discrete-device-based board-level system, the parasitic effect of a long cable connection can be reduced, and results are more accurate. Furthermore, a smaller system area and a lower power consumption can be achieved in this monolithic system. A discrete-continuous mixed mode bandpass AFE is proposed to filter out low-frequency flicker noise and high-frequency white noise. In order to improve the quantization rate of the sensor readout circuit and further suppress the high-frequency noise, a two-way alternate sample-and-hold circuit scheme is adopted in this design. The proposed tactile sensor is designed and fabricated in a 0.5-μm CMOS (Complementary metal oxide semiconductor)mixed-signal process with a 16 × 16 array and a total chip area of 1.9 × 1.9 cm2. This chip consumes 33.5 mW from a 5 V supply. The measurement results showed that the signal-to-noise and distortion rate (SNDR) was 65.2894 dB and that the effective number of bits (ENoB) was 10.553 dB. Moreover, this sensor could achieve a pressure measurement range of 0.002–0.5 N with a resolution of 0.4 mN.