An Ultra-Low Power Energy Harvesting and Imaging (EHI) Type CMOS APS Imager With Self-Power Capability

Abstract

A novel ultra-low power energy harvesting and imaging (EHI) type CMOS active pixel sensor (APS) imager with self-power capability is presented. The proposed EHI type CMOS APS pixel harvests one order of magnitude higher power than that of the other pixel technologies reported in the literature. It produces 46 $\mu{\rm W}$ of power under 57 klux illumination. The EHI imager presented has decoupled imaging and harvesting operations such that imaging related circuits are turned off while energy is harvested, and vice versa. The imager can operate on 1 V supply voltage consuming as low as 800 nW while capturing 1 frame per second (fps). Measured minimum full-chip imager FoM is 148 pJ/frame $\ast$ pixel while capturing 21.2 fps. The imager contains a 64 $\times$ 45 array of $18 \mu{\hbox{m}}\times 18 \mu{\hbox{m}}$ EHI pixels. It is manufactured in a standard 2P4M/3.3 V 0.35 $\mu{\rm m}$ CMOS process. Ultra-low power operation is achieved by developing new imaging electronics including current reference generator, readout circuits, and SAR type, 8-bit, analog-to digital converter (ADC). A new polarity inverting charge pump circuit was developed for managing the energy harvested by the new energy harvesting pixels on the focal plane.