An ultra-low power current-mode CMOS image sensor with energy harvesting capability

In this paper, an energy harvesting CMOS image sensor with ultra-low power consumption is presented. The proposed active pixel sensor (APS) operates in current-mode and a 9-bit flash series current-mode A/D converter unit together with its peripheral control circuitry are all integrated on chip. A power consumption as low as 84pW/frame per pixel is achieved by biasing the in-pixel transconductance amplifier in triode region and enabling the current-mode ADC only during the read-out phase. The imager can also be reconfigured into an energy harvesting mode, which can generate several micro watt power at K-lux illumination levels. The 128 × 96 array is fabricated in a 0.35μm technology. The total chip area is 8 mm² and the pixel pitch is 21μm with a 39% fill-factor. Experimental results of the fabricated chip illustrate its proper operation in both image capture and energy harvesting modes.