A compact, low-power, and fast pulse-width modulation based digital pixel sensor with no bias circuit

Abstract

A high-speed and compact in-pixel light-to-time converter (LTC), with low power consumption and wide dynamic range is presented. By using the proposed LTC, a digital pixel sensor (DPS) based on a pulse-width modulation (PWM) scheme has been designed and fabricated in a standard 180-nm, single-poly, six-metal complementary metal oxide semiconductor (CMOS) technology. The prototype chip consists of a 16 × 16 pixel array with an individual pixel size of 21 × 21 μm2 and a fill factor of 39% in the 180-nm CMOS technology. Experimental results show that the circuit operates at supply voltages down to 800 mV and achieves an overall dynamic range of more than 140 dB. The power consumption at 800 mV supply and room light intensity is approximately 2.85 nW.