A 137 dB Dynamic Range and 0.32 V Self-Powered CMOS Imager With Energy Harvesting Pixels

This work presents an 0.32 V self-powered high dynamic range (DR) CMOS imager in standard 0.18 μm CMOS technology with dual-mode operation: imaging (IMG) and optical energy harvesting (OEH) modes. In IMG mode, a dual-exposure extended-counting (DEEC) scheme is proposed and implemented with a 5-bit programmable current-controlled threshold (PCCT) generator. By combining the DR of a short-exposure (88 dB) and an extended long-exposure (49 dB) conversions, the DEEC achieves a high DR of 137 dB. The chip consumes 10.6 μW at 6.5 fps with 0.32 V operation and 32.1 μW at 16.5 fps with 0.4 V operation, which results in an iFoM of 8.1 f and 9.8 fJ/pixel·code. In OEH mode, the sensing pixels turns into energy harvesting pixels with an additional global micro solar cell and corresponding mode control circuit, which generates 455 mV and 14 μW at 60 klux (sunny day) and supports a self-powered imaging operation at 4.1 fps.