A 10mm3 Light-Dose Sensing IoT2 System With 35-To-339nW 10-To-300klx Light-Dose-To-Digital Converter

This paper presents a 10mm
³
Internet-of-Tiny-Things (IoT
²
) system that measures light dose using custom photovoltaic cells and a light-dose-to-digital converter (LDDC). The LDDC nulls diode leakage for temperature stability and creates headroom without power overhead by dual forward-biased photovoltaic cells. It also adaptively updates the current mirror ratio and accumulation weighting factor for a low, near-constant power consumption. The system can operate energy-autonomously at >500lx light level. The LDDC achieves a 3σ inaccuracy of ±3.8% and σ/μ of 2.4% across a wide light intensity range from 10lx to 300klx while consuming only 35 - 339nW.