A 1.3-μW 12-bit incremental ΔΣ ADC for energy harvesting sensor applications

This paper presents an ultra-low power, incremental ΔΣ ADC for sensor applications. The ADC is integrated in an energy harvesting chip, and its power consumption has to be less than 2 μW at temperatures ranging from -40° C to 85° C. The complete system including the ADC, interfacing sensors, and power management circuit is fabricated in 0.18 μm CMOS technology. The ADC works with a single on-chip reference voltage. The fabricated ADC occupies 0.21 mm², and consumes 1.3 μW from the 1.2-V supply voltage at room temperature. Power consumption increases almost linearly with temperature and reaches 1.7 μW at 85° C. The sleep current is less than 10 nA. In free-running mode at 40 kS/s, the ADC achieves 68 dB peak SNDR with OSR=200. This corresponds to FoM_w=1.58 pJ/conv., which is comparable to the state-of-the-art incremental ADCs, while power consumption is at least 5X lower. Measurements with the on-chip temperature sensor verified the ADC's performance.