21.2 A 3nW signal-acquisition IC integrating an amplifier with 2.1 NEF and a 1.5fJ/conv-step ADC

Signal acquisition systems for emerging applications, such as impiantatile or unobtrusively wearable autonomous sensors, large sensor arrays, or wireless self-powered sensors, require a minuscule form factor and very low power consumption. For example, the power available from a state-of-the-art 1mm
³
solid-state thin-film battery is limited to 4nWfora 10yr lifetime [1], and a 1mm
³
energy harvester attached to a running person delivers only 7.4nW [2]. While several low-power signal acquisition systems have been proposed [3-5], their consumption is still in the 20-to-1000nW range. Circuits aiming at low absolute power often result in low power-efficiency (due to overhead), high PVT sensitivity and poor reliability (due to the use of simplistic circuitry). This work presents a fully-integrated signal acquisition IC with six-fold lower power consumption than prior art, which provides state-of-the-art power-efficiency and ensures enough circuit reliability, precision and bandwidth to enable practical applications.