A 42nJ/conversion on-demand state-of-charge indicator for miniature IoT Li-ion batteries

Abstract

An energy efficient State-of-Charge (SOC) indication algorithm and integrated system for small IoT batteries are introduced in this paper. The system is implemented in a 180-nm CMOS technology. Based on a key finding that small Li-ion batteries exhibit a linear dependence between battery voltage and load current, we propose an instantaneous linear extrapolation (ILE) algorithm and circuit allowing on-demand estimation of SOC. Power consumption is 42nW and maximum SOC indication error is 1.7%.