A 635pW battery voltage supervisory circuit for miniature sensor nodes

We propose a low power battery voltage supervisory circuit for micro-scale sensor systems that provides power-on reset, brown-out detection, and recovery detection to prevent malfunction and battery damage. Ultra-low power is achieved using a 57 pA, fast stabilizing two-stage voltage reference and an 81 pA leakage-based oscillator and clocked comparator. The supervisor was fabricated in 180 nm CMOS and integrated with a complete 1 mm³ sensor system. It consumes 635 pW at 3.6 V supply voltage, which is an 850× reduction over the best prior work.