A Robust 90-nW Power-On Reset Circuit with Brown-Out Detection for RF Energy-Harvesting

This paper presents an ultra-low-power power-on reset (POR) circuit with integrated brown-out detection (BOD) for enhanced robustness in RF energy-harvesting power management systems. Implemented in a$180-\text{nm} 1 \mathrm{P} 6 \mathrm{M}$CMOS technology, the proposed POR circuit is part of a comprehensive power management system that also incorporates a power harvester, a dc limiter, and a low-dropout regulator (LDO) with voltage reference. The POR ensures safe startup, while the BOD ensures reliable operation after short supply voltage glitches occur. Operating from a supply voltage of 1 V, the circuit consumes only 90 nW static power and occupies$0.003 ~\text{mm}^{2}$of silicon area. It achieves stable trip voltages of$\mathrm{V}_{\mathrm{T}, \text{POR}}=0.73 ~\mathrm{V}$and$\mathrm{V}_{\mathrm{T}, \text{BOR}}=0.64 ~\mathrm{V}$with small variations of$\pm 22.9 \text{mV}$and$\pm 24.3 \text{mV}$, respectively, within a$1 \sigma$confidence interval. Brown-out events as short as$3.4 \mu ~\mathrm{s}$are reliably detected. The combination of ultra-low power, compact area, and robust BOD threshold stability makes the proposed POR circuit ideally suited for fully autonomous wireless RF-powered mixed-signal system-on-chip (SoC) and other low-power energy-harvesting applications that demand reliable startup and continuous operation under variable power conditions.