A 2.1-nW Burst-Pulse-Counting Supply Voltage Monitor for Biofuel-Cell-Combined Biosensing Systems in 180-nm CMOS

This brief presents a burst-pulse-counting supply voltage monitor for biofuel-cell-combined biosensing systems operating in a supply voltage range of 0.18-0.35 V. The proposed supply voltage monitor is designed to utilize the output of biofuel cells, which can be used to monitor biological signals, and to power circuits. A burst-pulse-counting signal conversion technique, which uses a dynamic leakage suppression (DLS) logic oscillator, a burst pulse generator, and a voltage-to-time converter, is employed to generate digital supply voltage code with fixed sampling timing and short conversion time at low power. The test chip of the proposed supply voltage monitor is implemented and fabricated in 180-nm CMOS technology, whose nominal supply voltage is 1.8 V, with an active area of 0.018 mm
²
. It consumes 2.1 nW at 0.3 V and achieves a conversion time range of 117-673 ms at 0.18-0.35 V with a voltage inaccuracy of +8.3/-5.5 mV.