Temperature-Robust 0.48-V FD-SOI Intermittent Startup Circuit with 300-nA Quiescent Current for Batteryless Wireless Sensor Capable of 1-μA Energy Harvesting Sources

A temperature-variation-tolerant intermittent startup circuit (ISC) that suppresses quiescent current to 300 nA at 0.48V was developed. The ISC is a key circuit for a batteryless wireless sensor that can detect a 1 mu A generation current of energy harvesting sources from the intervals of wireless signals. The ISC consists of an ultralow-voltage detector composed of a depletion-type MOSFET and low-Vth MOSFETs, a Dickson-type gate-boosted charge pump circuit, and a power-switch control circuit. The detector consists of a voltage reference comparator and a feedback-controlled latch circuit for a hysteresis function. The voltage reference comparator, which has a common source stage with a folded constant-current-source load composed of a depletion-type nMOSFET, makes it possible to reduce the temperature dependency of the detection voltage, while suppressing the quiescent current to 300 nA at 0.48V. The ISC fabricated with fully-depleted silicon-on-insulator (FD-SOI) CMOS technology also suppresses the variation of the quiescent current. To verify the effectiveness of the circuit, the ISC was fabricated in a 0.8-mu m triple-Vth FD-SOI CMOS process. An experiment on the fabricated system, the ISC boosts the input voltage of 0.48V to 2.4V while suppressing the quiescent current to less than 300 nA at 0.48V. The measured temperature coefficient of the detection voltage was +/- 50 ppm/degrees C. The fluctuation of the quiescent current was 250 nA +/- 90 nA in the temperature range from 0 degrees C to 40 degrees C. An intermittent energy harvesting sensor with the ISC was also fabricated. The sensor could detect a generation current of 1 mu A at EH sources within an accuracy of +/- 15% in the temperature range from 0 degrees C to 40 degrees C. It was also successfully applied to a self-powered wireless plant-monitoring sensor system.

Automated summary

This paper presents a temperature-variation-tolerant intermittent startup circuit (ISC) that suppresses quiescent current and can detect a generation current from energy harvesting sources. The ISC consists of an ultralow-voltage detector, a Dickson-type gate-boosted charge pump circuit, and a power-switch control circuit, providing hysteresis function for stable operation.