A Self-Start-Up Sub-Threshold DC/DC Boost Converter Using Bootstrap Driver for Self-Powered Sensor Nodes

In this paper, a fully autonomous and integrated sub-threshold DC-DC converter is presented for energy harvesting from ambient sources to self-powered IoT nodes. The proposed converter and its clock generator are designed by exploiting body biasing technique for low power operation and operate in sub-threshold regime. This bulk driven technique can dynamically enhance the on-current during conducting state and decrease reverse current during the non-conducting state. A bootstrap driver with dynamic body bias is employed to drive the phase generator at the output of the ring oscillator to decrease the settling time of the charge pump. This further improves the driving capacity of the clock along with extended rail to rail output voltage swing. Also, a novel cross clock scheme is proposed to improve the output voltage's transient response and conversion efficiency of a converter by reducing reverse current loss. The proposed circuit is implemented in CMOS 0.18 um process. The proposed design requires very low start-up voltage of 400 mV and exhibits output voltage of 1.98 V, settling time of 33 us, and pumping efficiency of 99% with a total power dissipation limited to just 1.5 uW.