Ultra-low-voltage power management unit for thermal energy harvesting applications

In this paper, an efficient ultra-low-voltage PMU working for TEG input voltages as low as 200mV is proposed. The PMU core, charging an energy buffer, employs a main DC/DC converter. It consists of a cascade of two Dickson-based charge pumps with a variable conversion factor and switching frequency. Feedback is provided from the load buffer by means of a current sensor to a control unit that maximizes the overall power transfer efficiency at low input voltages. System simulation results demonstrate a peak efficiency greater than 70% with a controller current consumption less than 2μA. The PMU core was simulated in Cadence environment using a UMC CMOS 180nm process and the layout of the basic core building blocks is presented. The fully-integreable design consumes an area of approximately 30mm².