Input-adaptive dual-output power management unit for energy harvesting devices

An input-adaptive dual-output charge pump (DOQP) with variable fractional conversion ratio and low dropout regulators (LDRs) in cascade is implemented for the power management unit (PMU) of implantable energy harvesting devices. The charge pump has one step-down and one step-up output adaptively converted from a 1.8 to 4.0V harvested energy source, and the outputs of the LDRs are 1V and 3V respectively. To improve the overall efficiency, conversion ratios of k/6 (k=2,..., 12) are realized by 1/2- and 1/3-capacitors using an interleaving scheme. The PMU is designed using a 0.13μm 3.3V CMOS process, and attains the peak efficiency of 81.3% and efficiency better than 55% for a wide input range.