20.7 A 0.45-to-3V reconfigurable charge-pump energy harvester with two-dimensional MPPT for Internet of Things

Compared with inductive DC-DC boost converters [1], the charge pump (CP) features no off-chip inductors and is suitable for monolithic low power energy harvesting applications such as Internet of Things (loT) smart nodes. However, the single conversion ratio (CR) CP has a narrow input voltage range. This induces a charge redistribution loss (CRL) and becomes a bottleneck preventing highly efficient energy harvesting [2]. CRL stems from two facts: 1) The operating voltages of energy sources vary with environment, and 2) Different energy sources feature a wide range of output voltages. By tuning the CR as one dimension, reconfigurable CPs can eliminate CRL; however, they need complex control algorithms, lack maximum power point tracking (MPPT) [3], and only provide fractional ratios [4]. Thus, they are not preferable for energy harvesting from various sources.