Voltage boosters for on-chip solar cells on focal-plane processors

This paper addresses voltage boosters for on-chip solar cells on a standard 0.18 μm CMOS technology. Voltage boosters, also referred to as DC/DC converters or charge pumps, are needed to make the open voltage of micro solar cells compatible with the power supply of current standard CMOS technologies. This paper is oriented to on-chip solar cells for focal-plane processors, where the photodiode array can be configured along time for both image acquisition and energy harvesting. The large area occupied by the focal-plane processor itself constrains the design of the charge pumps, as there is small room for them, forcing the use of relatively small capacitors too. This paper assesses the main performance metrics through electrical simulations of three charge pumps, namely, the Dickson, the Fibonacci and the heap charge pump. The paper has a clear practical orientation, outlining how to configure the photodiode array of a focal-plane processor along time to increase the power efficiency.