Multiple voltage conversion ratio (VCR) recursive switched-capacitor (SC) DC-DC
converters, based on a number of basic 2:1 converters, are widely used for on-chip power supplies due to their flexible VCRs for higher energy efficiency. However, conventional multi-VCR SC converters usually have one or more 2:1 converters unused for some VCRs, which results in lower power density and chip area wastage. This paper presents a new recursive DC-DC converter system, which is able to dynamically reconfigure the connection of all on-chip 2:1 converter cells so that the unused converters in conventional designs can be re-used in this new architecture for increasing the load-driving capacity,
power density and power efficiency.

To validate the design, a 4-bit-input 15-ratio system was designed and fabricated in a 180-nm BCD process, which can support a maximum load current of 0.71mA and achieve a peak power efficiency of 93.1% with 105.3μA/mm^2 chip power density from a 2V input power supply. The measurement results show that the load-driving capacity can become 6.826×, 2.236× and 2.175× larger than the conventional topology when the VCR is 1/2, 1/4 and 3/4, respectively. In addition, the power efficiency under these specific VCRs can also be improved considerably.