Power delivery for series connected voltage domains in digital circuits

This paper discusses a paradigm shift in power delivery which enables low supply voltages for digital circuits - methods for connecting the voltage domains in series to enhance system efficiency and performance. Multiple, independent voltage levels enabled by this approach can reduce power consumption dramatically in microprocessor applications. Since voltage regulators only process a fraction of total load power at the intermediate nodes, decreased size and lower conversion losses are attainable. The number of cascaded power conversion stages and the number of power pins can be reduced as the combined load voltage increases, even when individual circuits operate at supply levels far below 1 V. This paper introduces several power delivery architectures for voltage regulation in series connections. A variety of operating conditions are examined in simulation and experimental hardware.