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This paper describes design considerations for a digital inductive-switching DC/DC converter suitable for direct battery connection in a deep sub-micron CMOS process. Digital control techniques and robust circuit design methods take advantage of the advanced process technology while avoiding the barriers to direct battery connection and high efficiency, high power density voltage conversion. The approach is verified on a prototype converter, implemented in 40 nm standard bulk CMOS. The design achieves a peak efficiency of 95% for an input range of up to 5.5 V. The transient response is optimized for typical mobile SoC operating conditions and achieves step response times as fast as 35 μs/V under load.