A Fully Integrated Digital LDO With Adaptive Sampling and Statistical Comparator Selection

Digital LDOs are gaining attention for their operation with small output capacitance. Adaptive sampling with a large frequency scaling ratio is required for fast transient response with low-power operation. Furthermore, the design of a fluctuation detector to deal with large load steps is important. This letter describes an adaptive-sampling digital LDO with a built-in clock generator and fluctuation detector based on statistical comparator selection. Statistical comparator selection utilizes offset voltage variation to realize stable implicit references. We apply order statistics for run-time calibration. Our proposed LDO fabricated in a commercial 65-nm low-power CMOS process operates from 0.6 to 1.2 V and achieves a maximum current efficiency of 99.99 %. The transient FoM is 0.25 ps.