Energy-efficient DC-DC power supplies are becoming essential for battery life enhancement in portable devices with power-hungry circuits, such as RF PAs. However, the switching noise produced by such power supplies tends to degrade the performance of RF circuits, either directly or indirectly. This paper investigates the most common switching noise mitigation techniques in DC-DC power supplies and discusses their advantages and shortcomings. The paper then discusses a new technique that achieves completely spur-free switching noise performance at every node in DC-DC power supplies within a short number of switching cycles while maintaining minimal random noise floor peaking as well as low cost and design complexity. The technique can be adopted within preexisting power supplies operating with PWM or PFM control, both at high and light load conditions to power spur-sensitive RF PAs.
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