Energy Minimization of Duty-Cycled Systems Through Optimal Stored-Energy Recycling from Idle Domains

SoCs in sensing and wearable applications are aggressively duty-cycled to minimize leakage energy losses. Such systems operate predominantly in Sleep mode, regularly marked by brief intervals of Active operation to perform sensing or communication actions. During Sleep, the considerable electrical energy stored in the domain-decoupling capacitor $(C_{0})$ leaks away, requiring the battery to deliver the energy $(E_{\mathsf{wake}})$ needed to restore $C_{0}$ to $V_{\mathsf{dd}}$ during the Wake phase ahead of Active mode operation (Fig. 13.7.1). Because of the relatively limited energy dissipation incurred during the brief Active duration, the overhead presented by $E_{\mathsf{wake}}$ constitutes a significant fraction of total energy dissipation, which degrades battery life significantly.