Charge Recycling in Voltage-Dithered Circuits

Voltage dithering is a voltage scaling technique that consists in switching between two power supplies on the fly. This technique reduces the overall dynamic energy consumption of a system, but switching still consumes a considerable amount of additional energy. In this paper, we propose a new circuit to reduce the energy overhead of voltage switching. The innovation consists in redirecting some charge from one power supply line to another before the voltage is switched. This charge recycling technique decreases the current driven from the power supply during voltage switching, and thus reducing the energy overhead. Applying the charge recycling technique between two identical circuit blocks reduces the dynamic energy overhead of voltage switching by 36.6%. When charge recycling takes place between two distinct circuit blocks the dynamic energy overhead is reduced in a range between 23.5% and 27.7%.