Non-dissipative rail drivers for adiabatic circuits

Energy dissipation of CMOS circuits is becoming a major concern in the design of digital systems. Earlier, we presented a new form of CMOS charge recovery logic (SCRL), with an energy dissipation per operation that falls linearly with operating frequency, as opposed to the constant energy required for conventional CMOS circuits 1]. These SCRL circuits, along with most adiabatic circuit techniques proposed to date, require a set of gradually swinging power supply rails that in eeect force all charge transfers within the system to occur quasistatically. Proposals to date for generating these swinging rails have relied on a power MOSFET to gate the oscillation of an inductor, forming an RLC circuit. Even under ideal conditions, dissipation in this MOSFET degraded the overall energy savings of SCRL circuits from 1=T dependence to 1= p T. SCRL and other adiabatic circuits thus exhibited inferior overall energy saving performance when compared supply voltage scaling of conventional CMOS circuits. In this paper, we present a technique for generating the required rail waveforms without the series power MOSFET to gate the inductor. This new rail driver circuit relies on adding multiple harmonics of the base frequency to generate a rail waveform of any desired shape. Our Harmonic Rail Driver (HRD) can be built using only passive reactive components or by using correctly trimmed transmission line segments. It is non-dissipative to within the achievable Q's of these components. Using HRDs to power and control SCRL circuits, we restore the overall dissipation of SCRL circuits to its attractive 1=T dependence. In addition, adding harmonics allows us to construct a rail voltage that very closely approximates a linear voltage ramp instead of the sinusoidal waveform generated by previous techniques, improving the constant factor in the energy expression from 2 =8 to 1. This change markedly improves the performance of SCRL circuits, making their energy saving performance comparable to what is obtained by scaling the supply voltage in conventional CMOS when V TH is held constant, for all operating frequencies. Alternatively, with HRDs, we can push the energy-speed tradeoo in the direction of higher performance, since it becomes possible to overdrive a CMOS system beyond its maximum dc operating frequency for a given supply voltage, so long as the devices do not reach saturation, trading higher energy consumption for increased performance. The usefulness of HRDs extends beyond driving adiabatic circuits, to other applications such as driving the periodic control …