Two-Phase Resonant Clocking for Ultra-Low-Power Hearing Aid Applications

Resonant clocking holds the promise of trading speed for energy in CMOS circuits that can afford to operate at low frequency, like hearing aids. An experimental chip with 110k transistors and more than 2500 latches, has been designed, fabricated and tested. The measured energy con sumption of the design at 0.8 V is 62μW/MHz, about 7.5% less than the conventional single-edge-triggered benchmark. Closer analysis reveals that much of the energy savings brought about by resonant clocking at low supply voltages are lost when a CMOS circuit is operated at higher voltages. This is because of the crossover currents that persist for much of a clock period when a circuit is driven from sine-type clock waveform.