Low-power clock reference circuit for intermittent operation of subthreshold LSIs

A low power on-chip reference clock generator consisting of subthreshold MOSFET circuits is proposed. It uses a simple frequency-locked loop technique with no inductor, quartz resonator, or MEMS oscillator. Theoretical analyses and a SPICE simulation with 0.35-mum CMOS parameters showed that the clock frequency could be controlled in the frequency range of 10-1000 kHz. When operated at 170 kHz, the generator showed a temperature coefficient of 100 ppm/degC, a line sensitivity of 3%/V, and a power consumption of 20 muW. Our clock generator can be used as a reference clock for intermittent operation in power aware LSIs.