A 0.02-to-2-MHz Tunable Clock Reference Circuit for Intermittent Pulse Generators

An ultra-low power clock reference generator has been developed using a 0.35-μm CMOS parameters. The circuit is based on a simple frequency-locked loop technique with no inductors, quartz resonators, and MEMS oscillators. Theoretical analyses and measurement results showed that the clock frequency could be controlled over a frequency range of 20 kHz 2 MHz. The circuit showed a temperature coefficient of 170 ppm/̊ C, a line regulation of 1%/V, and a power dissipation of 3 μW, when operated at 200 kHz. A process sensitivity (σ/μ) was 5% without calibration technique. The proposed clock generator can be used as a reference clock for intermittent operation for use in subthreshold-operated, power-aware LSIs.