ppm/ ̋C on-Chip Clock Source Platform for Near-Human-Body Temperature Applications

We propose a fully on-chip clock-source system in which an ultra-low-power diode-based temperature-uncompensated oscillator (OSCdiode) serves as the main clock source and frequency locks to a higher-power temperature-compensated oscillator (OSCcmp) that is disabled after each locking event to save power. The locking allows the stability of the uncompensated oscillator to stay within the stability bound of the compensated design. This paper demonstrates the functionality of a locking controller that uses a periodic (counter-based) scheme implemented on-chip and a prediction (temperature-drift-based) scheme. The flexible clock source platform is validated in a 130 nm CMOS technology. In the demonstrated system, it achieves an effective average temperature stability of 7 ppm/ ̋C in the human body temperature range from 20 ̋C to 40 ̋C with a power consumption of 36 nW at 0.7 V. It achieves a frequency range of 12 kHz to 150 kHz at 0.7 V.