Low phase noise on-chip oscillator for implantable biomedical applications

On-chip accurate clock references are one of the essential building blocks in fully integrated Systems-On-Chips (SOC). In this paper, a low phase noise, temperature and supply voltage independent clock reference is presented. It provides the reference frequency for a biomedical implantable system. The simulated phase noise at 100 KHz offset from 2MHz carrier is - 113dBc/Hz. Simulations show the frequency remains within ±0.34% of the nominal oscillation frequency in the operating voltage range of 1.7 - 1.9 V without any calibration and its change in the temperature range of -20-to-100°C is ±0.5%. The circuit consumes 77μW and is designed in a 0.18μm technology with 1.8V supply voltage.