A Temperature Compensated Ring Oscillator with LC-based Period Error Detection

Abstract

This thesis presents a hybrid oscillator architecture that combines an LC resonator and an inverter-based ring oscillator to exploit the inherent benefit of an LC resonator for frequency accuracy with low power consumption. This architecture uses the period of the LC resonator as a reference time to control the period of the ring oscillator through a feedback loop. By intermittently activating the LC resonator only for the period error detection, its power consumption could be reduced to a reasonable level while benefitting from its frequency accuracy over environmental variations. The implemented oscillator in a 40-nm CMOS process achieves a temperature sensitivity of 7.65 ppm/°C in a temperature range of -20 °C to 80 °C after 2-point batch calibration with a second-order polynomial. A period jitter shows 2.44 psrms with an output frequency of 98 MHz. An accelerated aging experiment at 100 °C for one week results in a frequency drift of 400 ppm.