A Temperature Compensated Ring Oscillator With LC-Based Period Error Detection

This brief 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 turning on the $LC$ resonator 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–80 °C after two-point batch calibration with a second-order polynomial. A period jitter shows 2.44 psrms with an output frequency of 98 MHz.