An ultra-compact and low-power oven-controlled crystal oscillator design for precision timing applications

A novel design for a chip-scale miniature oven-controlled crystal oscillator (OCXO) is presented. In this design, all the main components of an OCXO--consisting of an oscillator, a temperature sensor, a heater, and temperature-control circuitry--are integrated on a single CMOS chip. The OCXO package size can be reduced significantly with this design, because the resonator does not require a separate package and most of the circuitry is integrated on a single CMOS chip. Other characteristics such as power consumption and warm-up time are also improved. Two different types of quartz resonators, an AT-cut tab mesa-type quartz crystal and a frame enclosed resonator, allow miniaturization of the OCXO structure. Neither of these quartz resonator types requires a separate package inside the oven structure; therefore, they can each be directly integrated with the custom-designed CMOS chip. The miniature OCXO achieves a frequency stability of +/- 0.35 ppm with an AT-cut tab mesa-type quartz crystal in the temperature range of 0 °C to 60 °C. The maximum power consumption of this miniature OCXO is 1.2 W at start-up and 303 mW at steady state. The warm-up time to reach the steady state is 190 s. These results using the proposed design are better than or the same as high-frequency commercial OCXOs.