Design of a Quick Startup Crystal Oscillator Circuit With Automatic Injection Frequency Calibration

High-quality factor crystal oscillator circuits have long startup times which result in anincrease in the average power consumption of duty-cycled systems. By injecting energy into a crystal for a precisely calculated time, the startup time can be significantly improved. This, however, requires that an injection frequency within 6000 ppm of the crystal's resonant frequency is available on chip. As such, for the precisely timed injection technique, each chip requires factory calibration of the ring oscillators to achieve the required accuracy. In this work we propose a re-configurable delay line which can be used to quickly match the period of a reference signal and can be reconfigured as a ring oscillator after the delay has been matched. Using this re-configurable delay line, we further propose a self-calibration scheme that uses the ringing voltage-step response of the crystal as a reference signal for the proposed delay-line. The delay line, after locking and re-configured as a ring oscillator, provides injection signal to energize the crystal for quick startup