Abstract: A push-start crystal oscillator (XO), an associated electronic device and a push-start method for performing a start-up procedure of an XO are provided. The push-start XO includes an inverting amplifier and a push-start logic control circuit, wherein the inverting amplifier is coupled to a crystal load. The inverting amplifier generates a first XO signal and a second XO signal. The push-start logic control circuit receives a feedback clock from a phase locked loop (PLL), and generates a phase control clock according to the feedback clock, wherein a push phase and a settle phase are specified by the phase control clock. During the settle phase, the PLL calibrates a frequency of the feedback clock according to the second XO signal. During the push phase, the feedback clock is transmitted to the inverting amplifier in order to increase the amplitude of the first XO signal.

Abstract: A method of tuning an RC time constant includes the steps of providing a predetermined time period value associated with a predetermined RC time constant, providing a DC reference signal, generating an second signal responsive to charging a capacitor until magnitudes of the second signal and the DC reference signal are matched, determining a charging time period of the capacitor, and adjusting a capacitance of the capacitor to comply with the predetermined RC time constant based on the time period and the predetermined time period value.