Abstract: The present self-calibratable oscillating device includes a phase comparator, a clock pad electrically connected to a first input port of the phase comparator, a crystal oscillator electrically connected to a second input port of the phase comparator, an analog/digital converter electrically connected to an output port of the phase comparator, and a memory electrically connected to an output port of the analog/digital converter. The crystal oscillator can be a temperature-compensated crystal oscillator or a surface acoustic wave crystal oscillator. The present self-calibratable oscillating device can further includes a first switch positioned between the first input port of the phase comparator and the clock pad, a second switch positioned between the crystal oscillator and the clock pad wherein the stream direction of the first switch is in reverse of that of the second switch, and a logic control device for controlling the first switch and the second switch.