Embodiments of a clock circuit are described. This clock circuit includes an oscillator, which includes a resonance circuit having a resonance frequency, that outputs a first clock signal having a first frequency. Furthermore, a digital controller is coupled to the oscillator. This digital controller modifies the resonance frequency of the oscillator during a first mode of operation of the clock circuit, and the modifying is ceased during a second mode of operation of the clock circuit. In addition, an injection circuit is coupled to the oscillator. This injection circuit provides a second clock signal having a second frequency to the oscillator. Note that the second clock signal injection locks a phase and/or the first frequency of the first clock signal. Also note that a ratio of the first frequency to the second frequency is greater than or equal to one.
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