A phase-locked loop includes a phase-to-digital converter that receives a first periodic input signal at a first input and a first feedback signal at a second input. The phase-to-digital converter generates digital signals. A digitally controlled oscillator includes a delay-locked loop that is responsive to the digital signals. The delay-locked loop generates a periodic output signal having an average frequency that is a product of a frequency of the first periodic input signal multiplied by a non-integer fractional number while a phase of the first periodic input signal is unchanging.