Phase-locked loop circuit and clock generator including the same

Abstract

A phase-locked loop (PLL) circuit may include a voltage-controlled oscillator, a sub-sampling PLL circuit, and a fractional frequency division control circuit. The fractional frequency division control circuit may include a voltage-controlled delay line that routes a feedback signal to generate delay information, a replica voltage-controlled delay line to which the delay information is applied and configured to route a reference clock signal to generate a plurality of delay reference clock signals each delayed by up to a different respective delay time, and a digital-to-time converter (DTC) configured to generate the selection reference clock signal from the plurality of delay reference clock signals and output the selection reference clock signal to the sub-sampling PLL circuit.