SPREAD SPECTRUM CLOCK GENERATOR, ELECTRONIC APPARATUS, AND SPREAD SPECTRUM CLOCK GENERATION METHOD

摘要

A spread spectrum clock generator includes a phase comparator that compares a reference clock with a feedback clock, a low-pass filter that passes a predetermined low-frequency component, a phase lock loop that includes a voltage-controlled oscillator generating an output clock whose frequency corresponds to the filtered signal, a triangular wave controller that generates a triangular wave signal for frequency-modulating the spread spectrum clock based on the output clock, a delay controller that generates the feedback clock by controlling delay of the output clock based on the triangular wave signal, a first counter that counts the output clock and output a first count value, a second counter that counts the reference clock and output a second count value, and a phase error correction circuit that compares the first count value with the second count value and corrects phase error of the output clock.

主权项

1. A spread spectrum clock generator, comprising:
a phase comparator to compare a reference clock with a feedback clock to obtain a comparison result; a low-pass filter to pass a predetermined low-frequency component from a signal of the comparison result to obtain a filtered signal; a phase lock loop including a voltage-controlled oscillator that generates an output clock whose frequency corresponds to the filtered signal; a triangular wave controller to generate a triangular wave signal for frequency-modulating the spread spectrum clock based on the output clock; a delay controller to generate the feedback clock by controlling delay of the output clock based on the triangular wave signal; a first counter to count the output clock to output a first count value; a second counter to count the reference clock to output a second count value; and a phase error correction circuit to compare the first count value with the second count value for period that is a cycle or a multiple of the cycle of the frequency modulation and correct phase error of the output clock by modifying a shape of the triangular wave signal so that the first count value matches the second count value based on the comparison result.