| 摘要 |
PROBLEM TO BE SOLVED: To solve a noise environment around a phase-locked loop circuit on an integrated circuit, which is difficult to predict beforehand, and device variations in the integrated circuit.SOLUTION: In the phase-locked loop circuit with a digital feed-forward path, especially using a bang-bang output phase comparator, an adjustment of a digital gain optimizes a loop band to minimize jitter of an output clock. Specifically a change in the digital feed-forward gain can readily change the loop band. For example, the magnitude of output jitter of a voltage-controlled oscillator is observed by a jitter amount measurement circuit, and the digital feed-forward gain is adjusted so as to minimize the jitter. |
