SIGMA - DELTA modulator-controlled phase-locked-loop circuit

摘要

A SIGMA DELTA modulator-controlled, phase-locked-loop circuit, and an associated method, generates a frequency-regulated signal which does not exhibit undesired tones. Dithering signals are generated and are provided to a SIGMA DELTA modulator. The SIGMA DELTA modulator forms a division-factor control signal used to control the division factor of a frequency divider forming a portion of the PLL circuit. The dithering signals applied to the SIGMA DELTA modulator reduce the likelihood that the SIGMA DELTA modulator shall enter a limit cycle and generate repetitive output signals.