| 摘要 |
PROBLEM TO BE SOLVED: To provide a PLL circuit which measures the characteristics of voltage-controlled oscillators, without introducing noise to a node, and which can be initialized. SOLUTION: A system includes a PLL circuit 200 having a charge pump 230 which receives "up" and "down" signals and maintains the voltage of outputs based on the signals, and a control circuit 200, coupled to the charge pump 230, for performing control to provide the "up" and "down" signals to the charge pump 230 in a first mode or a second mode. In the first mode, the control circuit 220 passes signals, received from a phase frequency detector 210 through the charge pump as the up and down signals. In the second mode, the control circuit overrides at least one of the signals received from the phase frequency detector 210 to drive an output voltage of the charge pump 230 to a selectable test voltage. COPYRIGHT: (C)2006,JPO&NCIPI
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