| 摘要 |
A feedback-controlled current pump is coupled to the loop filter capacitor of a phase lock loop to provide a coarse prepositioning voltage and thereby accelerate the lockup process on a new frequency. Two voltage comparators monitor the capacitor voltage with respect to a selectable "window" centered about the desired voltage, and when the capacitor has been charged or discharged to a voltage within the window, the current pump providing the charging or discharging current to the capacitor is shut off.
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