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METHODS OF AUTOMATICALLY CALIBRATING FREQUENCY FEATURES OF A PHASE LOCKED LOOP, AND PHASE LOCKED LOOPS INCLUDING AN OPEN-LOOP AUTOMATIC FREQUENCY CALIBRATION CIRCUIT
METHODS OF AUTOMATICALLY CALIBRATING FREQUENCY FEATURES OF A PHASE LOCKED LOOP, AND PHASE LOCKED LOOPS INCLUDING AN OPEN-LOOP AUTOMATIC FREQUENCY CALIBRATION CIRCUIT
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机译:自动校准锁相环的频率特性的方法,以及包括开环自动频率校准电路的锁相环的方法
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摘要
A PLL includes an open-loop automatic frequency calibration circuit. The open-loop automatic frequency calibration circuit includes a frequency detector, first and second sinks, a comparator and a bank selector. The frequency detector generates an up-signal and a down-signal responding to a frequency difference between a first phase difference signal having a phase difference from a reference oscillation signal and the second phase difference signal having a phase difference from a frequency division oscillation signal. The first and second sinks discharge the first and second capacitors respectively responding to the up-signal and the down-signal. The comparator compares voltages of the first and second capacitors. The bank selector selects a bank according to binary search, selects an optimum bank among two banks lastly searched, and outputs a bank selection signal. The voltage-controlled oscillation changes frequency features thereof in response to the bank selection signal.
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