| 摘要 |
A fractional-N PLL with programmable fractionality having a phase detector and an oscillator is disclosed. The phase detector is for receiving a reference signal having a reference frequency and the oscillator is for providing an output signal having an output frequency. The fractional-N PLL comprises a divider for performing frequency divisions by applying selectable divisors, the divider being disposed in the loop of the fractional-N PLL for receiving the output signal from the oscillator and in response thereto provide a first signal having an averaged frequency. The fractional-N PLL also comprises a first counter connected to the divider in the loop of the fractional-N PLL for receiving the first signal, the first counter for performing a first plurality of counts to a predetermined first integer in response to the averaged frequency of the first signal, wherein the first counter provides a second signal having a loop frequency in accordance with the first plurality of counts to the phase detector for providing the detection of the phase difference between the reference signal and the second signal.
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