PLL CIRCUIT AND CONTROL METHOD THEREOF
First Claim
1. A PLL circuit comprising:
- a voltage control oscillator configured to control a frequency of an oscillating signal based on a control signal;
a rough-adjusting loop part configured to perform a rough adjustment to the frequency of the oscillating signal based on a frequency-setting signal;
a fine-adjusting loop part configured to perform a fine adjustment to the frequency of the oscillating signal after the rough adjustment by the rough-adjusting loop part; and
a loop control part configured to operate either the rough- or fine-adjusting loop part,wherein the voltage control oscillator comprises;
a variable capacitor having a capacitance variable with the control signal;
a plurality of fixed capacitors each having a fixed capacitance and being connectable in parallel to the variable capacitor; and
a plurality of first switching parts each connected in series to a corresponding fixed capacitor among the a plurality of fixed capacitors and configured to switch whether or not to connect in parallel the corresponding fixed capacitor to the variable capacitor,the rough-adjusting loop part comprises;
a switching-information storing part configured to store switching information for the first switching parts;
a switching-information setting part configured to set switching information for the first switching parts;
a frequency divider configured to generate a frequency-divided signal by frequency-dividing the oscillating signal of the voltage control oscillator adjusted based on the switching information set by the switching-information setting part for the first switching parts;
an oscillating-frequency adjusting part configured to instruct the switching-information setting part to set again the switching information based on a result of comparing a frequency of the frequency-divided signal with a frequency of a reference signal; and
a comparator configured to generate differential information between the switching information set by the switching-information setting part and the switching information stored in the switching-information storing part, and to inform the loop control part of completion of the rough adjustment if the differential information belongs in a specific threshold range whereas instruct the switching-information setting part to set again the switching information if the differential information is out of the threshold range, andthe fine-adjusting loop part comprises;
a phase comparator configured to detect a phase difference between the frequency-divided signal obtained by frequency-dividing the oscillating signal at the frequency divider and the reference signal while a switched state of each of the first switching parts at a moment of the completion of the rough adjustment at the rough-adjusting loop part remains unchanged;
a charge pump configured to generate a voltage signal in accordance with the phase difference; and
a loop filter configured to remove noises included in the voltage signal to generate the control signal for controlling the capacitance of the variable capacitor.
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Accused Products
Abstract
A PLL circuit has a voltage control oscillator, a rough-adjusting loop part and a fine-adjusting loop part. The rough-adjusting loop part configured to perform a rough adjustment to the frequency of the oscillating signal based on a frequency-setting signal. The fine-adjusting loop part performs a fine adjustment to the frequency of the oscillating signal after the rough adjustment by the rough-adjusting loop part. The fine-adjusting loop part includes a phase comparator configured to detect a phase difference between the frequency-divided signal obtained by frequency-dividing the oscillating signal at the frequency divider and the reference signal while a switched state of each of the first switching parts at a moment of the completion of the rough adjustment at the rough-adjusting loop part remains unchanged.
10 Citations
20 Claims
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1. A PLL circuit comprising:
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a voltage control oscillator configured to control a frequency of an oscillating signal based on a control signal; a rough-adjusting loop part configured to perform a rough adjustment to the frequency of the oscillating signal based on a frequency-setting signal; a fine-adjusting loop part configured to perform a fine adjustment to the frequency of the oscillating signal after the rough adjustment by the rough-adjusting loop part; and a loop control part configured to operate either the rough- or fine-adjusting loop part, wherein the voltage control oscillator comprises; a variable capacitor having a capacitance variable with the control signal; a plurality of fixed capacitors each having a fixed capacitance and being connectable in parallel to the variable capacitor; and a plurality of first switching parts each connected in series to a corresponding fixed capacitor among the a plurality of fixed capacitors and configured to switch whether or not to connect in parallel the corresponding fixed capacitor to the variable capacitor, the rough-adjusting loop part comprises; a switching-information storing part configured to store switching information for the first switching parts; a switching-information setting part configured to set switching information for the first switching parts; a frequency divider configured to generate a frequency-divided signal by frequency-dividing the oscillating signal of the voltage control oscillator adjusted based on the switching information set by the switching-information setting part for the first switching parts; an oscillating-frequency adjusting part configured to instruct the switching-information setting part to set again the switching information based on a result of comparing a frequency of the frequency-divided signal with a frequency of a reference signal; and a comparator configured to generate differential information between the switching information set by the switching-information setting part and the switching information stored in the switching-information storing part, and to inform the loop control part of completion of the rough adjustment if the differential information belongs in a specific threshold range whereas instruct the switching-information setting part to set again the switching information if the differential information is out of the threshold range, and the fine-adjusting loop part comprises; a phase comparator configured to detect a phase difference between the frequency-divided signal obtained by frequency-dividing the oscillating signal at the frequency divider and the reference signal while a switched state of each of the first switching parts at a moment of the completion of the rough adjustment at the rough-adjusting loop part remains unchanged; a charge pump configured to generate a voltage signal in accordance with the phase difference; and a loop filter configured to remove noises included in the voltage signal to generate the control signal for controlling the capacitance of the variable capacitor. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A method of controlling a PLL circuit including:
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a voltage control oscillator configured to control a frequency of an oscillating signal based on a control signal; a rough-adjusting loop part configured to perform a rough adjustment to the frequency of the oscillating signal based on a frequency-setting signal; a fine-adjusting loop part configured to perform a fine adjustment to the frequency of the oscillating signal after the rough adjustment by the rough-adjusting loop part; and a loop control part configured to operate either the rough- or fine-adjusting loop part; wherein the voltage control oscillator has; a variable capacitor having a capacitance variable with the control signal; a plurality of fixed capacitors each having a fixed capacitance and being connectable in parallel to the variable capacitor; and a plurality of first switching parts each connected in series to a corresponding fixed capacitor among the a plurality of fixed capacitors and configured to switch whether or not to connect in parallel the corresponding fixed capacitor to the variable capacitor, the method comprising the steps of; in the rough-adjusting loop part, storing switching information for the first switching parts in a switching-information storing part; setting switching information for the first switching parts; generating a frequency-divided signal by frequency-dividing the oscillating signal of the voltage control oscillator adjusted based on the switching information set by the switching-information setting part for the first switching parts; instructing the switching-information setting part to set again the switching information based on a result of comparison between a frequency of the frequency-divided signal and a frequency of a reference signal; and generating differential information between the switching information set by the switching-information setting part and the switching information stored in the switching-information storing part, and informing the loop control part of completion of the rough adjustment if the differential information belongs in a specific threshold range whereas instructing the switching-information setting part of setting again the switching information if the differential information is out of the threshold range, and in the fine-adjusting loop part; detecting a phase difference between the frequency-divided signal obtained by frequency-dividing the oscillating signal at the frequency divider and the reference signal while a switched state of each of the first switching parts at a moment of the completion of the rough adjustment at the rough-adjusting loop part remains unchanged; generating a voltage signal in accordance with the phase difference; and removing noises included in the voltage signal to generate the control signal for controlling the capacitance of the variable capacitor. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20)
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Specification