| 摘要 |
<P>PROBLEM TO BE SOLVED: To solve the problem that a conventional phase comparator shows an input/output characteristic not well in linearity when the phase difference between incoming signals is close to zero, resulting in insufficient reduction of spurious signals when used in a non-integer PLL (phase-locked loop) employing a fraction PLL or a Δ-Σ technique, and is difficult to have an accurate offset when used in the fraction PLL. <P>SOLUTION: According to the phase comparator to be provided, a charge pump continues the discharge and absorption of current for a certain time even if the phase difference is close to zero, eliminating the non-linearity of the comparator due to an internal delay. In addition, by varying the value of the current discharged or absorbed by the charge pump or a time of the discharge and absorption, the phase comparator is made to have an accurate offset, enabling the fraction PLL operation. <P>COPYRIGHT: (C)2004,JPO |
