| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an analog frequency comparator which sets an internal frequency on the basis of a voltage and compares the internal frequency with an external frequency, to provide an analog frequency synthesizer which synthesizes a clock signal according to the same principles as the analog frequency comparator, and to provide an associated method. <P>SOLUTION: The frequency comparator includes a frequency detection circuit which generates a reference signal on the basis of a first signal and an input voltage; a frequency generator which generates a second signal on the basis of the input voltage; a charge pump circuit which is coupled to the frequency detection circuit and the frequency generator, enables a charging current on the basis of one of the reference signal and the second signal to increase a voltage level, and further enables a discharging current on the basis of the other of the reference signal and the second signal to decrease the voltage level; and a decision logic which is coupled to the charge pump circuit and indicates a frequency relationship between the first signal and the second signal on the basis of the voltage level. <P>COPYRIGHT: (C)2008,JPO&INPIT |
