Frequency comparator, frequency synthesizer and its related method

Abstract

A frequency comparator is disclosed in the present invention, for comparing frequency of a first signal and a second signal. The comparator comprises: a frequency detecting circuit for generating reference signal according to the first signal and input voltage; a frequency generator for generating the second signal according to the input voltage; a charge pump coupling at frequency detecting circuit and the frequency generator, for enabling charging current so as to promote voltage level according to one signal of the reference signal and the second signal, and or enabling charging current so as to diminish voltage level according to the other signal of the reference signal and the second signal; and a judging logic device coupling at the charge pump circuit, for determining the relationship between frequencies of the first signal and the second signal according to the voltage level.

Description

technical field [0001] The present invention relates to clock signal processing, especially an analog frequency comparator, which sets an internal frequency based on voltage and compares an external frequency with the internal frequency, and a frequency synthesizer, which uses the frequency comparator to synthesize a clock signal , and related methods. Background technique [0002] In the application field of integrated circuits, external pins (pins) are often used to receive an external clock, wherein the external clock has a frequency different from that of the internally generated clock. Therefore, the integrated circuit must be able to determine The two frequencies of the internal clock and the external clock, and the clock required to determine which clock is selected as the integrated circuit. In the known field, a phase frequency detector, a counter and a plurality of digital logic devices can be combined to form a frequency selector, which is used to determine the c...

AI Technical Summary

Problems solved by technology

In the known field, a phase frequency detector, a counter and a plurality of digital logic devices can be combined to form a frequency selector, which is used to determine the clock signal of the frequency required inside the circuit. However, the phase frequency detector, The counter and the frequency selector combined by the plurality of digital logic devices will occupy most of the area of ​​the integrated circuit, thus increasing the manufacturing cost of the integrated circuit

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