Loop bandwidth control device and method of phase locked loop

Abstract

The invention discloses loop bandwidth control device and method of a phase locked loop, which can greatly shorten the time required for controlling the voltage of a correction voltage-controlled oscillator. The loop bandwidth control device comprises a first loop filtering module, a second loop filtering module, a control module, a first switching module and a second switching module, wherein the first loop filtering module and the second loop filtering module respectively output a first voltage and a second voltage; the bandwidth of the second loop filtering module is different from the bandwidth of the first loop filtering module; the control module generates a bandwidth control signal according to the first voltage or the second voltage; the first switching module ensures that a charge pump and the first loop filtering module or the second loop filtering module form a passage according to a bandwidth control signal; and the second switching module ensures that the voltage-controlled oscillator and the first loop filtering module or the second loop filtering module form a passage according to the bandwidth control signal.

Description

technical field [0001] The present invention relates to a phase-locked loop, in particular, to a loop bandwidth control device and a loop bandwidth control method applied to a phase-locked loop. Background technique [0002] Generally speaking, a phase locked loop (Phase Locked Loop, PLL) can be regarded as a feedback circuit system of an output phase and an input phase, which is used to input a low-frequency periodic signal and output a high-frequency periodic signal, and There is some constant phase relationship between the input and the output. The phase-locked loop mainly includes a phase-frequency detector, a charge pump, a loop filter and a voltage-controlled oscillator. In fact, phase-locked loops have been widely used in the fields of electronics and communications, such as memory, microprocessors, hard disk drives, radio frequency wireless transceivers, and optical fiber transceivers. [0003] Please refer to figure 1 , figure 1 A functional block diagram of a t...

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Problems solved by technology

[0006] When the loop bandwidth of the loop filter 14 is small, although the loop filter 14 can effectively filter out the noise caused by the switching of the input reference frequency and the charge pump 12 and reduce the non-ideal effect caused by the jitter, but due to The length of the locking time is inversely proportional to the size of the loop bandwidth, so its disadvantage is that the locking time is too long

Conversely, if the loop bandwidth of the loop filter 14 is increased, although the locking time can be shortened, it may also cause the loop filter 14 to be unable to effectively suppress noise.

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