Jitter smoothing filter and jitter smoothing method for driving charge pump

Abstract

A jitter smoothing filter receives a direction signal and a phase error signal having a pulse width representing a phase error signal. The jitter smoothing filter generates an up proportional control signal and a down proportional control signal for driving a charge pump. For each pulse in the phase error signal, the jitter smoothing filter generates at least two pulses in the up or down proportional control signal. The number of pulses generated by the jitter smoothing filter depends on the pulse width of the corresponding pulse in the pulse error signal.

Description

technical field [0001] The invention relates to a filter, in particular to a digital jitter smoothing filter and a jitter smoothing method for driving a charge pump. Background technique [0002] Please refer to figure 1 . figure 1 A block diagram of a prior art digital phase locked loop (DPLL) 100 is shown. The digital phase-locked loop 100 includes: a digital phase detector 110, a digital gain multiplier 120, a digital difference-integration modulator 130, a first and a second digital-to-time converter 140 and 150, a first charge pump 160, a loop filter 170 , a second charge pump 180 and a voltage-controlled oscillator 190 . Digital phase detector 110 detects the phase difference between the reference frequency and the feedback frequency, and generates a phase error value ERR PD , wherein the feedback frequency is generated by the voltage controlled oscillator 190 . The digital phase detector 110 further generates an indication signal DIR indicating up or down. Digit...

AI Technical Summary

Problems solved by technology

Example: When power supply noise causes the reference signal to fluctuate, resulting in a correspondingly large cycle-to-cycle jitter

Images