McClure, Qualey & Rodack, LLP
Phase locked loop
Phase-locked loops (PLLs) are provided. A PLL includes a voltage-controlled oscillator (VCO), a frequency divider and a track-and-hold charge pump. The VCO is configured to provide an output clock corresponding to a pumping current. The frequency divider is configured to provide a feedback signal according to the output clock. The track-and-hold charge pump is configured to provide the pumping current according to a reference clock and the feedback signal. The track-and-hold charge pump includes a track-and-hold circuit, a pumping switch and a pulse width modulator (PWM). The track-and-hold circuit is coupled to the frequency divider and configured to sample the feedback signal according to the reference clock. The PWM is configured to provide a PWM signal to control the pumping switch according to the reference clock, so as to provide the pumping current corresponding to the sampled feedback signal.
TAIWAN SEMICONDUCTOR MANUFACTURING COMPANY, LTD.
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Chih-Hsien Chen-Ting Cheng-Hsiang Ting-Kuei Ruey-Bin
Chang Ko Hsieh Kuan Sheen