US Patent 10523218 Track-and-hold charge pump and PLL

Track-and-hold charge pumps and PLL are provided. A track-and-hold charge pump includes a track-and-hold circuit, a transconductance amplifier, a pulse width modulator (PWM), and a pumping switch coupled to the transconductance amplifier. The track-and-hold circuit samples an input signal according to a reference clock. The transconductance amplifier converts the sampled input signal into a current. The PWM provides a PWM signal according to the reference clock. The pumping switch is controlled by the PWM signal, to provide an output current according to the current.