Biasing circuit for setting bias volatges of current source circuit and current sink circuit in charge pump of phase-locked loop circuit by using current digital-to-analog converter and low-pass filter

A charge pump of a phase-locked loop (PLL) circuit, comprising:

• a current source circuit, arranged to provide a source current for charging an output node of the charge pump, wherein the source current is controlled by a first bias voltage applied to the current source circuit;
• a current sink circuit, arranged to provide a sink current for discharging the output node of the charge pump, wherein the sink current is controlled by a second bias voltage applied to the current sink circuit;
• and
• a biasing circuit, arranged to set the first bias voltage and the second bias voltage, wherein the biasing circuit comprises:
• a current digital-to-analog converter, arranged to provide a reference current in response to a current value setting, wherein a first voltage is established due to the reference current;
• and
• a low-pass filter, arranged to apply low-pass filtering to the first voltage to generate a filter output as a second voltage, wherein the first bias voltage and the second bias voltage are both controlled by the second voltage.