Patent ID: 8427210

Claim:
A charge pump for providing a current to a control node according to a phase comparing signal, the charge pump comprising: a first current source unit, electrically connected between a first voltage terminal and the control node, wherein the first current source unit provides a first switching current to the control node according to the phase comparing signal; and a second current source unit, electrically connected between the control node and a second voltage terminal, comprising: a first sub-switching current generator, electrically connected to the control node and the second voltage terminal, wherein the first sub-switching current generator generates a first sub-switching current according to the phase comparing signal; a second sub-switching current generator electrically connected to the control node and the second voltage terminal, wherein the second sub-switching current generator generates a second sub-switching current according to the phase comparing signal; and a select circuit electrically connected to the first sub-switching current generator and the second sub-switching current generator, wherein according to a voltage level at the control node, either the first sub-switching current or the second sub-switching current is selected by the select circuit so as to be provided to the control node.