Patent ID: 7271619

Claim:
A charge pump circuit for providing a VCO control output, the charge pump circuit comprising: a low pass filter having a resistor and a first capacitance that are connected in series between a first output terminal and a ground terminal, and a second capacitance connected in parallel to the first capacitance between the first output terminal and the ground terminal the VCO control output being output from the first output terminal; a first P-channel MOS transistor having a source, a drain connected to the first output terminal and a gate receiving a first signal; a first N-channel MOS transistor having a source, a drain connected to the first output terminal and a gate receiving a second signal; another P-channel MOS transistor having a source, a drain connected to a second output terminal which is connected between the resistor and the first capacitance, and a gate receiving the first signal; another N-channel MOS transistor having a source, a drain connected to the second output terminal and a gate receiving the second signal; a first current source for providing a current of first level to the source of the first P-channel MOS transistor; a second current source for providing a current of second level to the source of the first N-channel MOS transistor; a third current source for providing a current of third level to the source of the another P-channel MOS transistor; and a fourth current source for providing a current of fourth level to the source of the another N-channel MOS transistor.