Patent ID: 7151413

Claim:
A low noise charge pump comprising: a timing controller receiving a reference signal for generating a plurality of enable signals with non-overlapping phases, where the frequency of each enable signal is equal to the frequency of said reference signal divided by the number of said enable signals; a reference current source for supplying a bias current; a plurality of charge-pump circuits coupled in parallel and having a common output node, for generating a plurality of net output currents in a time-interleaved manner according to said plurality of enable signals where said plurality of net output currents are multiplexed together to form a charge-pump current at said common output node, each charge-pump circuit comprising: a first switch coupled to said reference current source and receiving a first control signal, for allowing said bias current to be mirrored as a pump-up current during assertion of said first control signal; a second switch coupled to said reference current source and receiving a second control signal, for allowing said bias current to be mirrored as a pump-down current during assertion of said second control signal; a first current steering unit coupled between said first switch and said common output node for steering said pump-up current; a second current steering unit coupled between said second switch and said common output node for steering said pump-down current; wherein said first and said second steering units are controlled by a corresponding enable signal from said timing controller; wherein said pump-up current is directed towards said common node and said pump-down current is directed away from said common output node during assertion of said corresponding enable signal, thereby one of said net output currents is developed at said common output node.