US Patent 7834707 Linearized charge pump having an offset

A charge pump provides charge based on a phase difference between a reference signal and a feedback signal. The relationship between the charge and the phase difference is referred to as the charge phase relationship. Charge pumps typically have a non-linear charge phase relationship. A non-linear portion of the charge phase relationship occurs about a point at which the charge and the phase difference are substantially zero. Points along charge phase relationship that represent the performance of charge pump are referred to as the charge phase characteristic of the charge pump. The charge pump includes an offset current circuit, which biases the charge pump to have a linear charge phase characteristic. For example, the charge pump is biased to have a charge phase characteristic that does not overlap with the non-linear portion of the charge phase relationship.