Look-ahead enabling charge pump in phase-locked loop circuits

摘要

A technique controls a charge pump bias circuit in a phase-locked loop (PLL) circuit. The charge pump bias circuit biases a charge pump circuit. A digital phase detector generates direction control signals based on reference and pre-scale count signals from reference and pre-scale counting circuits, respectively. The direction control signals control direction of current pumped by the charge pump circuit. A charge pump enable generator generates an enable signal based on look-ahead reference and pre-scale count signals from the reference and pre-scale counting circuits, respectively. The look-ahead reference and pre-scale count signals are generated before the corresponding reference and pre-scale count signals by a predetermined time interval. The enable signal powers down the charge pump bias circuit after the charge pump circuit pumps the current.