Phase locked loop with a charge pump current limiting arrangement

摘要

The PLL has charge pump which charges and discharges a capacitive filter as a function of charge and discharge control signals (HIGH,LOW). The control signals are modified at the output (HIGH3,LOW3) by a limiter unit. The limiter unit has two window circuits (840,860), one each for the high and low states. The window circuits limit the duration of the control signals when the PLL is in a locked state. The value of the charge and discharge current is limited when the PLL is not in a locked state.