Patent ID: 7405630
Filing Date: 2008-07-29
Classification: H03L

Abstract:
1. A loop filter for use in a frequency synthesizer, comprising: a first switched capacitor including a first metal capacitor having a first capacitance value and operable to charge to a first voltage corresponding to a current pulse indicative of a difference in phase or frequency between a reference signal and a feedback signal, and first switched capacitor further including a first switch coupled to said first metal capacitor and operable in a first state to enable said first metal capacitor to charge to said first voltage and in a second state to discharge said first metal capacitor; and a second switched capacitor having a second capacitance value and operable to charge to a second voltage from said first voltage and produce a control voltage based upon said second voltage; wherein said loop filter has a bandwidth determined by a ratio of said second capacitance value to said first capacitance value.