Invention Grant
US08854094B2 Phase locked loop 有权
锁相环

Phase locked loop
Abstract:
A disclosed exemplary embodiment is a phase locked loop comprising a main charge pump driven by a phase error signal, and providing a first input to a loop filter. An auxiliary charge pump driven by the phase error signal feeds a second input of the loop filter. The loop filter can be an active loop filter comprising an operational amplifier and a feedback RC network. The first input of the active loop filter can be an inverting input of the operational amplifier and the second input can be a non-inverting input of the operational amplifier. An on-chip stabilizing capacitor fed by the auxiliary charge pump and coupled to the second input of the loop filter is significantly smaller than the conventional stabilizing capacitors. The loop filter outputs a regulating voltage for regulating the oscillation frequency of a voltage controlled oscillator in the phase locked loop.
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