Patent ID: 7622996
Filing Date: 2009-11-24
Classification: H03L

Abstract:
1. A multi-loop phase locked loop apparatus, comprising: a first loop, comprising: a second loop, comprising: a loop filter, coupled to the first charge pump and the second charge pump, for generating a control signal; a voltage control oscillator, coupled to the loop filter, for generating an oscillating signal according to the control signal; a first frequency divider, coupled to the voltage control oscillator and the first phase/frequency detector, for frequency-dividing the oscillating signal to generate the first feedback clock signal; a second frequency divider, coupled to the voltage control oscillator and the second phase/frequency detector, for frequency-dividing the oscillating signal to generate the second feedback clock signal; a control circuit, coupled to the first loop and the second loop, for switching between the first loop and the second loop to generate the control signal according to at least one of the first control current, the second control current and the control signal; and a computing unit, for computing a time parameter, wherein the control circuit switches the original used loop to the other loop if the time parameter reaches a predetermined value.