Patent ID: 7692497
Filing Date: 2010-04-06
Classification: H03L

Abstract:
1. A phase locked-loop (PLL) capable of providing continuous frequency lock over a wide range of frequencies comprising: a reference frequency input; a sensing component coupled to compare the phase and frequency of the reference frequency input and a feedback frequency responsive to an output of the PLL; a low frequency filter (LF) driven by an output of the sensing component; a charge pump controlled solely by an output of the LF; a single voltage controlled oscillator (VCO) coupled to an output of the charge pump, the voltage controlled oscillator being coupled to a tunable variable load; the tunable variable load being comprised of a plurality of variable capacitors selected by load switches that are responsive to a control signal, each variable capacitor being tunable to cover a range of frequencies such that the range of frequencies is greater than the range of frequencies covered by any one variable capacitor; a comparator coupled to compare the output of the charge pump to a threshold voltage provided by a control unit; the control unit coupled to generate the control signal responsive to the output of the comparator and the threshold voltage responsive of the tunable variable load used; the high end of frequencies covered by each tunable variable load being overlapped by the low end range of frequencies covered by any tunable variable load covering the next higher range of frequencies and the low end of frequencies covered by any tunable variable load being over lapped by the high end range of frequencies covered by the any tunable variable load covering the next lower range of frequencies; the control unit, when switching the load switches from a first tunable variable toad covering a first range of frequencies to a second tunable variable load covering the next higher adjacent range of frequencies, causing the switching to occur at a higher frequency than when switching from the second tunable variable load to the first tunable variable load; enabling the PLL to operate with stability and in continuity over the fill range of frequencies covered by the VCO and the charge pump being indifferent to the variable load of the VCO.