Patent ID: 7042253
Filing Date: 2006-05-09
Classification: H03L

Abstract:
1. A frequency synthesizer having an input (“Vin”) and at least one output (“Vout”) with variable frequency, the output frequency varying as a capacitance within the frequency synthesizer varies, comprising: a voltage-controlled oscillator (“VCO”) integrated with said frequency synthesizer, said VCO generating said output with a variable frequency, said VCO having a discretely variable capacitance selectably controllable by a first control signal and a continuously variable capacitance selectably controllable by a second control signal; a frequency-locked loop circuit (“FLL”) integrated with said frequency synthesizer, said FLL receiving said Vin and generating said first control signal to said VCO, such that the frequency of said Vout approaches the frequency of said Vin; a phase-locked loop circuit (“PLL”) comprising said VCO, said PLL receiving said Vin and generating said second control signal, such that the phase of said Vout approaches the phase of said Vin, wherein: said first control signal generated by said FLL is a multi-bit signal which controllably increments and decrements the capacitance of said VCO based on a relative comparison between said Vin and said Vout as to which one has a higher frequency; said FLL generates a de-activate signal to de-activate a phase detector of said PLL to isolate said phase detector from said VCO while said FLL is operational by causing a fixed voltage to be applied to said variable capacitance of said VCO; said PLL is activated to control said VCO after said FLL's operation.