Supply voltage tolerant phase-locked loop circuit

Abstract

A phase-locked loop design is provide that can operate at a plurality of dissimilar supply voltages. By adjusting the frequency range of a PLL based on the power supply voltage, the same PLL design can operate at different supply voltages.

I claim: .[. 
     
       1.  A method for operating a phase-locked loop, comprising the steps of: detecting a supply voltage; and   adjusting the operating frequency of the phase-locked loop based upon the detected supply voltage..].   
     
     
       2. A method to adjust the frequency range of a phase-locked loop, comprising the steps of: detecting a supply voltage; and   enabling or disabling one or more frequency dividers in the PLL based upon the detected supply voltage. .[.3. A method to adjust the frequency range of a phase-locked loop (PLL), comprising the steps of:   detecting a supply voltage; and   adjusting a PLL reference voltage or current based upon the detected supply voltage..]..[.4. A phase-locked loop, comprising:   means for detecting a supply voltage; and   means for adjusting the operating frequency of the phase-locked loop based   
     
     
        upon the detected supply voltage..].5. A system for adjusting the frequency range of a phase-locked loop, comprising: means for detecting a supply voltage; and   means for selectively enabling at least one frequency divider in the PLL   
     
     
        based upon the detected supply voltage. .[.6.  A system for adjusting the frequency range of a phase-locked loop (PLL), comprising: means for detecting a supply voltage; and   means for adjusting a PLL reference voltage or current based upon the detected supply voltage..]..[.7. A phase-locked loop circuit powered by a supply voltage, comprising:   at least one current source which adjusts the reference operating point of an oscillator in said phase-locked loop based upon the supply voltage..]..[.8. A phase-locked loop circuit powered by a supply voltage, comprising:   a phase detector operatively coupled to a charge pump;   a filter operatively coupled to the charge pump;   an oscillator, operatively coupled to the filter, said oscillator having a reference operating point; and   adjusting means for dynamically adjusting the reference operating point based upon the supply voltage..]..[.9. The circuit of claim 8 wherein the adjusting means comprises a plurality of current sources..]..[.10. The circuit of claim 9 further comprising means for selectively enabling at   
     
     
        least one of the plurality of current sources..].11. A circuit for adjusting the .[.reference operating point.]. .Iadd.frequency range .Iaddend.of a phase-locked loop, comprising: a differential amplifier having a reference voltage input and a scaled supply voltage input.Iadd., said differential amplifier generating an output that is proportional to a difference between said reference voltage input and said scaled supply voltage input.Iaddend.;   a linear current source having at least one input coupled to .[.an.]. .Iadd.said .Iaddend.output of .[.the.]. .Iadd.said .Iaddend.differential amplifier.Iadd., said linear current source providing a current output related to said output of said differential amplifier.Iaddend.; and   a fixed current source coupled to an output of the linear current source.Iadd., said fixed current source generating an output and, together with said current output of said linear current source, being used to adjust a signal applied to the phase-locked loop.Iaddend.. .[.12. A phase-locked loop circuit powered by a supply voltage, comprising:   a phase detector operatively coupled to a charge pump;   a filter operatively coupled to the charge pump;   an oscillator, operatively coupled to the filter, said oscillator having a reference operating point; and   at least one current source which adjusts the reference operating point of   
     
     
        said oscillator based upon the supply voltage..]..Iadd.13.  A circuit of claim 11 wherein said scaled supply voltage input is provided using a supply voltage and said reference voltage input is provided independently of said supply voltage. .Iaddend.