Self-biased phase-locked loop
AssigneeInternational Business Machines Corporation
InventorsJohn E. Gersbach, Masayuki Hayashi, Charles J. Masenas
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Abstract
According to the preferred embodiment, a self-biased phase-locked loop is provided that overcomes the limitations of the prior art bias methods and apparatus. In general, a self-biased current controlled semiconductor device, typically a current controlled oscillator, is self biased by the use of a first feedback path, typically provided by a phase-locked loop, where the feedback path provides a control current for controlling the current controlled device. A second feedback path, typically a pair current mirrors, serves as a bias loop having unity gain. The bias loop provides a bias current that is responsive to the control current. This device has the advantage of being self biasing, thus no other biasing circuitry is required.
Claims22
A current controlled semiconductor device, wherein said current controlled semiconductor device is biased with a bias current, said device comprising:
- a) a first feedback path, said first feedback path dynamically controlling an output of said current controlled semiconductor device with a control current;
- and
- b) a second feedback path, said second feedback path including a bias loop, said bias loop determining the magnitude of said control current and thereby providing said bias current in response to said control current.
A self-biased current controlled oscillator in a phase-locked loop, wherein said current controlled oscillator generates an output signal with a frequency proportional to an input current, wherein said input current includes the sum of a bias current and a control current and wherein said control current is supplied by said phase-locked loop, said current controlled oscillator comprising:
- a) a first current mirror, said first current mirror sinking said input current;
- b) a second current mirror forming a feedback loop with said first current mirror, said feedback loop providing said bias current to said current controlled oscillator, wherein said bias current tracks said input current.
A self-biased phase-locked loop, wherein said phase-locked loop includes a current controlled oscillator, a voltage-to-current converter and a charge pump, wherein said current controlled oscillator generates an output signal with a frequency proportional to an input current, the self-biased phase-locked loop comprising:
- a) a first current mirror, said first current mirror mirroring a current responsive to said input current;
- b) a second current mirror forming a feedback loop with said first current mirror, said feedback loop having substantially unity gain and providing a first bias current to said current controlled oscillator which is dynamically controlled by said feedback loop to track said input current;
- c) a third current mirror, said third current mirror supplying a second bias current to said voltage-to-current converter that is proportional to said first bias current;
- d) a fourth current mirror, said fourth current mirror supplying a third bias current to said charge pump that is proportional to said first bias current of said current controlled oscillator;
- e) a start-up mechanism, said start-up mechanism supplying a start-up current to said second current mirror on power up of said phase-locked loop, said start-up mechanism turning off said start-up current when said first bias current is established.
A method for self biasing a current controlled device, wherein an output of said current controlled device is determined by an input current, the method comprising the steps of:
- a) providing an input current to said current controlled device:
- b) dynamically adapting said input current to control said output;
- c) mirroring back said input current along a feedback bias loop;
- d) inputting said mirrored input current to said current controlled device as a bias current.
A method for self-biasing a current controlled oscillator in a phase-locked loop wherein the frequency of an output of said current controlled oscillator is determined by an input current, the method comprising the steps of:
- a) providing a control current in response to a detected phase difference between said output and a reference input, said control current being proportional to said detected phase difference;
- b) driving said current controlled oscillator with said input current, said input current including the sum of said control current and a bias current;
- c) mirroring said input current back to said current controlled oscillator, said mirroring back supplying said bias current to said current controlled oscillator.
Dependencies are inferred from the claim text.