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US 6,664,828 B2Granted
Post-silicon control of phase locked loop charge pump current
AssigneeSun Microsystems, Inc.
InventorsClaude Gauthier, Brian Amick, Pradeep Trivedi, Dean Liu
Life of this patent
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Abstract
A post-silicon technique for adjusting a current of a charge pump in a phase locked loop is provided. The technique involves use of an adjustment circuit operatively connected to the charge pump, where the adjustment circuit is controllable to facilitate an internal biasing of the charge pump. Such control of the charge pump current in a phase locked loop allows a designer to achieve desired PLL performance characteristics after the PLL has been fabricated.
Claims16
An integrated circuit, comprising:
- a phase locked loop, comprising:
- a phase frequency detector that detects a phase difference between a system clock signal and a feedback clock signal,
- a charge pump, responsive to the phase frequency detector, that outputs a current on a control signal,
- a bias generator, responsive to the control signal, that generates a bias voltage, and
- a voltage controlled oscillator, responsive to the bias voltage, that generates an output clock signal;
- and
- an adjustment circuit arranged to generate independent of the feedback clock signal, an adjustment signal to the charge pump, comprising:
- a first device that selectively facilitates current flow between a power supply and the adjustment signal;
- and
- a second device that selectively facilitates current flow between the adjustment signal and ground,
- wherein the adjustment signal is controllable to adjust the current output from the charge pump.
8 more elements
An integrated circuit, comprising:
- phase locked loop means for generating an output clock signal, wherein the phase locked loop means comprises:
- comparing means for detecting a phase difference between an input clock signal and a feedback clock signal, wherein the feedback clock signal is based on the output clock signal,
- charge pumping means for generating a current on a control signal, wherein the charge pumping means is responsive to the comparing means,
- bias generating means for generating a bias voltage, wherein the bias generating means is responsive to the control signal, and
- oscillating means for generating the output clock signal, wherein the oscillator means is responsive to the bias voltage;
- and
- adjusting means for generating an adjustment signal independent of the feedback clock signal for adjusting the current output from the charge pump,
- wherein the charge pump means is responsive to the adjustment means, and
- wherein the adjusting means comprises:
- first controlling means for controlling a first current flow between a power supply and the adjustment signal;
- and
- second controlling means for controlling a second current flow between the adjustment signal and ground.
9 more elements
A phase locked loop, comprising:
- a phase frequency detector that detects a phase difference between a system clock signal and a feedback clock signal;
- a charge pump, responsive to the phase frequency detector and an adjustment circuit operatively connected to the charge pump, that generates a current signal,
- wherein the adjustment circuit is arranged to output independent of the feedback clock signal an adjustment signal that is controllable to adjust the current signal, and
- wherein the adjustment circuit comprises:
- a first device that selectively facilitates current flow between a power supply and the adjustment signal;
- and
- a second device that selectively facilitates current flow between the adjustment signal and ground;
- a bias generator, responsive to the current signal, that generates a bias voltage;
- and
- a voltage controlled oscillator, responsive to the bias voltage, that generates an output clock signal.
7 more elements
A method for post-silicon adjustment of a phase locked loop, comprising:
- comparing an input clock signal and a feedback clock signal;
- generating a current signal using a charge pump responsive to the comparing;
- selectively adjusting the current signal using an adjustment signal generated independent of the feedback clock signal by an adjustment circuit operatively connected to the charge pump, wherein selectively adjusting the current signal comprises:
- controlling a first current flow between a power supply and the adjustment signal;
- and
- controlling a second current flow between the adjustment signal and ground;
- and
- generating a bias voltage to a voltage controlled oscillator dependent on the selectively adjusting, wherein the voltage controlled oscillator generates an output clock signal.
5 more elements
Dependencies are inferred from the claim text.