Programmable current reference circuit
AssigneeAltera Corporation
InventorsWanli Chang, Gregory W. Starr
Life of this patent
Estimating the term…
Abstract
A programmable current reference circuit is described. The programmable current reference circuit includes a programmable resistance, where the programmable resistance is programmable to provide one of a plurality of resistances, where each of the plurality of resistances corresponds to one of a plurality of programmable current reference circuit outputs. In one embodiment, the programmable current reference circuit includes a current source coupled to the programmable resistance. In one embodiment, the plurality of programmable current reference circuit outputs includes a plurality of reference currents. A phase locked loop including the programmable current reference circuit is also described.
Claims39
A programmable current reference circuit comprising:
- a programmable resistance, wherein the programmable resistance is programmable to provide a plurality of resistances coupled in parallel, wherein each of the plurality of resistances comprises a plurality of resistors coupled in series and each of the plurality of resistances corresponds to one of a plurality of programmable current reference circuit outputs;
- and
- a plurality of shorting routes, wherein each shorting route comprises a switch and is coupled across at least one resistor of the plurality of resistors.
A programmable current reference circuit comprising:
- a current source;
- and
- a programmable resistance coupled to said current source, wherein the programmable resistance is programmable to provide:
- a plurality of resistances coupled in parallel, wherein each resistance of the plurality of resistances comprises a plurality of resistors coupled in series;
- and
- a plurality of shorting routes, wherein each shorting route comprises a switch and is coupled across at least one resistor of the plurality of resistors;
- wherein each of the plurality of resistances corresponds to one of a plurality of programmable current reference circuit outputs.
A phase locked loop circuit comprising:
- a signal generator;
- and
- a programmable current reference circuit coupled to said signal generator, wherein the programmable current reference circuit is programmable to provide one of a plurality of programmable current reference circuit outputs and comprises a current source and a programmable resistance coupled to the current source.
A method of providing an output clock signal, the method comprising:
- programming a programmable current reference circuit to provide one of a plurality of programmable current reference circuit outputs;
- providing a control signal to a signal generator, wherein the control signal corresponds to the one of the plurality of programmable current reference circuit outputs;
- and
- generating an output clock signal in response to the control signal.
Dependencies are inferred from the claim text.