Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Synchronizing
Reexamination Certificate
2003-01-14
2004-06-29
Le, Dinh T. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Synchronizing
C327S536000
Reexamination Certificate
active
06756830
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates to current switches, such as those utilized in phase-locked loops, and more particularly to a charge pump used with a current switch.
BACKGROUND OF THE INVENTION
Current switches are utilized to supply a constant current to a load circuit, such as a phase-locked loop. The input voltage of a phase-locked loop's voltage-controlled oscillator requires high precision, and when generating input voltage by charging or discharging capacitance proportional to phase difference, the current from a current source must be precisely supplied for charging/discharging purposes.
A need has developed for a charge pump for a current switch of a phase-lock loop circuit for accurately controlling the current sources In order to shorten the phase-locked loop loading, thereby substantially increasing the initial charging current and decreasing the charging current when the phase-locked loop controlling voltage reaches the loading (settled) range.
SUMMARY OF THE INVENTION
In accordance with the present invention, a charge pump for a current switch having at least one current source is provided. The charge pump includes a current summation circuit for generating an output to the current switch. A first current source supplies a first current to the summation circuit. A second current source selectively supplies a second current to the summation circuit. A switch connects the second current source to the summation circuit, such that the current source of the current switch is proportional to the output of the summation circuit.
REFERENCES:
patent: 5144156 (1992-09-01), Kawasaki
patent: 5475326 (1995-12-01), Masuda
patent: 6064243 (2000-05-01), Matsuda et al.
patent: 6163184 (2000-12-01), Larsson
patent: 2002/0041214 (2002-04-01), Ichimura
patent: 5129945 (1993-05-01), None
patent: 11027141 (1999-01-01), None
Le Dinh T.
Locke Liddell & Sapp LLP
Sharp Corporation
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