Charge pump circuit for phase locked loop free from spike curren

Details Charge pump circuit for phase locked loop free from spike curren Charge pump circuit for phase locked loop free from spike curren

1999-07-19

2000-12-19

Callahan, Timothy P.

Miscellaneous active electrical nonlinear devices, circuits, and

Signal converting, shaping, or generating

Synchronizing

327159, 327 66, 323312, 323315, 307110, H03L 706

Patent

active

061631876

ABSTRACT:
A phase locked loop has a charge pump circuit connected through a loop filter to a voltage controlled oscillator, and the charge pump circuit is controlled by a frequency/phase comparator, wherein the charge pump circuit includes a first current mirror circuit responsive to a first control signal for regulating a discharging current from the loop filter to a first target amount proportional to a constant current, a second current mirror circuit for regulating a reference current to a second target amount proportional to the constant current and a third current mirror circuit responsive to a second control signal for regulating a charging current to the loop filter to a third target amount proportional to the reference current, a first switching circuit for charging a first parasitic capacitor coupled to the first current mirror circuit from the constant current source and a second switching circuit for charging a second parasitic capacitor coupled to the third current mirror circuit through the second current mirror circuit, thereby setting a limit on a spike current generated at a change of the first and second control signals.

REFERENCES:
patent: 5045773 (1991-09-01), Westwick et al.
patent: 5512816 (1996-04-01), Lambert
patent: 5627490 (1997-05-01), Sushihara et al.
patent: 5656969 (1997-08-01), Pulvirenti et al.
patent: 5668501 (1997-09-01), Venes
patent: 5677621 (1997-10-01), Bult et al.

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