Charge pump steering systems and methods for loop filters of pha

Details Charge pump steering systems and methods for loop filters of pha Charge pump steering systems and methods for loop filters of pha

1997-08-28

2000-02-22

Pham, Chi H.

Pulse or digital communications

Synchronizers

Phase displacement, slip or jitter correction

327156, 331 1A, H03D 324, H03L 706, H03L 700

Patent

active

060289058

ABSTRACT:
Charge pump steering systems and methods force a charge pump of a loop filter of a phase locked loop to charge or discharge a capacitor for a predetermined time that it is independent of the phase detector error signal. Thereafter, the charge pump is activated in response to a phase detector error signal. Accordingly, rather than relying on the error signal to activate a charge pump, the charge pump may be activated for a period of time which will add or remove a requisite amount of charge to or from the loop filter. Decreased lock times can thereby be produced while allowing a reduction of the size and cost of the charge pump. The invention is preferably applied to an integral charge pump in a phase locked loop.

REFERENCES:
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patent: 5384551 (1995-01-01), Kennedy et al.
patent: 5483558 (1996-01-01), Leon et al.
patent: 5546053 (1996-08-01), Ichimaru
patent: 5614870 (1997-03-01), Sauer et al.
patent: 5734301 (1998-03-01), Lee et al.
International Search Report, PCT US98/17652, Dec. 11, 1998.
Sadowski, "PLL With Additional Speed-Up Charge Pump", RF Design, vol. 18, No. 1, Jan. 1995, pp. 83-87.
National Semiconductor Products for Wireless Communications Databook, Mar. 1997, pp. 1-98.
Semiconductors for Wireless Communications, Philips Data Handbook IC17, Philips Semiconductors, Feb. 1996 at p. 744.

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