Controlled slew reference switch for a phase locked loop

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United States of America Patent

PATENT NO 6362670
SERIAL NO

09632952

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Abstract

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A controlled slew reference switch circuit is provided for limiting the phase deviation of a phase locked loop (PLL) output signal in response to the PLL switching between a plurality of input reference clock signals. The PLL includes a phase detector for measuring the phase deviation between two input signals. The controlled slew reference switch circuit includes a transfer function generator that controls one or more selector circuits for operating the PLL in a normal mode of operation and a holdover mode of operation. In the normal mode of operation the PLL is locked to one of the reference clock signals, and the phase detector inputs are coupled to the reference clock signal and a PLL feedback signal. In the holdover mode of operation both inputs of the phase detector are coupled to the PLL feedback signal, thereby holding the PLL in its last operational state. By controlling the amount of time that the PLL operates in the holdover mode versus the normal mode of operation, the controlled slew reference switch circuit controls the gain of the PLL and thereby limits the phase deviation of the PLL output signal.

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Patent Owner(s)

Patent OwnerAddress
MARCONI INTELLECTUAL PROPERTY ( RINGFENCE) INC3000 MARCONI DRIVE WARRENDALE PA 15086

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Inventor(s)

Inventor Name Address # of filed Patents Total Citations
Beaulieu, Rejean Mercier, CA 5 31

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