Miscellaneous active electrical nonlinear devices – circuits – and – Signal converting – shaping – or generating – Synchronizing
Reexamination Certificate
2005-03-22
2005-03-22
Le, Dinh T. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Signal converting, shaping, or generating
Synchronizing
C327S158000, C331S017000
Reexamination Certificate
active
06870411
ABSTRACT:
An object of this invention is to provide a phase synchronizing circuit capable of automatically adjusting a VCO such that the VCO satisfies a predetermined frequency range even in a frequency range in which the VCO oscillates by a leak current generated if a low threshold process is applied. The phase synchronizing circuit is composed of a PLL consisting of a phase comparator, a charge pump, a loop filter, a VCO, and a divider, and a calibration circuit for automatically adjusting a frequency range of the VCO. Before a convergence operation is started, a switch is closed in response to a signal Rst of the calibration circuit such that an output of the loop filter is leveled to the ground and the PLL is set to be an open loop. A VCO output Fo is set at an upper limit frequency or a lower limit frequency in response to a Vcal signal, and its frequency is measured by comparing its period with a period of a reference signal Fr, and signals Hb, Lb used for adjusting the frequency of the VCO are updated. The signals Hb, Lb are updated until the VCO satisfies the predetermined frequency range, and subsequently their values are maintained. The switch opens in response to the signal Rst, and the PLL is changed over to a close loop to start phase synchronization.
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Kokubo Masaru
Shibahara Yoshiyuki
A. Marquez, Esq. Juan Carlos
Fisher Esq. Stanley P.
Le Dinh T.
Reed Smith LLP
Renesas Technology Corp.
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