Self-calibrating phase-lock loop with auto-trim operations for s

Details Self-calibrating phase-lock loop with auto-trim operations for s Self-calibrating phase-lock loop with auto-trim operations for s

1998-01-20

1999-08-24

Mis, David

Oscillators

Automatic frequency stabilization using a phase or frequency...

Particular error voltage control

331 1A, 331 11, 331 14, 331 25, 327157, 327159, H03L 7087, H03L 7099, H03L 710, H03L 7107

Patent

active

059429496

ABSTRACT:
A phase-lock loop (PLL) has an oscillator having a plurality of operating curves. During PLL auto-trim operations, the oscillator is automatically trimmed to an appropriate oscillator operating curve for use during normal PLL operations. In particular embodiments, the PLL is a charge-pump PLL having a phase/frequency detector (PFD) that generates error signals based on comparing an input signal and a PLL feedback signal; a charge pump that generates amounts of charge corresponding to the error signals; a loop filter that accumulates the amounts of charge to generate a loop-filter voltage; and a voltage-controlled oscillator (VCO), where the VCO output signal is used to generate the PLL feedback signal. During normal PLL operations, the loop-filter voltage is applied to the voltage input of the VCO. During the PLL auto-trim operations, a state machine applies a sequence of digital control input values to the VCO to select different VCO operating curves until an appropriate operating curve for the present PLL application is found. In different embodiments, the state machine uses different signals to determine whether the center frequency of each operating curve in the sequence is above or below the desired nominal operating frequency for the VCO, and select one such operating curve for use in normal operations.

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"Charge-Pump Phase-Lock Loops", by Floyd M. Gardner, IEEE Trans. Commun., vol. COM-28, pp. 1849-1858, Nov. 1980, pp. 321-329.

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