High-Speed Wide-Locking Range VCO with Frequency Calibration (Special Section on VLSI Design and CAD Algorithms)

概要

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High-speed systems require a wide-frequency-range clock system for data processing. Phase-locked loop(PLL) is used for such a system that requires wide-range variable frequency clock. Frequency calibration method enables the voltage-controlled oscillator(VCO) in a PLL to cover the expected frequency range for high-speed applications that require a wide locking range. Frequency range adjustment is implemented by means of a current digital to analog converter(DAC), which controls the performance curves of a VCO and a bias circuit. This method adjusts the VCO's frequency-voltage performance curves before functional operation so that a PLL can cover requested frequency range with its best condition. Both the limit of control voltage and its target reference voltage are given with same voltage reference. This ensures correct performance after frequency adjustment even under the temperature fluctuation. It eliminates post-production physical adjustment such as fuse trimming which increases the cost and TAT in manufacturing and testing. A high-speed wide-locking range VCO with an automatic frequency performance calibration circuit is implemented within small space in a high-speed hard disk drive channel with 0.25-μm 2.5V CMOS four-layer metal technology.
2000-12-25