Automatically ranging phase locked loop circuit for microprocess

Details Automatically ranging phase locked loop circuit for microprocess Automatically ranging phase locked loop circuit for microprocess

1998-01-30

1999-05-11

Mis, David

Oscillators

Automatic frequency stabilization using a phase or frequency...

Search sweep of oscillator

331 8, 331 17, 331 57, 331179, 331DIG2, 327156, H03L7/12;7/095

Patent

active

059031956

ABSTRACT:
An improved phase locked loop (PLL) circuit is provided for use in microprocessor clock generation. A ring oscillator provides an output frequency signal. A voltage to current converter converts differential control voltages to a variable reference current applied to the ring oscillator. A range control reference current generator applies a range control reference current to the ring oscillator. A range control operatively controls the range control reference current generator to sequentially change the range control reference current applied to the ring oscillator. A lock detector coupled to the range control compares the output frequency signal and a reference frequency signal and responsive to the compares signals applies a locked signal to the range control. Responsive to an applied locked signal, the range control stops changing ranges. The phase locked loop (PLL) circuit automatically sweeps through multiple frequency subranges responsive to the range control. A control signal is applied to the voltage to current converter for selectively controlling an operational mode of the voltage to current converter from a squelched operational mode to an unsquelched operational mode after a set time period. This control signal also is applied to the range control, so that the range control stops changing ranges.

REFERENCES:
patent: 5349311 (1994-09-01), Mentzer
patent: 5389898 (1995-02-01), Taketoshi et al.
patent: 5477198 (1995-12-01), Anderson et al.
patent: 5686864 (1997-11-01), Martin et al.
patent: 5757240 (1998-05-01), Boerstler et al.
patent: 5777520 (1998-07-01), Kawakami
Barret, W.M., "Automatic Detection of Oscillator Frequency Drift", Research Disclosure, Dec. 1992, No. 344, Kenneth Mason Publications Ltd, England.

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