Curtis R Robinson

US Patent:

55436978, Aug 6, 1996

Filed:

Oct 27, 1994

Appl. No.:

8/330316

Inventors:

Francesco Carobolante - Portola Valley CA
Curtis Robinson - Sunnyvale CA

Assignee:

SGS-Thomson Microelectronics, Inc. - Carrollton TX

International Classification:

G05B 1118

US Classification:

318594

Abstract:

A method and circuit for implementing a frequency lock loop circuit in a disk drive is disclosed. The circuit includes the motor control elements of a direct current motor plus a coarse counter, a fine counter, and a digital to analog converter. The coarse counter is used to count down from a programmed coarse count. The fine counter begins to count down from a fine count when the coarse counter reaches zero. The count in the fine counter, when a zero crossing occurs, represents the difference between the expected period and the actual period and is loaded into a digital to analog converter which converts the difference to an analog voltage which is used by the coil drive circuit to either speed up or slow down the motor. The digital to analog conversion may be realized by a charge pump circuit.