The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 09, 2003
Filed:
Mar. 31, 1999
Douglas R. Holberg, Wimberley, TX (US);
Sandra M. Johnson, Buda, TX (US);
Cirrus Logic, Inc., Austin, TX (US);
Abstract
A phase locked loop in an imaging system is used to generate signals on one of eight equal phase steps within a clock period. The phase locked loop outputs eight clock phases, or four clock phases and their complements, each running at the pixel rate, eliminating the need for higher speed circuitry. According to one embodiment, the phase locked loop employs an oscillator with three inverting stages and one non-inverting stage. The output of each stage is shifted in phase 45 degrees from the previous one, in terms of pixel clock rate. Differential stages are employed so that the delay of the inverting and non-inverting stage are the same. According to the present invention, the output of the last stage is swapped onto the input of the first stage, making it non-inverting without path delay, permitting oscillation with each stage's output remaining at 45 degrees of the previous stage's phase.