Patents Examined by Khareeem E. Almo
  • Patent number: 7071746
    Abstract: A variable delay circuit includes plural stages of first variable delay elements coupled in series for sequentially delaying a reference clock signal or a data signal, a second variable delay element coupled in parallel to the plural stages of first variable delay elements for delaying the reference clock signal, a phase comparator for comparing the phase of the reference clock signal delayed by the plural stages of first variable delay elements with the phase of the reference clock signal delayed by the second variable delay element, and a delay amount control unit for controlling the delay amount of each of the plural stages of first variable delay elements based on the comparison result of the phase comparator in order that the phase of the reference clock signal delayed by the plural stages of first variable delay elements is substantially the same as the phase of the reference clock signal delayed by the second variable delay element after predetermined cycles.
    Type: Grant
    Filed: April 29, 2004
    Date of Patent: July 4, 2006
    Assignee: Advantest Corporation
    Inventors: Masakatsu Suda, Satoshi Sudou, Toshiyuki Okayasu