Image Number 5 for United States Patent #8130016.
A feedback loop circuit includes a phase detector and delay circuits. The phase detector generates an output signal based on a delayed periodic signal. The delay circuits are coupled in a delay chain that delays the delayed periodic signal. Each of the delay circuits comprises variable delay blocks and fixed delay blocks that are coupled to form at least two delay paths for an input signal through the delay circuit to generate a delayed output signal. Delays of the variable delay blocks in the delay circuits vary based on the output signal of the phase detector. Each of the delay circuits reroutes the input signal through a different one of the delay paths to generate the delayed output signal based on the output signal of the phase detector during operation of the feedback loop circuit. Each of the variable delay blocks and the fixed delay blocks is inverting.