Chip level clock tree deskew circuit
AssigneeLSI Logic Corporation
InventorRichard Schultz
Life of this patent
Estimating the term…
Abstract
A signal deskew circuit is provided, which includes first and second signal branches, each branch extending between a start location and a respective end location. Each signal branch includes a send path and a return path, which have substantially the same propagation delays. An adjustable delay buffer is coupled in the send and return paths of a first of the signal branches and has a delay, which is adjustable based on a respective adjust signal. A skew sensor coupled to the return paths of the first and second signal branches, which generates the respective adjust signal for the adjustable delay buffer based on a phase difference between signals on the return paths of the first and second signal branches.
Claims19
A signal deskew circuit, comprising:
- first and second signal branches, each extending between a start location and a respective end location and having a send path and a return path that have substantially the same propagation delays;
- a first adjustable delay coupled in the send and return paths of the first signal branch and having a delay, which is adjustable based on a respective adjust signal;
- a first skew sensor coupled to the return paths of the first and second signal branches, which generates the respective adjust signal for the first adjustable delay based on a phase difference between signals on the return paths of the first and second signal branches;
- and
- a phase-locked loop having a reference input, a feedback input coupled to the send path of one of the first and second signal branches at the end location, and an output coupled to the send path at the start location of that signal branch.
A method of adjusting phase differences on an integrated circuit, the method comprising:
- passing periodic signals along a plurality of signal branches, which extend between a start location and respective end locations on the integrated circuit and have a send path and a return path that have substantially the same propagation delays;
- sensing a phase difference between the periodic signals along the return paths of a first and a second of the signal branches;
- adjusting a propagation delay along the send path and a propagation delay along the return path of the first signal branch based on the phase difference;
- receiving a reference periodic signal;
- driving a source periodic signal onto the send paths of the plurality of signal branches from the start location to form the plurality of periodic signals;
- and
- adjusting a phase of the source periodic signal such that phases of at least one of the periodic signals at the respective end location aligns with a phase of the reference periodic signal.
A signal deskew circuit, comprising:
- first and second signal branches, each extending between a common start location and a respective end location and having a send path and a return path that have substantially the same propagation delays;
- adjustable delay in the send and return paths of the first signal branch, which is adjustable based on an adjust signal;
- a skew sensor, which generates the adjust signal based on a phase difference between signals on the return paths of the first and second signal branches;
- and
- means for aligning a phase of a signal at the end location of at least one of the first and second signal branches with a phase of an external clock signal.
Dependencies are inferred from the claim text.