ALL-DIGITAL MULTIPOINT ADAPTIVE DELAY COMPENSATION CIRCUIT FOR LOW SKEW CLOCK DISTRIBUTION

The authors describe an all-digital circuit for automatically controll ing skew in the distribution of a cock or data signal over a single li ne. The circuit derives a compensating delay for any location such tha t a signal applied at one end emerges at the same global time at all s ites. This is an alternative to delay-equalised hierarchical trees for use in large ICs, computers, and digital switches. A 3 mu m CMOS prot otype at eight sites spread over 16 m shows adaptive skew control to w ithin +/- 1.5 primitive buffer delays of the process employed. A novel technique for accommodating metastability is involved in the design.