On-die clock jitter detector for high speed microprocessors

An on-die clock jitter detector has been designed for high speed microprocessor circuits and fabricated in 0.18 /spl mu/m CMOS technology. Variation of internal clock high/low time or period has been recorded. Innovative circuit techniques are used to provide fast initial DLL lock, adaptive filtering, granular jitter computation, and enhanced immunity to power-supply noise. It compares individual clock cycles to the average clock period, reporting the differences. The system has multiple output modes to allow more complete understanding of the jitter distribution and time dependence.