Jump the Q: A fast jitter tolerance measurement method using Q-statistical model

Abstract

With high-speed receivers and clock data recovery (CDR) blocks operating at speeds in excess of 10 Gbps, stringent CDR jitter tolerance test criteria are necessary to qualify device reliability. A robust CDR jitter tolerance test should accommodate test criteria with extremely low bit error rate (BER) values, usually 10−12 or lower for typical industrial protocols. Using conventional methods, the time required to measure a complete set of CDR jitter tolerance values can stretch into weeks depending on the data rate. In general, measurement time increases tenfold for a similar tenfold reduction in BER. This translates to prohibitively long measurement times for BER values of 10−15 and lower. Statistical extrapolation for low BER measurement such as Q scale has been widely used in the industry, but this is only applied for transmitter measurements, specifically jitter measurements. This paper introduces a novel, fast measurement method for receiver testing based on the Q-statistical method to predict the BER for high-volume data transmission based on small sample data sets. Experimental data using this method show that extrapolated jitter tolerance values for BER values down to 10−15 can achieve an accuracy of 1.25 mUI. This innovative method improves the efficiency of jitter tolerance tests by significantly reducing measurement time. Furthermore, the method allows for the extension of measurement scope to cover previously unattainable jitter tolerance values for lower BER values. With these advantages, full jitter tolerance characterization on Altera Stratix® IV GX devices successfully meets very aggressive product rollout and time-to-market schedule, even with measurements for 24 protocols and support for BER of 10−12 and lower.