A production-oriented multiplexing system for testing above 2.5 gbps

A system for testing multi-gigahertz digital devices is described that uses conventional automated test equipment (ATE), supplemented with multiplexing and sampling logic. The approach is similar to earlier work [I] that demonstrated feasibility. However, this current paper solves many of the practical problems that limited application in production environments. Specifically, embedded logic is used for fastheliable auto-calibration of critical timing signals to achieve improved accuracy (typically 225~s). Variable output-level buffers are included in the multiplexing logic to provide a range of input levels to the device under test. Coaxial relays selectively switch between high-speed and DC modes of testing. Air- and liquid-cooling is used to maintain the electronics temperature, and thereby stabilize time delays. The production version of the system is scalable up to 144 high speed differential pairs, each operating at 2.5 Gbps. Overall timing accuracy (OTA) is about +loops, and is typically much better. Timing errors are found to be dominated by the ATE timing uncertainty, which is nevertheless improved through the use of the embedded calibration logic [patent pending]. The OTA includes peakto-peak jitter (at a bit error rate of 10'l2). The system is demonstrated by applying it to an AMCC 17x17 cross point switch that supports data rates as high as 3.2 Gbps. Additional electronic modules are under development that will further extend the maximum data rate (initially to 3.2 Gbps, then to 5 Gbps and above), while tightening the OTA.