Multi-GHz loopback testing using MEMs switches and SiGe logic

This paper demonstrates the application of micro-electromechanical switches (MEMs) and SiGe logic devices for passive and active loopback testing of wide data buses at rates up to 6.4Gbps per signal. Target applications include HyperTransport, Fully-Buffered DIMM, and PCIexpress, among others. Recently-commercialized MEMs technology provides high bandwidth (>7GHz) in very small packages in order to support wide parallel buses. SiGe logic also supports >7 Gbps signals when active shaping of the waveform is required. Loopback modules are described with between 9 and 16 differential channels. Multiple cards handle very wide buses or multiple ports. Passive cards utilize MEMs for switching between the Loopback (self-test) mode and traditional ATE source/receiver channels (which are also used for DC parametric tests). It is this switching function that benefits from the MEMs increased density. Active loopback cards provide additional waveform-shaping functions, such as buffering, amplitude attenuation or modulation, deskew, delay adjustment, jitter injection, etc. The modular approach permits pre-calibration of the loopback electronics, and easy reconfiguration between design validation, characterization testing, and high-volume production testing.