REAL-TIME DATA COMPARISON FOR GIGAHERTZ DIGITAL TEST

A system hus been described [I -61 for testing digital ECL or GaAs devices at rates above 1 Gbps. This system utilizes GaAs multiplexers for combining data ffom several (4 or 8) tester channels to form high speed data sources which are then used as DUT stimuli. Until recently, one of the main limitations of this approach has been the lack of comparable performance &multiplexers or, alternatively real time comparator electronics. In place of these, multi-pass testing can be used if the test system comparators have a high enough bandwrdth [7]. In ths paper, recent enhancements to the data generation electronics of the UHF test system are first reviewed. Next, designs are presented for high speed comparison circuits. These perform real-time comparison of DUT output patterns with expected data at rates above 500 Mbps.