Automated AC (timing) characterization for digital circuit testing

One of the major requirements for testing VLSI devices is the validation of its timing specifications. Timing specifications would typically include frequency, propagation delays, minimum pulse width, phase offsets, setup time and hold time measurements. Although parametric specifications may exist for a nominal speed (frequency) of operation of the digital device, it may be necessary to characterize the device under test (DUT) to determine the highest operating frequency of the DUT and the required environmental parameters to run at the highest frequency. Characterization involves measurement of setup time, hold time and pulse width of the signals. In this paper, we have presented an automated AC (timing) characterization flow for digital circuit testing. We have recommended a STIL (Standard Tester Interface Language) like syntax for the timing tests. Various timing data (setup and hold time, propagation delay etc.) are measured in the first pass of the characterization process and are automatically back annotated to the timing test flow to reduce the total test cycle time. The approach will also help in finding the maximum operating frequency of the DUT and speed binning (i.e., sorting the devices based on their operating frequency).