Characteristic faults and spectral information for logic BIST

We present a new method of built-in-self-test (BIST) for sequential circuits and system-on-a-chip (SOC) using characteristic faults and circuit-specific spectral information in the form of one or more Hadamard coefficients. The Hadamard coefficients are extracted from the test sequences for a small set of characteristic faults of the circuit. By extracting a few characteristic faults from the circuit, we show that detection of these characteristic faults is sufficient in detecting a vast majority of the remaining faults in the circuit. The small number of characteristic faults allows us to reduce the coefficients necessary for BIST. State relaxation is performed on the compacted test sequences to reduce the spectral noise further. Since we are targeting only a very small number of characteristic faults, the execution times for computing the spectra are greatly reduced. Our experimental results show that our new method can achieve high BIST coverage with both lower computational efforts and storage, with very few characteristic faults.