IC Mixed-Signal BIST: Separating Facts from Fiction

Introduction The first papers that proposed on-chip mixed-signal built-in self-test (MS-BIST) were published about ten years ago [1]. The first commercial products were announced five years ago at ITC’97 – LogicVision’s adcBIST [2] and pllBIST [3]. The latter tests more PLL parameters than most companies do, and everything is done on-chip in 4K gates: stimulus, response analysis, and comparison to limits. However, PLLs are not what most IC designers consider mixed-signal functions. Mixedsignal functions are more popularly deemed to be ADCs, DACs, filters, amplifiers, power regulators, mixers, etc.. BIST, by definition, requires on-chip generation of the stimulus, and on-chip analysis of the response, sufficient to produce a pass/fail result or a series of bits that any tester can compare bit-wise to the expected bit values. Many so-called MS-BIST approaches in fact require the ATE to supply the stimulus (analog waveform, or sigmadelta bit stream), or perform some response analysis (DSP, histogram processing, or RMS calculation), especially when >10 bits linearity is being tested.