Practical considerations in applying Σ-Δ modulation-based analog BIST to sampled-data systems

摘要

The analog built-in self-test (BIST) scheme, with stimulus generation and response extraction based on the Σ-Δ modulation, is proven to be quite effective for sampled-data systems. We show that the Σ-Δ modulators can be selected optimally for certain applications and functional tests. The criteria for valid tests are also derived. In particular, a valid frequency response test is determined by the frequency response observation range FRORBIST(z) of the BIST circuit. Given the transfer function HCUT(z) of the circuit under test, the requirement becomes FRORBIST(z)≫|1/HCUT(z)|. Using the MOSIS 0.35-μm CMOS process, we have implemented a test chip containing a Fleischer-Laker biquadratic low-pass filter as the circuit under test. An on-chip one-bit digital-to-analog converter provides the analog stimulus from a bit stream which is applied externally. For each test item, different bit streams, synthesized by first-, second-, and fourth-order Σ-Δ modulators that are programmed by software, are compared for performance. First- and second-order Σ-Δ modulators are implemented on the test chip as the candidates for the analog response extractor. The measurement results by single-tone tests and multitone tests validate the feasibility of the BIST scheme.