Practical considerations in applying (sigma)-(delta) modulation-based analog BIST to sampled-data systems

The analog built-in self-test (BIST) scheme, with stimulus generation and response extraction based on the (sigma)-(delta) modulation, is proven to be quite effective for sampled-data systems. We show that the (sigma)-(delta) 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 FROR/sub BIST/(z) of the BIST circuit. Given the transfer function H/sub CUT/(z) of the circuit under test, the requirement becomes FROR/sub BIST/(z)>|1/H/sub CUT/(z)|. Using the MOSIS 0.35-(mu)m 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 (sigma)-(delta) modulators that are programmed by software, are compared for performance. First- and second-order (sigma)-(delta) 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.