A Cost Effective Output Response Analyzer for sum - delta Modulation Based BIST Systems

A cost effective output response analyzer (ORA) for Sigma-Delta modulation based BIST systems is presented. Instead of using fast Fourier transform (FFT) to derive the signal-to-noise-and-distortion ratio (SNDR) in frequency domain, the proposed ORA using the modified controlled sine wave fitting procedure to calculate the signal power and the total-harmonic-distortion-and-noise power in time domain separately. It requires neither parallel multiplier nor complex CPU/DSP and bulky memory thus has a low cost. A second-order design-for-digital-testability Sigma-Delta modulator is used as the circuit under test example. Simulation results show that the SNDR differences between conventional FFT analysis and the proposed ORA have a mean and standard deviation of 0.64 dB and 0.36 dB respectively. The cost effectiveness and satisfying accuracy features make it suitable for embedded BIST applications