Test Methods For Sigma-Delta Data Converters and Related Devices

ABSTRACT

This tutorial will look at the fundamental methods of digital sampling and how to apply it to sigma-delta modulators and other sigma-delta based devices. We begin by describing the principles of digital sampling and how one extends this theory to the test of sigma-delta based data converters and related devices. A review of the basic ideas of coherent testing will be given, such as the application of the M/N coherency principle for performing gain, frequency and distortion type measurements. The impact of clock jitter will also be emphasized. Next, we'll extend the sampling principle to the non-coherent test situation and describe how one performs measurements of deterministic and random signals using a pre-processing step involving windowing. Subsequently, the concept of a periodogram will be introduced and shown how it is used to estimate the power spectral density of a random signal (i.e., noise). At this point in the discussion we'll review the basic ideas behind sigma-delta modulators and their application to data conversion. We'll look at lowpass and bandpass type modulators, as well as single-loop, multi-loop multi-stage, continuous-time and sampled-data implementations. The goal is to expose the students to the underlying principles behind new IC developments and trends, rather than expose the students to detail design issues. At this point, specific issues related to estimating the power spectral density of a sigma-delta modulator using a periodogram will be described. The remainder of the tutorial will look at different ways in which sigma-delta techniques can be used for Design-For-Test. One section will describe different methods in which to generate high-precision analog signals, such as DC, sinusoids, multi-tones, Gaussian noise signals, phase and frequency modulated signals, etc. Such methods have application for retrofitting digital testers as mixed-signal testers, as well as extending the capability of existing testers. Subsequently, we'll demonstrate how sigma-delta methods can be used in a wide range of DFT/BIST circuits for SOC applications. This will include signal sources, digitizers, coherent samplers, time-domain reflectometry and transmission, and noise and jitter analyzers.

INDEX TERMS

Primary Classification:
  B. Hardware
  B.7 INTEGRATED CIRCUITS
      B.7.3 Reliability and Testing**

General Terms:
Design

Keywords:
mixed-signal testing, sigma-delta converter