SAMPLED-DATA SIMULATION OF OVER-SAMPLED SIGMA-DELTA MODULATORS - Computer Methods for Analysis of Mixed-Mode Switching Circuits - page 189

Chapter 9
SAMPLED-DATA SIMULATION OF
OVER-SAMPLED SIGMA-DELTA
MODULATORS
This chapter applies the sampled-data simulation algorithm for peri-
odically switched linear circuits presented in Chapter 6 to a special class
of nonlinear circuits - over-sampled sigma-delta modulators. Section
1 presents the characteristics of over-sampled sigma-delta modulators
and the difficulties encountered in analysis of these circuits. In Section
2, the behavior modeling of clocked quantizers of over-sampled sigma-
delta modulators that convert analog signals into a sequence of digital
bits is investigated. Unclocked quantizers are addressed in Section 3.
We show that by utilizing the methods for circuits with internally con-
trolled switches, sigma-delta modulators with unclocked quantizers can
be analyzed. Section 4 investigates the modeling of single-bit digital-
to-analog data converters. The modeling of other blocks of sigma-delta
modulators are dealt with in Section 5. In Section 6, the simulation
methods that utilizing both the behavioral modeling of the quantizers
and the sampled-data simulation of periodically switched linear circuits
are addressed in detail. In Section 7, both continuous-time and switched
capacitor over-sampled sigma-delta modulators are analyzed using the
method developed in this chapter and the results are presented. Con-
cluding remarks are given in Section 8.