Sigma-Delta Converters: Practical Design Guide, 2nd Edition

7 Electrical Design of Ms: From Systems to Circuits

The modeling, simulation and optimization techniques described in Chapters 5 and 6 are needed for the high‐level synthesis and verification of Ms, so that the modulator‐level performance metrics are efficiently mapped onto building‐block (circuit‐level) specifications. Thus, at this stage of the design cycle, the modulator is still realized at system‐level, but the electrical performance parameters of all M circuit elements (switches, capacitors, amplifiers, transconductors, comparators, and so on) have already been determined in the high‐level sizing process. These parameters are in turn the circuit‐level specifications, which constitute the start point for the electrical (transistor‐level) and physical design of the modulator. This process – conceptually illustrated in Figure 7.1 – comprises a number of successive steps in which the initial (system‐level) behavioral‐model version of the modulator is transformed into a circuit schematic – initially implemented with macromodels and finally with transistors – afterwards into a layout, and finally into a chip implementation for experimental measurement in a laboratory.