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This paper demonstrates the possibility to automate most critical parts of the design of high-resolution interface circuits. We present measurements from CMOS prototypes of a 16bit@16Khz second-order ΔΣ modulator and a 17bit@40Khz fourth-order ΔΣ modulator. Both use fully-differential switched-capacitor (SC) circuits and have been designed in full-custom style with the help of a CAD tool which uses innovative statistical optimization heuristics for high-level synthesis (the calculation of cell specifications from modulator specifications) and cell sizing (the calculation of transistor sizes from cell specifications). This proposed tool uses an equation-based approach at the modulator level, a simulation-based approach at the cell level, and incorporates an advanced ΔΣ behavioral simulator for monitoring and design space exploration. This tool has enabled us to complete the design of the fourth-order modulator in 3man/week, of which 65% was for the layout.
Date of Conference: 20-22 Sept. 1994