Design of a 1.2-V 130nm CMOS 13-bit@40MS/s Cascade 2-2-1 Continuous-Time ΣΔ Modulator

Abstract

This paper presents the design of a continuous- time multibit cascade 2-2-1 ΣΔ modulator for broadband telecom systems. The modulator architecture has been synthesized directly in the continuous-time domain instead of using a discrete-to-continuous time transformation. This method results in a more efficient modulator in terms of noise shaping, power consumption and sensitivity to circuit element tolerances. The design of the circuit, realized in a 130nm CMOS technology, is based upon a top-down CAD methodology which combines simulation and statistical optimization at different levels of the modulator hierarchy. The estimated power consumption is 60mW from a 1.2-V supply voltage when clocked at 240MHz. Simulation results show 80-dB effective resolution within a 20-MHz signal bandwidth.