Analytical method to determine optimal out-of-band gain in multi-bit delta-sigma modulator

Awinash Anand; Nischal Koirala; Ramesh K. Pokharel; Haruichi Kanaya; Keiji Yoshida

doi:10.1587/elex.9.1598

Awinash Anand, Nischal Koirala, Ramesh K. Pokharel, Haruichi Kanaya, Keiji Yoshida

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Keywords: analog-to-digital conversion, continuous-time delta-sigma modulator, feedforward, excess loop delay

JOURNAL FREE ACCESS

2012 Volume 9 Issue 20 Pages 1598-1603

DOI https://doi.org/10.1587/elex.9.1598

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Abstract

A simple, systematic and deterministic MATLAB simulation which employs Risbo method and analytical simulation is proposed to determine the optimal out-of-band gain to achieve a maximal SNR and the maximum stable amplitude in a multi-bit delta-sigma modulator. Using the proposed method, a 128MS/s, 2MHz signal bandwidth 4^th order 2-bit continuous-time delta-sigma modulator is designed and implemented in 0.18µm CMOS technology to verify the concept. As a result, the modulator achieves a peak SNDR of 79.3dB and a dynamic range of 83dB for a 2MHz signal bandwidth (OSR = 32) while consuming only 7.8mW from 1.8V supply.

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