A self-calibrated 2–1–1 cascaded continuous-time ΔΣ modulator

Abstract

A 2-1-1 cascaded continuous-time ΔΣ modulator (DSM) is self-calibrated with LMS-based adaptation. Its noise cancellation filter (NCF) is derived using a parameter-based continuous-time (CT) to discrete-time (DT) transform. These techniques reduce the quantization noise leakage due to the mismatch between analog modulator and digital NCF. A 0.18-μm CMOS prototype operating at 360MHz with a 1-V pp full-scale demonstrates a leakage noise spectral density below 10nV/√Hz over a 30-MHz bandwidth after the capacitors in the Gm-C loop filters are self-trimmed with a 1.1% step. This level of noise leakage is well below the noise floor of most CT DSM designs.

An ARMA-Model-Based NTF Estimation on Continuous-Time <inline-formula> <tex-math notation="LaTeX">$\Delta\Sigma$</tex-math></inline-formula> Modulators

“…The mean square error after convergence is 1.63×10 −6 V 2 for a ±0.6Vpp signal range. More importantly, 4 (a) Fig. 5.…”

“…It is necessary to estimate the practical NTF at every step of designs and ensure its effectiveness as the intended one. Another application of precise NTF estimation is to cancel the leakage noise of cascaded ∆Σ loops, such as cascaded [4] [5] and Leslie-Singh architecture [3].…”