This paper presents a detailed study of the effect of the non-linear settling on the harmonic distortion of BandPass SD Modulators (BP-ΣΔMs) realized using Fully Differential (FD) SwItched-current (SI) circuits. Based on the analysis of building blocks, closed-form expressions are derived for the third-order intermodulation distortion of BP-ΣΔMs due to defective settling, on the one hand, and to the non-linearities of the sampling process, on the other. Time-domain simulations and measurements taken from a 0.8μm CMOS 4th-order BP-ΣΔM silicon prototype validate our approach.This work has been supported by the Spanish CICYT Project TIC 97-0580.Peer reviewed