A 0.5μm CMOS programmable discrete-time Δ-Σ modulator with floating gate elements

This paper describes a tunable Δ-Σ modulator using floating gate elements. In a previous work, the feasibility of using these structures in a conventional switch capacitor modulator was shown. Floating gate electronic potentiometers (e-pots) in the modulator loop were used to provide convenient and accurate programmable on-chip reference voltages. These voltages determined the feedback coefficients of the modulator. In this work time-domain modelling of the modulator in SIMULINK as well as SPICE simulations is used to predict optimal coefficients, which are programmed into the modulator at runtime. Simulation and experimental results for a 2nd order modulator are presented. The modulator achieves 57 dB peak SNR and 55 dB SINAD giving ENOB=9 bits.