High resolution current-mode CCO-based continuous time delta-sigma modulators for sensor-array applications

A current-mode delta-sigma modulator is presented for electrochemical sensor arrays utilizing a Current Conveyor and a Current Controlled Oscillator (CCO). Second order noise shaping is achieved although a very simple topology is used with only one integrator. The impact of oscillator non-linearity is kept low thanks to a pseudo-differential design. Simulations predict an SNDR of 102 dB at 10 kHz bandwidth, 5 MHz sampling frequency, oversampling ratio of 256, and a CCO non-linearity of 1%. Even at 5% oscillator non-linearity an SNDR of 72 dB is achieved. A feasibility check is accomplished by designing the proposed topology on transistor-level.