Stable one-bit delta-sigma modulators based on switching control

We present a globally stable arbitrary-order single-bit delta-sigma modulator architecture with continuous-time loop filtering. Using Lyapunov arguments and the method of equivalent control, it is shown that stability is guaranteed for any input signal with peak magnitude less than L>0, where -L and +L denote the quantization levels. The design augments the conventional delta-sigma modulator with switching feedback and the use of distinct operating modes; the additional circuitry required for the implementation of these stabilizing measures is nominal. For a given noise transfer function and fixed oversampling ratio, the new architecture achieves the same peak signal-to-noise-plus-distortion ratio as a traditional delta-sigma modulator. The proposed design can also yield near-peak performance for inputs which destabilize the conventional delta-sigma data converter. Simulation results are provided for the proposed modulator and a comparable standard interpolative design.