Adaptive integrator-output bounding (AIB) for second order sigma-delta ADC

One of the essential issues of sigma-delta modulator (ΣΔM) design is to properly scale the integrators to avoid clipping, which may cause information loss and hence severe degradation in SNR. This paper presents a new approach, adaptive integrator-output bounding (AIB), to second order 1-bit ΣΔM design. By adaptively controlling the feedback coefficient of the first integrator, the AIB design significantly extends the unclipping input level to full scale, while that of the standard design is usually 3dB lower. Therefore, provided that the integrator scaling factors are the same, the AIB scheme increases the actual dynamic range of an unclipped system, and thus improves the peak SNR. Moreover, simulation results show that, compared to the standard system, the quantization noise of the AIB design is less dependent on the input levels, which indicates that the AIB scheme is closer to the linear model of the ΣΔMs