Reducing the number of comparators in multi-bit ΔΣ modulators

Multi-bit feedback, being one way of lowering ΔΣ modulators power consumption, has a major obstacle: the number of components in the internal analog-to-digital converter (ADC) and digital-to-analog converter (DAC). Nevertheless, the number of comparators in the ADC can be significantly reduced depending on the order of noise-shaping and the oversampling ratio. In this paper, we propose an auto-ranging algorithm with a mechanism to keep the structure stable that emulates more quantization levels than that allowed by the number of comparators. As the recourse to segmented DACs allows lowering the complexity of the mismatch shaping encoder, the auto-ranging ADC brings the benefits of multibit feedback without the usual increase in size and power consumption. The internal number of bits in Δ Σ modulators is no more restricted by the difficulty of building the flash ADC with a low voltage supply. © 2008 IEEE.