Abstract:
A new approach to oversampled delta-sigma A/D converters ( AZ modulators ) is introduced, where a differential pseudo-Npath filter stage is used as a basic cell. In this band-pass application, the z to -zN transformation is employed to realize a
RAM-type pseudo-2-path lossless integrator. The bandpass second-order and 4th-order delta-sigma A/D converters are implemented by
switched-capacitor ( SC ) circuits using this kind of integrator. The effects of components inaccuracy, finite op-amp gain, as well as
clock feed-through noise are studied in simulations. The results verify that such A/D converters possess a remarkable insensitivity
to imperfect components and a high signal-to-noise ratio (SNR). A 6th-order dual-quantizer delta-sigma A/D converter with a digital canceller is then designed, which achieves 86 dB (>14 bit) conversion accuracy and 95 dB (>15 bit) dynamic range for a low
oversampling ratio (OSR=32) even with low-accuracy analog components (4-bit internal D/A with 6-bit linearity).
