A Reconfigurable Continuous-Time Delta-Sigma Modulator Structure Using Hybrid Loop Filter and Time-Interleaved Quantizer

This work presents a reconfigurable continuous-time delta-sigma modulator (CTDSM) structure with hybrid loop filter using a time-interleaved successive approximation register (TI-SAR) as its quantizer for multi-mode application. Except the first OTA-based integrator, the rest part of the loop filter is put in the digital domain, including a 2rd-order digital integrator and a digital excess loop delay (ELD) compensation block, which can provide convenience for outstanding structure reconfiguration and compensation for ELD over one clock cycle. A cascade of integrators with feedback and feedforward (CIFB-F) structure with well controlled STF out-of-band peaking is also proposed at the price of a little more power than the cascade of integrators with feedforward (CIFF) structure. The oversampling ratio (OSR), bandwidth (BW), sampling frequency (fs) and even the structure can be easily configured to adapt for different application. A circuit-level simulation of a reconfigurable CTDSM modeled by Verilog-A is conducted, which reveals signal-to-quantization noise ratio (SQNR) > 78dB over a wide input signal BW (25MHz) under 1.2GHz sampling frequency.