An intermediate frequency reconfigurable bandpass noise‐shaping SAR ADC for IoT and mobile application

This letter proposes a reconfigurable bandpass noise‐shaping successive approximation register analog‐to‐digital converter (ADC) with a cascade of integrators with feedforward (CIFF) structure. Unlike conventional CIFF structures that use a passive feedforward path, the new design incorporates an amplifier within the filter, providing effective bandpass noise transfer function regardless of passband location, and facilitating the use of a unity gain 2‐input comparator for low noise and high stability. The loop filter includes amplification by a low power Gm‐R amplifier and two‐step charge sharing. The proposed ADC supports three different intermediate frequencies (IFs), and 12‐bit resolution is achieved for all IFs in a 28‐nm complementary metal‐oxide‐semiconductor (CMOS) process.