A 0.08mm², 2V_pp-Input-Range, 95dB-SNDR, 178.5dB-FOM_s Noise-Shaping SAR ADC for Closed-Loop Neural Interfaces

In closed-loop neural interfaces, simultaneous recording and stimulation impose significant challenges on the recording path, demanding a frontend capable of accommodating large amplitudes and a wide dynamic range. This paper presents a Noise-Shaping SAR ADC with large input amplitude and high dynamic range for closed-loop interfaces, featuring in-loop Serial-to-Parallel Amplification (SPA) and a fully dynamic Capacitor-Stacking-and-Buffering (CSB) integrator with a Fully Dynamic Voltage Buffer (FDVB). Fabricated in 65-nm CMOS, the proposed design achieves 2-Vpp input range, 95-dB SNDR, and 178.5-dB FOMs with only 2.26 µW within a compact 0.08 mm2 area. In-vitro experiments using pre-recorded neural data with stimulation artifacts demonstrate robust, artifact-resilient neural recording.