LAUSR

This article presents a G_m-C-based continuous-time delta–sigma modulator (CTDSM) for artifact-tolerant neural recording interfaces. We propose the feedback-assisted G_m linearization technique, which is applied to the first G_m-C integrator by using a resistive feedback digital-to-analog converter (DAC) in parallel to the degeneration resistor of the input G_m. This enables the input G_m to process the quantization noise, thereby improving the input range and linearity of the G_m-C-based CTDSM, significantly. An energy-efficient second-order loop filter is realized by using a voltage-controlled oscillator (VCO) as the second integrator and a phase quantizer. A proportional–integral (PI) transfer function is employed at the first integrator, which minimizes the output swing while maintaining loop stability. Fabricated in a 110-nm CMOS process, the prototype CTDSM achieves a high input impedance, 300-mV_pp linear input range, 80.4-dB signal-to-noise and distortion ratio (SNDR), 81-dB dynamic range (DR), and 76-dB common-mode rejection ratio (CMRR) and consumes only 6.5 $\mu \text{W}$ with a signal bandwidth of 10 kHz. This corresponds to a figure of merit (FoM) of 172.3 dB, which is the state of the art among the neural recording ADCs. This work is also validated through the in vivo experiment.