A 91.2dB-SNDR 250kHz-BW CT Zoom ADC Achieving a 6-Bit Linear Zoom-in with Interstage LPF and 1.5-Bit DAC

This paper presents a continuous time (CT) zoom ADC that achieves a 6-bit linear zoom-in with an interstage LPF and an intrinsically linear 1.5-bit DAC. By using the interstage LPF, the shaped residue signal of the coarse $\Delta\Sigma \mathrm{M}$ is properly filtered, enabling 6-bit linear zoom-in, boosting the SQNR by $> 36\text{dH}$. Fabricated in 28nm CMOS process, the ADC consumes only $392\mu \mathrm{W}$ while achieving 101.F 4dB SFDR, 91 2dB SNDR, and 92. 7dH DR in a signal bandwidth of 250kHz. This corresponds to a state-of-the-art FoM of 180. 7dB.