The design of ΔΣ modulators for multichannel biomedical applications introduces challenges with high density and very low power consumption. While possible solutions in the form of VCO and passive integrator-based ΔΣ modulators have been reported, these modulators suffer from limited resolution. Hybrid ΔΣ modulators provide an excellent tradeoff between area, power, and achievable resolution compared to the counterpart active and passive integrator ΔΣ modulators. This work explores hybrid continuous-time delta–sigma modulator (CTDSM) architectures for multichannel biomedical applications, operating with a single clock phase. To alleviate the high power consumption of the active integrators in the CTDSM, an auxiliary digital-to-analog converter (DAC)-based and a passive RC front-end-based hybrid CTDSMs are proposed. Through a detailed analysis and performance comparison, we demonstrate that the two proposed hybrid architectures exhibit the classical area–power tradeoff for a target resolution. We demonstrate the designs in standard 180-nm mixed-mode CMOS technology for biomedical bandwidth. Measurement results show that the auxiliary DAC and the PRC-FE-based hybrid CTDSMs achieve an SNDR and DR of 65.18 and 68.3 dB and 66.85 and 71.1 dB while consuming 845- and 730-nW power and achieving an FoM of 28.48 and 20.3 fJ/conv, respectively, ideal for multichannel biomedical applications. In vitro and in vivo measurements are also performed to validate the proposed hybrid CTDSM designs.
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Continuous-Time Hybrid ΔΣ Modulators for Sub-μW Power Multichannel Biomedical Applications