A zero-crossing-based integrator with bidirectional two-phase charging and selective-reset operations for ΔΣ ADCs

초록

Zero-crossing-based integrators (ZCBIs) are energy-efficient alternatives to conventional switched-capacitor integrators that are typically implemented using operational transconductance amplifiers (OTAs). However, ZCBIs suffer from signal-dependent overshoot errors and increased dynamic power consumption due to inherent reset operation. This paper presents a ZCBI that employs a bidirectional two-phase charging scheme and performs the reset operation selectively. A 3rd-order Delta-Sigma modulator has been fabricated in a 28-nm CMOS technology using the proposed integrators. The prototype modulator achieves 67-dB SNR and 63-dB SNDR over the bandwidth of 196 kHz with an oversampling ratio of 64. It consumes 184 mu W, which translates to the figure-of-merits of 154 dB (FoMs) and 390 fJ/conv-step (FoMw).

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