A 7-bit 2 GS/s Time-Interleaved SAR ADC With Timing Skew Calibration Based on Current Integrating Sampler

This paper presents a two-way time-interleaved (TI) 7-bit 2-GS/s successive-approximation-register (SAR) analog-to-digital converter (ADC) in 28 nm CMOS. The design achieves wideband operation with an effective resolution bandwidth (ERBW) in the 3rd Nyquist zone. The converter’s front-end employs current integrating (CI) sampler that provide both buffering and anti-alias (AA) filtering at low power dissipation. Facilitated by the CI-samplers’ inherent inter-sample interactions, the timing mismatch among the TI channels can be detected in the amplitude domain, obviating the need for a dedicated reference channel for background calibration. After calibration, the ADC achieves 36.4 dB signal-to-noise-and-distortion ratio (SNDR) near Nyquist and >2.6 GHz ERBW at a sampling rate of 2 GS/s. The ADC’s power consumption is 7.62 mW (including the CI buffer) and its Walden figure of merit (FoMw) is 70.8 fJ/conversion-step.

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