A SAR-Assisted Two-Stage Pipeline ADC

Successive approximation register (SAR) ADC architectures are popular for achieving high energy efficiency but they suffer from resolution and speed limitations. On the other hand pipeline ADC architectures can achieve high resolution and speed but have lower energy-efficiency and are more complex. We propose a two-stage pipeline ADC architecture with a large first-stage resolution, enabled with the help of a SAR-based sub-ADC. The prototype 12b 50 MS/s ADC achieves an ENOB of 10.4b at Nyquist, and a figure-of-merit of 52 fJ/conversion-step. The ADC achieves low-power, high-resolution and high-speed operation without calibration. The ADC is fabricated in 65 nm and 90 nm CMOS and occupies a core area of only 0.16\ mm².