A 12-bit High-Speed Time-Interleaved Pipelined Asynchronous Successive-Approximation ADC in 22-nm FDSOI CMOS

Abstract

A 12-bit time-interleaved (TI) analog-to-digital converter (ADC) with pipelined successive-approximation (SAR) channels is presented in this paper. The ADC consists of four TI channels, each incorporating a two-stage pipelined asynchronous SAR ADC. To facilitate clock distribution, a common bootstrapped sampler in front of the four channels is employed. The reset switch in the capacitive digital-to-analog converter (CDAC) of each channel is also bootstrapped to enhance the speed and linearity. A prototype ADC has been designed and implemented in a 22-nm FDSOI CMOS technology, with a core occupation area of 0.43 mm2. Measurements show that the ADC achieves a signal-to-noise-and-distortion ratio of 50dB with a low-frequency input, and of 48.5 dB at Nyquist. The total power consumption is 37.5 mW; the core ADC consumes 19.3 mW from a 0.8V supply. With a 1.4 GS/s sampling rate and input at Nyquist, the ADC achieves a Walden’s figure of merit of 114 fJ/conversion.

Keywords

• Analog-to-digital converter (ADC)
• CMOS
• comparator
• bootstrapped switch
• dynamic amplifier (DA)
• asynchronous SAR