Search

This paper presents a 4-b phase-domain analog-to-digital converter (ADC) that utilizes the time-domain reference generation scheme for low-power operation. Rather than prior arts that rely on power-hungry resistive/current combiners or the IQ-assisted binary-search algorithm with large power T&H circuits for the reference generation, this design benefits from the fully dynamic power characteristic of the time-domain operation, thus leading to an energy-efficient phase ADC design. By introducing several on-chip calibration techniques, the design achieves good robustness with the proposed time-domain operation. The prototype is fabricated in the standard 65-nm CMOS technology, achieving an ENOB of 3.42 bits at 1 MS/s with near Nyquist input, while dissipating $7~\mu \text{W}$ from a 1-V supply. It leads to a 1.36-pJ/conversion-step Walden Figure of Merit at Nyquist input (FoM@Nyquist). [ABSTRACT FROM AUTHOR]

The high-speed successive-approximation-register (SAR) analog-to-digital converters (ADCs) rely on the switched capacitive digital-to-analog converter (CDAC) to perform the fast transition, which causes voltage ripples at the output of the reference circuits. Such ripples lead to the reference error that eventually prolongs the time for DAC settling. To minimize such error with a short available time, it either demands a power-hungry reference buffer or large die area for the decoupling. In this paper, we offer a comprehensive analysis of the reference errors in SAR ADCs with a practical reference network circuit (RNC) in consideration. A circuit model is developed in order to quantify the error amplitude for the critical DAC settling condition. Based on the proposed model, the settling behavior of the DAC with reference buffer can be precisely characterized, leading to a better understanding about the design tradeoff of the RNC. Finally, the developed model is verified by both circuit level simulations and measurement results. [ABSTRACT FROM AUTHOR]

This paper presents a 2.3 GS/s 12-way time-interleaved pipelined-SAR ADC achieving 1.1 GHz input bandwidth with 47.4 dB signal-to-noise distortion ratio (SNDR). Here, we propose a hierarchical interleaving with passively shared sub-sampling front-end to eliminate the timing skews, thus avoiding the timing calibration for design simplicity as well as better area and power efficiency. To provide a fast signal transfer with good power efficiency to the sub-ADCs, the power and bandwidth trades off by using the passive sharing or active buffers are analyzed according to our developed mathematic model. The analysis is based on two scenarios: noise and matching limited sampling. Moreover, we propose a boosting-capacitor-sharing technique to enhance the compactness of the time-interleaved bootstrapped sampling front-end, which is particularly critical when omitted the time calibration in this design. Measurement results on a 65 nm CMOS prototype operated at 2.3 GS/s and 1.2 V supply show 31 mW total power consumption with a SNDR of 47.4 dB @Nyquist leading to a FOM of 69 fJ/conv.step. [ABSTRACT FROM AUTHOR]

This paper presents a 12b 180 MS/s 0.068 mm2 $2\times$ time-interleaved pipelined-SAR analog-to-digital conver-ter (ADC) with gain and offset calibrations fully embedded on-chip. The proposed binary-search gain calibration (BSGC) technique corrects the inter-stage gain error caused by the open-loop residue amplifier. The BSGC, fully integrated into the second-stage SAR ADC, contributes to a compact area. We improve the noise performance by implementing a merged-residue-DAC operation in the first-stage ADC. Also, we propose a dual-phase bootstrap technique to improve the sampling linearity in the partial interleaving architecture. The measurement results of the ADC prototype in 65 nm CMOS demonstrate the effectiveness of the proposed calibration through the enhancement of the signal to noise-and-distortion ratio from 51.5 to 60.9 dB at a Nyquist input, leading to a FoM@Nyq of 36.7 fJ/conversion-step. [ABSTRACT FROM AUTHOR]