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An 11-bit, power efficiency, two-stage SAR-voltage-controlled oscillator (VCO) hybrid ADC is proposed in this work. Taking full advantage of the voltage-to-phase and voltage-to-frequency characteristics, the reused ring-VCO circuit acts as not only a time-domain comparator with the phase detector assistance for low power consumption in the first SAR stage but also a fine quantizer in the second stage. More importantly, the gain nonlinearity of the VCO can be effectively suppressed due to the small residue voltage after the coarse quantization. In addition, the VCO-based ADC (except for the ring-VCO circuit) only works in the quantization phase instead of the whole conversion period. As a result, the power consumption and area of the comparator in the previous SAR-VCO ∆Σ ADC can be thoroughly avoided. Besides, compared to an 11-bit SAR ADC, the capacitor mismatch can be relaxed theoretically by 2 × in the identical capacitor array area. Post-simulation results demonstrate that the proposed ADC in a 0.18 μm CMOS process exhibits a signal-to-noise and distortion ratio (SNDR) of 63.8 dB, and it dissipates 2.1 μW power from a 0.6 V supply with a sampling rate of 50 kS/s and a Nyquist input rate. To the author's knowledge, the hybrid ADC can achieve the best Walden figure of merit (FoMw) of 33.3 fJ/conversion-step compared with the previous SAR-VCO hybrid ADC, and its active area is only 0.109 mm2. [ABSTRACT FROM AUTHOR]

A new 1-bit digital comparator named 14T-SR-GDI is presented with gate-diffusion-input (GDI) and single-swing-restoration (SR) techniques to attain internal gates with high driving capability. The comparator has 14 transistors which produce full-swing outputs with low power consumption. In the 14T-SR-GDI, boosted inner signals are used to activate the output gates which result in a high-speed circuit with effective scalability and the enhanced driving capability for multi-bit structures. The comparator has a low power delay product (PDP) due to the small numbers of internal nodes and capacitances and efficient power-ground-free gates. The 14T-SR-GDI comparator, fully SR-GDI-based AND, and OR gates, construct a new tree structure for multi-bit magnitude comparators including 2-bit, 4-bit, 8-bit, and 16-bit comparators. The proposed 1-bit comparator is used in image processing for difference detection, and its efficiency is proved by image quality parameters. The post-layout simulations are performed for the 1-bit to 16-bit structures under TSMC 90 nm technology. The extracted results express a PDP with an average difference of 9.59% between the regular and post-layout modes. Also, the proposed 16-bit comparator is embedded in a pad with a total area of 4331.25 μm2. The designed magnitude comparators are key components in digital signal processors (DSPs). [ABSTRACT FROM AUTHOR]

Reconfigurability is an important capability that provides flexibility in computing architecture and low-power technique. It is challenging in digital-in-concept for designing smart analog circuits operated on low power. This work presents a low-power, low-noise, and high-speed multistage feed-forward reconfigurable comparator for medium-to-high-speed analog-to-digital converter. A power-efficient reconfigurable comparator design at 180 nm is presented with a new power reduction and offset compensation technique. The proposed dynamic latch-based 2-stage comparator gives an 83.2% power saving compared with a 3-stage comparator. The reduced number of active stages in comparator lowers the load capacitance to the post-amplifier and the power consumption. The 2-stage comparator gives a high slew rate, low power consumption, and better result at a Nyquist rate of 2.4 GS/s as compared with the previous state of the art. We have also proposed the reconfigurable multistage comparator, which gives the features of both 2-/3-stage comparators. We have performed the post-layout simulation to validate the design for process variation and mismatch with proposed circuit and compared with state of the art. Further, the voltage gain is 100 dB with power supply 1.8 V while consuming 523.4 μ W and 86.15 μ W for 3-stage and 2-stage comparator, respectively. [ABSTRACT FROM AUTHOR]