A 0.69-Noise-Efficiency-Factor 55 \times -Preamp-Gain Dynamic Comparator With a Stacking FIA

• Published in: IEEE journal of solid-state circuits pp. 1 - 14
• Main Authors: Zhuang, Haoyu, Cao, Yirui, Tao, Linzhi, Li, Qiang
• Format: Journal Article
• Language: English
• Published: IEEE 28.08.2024
• Subjects: Capacitors; Current reuse; dynamic comparator; Latches; Logic gates; low noise; low power; Noise; Power demand; stacking floating inverter amplifier (FIA); Transistors; Voltage
• ISSN: 0018-9200; 1558-173X
• DOI: 10.1109/JSSC.2024.3446175

This article presents a fully dynamic, low-noise, low-power comparator. Its key highlight is the four-times current-reuse factor, which improves the pre-amplifier gain by at least two times without increasing the power consumption. This causes the proposed design to have a two-times smaller input-referred noise and a two-times better noise-efficiency factor (energy <inline-formula> <tex-math notation="LaTeX">\times</tex-math> </inline-formula> noise power). In prior comparators, the maximum current-reuse factor of the pre-amplifier was only two times. This small current-reuse factor limits the pre-amplifier gain to 30 times, which restricts the further improvement in the noise-efficiency factor. By contrast, this work stacks two floating inverter amplifiers (FIAs) in order to greatly increase the current-reuse factor to as large as four times. As a result, the pre-amplifier gain is increased by 55 times, which is helpful for improving the noise-efficiency factor. Implemented in a 28 nm CMOS process, the prototype comparator achieves a 38 <inline-formula> <tex-math notation="LaTeX">\mu</tex-math> </inline-formula>V input-referred noise and a 0.48 pJ energy consumption per comparison under a 0.9 V supply. The noise-efficiency factor is as good as 0.69 nJ<inline-formula> <tex-math notation="LaTeX">\cdot\mu </tex-math> </inline-formula>V<inline-formula> <tex-math notation="LaTeX">^{2}</tex-math> </inline-formula>, which is three times better than the prior FIA-based comparator and 23 times better than the classic StrongArm latch (SA latch). This noise-efficiency factor is the best among all reported works so far.