An Ultra-Low-Energy Analog Comparator for A/D Converters in CMOS Image Sensors

Waldemar Jendernalik

doi:10.1007/s00034-017-0630-6

An Ultra-Low-Energy Analog Comparator for A/D Converters in CMOS Image Sensors

Abstract

This paper proposes a new solution of an ultra-low-energy analog comparator, dedicated to slope analog-to-digital converters (ADC), particularly suited for CMOS image sensors (CISs) featuring a large number of ADCs. For massively parallel imaging arrays, this number may be as high as tens-hundreds of thousands ADCs. As each ADC includes an analog comparator, the number of these comparators in CIS is always high. Detailed analysis shows that power dissipation of a comparator contributes significantly to a total power consumption of an ADC. Thus, minimization of the comparator energy consumption during the analog-to-digital (A/D) conversion of an image frame is crucial for design of CMOS image sensors. Compared to classical dynamic or continuous-time comparators operating in the slope ADC, under the same bias conditions, the proposed comparator shows a 2–3 orders of magnitude reduction of the power consumption. In addition, the proposed topology shows a simple and compact layout and does not require a power-down mechanism. The circuit has been simulated in detail for a 0.18-μm CMOS technology under two different power supply voltages of 1.8 and 1 V. While implemented in a 12-bit slope ADC of a massively parallel CIS, operating at a speed 1000 fps, the energy required for A/D conversion is 0.5 pJ.

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Waldemar Jendernalik dr hab. inż.

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Category:: Articles
Type:: artykuł w czasopiśmie wyróżnionym w JCR
Published in:: CIRCUITS SYSTEMS AND SIGNAL PROCESSING no. 36, edition 12, pages 4829 - 4843,
ISSN: 0278-081X
Language:: English
Publication year:: 2017
Bibliographic description:: Jendernalik W.: An Ultra-Low-Energy Analog Comparator for A/D Converters in CMOS Image Sensors// CIRCUITS SYSTEMS AND SIGNAL PROCESSING. -Vol. 36, iss. 12 (2017), s.4829-4843
DOI:: Digital Object Identifier (open in new tab) 10.1007/s00034-017-0630-6
Verified by:: Gdańsk University of Technology