A linearity improvement method for CIS column-parallel SAR ADC using two-step conversion

A linearity improvement method for CIS column-parallel SAR ADC using two-step conversion

Lee, J. (TU Delft Electronic Instrumentation)
Theuwissen, A.J.P.A.M. (TU Delft Electronic Instrumentation; Harvest Imaging)

2023

This paper presents a new 2-step SAR ADC architecture for image sensors in machine vision applications. This structure effectively improves the structural problems of the image sensor caused by the area occupied by the ADC, such as linearity and temporal noise performance. In this work, we designed a two-step SAR ADC using a 6-bit SAR ADC and a PGA generating residue and offset. Since the number of unit capacitor's is reduced, the common centroid method is applied in the capacitor layout to improve the linearity. As a result, the capacitor mismatch characteristic is improved, and the differential nonlinearity (DNL) obtained is +0.36/-0.28LSB. In addition, the temporal noise is about 530 μ Vrns due to the small bandwidth of the column-parallel structure in an image sensor. The implemented ADC achieves 250 kS/ s as a maximum speed. The maximum frame rate of the sensor is 2500fps. The power consumption of the sensor, except for the LVDS interface, is 37.5 ∼mW. This sensor is designed in TowerJazz CIS 180 ∼nm process with one poly and four metal layers. The supply voltage of the analog and digital domains are 3.3 ∼V and 1.8 ∼V, respectively.

CMOS Image Sensor
SAR ADC
Linearity
Column-parallel structure

http://resolver.tudelft.nl/uuid:c00c4284-d8ae-4663-ad50-cac0cf2637f4

https://doi.org/10.1109/ESSCIRC59616.2023.10268814

IEEE

2024-04-06

979-8-3503-0421-3

Proceedings of the ESSCIRC 2023- IEEE 49th European Solid State Circuits Conference (ESSCIRC)

European Solid-State Circuits Conference, 1930-8833, 2023-September

Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.

Institutional Repository

conference paper

© 2023 J. Lee, A.J.P.A.M. Theuwissen