A highly digital microbolometer ROIC employing a novel event-based readout and two-step time to digital converters

Abbasi, Shahbaz (2019) A highly digital microbolometer ROIC employing a novel event-based readout and two-step time to digital converters. [Thesis]

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Uncooled infrared imaging systems are a light weight and low cost alternative to their cooled counterparts. Uncooled microbolometer IR focal plane arrays (IRFPAs) for applications such as medical imaging, thermography, night vision, surveillance and industrial process control have recently been under focus. These systems have small pixel pitches (< 25µm) and require power efficiency, low noise equivalent temperature difference (NETD) (< 50 mK) and adequate scene dynamic range (> 250 K). Low NETD demands excellent microbolometer and readout noise performance. If sensitive analog circuits, driving long metal interconnects, are part of the predigitization readout channel, this necessitates the use of power consuming buffers, potentially in conjunction with noise cancellation circuits that result in power and area overhead. Thus re-thinking at the architectural level is crucial to meet these demands. Accordingly, in this thesis a column-parallel readout architecture for frame synchronous microbolometer imagers is proposed that enables low power operation by employing a time mode digitizer. The proposed readout circuit is based on a bridge type detector network with active and reference microbolometers and employs a capacitive transimpedance amplifier (CTIA) incorporating a novel two-step integration mechanism. By using a modified reset scheme in the CTIA, a forward ramp is initiated at the input side followed by the conventional backward integrated ramp at the output. This extends the measurement interval and improves signal-to-noise ratio (SNR). A synchronous counter based TDC measures this interval providing robust digitization. This technique also provides a way of compensating for self-heating effects. Being highly digital, the proposed architecture offers robust frontend processing and achieves a per channel power consumption of 66 µW, which is considerably lower than the most recently reported designs, while maintaining better than 10mK readout NETD.
Item Type: Thesis
Uncontrolled Keywords: Long-wave infrared. -- Uncooled microbolometer. -- Readout integrated circuit. -- Time-mode processing. -- Low power. -- NETD. -- self-heating. -- Uzun-dalga kızıl ötesi. -- Soğutmasız bolometre. -- Öngörücü model. -- TACAD. -- Si/SiGe çoklu-kuantum kuyusu. -- Yüksek Ge içeren SiGe bolometre. -- Yüksek TCR (sıcaklığa bağlı direnç değişim katsayısı). -- Düşük gürültülü bolometre.
Subjects: T Technology > TK Electrical engineering. Electronics Nuclear engineering > TK7800-8360 Electronics
Divisions: Faculty of Engineering and Natural Sciences > Academic programs > Electronics
Faculty of Engineering and Natural Sciences
Depositing User: IC-Cataloging
Date Deposited: 28 Jun 2019 10:49
Last Modified: 26 Apr 2022 10:30
URI: https://research.sabanciuniv.edu/id/eprint/37291

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