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Proceedings Paper

A PFM-based MWIR DROIC employing off-pixel fine conversion of photocharge to digital using integrated column ADCs
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Paper Abstract

A 32x32 prototype of a digital readout IC (DROIC) for medium-wave infrared focal plane arrays (MWIR IR-FPAs) is presented. The DROIC employs in-pixel photocurrent to digital conversion based on a pulse frequency modulation (PFM) loop and boasts a novel feature of off-pixel residue conversion using 10-bit column SAR ADCs. The remaining charge at the end of integration in typical PFM based digital pixel sensors is usually wasted. Previous works employing in-pixel extended counting methods make use of extra memory and counters to convert this left-over charge to digital, thereby performing fine conversion of the incident photocurrent. This results in a low quantization noise and hence keeps the readout noise low. However, focal plane arrays (FPAs) with small pixel pitch are constrained in pixel area, which makes it difficult to benefit from in-pixel extended counting circuitry. Thus, in this work, a novel approach to measure the residue outside the pixel using column -parallel SAR ADCs has been proposed. Moreover, a modified version of the conventional PFM based pixel has been designed to help hold the residue charge and buffer it to the column ADC. In addition to the 2D array of pixels, the prototype consists of 32 SAR ADCs, a timing controller block and a memory block to buffer the residue data coming out of the ADCs. The prototype has been designed and fabricated in 90nm CMOS.

Paper Details

Date Published: 3 May 2017
PDF: 8 pages
Proc. SPIE 10177, Infrared Technology and Applications XLIII, 101771Z (3 May 2017); doi: 10.1117/12.2262451
Show Author Affiliations
S. Abbasi, Sabanci Univ. (Turkey)
A. Galioglu, Sabanci Univ. (Turkey)
A. Shafique, Sabanci Univ. (Turkey)
O. Ceylan, Sabanci Univ. (Turkey)
M. Yazici, Sabanci Univ. (Turkey)
Y. Gurbuz, Sabanci Univ. (Turkey)

Published in SPIE Proceedings Vol. 10177:
Infrared Technology and Applications XLIII
Bjørn F. Andresen; Gabor F. Fulop; Charles M. Hanson; John Lester Miller; Paul R. Norton, Editor(s)

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