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Proceedings Paper

A SPAD-based 3D imager with in-pixel TDC for 145ps-accuracy ToF measurement
Author(s): I. Vornicu; R. Carmona-Galán; Á. Rodríguez-Vázquez
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Paper Abstract

The design and measurements of a CMOS 64 × 64 Single-Photon Avalanche-Diode (SPAD) array with in-pixel Time-to-Digital Converter (TDC) are presented. This paper thoroughly describes the imager at architectural and circuit level with particular emphasis on the characterization of the SPAD-detector ensemble. It is aimed to 2D imaging and 3D image reconstruction in low light environments. It has been fabricated in a standard 0.18μm CMOS process, i. e. without high voltage or low noise features. In these circumstances, we are facing a high number of dark counts and low photon detection efficiency. Several techniques have been applied to ensure proper functionality, namely: i) time-gated SPAD front-end with fast active-quenching/recharge circuit featuring tunable dead-time, ii) reverse start-stop scheme, iii) programmable time resolution of the TDC based on a novel pseudo-differential voltage controlled ring oscillator with fast start-up, iv) a global calibration scheme against temperature and process variation. Measurements results of individual SPAD-TDC ensemble jitter, array uniformity and time resolution programmability are also provided.

Paper Details

Date Published: 13 March 2015
PDF: 6 pages
Proc. SPIE 9403, Image Sensors and Imaging Systems 2015, 94030I (13 March 2015); doi: 10.1117/12.2078777
Show Author Affiliations
I. Vornicu, Instituto de Microelectrónica de Sevilla (Spain)
R. Carmona-Galán, Instituto de Microelectrónica de Sevilla (Spain)
Á. Rodríguez-Vázquez, Instituto de Microelectrónica de Sevilla (Spain)

Published in SPIE Proceedings Vol. 9403:
Image Sensors and Imaging Systems 2015
Ralf Widenhorn; Antoine Dupret, Editor(s)

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