This paper presents a new experimental setup (to our knowledge, the first ever) and results obtained with that setup from which we report extra combinational delays in an SRAM FPGA (Virtex-5) due to transient ionizing radiations. The results, obtained by proton irradiation at the TRIUMF laboratory, show that our setup can detect extra combinatorial delays as small as 40 ps, and that delays of more than 400 ps can affect the targeted FPGA. These results strongly suggest that delay faults can potentially be induced by transient ionizing radiations.
We describe in this paper a new CMOS multimode image pixel sensor (MIPS) dedicated to an implantable visual cortical stimulator. Each 16 µm × 16 µm pixel area contains a photodiode, with a fill factor of 22%, a comparator used to convert the pixel level from analog to digital (A/D) values and an 8-bit DRAM, resulting in a total of 44 transistors per pixel. The A/D conversions use one common digital to analog converter to deliver the voltage reference needed to determine the pixel voltage. Three selectable operation modes are combined in the proposed MIPS: A high dynamic range logarithmic mode, a linear integration mode, and a novel differential mode between two consecutive images. This last mode that allows 3D information is required for a visual cortical stimulator. A test chip has been fabricated in CMOS 0.18 µm technology and tested to validate the full operation of the different proposed modes.
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