1 February 2008 Design approaches for digitally dominated active pixel sensors: leveraging Moore's Law scaling in focal plane readout design
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Abstract
Although CMOS technology scaling has provided tremendous power and circuit density benefits for innumerable applications, focal plane array (FPA) readouts have largely been left behind due to dynamic range and signal-to-noise considerations. However, if an appropriate pixel front end can be constructed to interface with a mostly digital pixel, it is possible to develop sensor architectures for which performance scales favorably with advancing technology nodes. Although the front-end design must be optimized to interface with a particular detector, the dominant back end architecture provides considerable potential for design reuse. In this work, digitally dominated long wave infrared (LWIR) active pixel sensors with cutoff wavelengths between 9 and 14.5 μm are demonstrated. Two ROIC designs are discussed, each fabricated in a 90-nm digital CMOS process and implementing a 256 x 256 pixel array on a 30-μm pitch. In one of the implemented designs, the feasibility of implementing a 15-μm pixel pitch FPA with a 500 million electron effective well depth, less than 0.5% non-linearity in the target range and a measured NEdT of less than 50 mK at f/4 and 60 K is demonstrated. Simple on-FPA signal processing allows for a much reduced readout bandwidth requirement with these architectures. To demonstrate the potential for commonality that is offered by a digitally dominated architecture, this LWIR sensor design is compared and contrasted with other digital focal plane architectures. Opportunities and challenges for application of this approach to various detector technologies, optical wavelength ranges and systems are discussed.
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Brian Tyrrell, Robert Berger, Curtis Colonero, Joseph Costa, Michael Kelly, Eric Ringdahl, Kenneth Schultz, James Wey, "Design approaches for digitally dominated active pixel sensors: leveraging Moore's Law scaling in focal plane readout design", Proc. SPIE 6900, Quantum Sensing and Nanophotonic Devices V, 69000W (1 February 2008); doi: 10.1117/12.767272; https://doi.org/10.1117/12.767272
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