A Systematic Design Methodology of Time-Based Non-Uniform In-Pixel Quantizers for IR Sensors

Trends in image sensor design increasingly demand high resolution, small pixel pitch, low power consumption, and high dynamic range. Digital pixel sensors, in which each pixel directly produces a digital output, are an emerging technology capable of meeting these requirements, with the potential to incorporate in-array image post-processing. This paper presents an implementation for infrared readout circuits based on pulse-frequency modulation. A non-uniform time-based second conversion stage featuring an input-dependent resolution selection enhances dynamic range without increasing pixel area. The effects of key design variables are analyzed, and design guidelines are provided for optimizing system performance. A prototype chip with pixel-parallel conversion in a$10~{\mu }$m pixel pitch is developed following these guidelines, and mathematical simulations validate the effectiveness of the proposed methodology. Finally, even if this work focuses on infrared readout, the design guidelines provided in this work applies and can be extended to any current-sensing system.