Low Power Pixel-Level ADC Readout Circuit for an Amorphous Silicon-Based Microbolometer

概要

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A new readout integrated circuit is developed for application in an amorphous silicon-based microbolometer array with a pixel pitch of 35µm. The proposed circuit lowers the power dissipation for a pixel-level analog-to-digital converter (ADC), which uses a comparator and a counter for its data conversion. The infrared current of a microbolometer is proportional to the resistivity changes of the microbolometer. Thus, the required number of counter operations for the pixel ADC can be determined according to the microbolometer current variation. The counting number precisely determines how much infrared flux is absorbed. A 14bit counter should normally be used for the pixel ADC for this kind of operation. However, when the proposed current skimming scheme is adopted, the total bits for the counter in the pixel ADC can be reduced to 12bits. Due to the proposed mechanism, the required operational speed of the comparator can lower than that of a conventional circuit. Consequently, the overall power dissipation in the comparator and counter is less than that of a conventional structure. This low power approach is very suitable in the pixel-level ADCs of microbolometers.
（社）電子情報通信学会の論文
2009-05-01