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1 May 2008 CMOS readout integrated circuit involving pixel-level ADC for microbolometer FPAs
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The function of most readout integrated circuits (ROIC) for microbolometer focal plane arrays (FPAs) is supplying a bias voltage to a microbolometer of each pixel, integrating the current of a microbolometer, and transferring the signals from pixels to the output of a chip. However, the scale down of CMOS technology allows the integration of other functions. In this paper, we proposed a CMOS ROIC involving a pixel-level analog-to-digital converter (ADC) for 320 × 240 microbolometer FPAs. Such integration would improve the performance of a ROIC at the reduced system cost and power consumption. The noise performance of a microbolometer is improved by using the pixelwise readout structure because integration time can be increased up to 1ms. A Pixel circuit is consisted of a background skimming circuit, a differential amplifier, an integration capacitor and a 10-bit DRAM. First, the microbolometer current is integrated for 1ms after the skimming current correction. The differential amplifier operates as an op-Amp and the integration capacitor makes negative feedback loop between an output and a negative input of the op-Amp. And then, the integrated signal voltage is converted to digital signals using a modified single slope ADC in a pixel when the differential amplifier operates as a comparator and the 10-bit DRAM stores values of a counter. This readout circuit is designed and fabricated using a standard 0.35μm 2-poly 3-metal CMOS technology.
© (2008) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
C. H. Hwang, I. W. Kwon, Y. S. Lee, and H. C. Lee "CMOS readout integrated circuit involving pixel-level ADC for microbolometer FPAs", Proc. SPIE 6940, Infrared Technology and Applications XXXIV, 694029 (1 May 2008);


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