CMOS readout integrated circuit involving pixel-level ADC for microbolometer FPAs

C. H. Hwang; I. W. Kwon; Y. S. Lee; H. C. Lee

doi:10.1117/12.780466

1 May 2008 CMOS readout integrated circuit involving pixel-level ADC for microbolometer FPAs

C. H. Hwang, I. W. Kwon, Y. S. Lee, H. C. Lee

Proceedings Volume 6940, Infrared Technology and Applications XXXIV; 694029 (2008) https://doi.org/10.1117/12.780466
Event: SPIE Defense and Security Symposium, 2008, Orlando, Florida, United States

Abstract

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.

Citation Download Citation

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); https://doi.org/10.1117/12.780466

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