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A Small-Area and Energy-Efficient 12-bit SA-ADC With Residue Sampling and Digital Calibration for CMOS Image Sensors

Title
A Small-Area and Energy-Efficient 12-bit SA-ADC With Residue Sampling and Digital Calibration for CMOS Image Sensors
Author
권오경
Keywords
CMOS image sensor (CIS); column-parallel readout; foreground digital calibration; successive approximation analog-to-digital converter (SA-ADC)
Issue Date
2015-10
Publisher
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
Citation
IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS II-EXPRESS BRIEFS, v. 62, NO 10, Page. 932-936
Abstract
This brief proposes a small-area and energyefficient 12-bit successive approximation analog-to-digital converter (SA-ADC) for CMOS image sensors with a column-parallel readout structure. The proposed SA-ADC, which uses only a 6-bit capacitor digital-to-analog converter (DAC) for residue sampling, reduces the capacitor area to 1/64th of that for the 12-bit capacitor DAC and adopts the scaled reference voltages for 12-bit conversion. It also achieves 88% lower switching energy of the capacitor DAC compared with the 12-bit SA-ADC with split capacitor structure. A foreground digital calibration is employed to compensate for the linearity error caused by the inaccurately scaled reference voltages. A test chip, which has 100 readout channels with the proposed SA-ADC, is fabricated using a 0.18-mu m CMOS process. The measurement results show that the proposed SA-ADC with the proposed digital calibration has differential nonlinearity (DNL) of -0.8/+1.7 LSB and integral nonlinearity (INL) of -2.3/+2.4 LSB, and without the calibration, it has DNL of -1/+14.9 LSB and INL of -15.8/+12.7 LSB. In addition, a digital correlated double sampling method improves the standard deviation of the readout channel outputs from 62.1 to 1.4 LSB.
URI
http://ieeexplore.ieee.org/document/7161297/?arnumber=7161297&tag=1http://hdl.handle.net/20.500.11754/28308
ISSN
1549-7747; 1558-3791
DOI
10.1109/TCSII.2015.2457812
Appears in Collections:
COLLEGE OF ENGINEERING[S](공과대학) > ELECTRONIC ENGINEERING(융합전자공학부) > Articles
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