Title :
Indirect-Feedback Sigma-Delta Image Sensors: Theory, Modeling and Design
Author :
Zhe Gao ; Liobe, John C. ; Bocko, M.F. ; Ignjatovic, Zeljko
Author_Institution :
Electr. & Comput. Eng. Dept., Univ. of Rochester, Rochester, NY, USA
Abstract :
A novel architecture for a CMOS image sensor that incorporates a column-level sigma-delta (ΣΔ) analog-to-digital converter is presented. An indirect-feedback readout architecture where the digital output of the ΣΔ modulator is accumulated by a digital counter and converted to an analog voltage that serves as the reference voltage in the modulator´s comparator is employed. A time-domain pixel simulator that enables assessment of the major noise contributions in this type of imager is also presented. Theoretical calculations agree with simulation results, showing a minimum readout noise of 2.18e- and a dynamic range (DR) of over 100 dB. Prototype chip tests without multiple resets show an 87 dB dynamic range with a readout noise of 2.17e-.
Keywords :
CMOS image sensors; circuit feedback; comparators (circuits); counting circuits; integrated circuit design; integrated circuit modelling; integrated circuit noise; readout electronics; reference circuits; sigma-delta modulation; time-domain analysis; ΣΔ analog-to-digital converter; ΣΔ modulator; CMOS image sensor; column-level sigma-delta analog-to-digital converter; comparator; digital counter; gain 87 dB; indirect-feedback readout architecture; indirect-feedback sigma-delta image sensor; reference voltage; time-domain simulator; Integrated circuit modeling; Modulation; Noise; Photodiodes; Quantization (signal); Simulation; Transistors; High dynamic range; indirect-feedback $SigmaDelta$ image sensor; noise modeling; time-domain simulator;
Journal_Title :
Circuits and Systems I: Regular Papers, IEEE Transactions on
DOI :
10.1109/TCSI.2013.2268512
