Title :
Noise model of indirect-feedback sigma-delta image sensors
Author :
Zhe Gao ; Liobe, John C. ; Ignjatovic, Zeljko ; Bocko, M.F.
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 to which the buffered photodiode voltage is compared is shown. A time-domain pixel simulator that enables assessment of major noise contributors in this type of imager is also presented. Theoretical calculations align with simulation results, showing a minimum readout noise of 2.18e- and a dynamic range of over 100dB. A prototype chip has been developed in TSMC´s 0.35-μm technology and its performance will be assessed.
Keywords :
CMOS image sensors; buffer circuits; circuit feedback; circuit noise; counting circuits; photodiodes; readout electronics; reference circuits; sigma-delta modulation; time-domain analysis; ΣΔ modulator; TSMC technology; analog voltage convertor; buffered photodiode voltage; column-level sigma-delta analog-to-digital converter; digital counter; indirect-feedback readout architecture; indirect-feedback sigma-delta CMOS image sensor; noise model; reference voltage; time-domain pixel simulator; Image sensors; Integrated circuit modeling; Noise; Photodiodes; Quantization (signal); Thermal noise; Time-domain analysis; Indirect-feedback ΣΔ image sensor; high dynamic range; noise modeling; time-domain simulator;
Conference_Titel :
Circuits and Systems (ISCAS), 2013 IEEE International Symposium on
Conference_Location :
Beijing
Print_ISBN :
978-1-4673-5760-9
DOI :
10.1109/ISCAS.2013.6572311
