DR. QUAZI DELWAR HOSSAIN a SELF-ADJUSTING LIN-LOG ACTIVE PIXEL FOR WIDE DYNAMIC RANGE CMOS IMAGE SENSOR PRESENTED BY Md.Akramul Islam Minhaz Ibna Abedin ID no. 1002003 ID no. 1002053 SUPERVISED BY DR. QUAZI DELWAR HOSSAIN ASSOCIATE PROFESSOR DEPARTMENT OF EEE,CUET. Department of EEE, CUET

OUTLINE Objectives Pixel Literature Review Dynamic Range DR Extension by Logarithmic Response Proposed Pixel Simulation Results Layout Design Summary Future Works Conclusion Department of EEE, CUET

Objectives To design a pixel to increase Dynamic Range maintaining high Fill Factor. Simulation and Comparison with the standard linear and logarithmic response pixels. 11.5 µm× 11.5 µm layout design of the proposed pixel in 180nm technology. Department of EEE, CUET

Pixel Pixel is short of Picture Element. Thousands of Pixels form an image. PHOTODIODE RESET TRANSISTOR SOURCE FOLLOWER READ-OUT CIRCUIT Figure: Basic components of a Pixel “Review of CMOS image sensors “M. Bigas, E. Cabruja, J. Forest, J. Salvi Microelectronics Journal 37 (2006) 433–451 Department of EEE, CUET

Literature Review Logarithmic Active Pixel Sensor Linear Active Pixel Sensor Logarithmic Active Pixel Sensor Advantage: Low illumination, good performance Advantage: High illumination, good performance Disadvantage: High illumination, bad performance Disadvantage: Low illumination, bad performance “Wide-Dynamic-Range Pixel with Combined Linear and Logarithmic Response and Increased Signal Swing”,Eric C. Fox, Jerry Hynecek, and Douglas R. Dykaar DALSA Department of EEE, CUET

Figure:The pixel with comparator and its reference signal . Literature Review Comparator Reference signal Figure:The pixel with comparator and its reference signal . Advantage : Wide Dynamic Range. Disadvantage: Additional in-pixel comparator decreases Fill Factor and external analog signal required. “A High-Dynamic-Range Integrating Pixel With an Adaptive Logarithmic Response” Hsiu-Yu Cheng,, Bhaskar Choubey, and Steve Collins, IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 19, NO. 15, AUGUST 1, 2007 Department of EEE, CUET

Literature Review (a) (b) Figure: (a) A schematic circuit with PMOS reset and switch transistors (Mp1 and Mp2) [1] and (b) A schematic circuit with NMOS isolator (M4) [2]. [1]“A Wide Dynamic Range CMOS Image Sensor with an Adjustable Logarithmic Response” Bhaskar Choubey, Hsiu-Yu Cheng and Steve Collins, IEEE TRANSACTIONS ON ELECTRON DEVICES, VOL. 56, NO. 11, NOVEMBER 2009 [2]“On Threshold Comparing Biomorphic Image Sensors” Waqas Mughal Luiz Carlos Gouveia, and Bhaskar Choubey University of Glasgow,Glasgow, U.K. Procedia Computer Science Volume 41, 2014, Pages 140–145 Department of EEE, CUET

Dynamic Range Dynamic Range can be defined as the ratio of maximum unsaturated photocurrent to the minimum detectable photocurrent. Techniques for Dynamic Range extension Logarithmic Response Well Capacity Adjustment Time to Saturate Multiple Capture Department of EEE, CUET

DR Extension by Logarithmic Response Figure: Pixel output voltage of Linear and Logarithmic APS to show their responses throughout the illumination (Photocurrent) range. Department of EEE, CUET

Proposed Pixel Reset Transistor to provide linear response Vdd Reset Transistor to provide linear response Row Select Vout Photodiode N1 N2 P1 N3 N4 Gate to Drain connected NMOS to provide logarithmic response Reset Source Follower Transistor PMOS to allow or block logarithmic response Row Select Transistor Figure: Schematic diagram of Proposed Pixel. Department of EEE, CUET

Pixel in Logarithmic Mode Proposed Pixel Vdd Row Select Vout Photodiode N1 N2 P1 N3 N4 PMOS in “On” state PMOS in “Off” state Pixel in Linear Mode Pixel in Logarithmic Mode Reset Gate Voltage Figure: DC Analysis of PMOS in Cadence Virtuoso shows the source to drain current versus gate voltage. Department of EEE, CUET

Simulation Results Photo Current Linear APS Logarithmic APS Table : Pixel Output Voltage of Linear APS, Logarithmic APS and Proposed Pixel Photo Current Linear APS Logarithmic APS Proposed Pixel 250n A 0 V 814m V 17.59m V 25n A 893m V 79.84m V 2.5n A 965m V 176m V 250p A 1 V 285m V 25p A 365m V 1.089 V 400m V 2.5p A 588m V 1.11 V 578m V 250f A 650m V 1.12 V 734m V 25fA 789m V 798m V 2.5f A 801m V Department of EEE, CUET

And dynamic range of 120dB for Logarithmic APS. Simulation Results . Figure: Pixel output voltage versus Photocurrent of linear and logarithmic active pixels. It shows dynamic range of 100dB for Linear APS And dynamic range of 120dB for Logarithmic APS. Department of EEE, CUET

Simulation Results . Figure: Pixel output voltage versus Photocurrent of the Proposed Pixel. It shows a wider dynamic range of 160dB. It shows better response in both high and low illumination. Department of EEE, CUET

Layout Design Photodiode Source Follower Reset Transistor PMOS Gate to Drain connected NMOS Figure: 11.5µm × 11.5µm layout design of the proposed pixel in 180nm CMOS Technology. It has a Fill Factor of 45%. Department of EEE, CUET

Layout Design Photodiode a) b) Metal Layer 2 Metal Layer 1 c) Figure: a) 3D view of the pixel b) Top view of the pixel c) Cross-sectional view of the pixel. Department of EEE, CUET

180nm CMOS Technology Node Summary Technology 180nm CMOS Technology Node Pixel Size 11.5µm × 11.5µm Photo Detector Photodiode Transistor Per Pixel 5 Fill Factor 45% Dynamic Range 160dB Department of EEE, CUET

Future Works To design and fabricate a 512 x 512 pixel array to analyze the performance of the proposed pixel. To design Double Sampling circuit for column readout. Reduction of FPN and Image lag. Implementation of Anti-Blooming transistor or In-pixel current calibration. Department of EEE, CUET

Conclusion A simple technique has been found for self adjusting Linear-Logarithmic response. A Wide Dynamic Range of 160dB and Fill Factor of 45% has been found which satisfies the objective of the project. Department of EEE, CUET

Thank You Department of EEE, CUET