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A 20ch TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique

A 20ch TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique

ISSCC 2018

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Kentaro Yoshioka

January 07, 2022
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  1. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 1 of 50 A 20ch TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique Kentaro Yoshioka, Hiroshi Kubota, Tomonori Fukushima, Satoshi Kondo, Ta Tuan Tan, Hidenori Okuni, Kaori Watanabe, Yoshinari Ojima, Katsuyuki Kimura, Sohichiroh Hosoda, Yutaka Oota, Tomohiro Koizumi, Naoyuki Kawabe, Yasuhiro Ishii, Yoichiro Iwagami, Seitaro Yagi, Isao Fujisawa, Nobuo Kano, Tomohiko Sugimoto, Daisuke Kurose, Naoya Waki, Yumi Higashi, Tetsuya Nakamura, Yoshikazu Nagashima, Hirotomo Ishii, Akihide Sai, Nobu Matsumoto Toshiba Corporation, Kawasaki, Japan Toshiba Memory, Kawasaki, Japan
  2. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 2 of 50 Outline • Motivation • LiDAR Fundamentals and Error Sources • Smart Accumulation Technique • SoC implementation • Measurement Results • Conclusion
  3. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 3 of 50 Motivation Waymo / Pacifica General Motors / Cruise Tesla / ModelS www.tesla.com waymo.com wired.com Ultrasonic Camera mm-wave Radar LiDAR Max Distance × × △ ◎ Resolution × ◎ × ◯ Environment robustness ◦ △ ◦ △ General Benchmark of Depth Sensors
  4. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 4 of 50 LiDAR Requirements • Urban area driving: – High image quality for early and certain pedestrian detection • Highway driving: – Long range (200m) vehicle detection Our Goal: Realization of 200m & High image quality LiDAR system !! Pedestrian APedestrian B Car A Car B Car C 200m Braking distance@120km/h >150m
  5. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 5 of 50 Outline • Motivation • LiDAR Fundamentals and Tradeoffs • Smart Accumulation Technique • SoC implementation • Measurement Results • Conclusion
  6. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 6 of 50 LiDAR Fundamentals • LiDAR measures the distance to object by Time-of-Flight (ToF) Laser emitted Laser pulse time time SiPM output LiDAR System Laser SoC SiPM Polygon mirror [Niclass, ISSCC2013]
  7. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 7 of 50 LiDAR Fundamentals • LiDAR deviates the distance to object by Time-of-Flight (ToF) Light Reflected ToF Laser emitted Laser pulse time time SiPM output ToF Distance to object =Light speed x ToF 2 LiDAR System Laser SoC SiPM Polygon mirror [Niclass, ISSCC2013]
  8. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 8 of 50 LiDAR Fundamentals 240~2000pix 96~120pix SiPM channels 2-D scan of the laser beam is conducted by rotating the 6-way polygon mirror. LiDAR System Laser SoC SiPM Polygon mirror 10 frames/sec(FPS)
  9. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 9 of 50 LiDAR Sunlight Problem • Sunlight is the largest noise source in LiDAR – Strong sunlight degrades SNR significantly SiPM Laser SoC SNR: Num. laser photons Num. noise photons = Laser time time SiPM Wrong ToF! Sunlight Laser LiDAR System Laser SoC SiPM Polygon mirror
  10. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 10 of 50 LiDAR Measurement Distance • Laser power loss follows inverse square law – More worsened SNR @ 200m LiDAR System SiPM Laser SoC @200m Laser time time SiPM Wrong ToF! Sunlight Laser Laser SoC SiPM Polygon mirror SNR: Num. laser photons Num. noise photons = Laser time time SiPM Wrong ToF! Sunlight Laser
  11. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 11 of 50 Method of SNR Improvement While sunlight photons are random events, Laser photons are periodic  Accumulation improves SNR by square root of acc. pixels Pix.1 Pix.2 Pix.3 Laser Accumulation of pix.1~3 ToF Sunlight • “Simple” accumulation – If the pixel is “watching” the same object, SNR improves – Improves max. distance & sunlight, but image quality? [Niclass, ISSCC2013]
  12. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 12 of 50 Problem of Simple Accumulation • Image quality degrades with simple accumulation – Can lead to misdetection of pedestrians – Image quality is crucial for self-driving LiDARs Non-target reflection Target reflection Target object Non-target A D G B E H C F I Measuring pixel (MP) Pixel A,B,C Pixel E Pixel D,F,G,H,I time time time Target reflection Simple accumulation A+B+C+D+E+F+G+H+I time Detected peak Wrong! 
  13. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 13 of 50 Problem of Simple Accumulation Non-target reflection Target reflection Target object Non-target A D G B E H C F I Measuring pixel (MP) Pixel A,B,C Pixel E Pixel D,F,G,H,I time time time Target reflection Simple accumulation A+B+C+D+E+F+G+H+I time Detected peak Wrong!  Function similar to “blur” algorism
  14. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 14 of 50 Main Tradeoffs in LiDAR Design • Requirement extremely strict for self-driving LiDARs Importantly: Laser power limited by eye-safety Measurement Distance Sunlight Tolerance Image Quality (FPS, num.pixels) Target Image Quality High Low Measurement Distance [m] 100 200
  15. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 15 of 50 Main Tradeoffs in LiDAR Design • Break the performance tradeoff by SAT Importantly: Laser power limited by eye-safety Measurement Distance Sunlight Tolerance Image Quality (FPS, num.pixels) Image Quality High Low Smart accumulation technique (SAT) Measurement Distance [m] 100 200
  16. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 16 of 50 Outline • Motivation • LiDAR Fundamentals and Noise Sources • Smart Accumulation Technique • SoC implementation • Measurement Results • Conclusion
  17. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 17 of 50 Concept of Smart Accumulation Technique (SAT) • Classify objects utilizing LiDAR raw-data characteristics • Accumulate pixels watching the same object only; SNR improves significantly – Peak level has high correlation with distance and reflectivity of the object – Floor level also has strong correlation with the object distance and reflectivity A D G B E H C F I Pixel A,B,C Pixel D,E,F,G,H,I time time Peak level Peak level Floor level Floor level
  18. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 18 of 50 Smart Accumulation Algorism Target object Non-target A D G B E H C F I Measuring pixel Pixel A,B,C Pixel E Pixel D,F,G,H,I PL Peak level Floor level FL Correlation of PL & FL above threshold? Accumulate Skip SAT Algorism D,F,G,H,I A,B,C Yes No PL FL
  19. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 19 of 50 Smart Accumulation Algorism Target object Non-target A D G B E H C F I Measuring pixel Pixel A,B,C Pixel E Pixel D,F,G,H,I PL Peak level Floor level High correlation! FL Correlation of PL & FL above threshold? Accumulate Skip SAT Algorism D,F,G,H,I A,B,C Yes No PL FL
  20. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 20 of 50 Smart Accumulation Algorism Target object Non-target A D G B E H C F I Measuring pixel Pixel A,B,C Pixel E Pixel D,F,G,H,I PL High correlation! Peak level Floor level FL Correlation of PL & FL above threshold? Accumulate Skip SAT Algorism D,F,G,H,I A,B,C Yes No Simple accumulation A+B+C+D+E+F+G+H+I time Detected peak Wrong!  Smart accumulation(SAT) D+E+F+G+H+I time Detected peak Correct!  Accumulated waveforms Long meas. range + High image quality
  21. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 21 of 50 Quantitive Analysis of SAT Simulation result of 200m range distance measurement 20 30 40 50 60 70 80 90 100 0 5 10 15 20 25 30 35 40 Succesion rate [%] Target Size [pixel2] 9 pixels w/simple accumulation [1] 9 pixels w/SAT 90% succession SAT achieves 4x higher effective pixel-resolution Target: Reflectivity 10%@200m Random width NonTarget objects: Reflectivity 100% Random distance
  22. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 22 of 50 Outline • Motivation • LiDAR Fundamentals and Noise Sources • Smart Accumulation Technique • SoC Implementation – Implementation Challenges – TDC/ADC Hybrid Architecture – Residue-Quantizing Noise Shaping (RQNS) SAR ADC • Measurement Results • Conclusion
  23. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 23 of 50 Implementation Challenges • Sub-cm distance resolution required for short-range(<20m) measurements (e.g. parking assists, curb detection) – TDC are easy to implement, but cannot use SAT – GS/s ADCs require huge silicon area but SAT enhances SNR Sampling rate 1G 10G Distance Resolution Several cm Sub-cm 10GS/s ADC area: 1mm2! 20ch=20mm2 [Cui, ISSCC2016] Pros: Very fast and small area Cons: Acquires ToF data only  Pros: Can acquire amplitude data Enable use of SAT Cons: Slow and large area  TDC Time-to-Digital Converter ADC LiDAR Quantizer circuitry
  24. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 24 of 50 Hybrid Architecture Concept Difficult to implement ToF Measurement Error Measurement Distance 20m 25GS/s ADC ToF Error 200m Use ADCs Target Spec Sub- cm Several- cm
  25. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 25 of 50 Hybrid Architecture Concept Use TDCs Use ADCs 25GS/s TDC 20ch TDC array 400MS/s ADC 20ch ADC array Used for short-range measurements (0-20m) Used for long-range measurements (20-200m) • Use TDCs to obtain sub-cm resolution with small circuits – ADC used for long-range(20-200m) only Sampling rate greatly relaxed ToF Measurement Error Measurement Distance 20m Sub- cm Several- cm 400MS/s ADC ToF Error 200m Target Spec 25GS/s TDC ToF Error
  26. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 26 of 50 LiDAR SoC Block Diagram Digital block Smart Accumulation (SAT) R I Image Construction Short-Range(SR) measurement block TIA CFD 12b TDC 20ch From SR SiPM Long-Range(LR) measurement block TIA DC-Calibration 20ch From LR SiPM 400MS/s 5b NS-SAR ADC 20ch D ADC 20ch D TDC Vth Custom designed SiPMs SR: High saturation value LR: High sensitivity SAT algorithm Used for ADC outputs only; Requires amplitude info. NS-ADCs Novel design for LiDAR
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    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 27 of 50 Conventional NS SAR ADCs C-DAC area dominating SAR ADCs Input C-DAC Logic Logic Noise shaping circuit Reduced C-DAC area  Large noise shaping circuit  Noise shaping SAR ADCs Input C-DAC Resolves more ENOBs with fewer cycles
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    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 28 of 50 Proposed RQNS SAR ADC C-DAC area dominating SAR ADCs Input C-DAC Logic Logic RQ circuit Reduced C-DAC area  Small noise shaping circuit  Residue Quantizing NS (RQNS) SAR ADC Input C-DAC Moves noise shaping to digital domain
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    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 29 of 50 RQNS SAR ADC Block Diagram Vres Residue Quantizing 3b SAR + - Proposed 2nd order RQNS Main 5b SAR C-DAC SAR Logic Fin Vin 1 - 2z-1 + z-2 =(1-z-1)2 2nd order NS Dres [z-2] Dres [z-1] Dres Fin Digital domain Residue Feedback Residue is digital; S&H, amplification easily done by FF & bitshifts 2nd order NS is realized with optimized zeros
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    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 30 of 50 ADC Measurements 30 0.001 0.01 0.1 1 0.0001 0.001 0.01 0.1 1 Area [mm2] Power [W] This Work ISSCC 1997-2017 SNDR>35dB BW=50-400MHz RQNS ADC SNDR@BW 100MHz 37.7dB fs [MS/s] 400 Active area [mm2] 0.0011 Power [mW] 1 -90 -80 -70 -60 -50 -40 -30 -20 -10 0 0.1 1 10 100 Power [dBFS] Frequency [MHz] 40dB /dec. fs =400MS/s fin =9.8MHz SNDR=37.7dB BW=100MHz BW=100MHz B. Murmann, “ADC Performance Survey 1997-2017,” [Online] Available: http://web.Stanford.edu/~Murmann/adcsurvey.html
  31. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 31 of 50 Outline • Motivation • LiDAR Fundamentals and Noise Sources • Smart Accumulation Technique • SoC implementation • Measurement Results • Conclusion
  32. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 32 of 50 Fabricated LiDAR SoC 5mm 2.5mm PLL+ BGR 22ch TIA for TDC 22ch TIA for ADC 22ch TDC 11ch ADC 11ch ADC Digital Circuits 28nm CMOS 22ch respectively For calibration and measurement
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    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 33 of 50 200m Outdoor Measurement Setup 200m Lidar System Developed LiDAR System Measured under 100klux sunlight (70klux@LiDAR input) 10% reflectivity moveable target Ground truth measured by line scanner
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    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 34 of 50 200m Outdoor Measurement Results 50 60 70 80 90 100 0 50 100 150 200 250 Succession rate* [%] Distance [m] 90% succession 92.7%@200m 0 50 100 150 200 250 0 50 100 150 200 250 Measured Distance [m] Actual Distance [m] Accuracy 99.9% Computed from successful measurements [Niclass, ISSCC2013] *Succession determined as DM with <±1% error 0 50 100 150 200 250 300 0 50 100 150 200 250 Standard deviation [mm] Distance [m] s=0.125% of distance
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    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 35 of 50 Effect of Smart Accumulation Algorithm Imaged blurred Road detected Pedestrian undetected Road undetected Pedestrian Camera image “Simple” Accumulation Without Accumulation High image quality, but only short distance Poor image quality, Unable to small objects
  36. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 36 of 50 Effect of Smart Accumulation Algorithm Pedestrian undetected Road undetected Pedestrian Camera image “Simple” Accumulation Without Accumulation Road detected Pedestrian detected “Smart” Accumulation High image quality, Able to detect small obj.
  37. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 37 of 50 3D Point Cloud
  38. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 38 of 50 Benchmarking [1] [2] This Work SPADs APD SiPM SiPM Architecture ADC TDC Hybrid Pixel-Resolution 600X96 202X96 240X96 Effective Pixel-Resolution N.A. 1x 4x Accumulation N.A. Simple Smart Sunlight [klux] N.A. 70 70 Max. Distance 100m 100m 200m [1] Velodyne, “High Definition Lidar White Paper” [Online]. Available: http://velodynelidar.com/docs/papers/HDL%20white%20paper_OCT2007_web.pdf [2] C. Niclass, et al, “A 0.18um CMOS SoC for a 100m-Range 10fps 200x96 Pixel Time-of-Flight Depth Sensor,” ISSCC 2013.
  39. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 39 of 50 Conclusion • A LiDAR SoC realizing 200m measurement with high image quality has been proposed. • Smart accumulation technique was proposed, breaking the distance and image quality tradeoff – SAT effectively was confirmed in real environment – 4x effective pixel-resolution enhanced compared to simple accumulations • To achieve high measurement accuracy in short range with low SoC cost, TDC/ADC hybrid architecture was proposed. – RQNS SAR ADC was proposed to further downscale ADC area
  40. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 40 of 50 Demonstration • First LiDAR demo at ISSCC! – 5-7PM tonight @ Golden Gate Hall – Class1 eye safety  40 3D point cloud view ADC Image TDC Image Luminescence
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    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 41 of 50 TDC/ADC Hybrid Architecture 41 Digital block Smart Accumulation (SAT) Ra Im Image Construction Short-Range(SR) measurement block TIA CFD 12b TDC 20ch From SR SiPM Long-Range(LR) measurement block TIA DC-Calibration 20ch From LR SiPM 400MS/s 5b NS-SAR ADC 20ch D ADC 20ch D TDC Vth
  42. © 2018 IEEE International Solid-State Circuits Conference 5.7: A 20ch

    TDC/ADC Hybrid SoC for 240x96-pixel 10%-Reflection <0.125%-Precision 200m-Range-Imaging LiDAR with Smart Accumulation Technique 42 of 50 Robustness against variation 42 + Vin Dout Vres z-1 +- z-2 2 -1 k 30 31 32 33 34 35 36 37 38 39 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 SNDR/SQNR[dB] k Default k