A 30-frames/s, 252 x 144 SPAD Flash LiDAR With 1728 Dual-Clock 48.8-ps TDCs, and Pixel-Wise Integrated Histogramming

Chao Zhang*, Scott Lindner, Ivan Michel Antolovic, Juan Mata Pavia, Martin Wolf, Edoardo Charbon

*Corresponding author for this work

    Research output: Contribution to journalArticleScientificpeer-review

    125 Citations (Scopus)


    A 252 × 144 single-photon avalanche diode (SPAD) pixel sensor, called Ocelot, is reported for light detection and ranging (LiDAR). The sensor, fabricated in the 180-nm CMOS technology, features 1728 12-bit time-to-digital converters (TDCs) with 48.8-ps resolution (LSB). Each 126 pixels in a half-column are connected to six TDCs through a collision detection bus, which enables effective sharing of resources, and consequently a fill factor of 28% with a pixel pitch of 28.5 μ text{m}. The column-parallel TDCs, based on dual-clock architecture, exhibit a DNL of +0.48/-0.48 LSB and an INL of +0.89/-1.67 LSB; they are dynamically reallocated in a scalable daisy chain approach that enables a maximum of five photon detections per illumination cycle per half-column. The sensor can operate in time-correlated single-photon counting (TCSPC) and single-photon counting (SPC) modes, while peak detection (PD) and partial histogramming (PH) are included in the operation of the sensor. The PD and PH modes are enabled by the first implementation of integrated histogramming for a full array via 3.32-Mb SRAM-based PH readout (PHR) scheme providing a 14.9-to-1 compression. Telemetry measurements up to 50 m achieve an accuracy of 8.8 cm and worst-case precision of 1.4 mm ( σ ). A flash LiDAR using direct time of flight (dTOF) and based on Ocelot is demonstrated, achieving depth imaging at short distances with a frame rate of 30 frames/s, employing an ultra-low power laser with an average power of 2 mW and peak power of 0.5 W.

    Original languageEnglish
    Article number8595429
    Pages (from-to)1137-1151
    Number of pages15
    JournalIEEE Journal of Solid-State Circuits
    Issue number4
    Publication statusPublished - 2019


    • 3-D imaging
    • advanced driver-assistance systems (ADAS)
    • autonomous driving
    • CMOS
    • direct time of flight (dTOF)
    • histogramming
    • image sensor
    • indirect TOF (iTOF)
    • light detection and ranging (LiDAR)
    • self-driven cars
    • single-photon avalanche diodes (SPADs)
    • TDC sharing architecture
    • time-to-digital converter (TDC)
    • TOF


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