Speaker
Description
LIDAR is a distance and speed measurement device using reflection characteristics of emitted light. In space applications, time-tagging LIDAR allows scanning planet surface before landing missions, formation flights by measuring distances between spacecrafts or atmospheric backscatter measurements. The main requirements for the read-out electronics are trifold: single-photon time-tagging capabilities for long range measurements, timing resolution better than LIDAR system (SiPM intrinsic resolution, laser pulse-width, etc.) and minimized dead time.
LIROC is a 64-channel front-end R&D ASIC designed to read silicon photomultipliers delivering charges in the range 50 fC - 10 pC. The ASIC is composed of a 1 GHz RF preamplifier followed by a fast discriminator and low swing LVDS fast driver with a power consumption of 3 mW per channel. The circuit exhibits also a fast return to baseline thanks to its tunable pole zero cancellation circuit prior to the preamplifier. The ASIC also embeds channel-wise DAC for SiPM overvoltage adjustment. Designed in TSMC 130nm, LIROC can furthermore withstand radiation environments up to multi-MRad radiation levels. LIROC configuration can be programmed using an I2C interface that has been triplicated for SEU tolerance.
LIROC has been extensively characterized: first, a pulser has been used to inject an equivalent charge using a detector-like capacitance connected to the channel under test, second measurements have been performed with multiple SiPM devices using a LASER testbench. The ASIC has a Single Photon Timing Resolution of 3.9 ± 0.4 ps RMS when coupled to a detector-emulated capacitor of 100 pF (with an injected charge of 160 fC obtained with a 200 ps transition time voltage step through a 10 pF capacitance). When coupled to SiPM, LIROC time resolution is therefore limited by SiPM intrinsic performances, as state-of-the-art devices have around 70 ps FWHM time resolution (expressed as FWHM to take into account the tail of the Time-Of-Arrival distribution due to delayed photon conversion). LIROC has also shown excellent double-peak separation with 100% efficiency for double pulses separated above 3 ns, which is consistent with photocounting capability of up to 300 MHz. LIROC allows also time-walk correction and input charge estimation thanks to Time-Over-Threshold/discriminator width measurements. Results from LASER testbench will be detailed and compared with simulation.
LIROC architecture will be described, as well as foreseen spatial LIDAR with CERN PicoTDC enabling sub-centimeter resolution with picosecond TDC precision. This project results from the work of the collaboration between WEEROC and OMEGA and has received funding from the ATTRACT project funded by the EC under Grant Agreement 777222.
