A Low-Voltage Sub-ns Pulse Integrated CMOS Laser Diode Driver for SPAD-based Time-of-Flight Rangefinding in Mobile Applications

A fully integrated laser diode driver being currently manufactured in 40nm CMOS technology is presented. It is dedicated for fast sub-ns laser pulses generation with the aim of improving accuracy and resolution of SPAD-based time-of-flight (TOF) rangefinder in mobile devices. The proposed driver circuit is based on capacitive charge transfer. Its specific features are a voltage doubler design for increase laser power at low input voltage (<3V), as well as a reverse bias voltage scheme to address typical laser diode slow turn-off transient (optical tail). Simulation results based on electro-optical laser diode model and post-layout extraction shows that, for a 2.5V supply voltage, the driver can produce a typical 460ps laser drive current pulse up to 230mA. With these settings, a 208ps laser pulse with a 238mW peak power is generated. In addition, the current pulse width can be configured down to 375ps to generate sub-100ps laser pulses. The power consumption of the proposed driver circuit is 113mW at 200MHz repetition rate.