A 3A Low Voltage Laser Diode Driver IC in a CMOS technology for an iToF-based 3D image sensor

This paper presents a Laser Diode Driver (LDD) intended for a 3D image sensor used in mobile phones and based on the indirect Time-of-Flight (iToF) measurement. The work is focused on the study and design of the Integrated Circuit (IC) considering constraints related to mobile applications (low input voltage range, strong integration). The architecture relies on a classical driving topology where a buck-boost DC/DC converter is employed for controlling the current through the laser diode with a high power efficiency while a switching element is connected in series with the diode for generating laser pulses. The novelty here concerns the feasibility of integrating the whole solution (except laser diode and off-chip passive components) on a single chip. A LDD prototype has been implemented in a 130nm CMOS technology from STMicroelectronics. It is able to provide current pulses up to 3A with a 2.5ns pulse width at a maximum 200MHz Pulse Repetition Frequency (PRF) for a 3.6V supply voltage. Under theses conditions, the prototype delivers an average output electrical power of 4.5W to the laser diode with an electrical efficiency of 63%.