A 32-Channel 8-bit DAC-based Driver IC with Channel Uniformity Optimization for Optical Phased Arrays

Light detection and ranging (LiDAR) technology, which leverages light instead of radio waves as the source, offers superior resolution and resistance to jamming, making it a promising alternative to radio detection and ranging (RADAR) for 3D imaging and object detection. Silicon photonics-based optical phased arrays (OPAs) enable non-mechanical beam steering, overcoming the limitations of traditional rotating LiDAR systems. In OPAs, optical phase shifts are realized with the driver IC, which provides the necessary analog voltages to the optical phase shifters. This paper presents a 32-channel OPA driver IC designed to achieve high linearity and enhanced channel-to-channel uniformity. The proposed IC integrates an 8-bit digital-to-analog converter (DAC) based on an R-2R ladder, a high-gain rail-to-rail amplifier, and an I²C serial interface to support scalable multi-chip operation up to 128 channels. Key design strategies include layout optimization of resistors and MOSFETs within the driver to reduce mismatch and improve channel consistency under process variations. Fabricated in a 180 nm CMOS process, the proposed IC delivers monotonic DAC operation with a worst-case differential nonlinearity (DNL), which quantifies the deviation in step size between adjacent codes, of 0.52 least significant bits (LSB), and an integral nonlinearity (INL), which measures the deviation of the DAC transfer function from an ideal straight line, of 0.81 LSB, validating its process-robust design. Beamforming simulations using measured DAC performance demonstrate minimal performance degradation, with less than 0.2% main lobe intensity loss and negligible side lobe suppression ratio degradation. These results confirm that the proposed driver IC is suitable for robust and scalable OPA-based LiDAR systems.