A CMOS LiDAR Sensor Using Time-to-Voltage Converter for Elder-Care Applications

Abstract

This paper presents an optoelectronic readout integrated circuit (ORIC) fabricated in 180-nm CMOS technology, tailored for high-resolution, short-range LiDAR sensing applications. The ORIC pixel integrates an on-chip P+/Nwell/Deep N-well avalanche photodiode and a CMOS transimpedance-limiting amplifier employing active feedback for low-noise performance. Then, a time-to-voltage (T2V) conversion scheme is adopted to enable precise signal quantization with minimal walk error, which is followed by a voltage-domain successive approximation register (SAR) analog-to-digital converter (ADC). This architecture is suggested to replace conventional time-to-digital converters (TDCs), thereby significantly reducing system complexity while maintaining wide dynamic range and high scalability. Post-layout simulations indicate an input dynamic range of 47.4 dB that corresponds to the detectable photocurrent levels ranging from 15 μA_pp to 3.5 mA_pp. This can be translated to a measurable distance of 31 centimeters to 4.76 meters under typical operating conditions. To the best of the authors’ knowledge, this is the first attempt to substitute a TDC with a T2V-SAR ADC pipeline for LiDAR sensors, offering a compact, low-power, and scalable solution for emerging applications such as ambient-assisted living and elderly monitoring systems.