# A CMOS Optoelectronic Transceiver with Concurrent Automatic Power Control for Short-Range LiDAR Sensors

## TL;DR

This paper introduces a CMOS-based optoelectronic transceiver for short-range LiDAR sensors with automatic power control to improve performance and efficiency.

## Contribution

A novel concurrent automatic power control circuit in a CMOS optoelectronic transceiver for short-range LiDAR is proposed.

## Key findings

- The transceiver uses a modified VCSEL driver and a differential transimpedance amplifier for improved performance.
- The APC circuit adjusts the VCSEL bias current to compensate for threshold current increases.
- Test chips showed a DC bias current increase from 0.93 mA to 1.42 mA as input current decreased.

## Abstract

This paper presents an optoelectronic transceiver (OTRx) realized in a 180 nm CMOS technology for applications of short-range LiDAR sensors, in which a modified current-mode single-ended VCSEL driver (m-CMVD) is exploited as a transmitter (Tx) and a voltage-mode fully differential transimpedance amplifier (FD-TIA) is employed as a receiver (Rx). Especially for Tx, a concurrent automatic power control (APC) circuit is incorporated to compensate for the inevitable increase in the threshold current in a VCSEL diode. For Rx, two on-chip spatially modulated P+/N- well avalanche photodiodes (APDs) are integrated with the FD-TIA to achieve circuit symmetry. Also, an extra APD is added to facilitate the APC operations in Tx, i.e., concurrently adjusting the bias current of the VCSEL diode by the action of the newly proposed APC path in Rx. Measured results of test chips demonstrate that the proposed OTRx causes the DC bias current to increase from 0.93 mA to 1.42 mA as the input current decreases from 250 µApp to 3 µApp, highlighting its suitability for short-range sensor applications utilizing a cost-effective CMOS process.