Ensuring LiDAR automotive distance sensor precision with the right TIA

Author : Rolf Horn | Applications Engineer | Digi-Key Electronics

01 April 2021

Digi-Key_Ensuring LiDAR automotive distance sensor precision with the right TIA
Digi-Key_Ensuring LiDAR automotive distance sensor precision with the right TIA

For autonomous vehicles to succeed, passengers must trust the car’s sensors & software to guide them safely & accurately to the destination. The key to delivering on this trust lies in the fusion of inputs from various sensor types to enhance accuracy, redundancy & safety, a technique that has been enabling advanced driver assistance systems (ADAS).

The full version of this article was originally featured in Digi-Key Article Library and in the April 2021 issue of EPDT magazine [read the digital issue]. Sign up to receive your own copy each month.

As Rolf Horn, Applications Engineer at electronic component distributor, Digi-Key Electronics explains here, one of the primary sensor modalities is light detection and ranging (LiDAR) – and design engineers need to ensure the LiDAR system has the highest reliability, resolution, precision and response time for self-driving cars.

LiDAR performance relies significantly upon the front-end transimpedance amplifier (TIA), which quickly recovers an avalanche photodiode (APD) signal to provide digital feedback. By comparing the time stamp of the feedback signal to the transmitted signal time stamp, the time-of-flight (ToF) can be calculated for ranging.

This article will briefly discuss the issues associated with developing the feedback circuitry performance for precise object detection using LiDAR. It will then introduce an Analog Devices TIA. It will show how to take advantage of its high speed, bandwidth and low input impedance for quick recovery from reflected light which can produce nanosecond (ns) photodiode rise time. To achieve the best overall performance, it will also show how to reject the APD dark current and ambient light through AC coupling to allow accurate ToF estimations.

Key elements of ADAS
At the heart of ADAS are sophisticated sensing systems to analyse external objects. The identification and location of these objects enable a vehicle to either notify the driver or take the appropriate action (or both) to avoid incidents. The sensor technologies behind ADAS can include an image camera, inertial measurement units (IMUs), radar and, of course, LiDAR. Of these, LiDAR is a critical optical technology that performs autonomous vehicle poor weather and lateral distance sensing and ranging. It forms an integral part of an ADAS system...

Read the full article in EPDT's April 2021 issue...

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