Page 17 - EE Times Europe Magazine | April2019

EE|Times EUROPE 17

AUTOMOTIVE
Maxim LiDAR Module Revs Self-Driving

Safe Speeds

By Maurizio Di Paolo Emilio

he advent of self-driving has decisively expanded the pres- Maxim Integrated’s Maurizio
ence of laser-imaging detection and ranging (LiDAR) sensors Gavardoni demonstrates the
in the automotive-electronics platform. LiDAR works accord- evaluation board for a four-
T ing to the radar principle but uses light pulses emitted by an channel LiDAR receiving system.
infrared laser diode. It includes optical photodiodes
Maxim Integrated’s new MAX40026 high-speed comparator and from First Sensor and Maxim’s
MAX40660/MAX40661 high-bandwidth transimpedance amplifiers newly launched TIA and high-
(TIAs) enable 15 km/h faster autonomous driving at highway speed speed comparator.
by doubling the bandwidth and adding 32 channels (for a total of 128 (Image: Maxim Integrated)
instead of 96) in a LiDAR module of the same size.
WHAT’S LIDAR?
Along with artificial intelligence, cameras, and radar, sensors are indis-
pensable to assisted and autonomous driving. Because they can provide
accurate measurements of objects and detect obstacles on the road —
fallen tree limbs, other cars, or even a child who darts out into traffic
— LiDAR sensors have helped advance the adoption of advanced
driver-assistance systems (ADAS) and are critical to autonomous-
vehicle (AV) development. An AV’s perception of the surrounding
environment must be extremely precise, which is why experimental
robo-cars are full of sensors. The use of a laser lighting system allows
self-driven cars to be operated under low- or no-visibility conditions
and even in the absence of road markings.
“LiDAR sensors are playing an increasing role in the fusion of vehicle
sensors for their ability to provide accurate distance measurement of Figure 3: General layout of a TIA with a reverse polarization
objects,” said Maurizio Gavardoni, principal member of the technical photodiode (Image: Wikipedia)
staff at Maxim Integrated. “A typical LiDAR sensor sends light pulses
that, reflected by objects and detected adequately by photodiodes,
allow you to map the surrounding environment.”
LiDAR systems are based on time of flight (ToF), which measures
precise timing events (Figure 1). The latest developments have seen
several multibeam LiDAR systems, which generate a precise, 3D image
of the environment around the vehicle. This information is used to
choose the most appropriate driving maneuvers.
Figure 2 shows the basic layout of a LiDAR sensor. There are two
basic types of LiDAR systems: micropulse LiDAR and high-energy.
Micropulse systems have been developed as a result of the ever-
Figure 1: Time-of-flight functional diagram increasing computing power available and advances in laser technol-
(Image: Maxim Integrated) ogy. These new systems use very low power, in the order of 1 W, and
are entirely safe for most applications. High-energy LiDAR, on the
other hand, is common in atmospheric monitoring systems, where
the sensors are used to detect atmospheric parameters such as height,
stratification, and cloud density.
“Automotive self-driving systems are evolving from 35 mph to
65 mph and beyond, but faster autonomous self-driving systems are
essential,” said Gavardoni. “The challenges in meeting these demands
[translate] into high-precision distance measurements of objects,
[requiring] more accuracy, more channels to fit in space-constrained
platforms, [and compliance with] stringent safety requirements.”
LIDAR HARDWARE
In a LiDAR project, the transimpedance amplifier is the most critical
part of an electronic layout. Low noise, high gain, low group delay,
Figure 2: General layout of a LiDAR sensor with the main and fast recovery from overload make the new Maxim TIAs ideal for
electronic parts shown (Image: Maxim Integrated) distance-measurement applications.

www.eetimes.eu | APRIL 2020