Magnetics Business & Technology - January/February 2020 - 30

TECH TIPS

How Hall Effect Switches Enable Autonomous Vehicles
By Charles Kuo, Sensor Marketing Manager, Diodes Inc.

Automotive engineers around the world are immersed in harnessing
the latest technologies to bring smart, autonomous vehicles to our
roads. Those technologies will also enhance the driver and passenger
experience far beyond today's norm, through intuitive human-machine interfaces and highly personalized cockpits.

The Hall Effect in Automotive

Safety will be paramount in the operation of fully autonomous vehicles and we have already seen 'intelligence' built into crash detection
with air bag and seat belt activation as well as blind spot activation,
lane departure and more. However, the autonomous vehicle of the
future will also have convenience and comfort central to its design.
We already have vehicles that 'know' their drivers and are able to adjust parameters that are specific to the person sitting in the seat - but
the level of automation will continue to increase. It has been predicted
that autonomous vehicles will be able to sense body temperature and
humidity, to detect a driver's heart activity, breathing or even a tilt of
the head to monitor whether the driver is becoming unwell, stressed
or getting tired.
Essential to the development of fully autonomous vehicles are Hall effect switches which have proved to be ideal for a range of position and
proximity sensing applications. These include: detecting the position
of seats and seatbelt buckles, implementing vehicle immobilization
systems or steering locks, gear stick position detection, transmission
actuator and gear status.
Hall effect switches are also used in sensing accelerator or brake pedal
position, in sensing distances or speeds, in adaptive systems (for example, front lights and suspension), in the steering system (detecting
angle and torque), and in fuel monitoring systems. They can also be
found in less exotic applications within a vehicle, such as heating ventilation and air conditioning (HVAC) compression, windscreen wiper
operation, automatic closing of doors or trunk, detecting whether
doors are open, and sensing various levels and flows.

Why Hall Effect?

Based on well-established technology, Hall effect switches have proven to be the ideal solution for autonomous vehicle applications. They
are low-cost, have no moving parts and offer extremely high levels of
reliability.

Magnetics Business & Technology * January/February 2020

Other key factors that are required for any component used in a modern vehicle are a small footprint, low power consumption, high-performance, and the ability to operate in a range of locations and environments, including some of the lowest and highest temperatures.
It is also important for automotive-compliant Hall effect switches to
have the ability to respond to the presence of differing magnetic field
polarities. Such low-power and compact omnipolar switches - often
found in gear lever sensing applications - are turned on in the presence of a strong positive or negative magnetic field and off in a moderate magnetic field.

Using High-quality Switches is Paramount

It's clear that in the development of fully autonomous vehicles today
and in the future, high-quality Hall effect switches will play a crucial
role. Particularly important will be true solid-state omnipolar switches
with operating voltage ranges of 3V to 28V (and 8kV HBM ESD rating),
while offering exceptional stability over temperatures ranging from
-40°C to +150°C.
That's exactly what's on offer from Diodes Incorporated's AH356xQ
family of omnipolar Hall effect switches for proximity, position, and
level sensing in automotive applications. Combining high voltage with
high sensitivity, these AEC-Q100 Grade 0 qualified switches come with
a chopper-stabilized architecture - for superior temperature stability,
minimal switch point drift and excellent immunity to stress - as well as
an internal bandgap regulator which delivers temperature compensated supply for internal circuits. With a reverse blocking diode and a
Zener clamp on the supply, all devices in the AH356xQ family provide
single open drain output with an overcurrent limit and good radio frequency (RF) noise immunity. Other features include rapid power-up
(10µs) and response times (3.75µs).
For automotive engineers tasked with creating fully autonomous
vehicles, it's important to work with someone who understands Hall
effect technology and has a growing portfolio of switches designed
specifically for the most demanding automotive applications.
For more information on these switches visit www.diodes.com.

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Magnetics Business & Technology - January/February 2020

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