By Daniel Ma, Systems Engineer, Automotive Infotainment Systems, Texas Instruments (TI)
Technologies on the Road
As the demand for information and entertainment increases—regardless of your location—automakers are integrating
larger and more advanced displays into vehicles.
Automotive displays are the primary way drivers and passengers receive vehicle information. With the
number of displays in vehicles steadily increasing, so is
the quality of information. However, multiple displays
in the cluster, head unit, rear- and side-view mirror
replacements, along with rear-seat entertainment systems
are presenting challenges for automotive infotainment and
Just adding functional displays to vehicles is no longer
enough, as automakers need to differentiate themselves
by meeting consumer demands for aesthetically pleasing
interiors, and a seamless experience between smartphones
and vehicles. The transition in the consumer display market
from standard to high-definition (HD) and then to ultra-HD (4K-UHD) for televisions is also affecting expectations
for vehicle displays.
Figure 1: The number of displays in vehicles is expected to increase,
including larger head unit screens in infotainment systems.
To meet these challenges, automakers are enlisting
designers to create environments that are more attractive,
like the head unit in Figure 1; however, mechanical and
electrical engineers will also play a major role in these
Consumers marvel at picture quality, the detail of images,
and appreciate the realism and beauty of the objects.
Accomplishing this effect requires consideration of both
the viewing distance from the display and pixel density.
When there are more dots in a given area, an image can
appear smoother and more natural. As distance between
the viewer and display decreases, pixel density must
increase in order to achieve the same viewing experience
from a longer distance.
The average automotive displays on the road today range
from a mere 1.5 to more than 12 inches. Inside a vehicle,
regardless of display size, a typical viewing distance of 70
cm ( 27. 5 inches) will require a display with a pixel density
of at least 300 pixels per inch (ppi) in order for occupants
to see a quality image.
Automotive Display Technologies
Liquid crystal display (LCD) panels are dependable,
durable, and can support a wide range of screen sizes and
resolutions, which makes them the most widely used
displays in vehicles. The two common LCD technology
variants are passive and active matrix using thin-film
transistors (TFTs), shown in Figure 2.
Heating, ventilation, and air conditioning (HVAC) or
audio settings commonly use passive matrix or segment
displays that show a pre-defined row (or sections) of
numbers, letters, or graphics.
Full-color, active matrix LCD (AMLCD) TFTs remain
the incumbent technology for complex graphical displays
in automotive systems. However, one key disadvantage of
LCD displays is the need for an external light source (like
a backlight). Human image perception factor is governed
by the quality of the backlight driver—a feature-specified,
cost-optimized device that drives the LEDs in a multitude
of configurations, with the goal of providing a seamless
viewing experience anywhere in the vehicle.
In comparison, active matrix OLED (AMOLED) panels
are lighter, sharper, and support luxurious styling with
their perfect hue of black without an external backlight.
Plastic OLED enables even greater design freedom with
curved or flexible displays, and works well in automotive
environments. Despite these advantages, the challenges of
high-temperature reliability, long life span, and low-cost
requirements are limiting the number of automakers using
OLEDs in the luxury market.
Key Design Requirements For Automotive LCDs
Unlike other display applications, the automotive
display market is highly customized. There are stringent
test requirements for thermal operation, mechanical
reliability, and electromagnetic compatibility (EMC)