Voltage References for Rear Vision Systems
A voltage reference
produces a constant level of voltage over time regardless of load, changes in power supply, or
temperature. Voltage references are used in power supplies, analog-to-digital converters,
digital-to-analog converters, and many other applications where voltage levels must be
maintained at a steady level. Without a voltage reference, precision is greatly affected and may
render the device inoperable. Voltage references can vary greatly in performance. A voltage
reference for a power supply might hold its output to within only a few percentage points off of
its nominal or stated value; however, a voltage reference to instrumentation-level standards are
measured in parts per million regarding stability and precision to the nominal or specified
value.
Flash Memory for Rear Vision Systems
Easily the most common
type of non-volatile, solid-state data storage used today, NAND flash memory can be found in USB
flash drives, solid-state drives, memory cards, smartphones, notebooks, and more. Its ubiquity
is due in no small part to the affordability of NAND flash and its high memory storage density,
packing gigabytes of data into thumbnail-size packages, and at relatively low cost. Like any
memory, however, flash has its limitations; it may not be the best choice for applications that
require a great many program-erase cycles, or that must access small amounts of data on a
bit-wise basis – tasks which are much better suited for random access memory (RAM).
Memory for Rear Vision Systems
Memory stores data and
programs for later use. Some memory is Read-Only, which means nothing new can be stored, and
other memory is Read/Write memory where a processor can read from or write to this method of
data storage. Some memory is non-volatile, meaning that a power source is not required to
preserve stored information. Other types of memory lose their information and become a blank
slate every time power is removed from the device. Two types of memory, EEPROM and flash, share
many of the same qualities – in fact, flash memory is often considered an advanced form of
EEPROM. However, one of the largest functional distinctions between the two lies in how the
memory can be erased: unlike flash, EEPROM is erasable at a more precise, byte-wise level. For
this reason among others, EEPROM continues to see industry use in applications that must store
small amounts of non-volatile data.
Power Management ICs for Rear Vision Systems
A Power Management
Integrated Circuit (PMIC) is a special-purpose IC that provides one or more power management
related functions. These can include voltage regulation, DC/DC conversion, battery management
capability and more. Many PMICs offer an I2C and/or SPI bus interface, and some might provide
additional features such as an integrated touch screen interface.
Analog-to-Digital Converters for Rear Vision Systems
An Analog-to-Digital
Converter (ADC or A/D converter) measures the magnitude of an input analog signal and converts
it to a digital number that is proportional to the magnitude of the voltage or current. An ADC
often converts signals collected from the real-world to digital signals for processing. One of
the more important specifications of an ADC is the resolution that it offers, which is the
number of discrete values (represented in bits) that the ADC produces in relation to the analog
signal it is converting. The more bits, the higher the resolution. A higher resolution yields a
more accurate approximation of the analog input.
Low-Dropout Regulators for Rear Vision Systems
A Low Drop Out (voltage)
Regulator is a voltage regulator that automatically maintains a constant voltage level and
features a low potential at below which it can no longer reliably regulate. LDOs stabilize input
or supply voltages. LDOs are instrumental in enabling the power-efficient portables in use today
because they enable very low minimum operating voltages.
Processors for Rear Vision Systems
The term "processor"
refers to an electronic device that performs computational functions and carries out the
instructions of a stored program. Other terms for processor are microprocessor, central
processing unit, and digital signal processor. Essentially, the processor refers to "the brains
of a computer."
DC/DC Converters for Rear Vision Systems
DC/DC regulators
are circuits that convert DC voltage from one level to another and maintain that voltage at a
constant level. Electronic systems often have several sub-circuits, each with its own voltage
level requirement that may be higher or lower than the main power supply. Step-up (boost)
converters raise a voltage to a higher level, while step-down (buck) converters lower it. Some
DC/DC converter types can raise or lower voltage, such as "buck-boost" converters. DC/DC
converters may offer options such as multiple softstart levels, undervoltage lockout, protection
against overvoltage and undervoltage, and programmable short-circuit protection. All of these
devices are considered to be in the same category of integrated chips, typically categorized as
power management devices.
LED Backlights for Rear Vision Systems
A backlight is
used in or with a liquid crystal display (LCD). Because LCDs do not produce any light
themselves, backlight illumination is often necessary to make the screen acceptably readable.
Many of today’s backlights use either light emitting diodes (LEDs) or cold cathode fluorescent
lamps (CCFL) as a light source. As its name suggests, a backlight typically illuminates the
display from the back side of (i.e. beneath) the display.
Touch Screens for Rear Vision Systems
A touchscreen is an
electronic visual display that can detect the presence and location of a touch within the
display area. A resistive touch screen works by applying a voltage across a resistor network and
measuring the change in resistance at a given point on the matrix where a screen is touched by
an input stylus, pen, or finger. The change in the resistance ratio marks the location on the
touch screen. With most capacitive touchscreen panels, touching the surface of the screen
changes the screen's electrostatic field, which is measured as a change in capacitance. There
are different technologies to determine the location of the touch; but in any case the location
is then sent to the controller for processing. Unlike a resistive touchscreen, most capacitive
touchscreens cannot be used with electrically insulating material, such as gloves.
Touch Screen Controllers for Rear Vision Systems
Touch
controllers interact with a touch sensor to measure tiny changes in capacitance or resistance,
which are then translated into digital signals. Most controllers are designed to interface with
a host processor to indicate finger/stylus positions (in the case of touchscreen controllers),
taps, and other useful input. There are many reasons for using a dedicated touchscreen
controller instead of the common A/D converters found in a microcontroller. For example,
implementing capacitive sensing with a generalized MCU can drastically increase the amount of
"on-state" time and may require more A/D inputs than are available. Touch controllers and
specialized touch-sensing MCUs can provide superior accuracy, noise handling, algorithm
efficacy, and environmental compensation techniques
CAN Transceivers for Rear Vision Systems
CAN is an acronym for
Controller Area Network and refers to a fault-tolerant communications protocol that is flexible
for system design, supports multiple network topologies, and has become a de facto standard for
high integrity serial communications in industrial and automotive embedded applications. In a
CAN network, several short pieces of data like a motor’s run status, temperature, or RPM is
broadcast over the entire network at up to 1 megabit per second (Mbps.) CAN is meant for
applications that have to report and consume numerous but small pieces of data consistently
among nodes and has the ability to self-diagnose and repair data errors. CAN is well-suited to
environments with machinery, since CAN is designed to be reliable in rugged environments that
include interference or introduce noise. CAN is also well-suited to the transportation industry.
LIN Transceivers for Rear Vision Systems
LIN (Local
Interconnect Network) is a vehicle network protocol for communication between automotive
components. Inexpensive and relatively simple to implement, a LIN network uses a broadcast
topology with a single master – typically an MCU – and up to 12 slave devices. As such, it is
often used for networking small subsystems, with the master device connecting the subsystem to
the vehicle’s main bus line, such as a CAN bus.
Step-Down Regulators for Rear Vision Systems
A step-down
(buck) regulator maintains a constant output DC voltage level that is lower than its input DC
voltage while preserving polarity. Electronic systems often have several sub-circuits, each with
its own voltage level requirement that may be lower than the main power supply, therefore
step-down regulators may be required. The switching regulator offers the advantages of high
power conversion efficiency and increased design flexibility; multiple output voltages of
different polarities can be generated from a single input voltage. Since the output voltage of
the buck is lower than the input voltage, it follows that the output current must be higher than
the input current.
Buck/Boost Regulators for Rear Vision Systems
A buck
converter is a power efficient voltage step-down converter that changes a higher voltage to a
lower voltage. Whereas a linear regulator can achieve the same purpose, regulators can waste
more energy via conversion of excess energy to heat. For this reason, a buck DC/DC converter is
the preferred choice for power-efficient designs. A DC/DC boost converter, also known as a
step-up converter, is a semiconductor device or electrical circuit that has an output DC voltage
that is greater than the DC input voltage. The amount of output current will be lower than the
source current, however. Boost converters can increase the voltage and thus reduce the total
number of battery cells required for portable applications.
