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Maxim > Design Support > Technical Documents > Application Notes > Power-Supply Circuits > APP 1845
Keywords: Choosing the Right DC-DC Converter for Automotive Applications
APPLICATION NOTE 1845
Choosing the Right DC-DC Converter for
Automotive Applications
Dec 29, 2002
Abstract: Choosing the right DC-DC converter for automotive applications can be a challenging task
when one considers all the requirements that need to be met. Power management in automobiles has
come a long way from being the ubiquitous load-dump-protected 5V linear regulator. This article provides
an insight into what is required in some common automotive applications and provides solutions.
Introduction
Power-supply requirements for automotive applications can be complex. Designs may have nonstandard
restrictions imposed by the nature of the automotive environment and call for a large number of output
voltages. This article reviews some of the special cases encountered in automotive applications and
suggests some starting-point designs.
Table 1 lists a set of system requirements for an in-car infotainment-system power supply. Each
requirement will be examined. Circuit details are available in the identified product data sheets.
Table 1. Power-Supply Requirements for In-Car Infotainment System
System Requirements Reason Suggestions
Multiple output voltages: 1.9V, 2.5V
(0.3A to 0.5A), 5V, 3.3V (0.3A to
1A), 8V, 9V (0.3A to 3A)
µP (core, I/O), CD/DVD drive, tuner module,
alarm, GPS system, displays
Combination of
switching and linear
regulators
Wide input-voltage range: 3.5V to
28V, depending upon the car
manufacturer's requirements
Cold-cranking causes unwanted system
reset. Load dump and battery jumping
require protection from high voltage
Buck-boost
converter
Low quiescent current: < 300µA
Prevents battery drain from standby systems
when car ignition is off
Idle
Mode™operation for
high-efficiency at
light loads
Low noise
EMI interferes with radio reception and video
displays
Fixed frequency or
linear post
regulators
Low cost Carmaker requirement
Low parts count
and/or system
solution
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