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Maxim > Design Support > Technical Documents > Application Notes > General Engineering Topics > APP 4213
Keywords: Automotive power supply, power supply design, automotive infotainment
APPLICATION NOTE 4213
Trends in High-Performance Power-Supply Design
for Automotive Infotainment
Dec 15, 2008
Abstract:
This article
provides a practical framework for selecting and optimizing power-supply architectures
for automotive infotainment electronics. First, a summary of design constraints and application requirements is
provided. Then, the most popular power-supply architectures are discussed within the context of the
application requirements. Finally, a selection of Maxim automotive power-management ICs (PMICs) is
presented as building blocks of the power-supply architectures explored in the article.
Introduction
More than half of the 2012 model year cars in the EU, Japan, and U.S. will feature a color screen, a
navigation system, satellite radio, or some other form of in-car infotainment. Consequently, the automotive
power supplies in year 2012 will look significantly different than their predecessors a decade earlier.
The conflicting expectations of high reliability, lower cost, and faster design cycles have forced power-supply
designers to adopt techniques not previously used in a typical automotive power supply.
Six Common Constraints of Power-Supply Design for Automotive
Most automotive power-supply architectures are shaped by six generic constraints:
1. V
IN
Range: The voltage transient range on a 12V battery powerline determines the input voltage range of
converter ICs.
A typical car battery operates in the 9V to 16V range. The nominal voltage of a healthy battery is 12V
when the engine is off, and around 14.4V when the engine is on. This range, however, easily extends to
±100V when the transient conditions are involved. For the full specification of these transients, please
refer to the ISO7637-1 industry standard. Figures 1 and 2 are part of this ISO7637 standard and outline
the most critical conditions that need to be addressed by a high-voltage converter in an automotive
power supply. Besides the ISO7637-1, there are new transient conditions defined for battery-operated or
environmentally friendly gas engines. Most of the new specifications are driven by individual OEMs and
do not necessarily follow an industry standard. Nonetheless, overvoltage and undervoltage protection are
required for all new systems.
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