ADAS Demand Multi-Rail DC/DC Converters

March 07, 2017 // By Tony Armstrong, Linear Technology
Advanced Driver Assistance Systems, commonly known as ADAS, facilitate safe driving and warn the driver if the system detects risks from surrounding objects – whatever they might be. These systems are one of the major trends in automobiles for the second half of this decade.

ADAS typically provide dynamic features such as adaptive cruise control, blind spot detection, lane departure warning, drowsiness monitoring, night vision and even more. As a result, it is the increasing focus of consumers on safety, demands for comfort while driving and the continued increase of government safety regulations that are fueling the growth of ADAs in automobiles.

At the heart of most ADAS systems is some kind of microprocessor to process all the input from the various sensors within the vehicle and to then process it so that it can be easily presented to the driver in a way that it can be easily seen and understood. Moreover, these systems are usually powered directly from the vehicles main battery that is a nominal 9V to 18V, but could be as high as 42V due to voltage transients within the system, and as low as 3.5V during a cold-crank condition. Thus, it is clear that any DC/DC converter to be used must be able to handle a broad input voltage range of 3.5V to 42V.

Many ADAS systems will need a 5V and 3.3V rail to power its various analog and digital IC content; however, it will be the processor I/O and Core voltages that will be in the sub-2V realm. Furthermore, there are space and thermal considerations that must also be taken into account. While it is commonplace to use a high voltage DC/DC converter for a 5V and 3.3V rail, utilizing this kind of converter for sub-2V rails is not always practical due to the solutions size of using multiple single output converters and the potential thermal constraints. A more a suitable solution would be to use a single DC/DC converter with multiple outputs.

Multi-Rail DC/DC Converter

It was because of these constraints that Linear Technology developed its 4-output monolithic synchronous buck converter, the LT8602. Its 3V to 42V input voltage range makes it ideal for automotive applications, including ADAS, which must regulate through cold-crank and stop-start scenarios with minimum input voltages as low as 3V and load dump transients in excess of 40V.

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