Innovative Power Solutions: Why Four is the Ultimate Advantage
Tony Armstrong from Linear Technology emphasizes the importance of multi-rail DC-DC converters for advanced driver assistance systems (ADAS).
ADAS help make driving safer by alerting drivers to potential dangers around their vehicles. These systems have become a key trend in the automotive industry, particularly in the latter half of this decade. They offer features like adaptive cruise control, blind spot detection, lane departure warnings, drowsiness monitoring, and night vision. Consumer demand for safer, more comfortable driving experiences and increased government safety regulations are driving the growth of ADAS in cars.
At the core of most ADAS is a microprocessor that processes sensor input from various parts of the vehicle. This data is then displayed to the driver in an easy-to-understand manner. These systems typically draw power directly from the car’s main battery, which usually ranges from 9 to 18V but can spike up to 42V due to voltage transients or drop to as low as 3.5V during cold-start conditions. Therefore, any DC-DC converter used in these systems must handle a wide input voltage range of 3.5 to 42V.
ADAS components often require 5V and 3.3V power rails for their analog and digital ICs, while the processor’s IO and core voltages are usually below 2V. Space and heat dissipation are also critical considerations. While high-voltage DC-DC converters are common for 5V and 3.3V rails, they are less practical for sub-2V rails due to their larger size and thermal constraints. A more efficient solution is using a single DC-DC converter with multiple outputs.
For instance, a four-output monolithic synchronous buck converter is ideal for automotive applications, including ADAS. This converter supports an input voltage range of 3 to 42V, suitable for handling cold-crank and stop-start scenarios with minimum voltages as low as 3V and load dump transients exceeding 40V.
This quad-channel converter combines two high-voltage channels (2.5V and 1.5A) with two lower-voltage channels (1.8A) to deliver four independent outputs, offering voltages as low as 0.8V. This makes it capable of powering the lowest-voltage microprocessor cores available. Its synchronous rectification design ensures up to 94% efficiency, while burst-mode operation keeps the quiescent current under 30µA with all channels on in no-load standby conditions, making it perfect for always-on systems. The switching frequency is programmable from 250kHz to 2MHz and can be synchronized across this range. Its 60ns minimum on-time allows for 16Vin to 2.0Vout step-down conversions on the high voltage channels with a 2MHz switching frequency.
Tony Armstrong serves as the Director of Marketing for Power Products at Linear Technology, now part of Analog Devices.
