Enhancing Safety: Shielding Advanced Driver Assistance Systems
Tony Armstrong from Analog Devices talks about why automotive ADAS (Advanced Driver Assistance Systems) need low Electro-Magnetic Interference (EMI) and Electro-Magnetic Compatibility (EMC) emission switching converters.
According to Allied Market Research, the ADAS market is projected to hit $60 billion globally by 2020, with a 22.8% compound annual growth rate (CAGR) from 2014 to 2020. This rapid growth presents a massive opportunity for semiconductor content.
ADAS refers to advanced driver assistance systems found in many modern cars. These systems help ensure safe driving by alerting drivers to potential risks from surrounding objects, like wandering pedestrians, cyclists, or other vehicles on a collision course. They also offer features such as adaptive cruise control, blind spot detection, lane departure warnings, driver drowsiness monitoring, automatic braking, traction control, and night vision.
The surge in consumer interest in safety, demand for driving comfort, and stricter government regulations on safety are the main growth drivers for ADAS in the latter half of this decade. However, the industry faces challenges like pricing pressure, inflation, complexity, and testing difficulties. Europe’s automotive industry is leading the way in innovation and ADAS adoption, but American and Japanese automakers are catching up. Ultimately, the goal is to achieve fully autonomous driving vehicles.
Challenges
ADAS typically uses a microprocessor to collect input from various sensors and processes it to be presented clearly to the driver. These systems are usually powered directly from the vehicle’s main battery, which ranges from a nominal 9 to 18V, can spike up to 42V due to voltage transients, and can drop to as low as 3.5V during cold-crank conditions. Therefore, any DC-DC converters in these systems must handle an input voltage range of 3.5 to 42V.
Many ADAS systems use 5V and 3.3V rails to power different analog and digital integrated circuits (ICs), but processor IO and core voltages often require sub-2V operation, going as low as 0.8V. These systems are often installed in areas of the vehicle with limited space and thermal constraints, restricting the options for cooling.
Modern ADAS requires switching regulators that operate at 2MHz or higher, instead of the traditional sub-500kHz. This shift is driven by the need for smaller footprints and to avoid interference with the AM frequency band. Additionally, designers must ensure that ADAS comply with various noise immunity standards within vehicles. In automotive environments, switching regulators are preferred over linear regulators when low heat dissipation and high efficiency are important.
Switching regulators are usually the first active component on the input power bus line, significantly impacting EMI performance. There are two types of EMI emissions: conducted and radiated. Conducted emissions travel along wires and traces connecting to the product. Since this noise is localized, ensuring compliance with conducted emissions requirements is relatively straightforward with good design practices early in the development process.
