Regulate Car Battery Voltages for ADAS Applications
July 31, 2018
|By: Warren Tsai, Jangho Jeon, Chintan Parikh, and George Chen;
Automotive Business Unit, Maxim Integrated
Cameras, sensors, sophisticated algorithms, and microprocessors are teaming up to be a second pair of eyes for drivers, alerting them to roadway obstructions and blind spots, braking for them when necessary, and even helping them park their vehicles. These components are essential in enabling advanced driver assistance systems (ADAS) to help make our roadways safer. In order for ADAS applications to operate properly, they need power supplies that meet certain voltage accuracy, load transient, and fault protection requirements.
Balancing power demands with power constraints in ADAS applications is no simple endeavor. On the one hand, these types of applications, with their advanced algorithms, are increasing the need for in-vehicle processing power. At the same time, the power supply must be aligned with system performance targets. All of this happens in a noisy environment consisting of multiple electronic subsystems.
Many automotive engineers opt to power each component in their ADAS modules with multiple power rails, often with specific voltage regulation precision requirements. To meet stringent system requirements, they need precise, flexible, and compact automotive power management solutions that address issues such as thermal constraints, electromagnetic interference (EMI), and heat dissipation.
Meet the power requirements of ADAS applications with precise, flexible, and small power management solutions
Walking the Power Tightrope
Processors, memories, displays, and other vehicle subsystem components need well-regulated voltages at various current levels. To minimize heat dissipation, the regulators must operate efficiently to deliver the power required to run these critical circuits. However, the situation gets complex when there are multiple power rails and, as a result, multiple voltage and current spikes to manage. Certain voltage rails have specific voltage accuracy requirements; if the voltage is out of spec, performance is impacted.
Another important consideration is the vehicle’s electrical and thermal environment. Large and sudden voltage drops occur when the car is started in various temperature situations (think cold cranking, warm cranking, or load dump scenarios). As an example, consider the processor, which could be in standby mode at one moment, consuming about one-third of its peak power. Then, when the processor is called to action, it could draw the full amount of its current. In this scenario, the switch-mode power supply’s output voltage would temporarily dip and then bounce around before settling in at its target voltage. Effectively addressing these load transients calls for a well-designed power converter to manage the output voltage swing.
EMI mitigation is another priority, given the RF electrical noise that stems from both internal and external sources. Automotive OEMs must ensure that electronic systems do not emit excessive EMI and that they are immune to noise from other subsystems (CISPR 25 from the International Special Committee on Radio Interference provides a standard for conducted and radiated emissions in vehicles.)
There are various methods to address the challenges we've highlighted, from using discrete power solutions for each voltage rail to using higher capacitance components. Some methods are more effective than others. There are also various automotive-grade power management ICs (PMICs) that are designed to address the performance and power requirements of ADAS applications. Learn more about these techniques by reading our new white paper, "Balancing Power Supply Requirements in ADAS Applications" or visiting our Power Management for ADAS webpage.