Thanks to the Advanced Driving Assist System (ADAS), car driving is getting flushed. The camera in these systems is combined with the sensor, mature algorithm, and microprocessor, and the driver can be reminded when discovered obstacles on the road, and if necessary, it is necessary to indicate the blind zone. To ensure proper work, the ADAS application requires power supply to comply with specific precision and load transient response. This paper explores the conditions required to ensure proper adjustment of automotive battery voltage to the ADAS camera, sensor, and processor.
Ensure safe driving
Applications such as ADAS are pushing the vehicle handling capacity to continuously improve, to run advanced algorithms to guide the driver more securely. Of course, as the processing ability is getting stronger, in order to meet the system performance goals, it is necessary to better manage the power supply. However, in view of the automotive noise work environment, a plurality of electronic subsystems, comprehensive balanced power supply requirements under power constraints face severe challenges.
In the rapid growth of the ADAS module, the information entertainment wireless audio unit and the smart dashboard, many of the automotive engineers are powered by multiple power rails, typically have specific voltage regulation accuracy requirements (Fig. 1). To meet these rigorous system requirements, it is important to provide high precision, high-spirited and small-sized automotive power management solutions. Heat restrictions, electromagnetic interference (EMI) and heat dissipation are also a key factor in need to solve.
Figure 1. Automobile information entertainment system is one of many automotive applications that benefit from high precision, high spirits and small-size power management solutions
Meet the electrical and power requirements of the car system
Managing the electrical and power of the Automotive System requires a smart comprehensively balance. Processors, memories, screens, and other components require a different current level of stable voltage. Therefore, the regulator must be sufficient to provide the power required for these critical circuits, and do not produce too much heat. If multiple power rails are needed, there will be more voltage and current spikes to be managed, and things will become very complicated. Specific voltages in the car require specific voltage accuracy. For example, in order to ensure performance, the core system (SOC) core typically has a specific voltage tolerance. If the voltage is outside the indicator range, the processor performance cannot be guaranteed. This is obviously unacceptable in view of the security characteristics of the ADAS application.
Next, the electrical and thermal environments of the automobile also have an impact on this. The noise of DC power rails in the automobile is large. When the car starts in different temperature environments, such as cold start, thermal start or throwing, there is a large, sudden pressure drop. Such load transients are basically occurring in the processor to suddenly face demand and consume greater current. For example, the power consumption of the processor is in standby mode only about one-third of the peak power consumption. When the processor is suddenly required to perform actions, the consumed current may reach the full load state. In this case, the output voltage of the switch mode power may occur in an instant, then jitter, and finally stabilizes its target voltage. The key to dealing with such load transient responses is to manage the output voltage swing to prevent swinging of the index range and affect processor performance.
Figure 2. Maxim's car PMIC passes through conduction and radiation launch test, fully compliant with strict CISPR 25 Level 5
EMI is another challenge that engineers need to consider. The car has a large number of radiofrequency (RF) noise from the internal and external, which may limit the performance of various car systems. The current car fuselage includes a large number of electronic subsystems from the automotive networking system to the security system, which are crowded in very narrow space. External, all devices such as mobile phones to the launch tower will transmit noise, which may affect automobile performance (Figure 2). Car OEM must ensure that the electronic system does not emit too large EMI, and can withstand noise from other subsystems (the CISPR 25 standard for the International Radio Interference Special Committee provides for the automotive conduction and radiation launch).
Since the options for solving the system power supply are limited, many existing systems use a discrete power supply scheme for each voltage rail. For example, some first-class companies use a set of linear and switch DC-DC regulators for each DC power rail. But this method requires professional knowledge, carefully selects the correct component to meet the requirements of each power rail. If the combination is improper, EMI and interference issues may occur due to mixing causes. Some people choose to integrate components with larger capacitance in their design to suppress voltage ribbed waves caused by load transients, but automotive-level components with large capacitance are very expensive. As for EMI, protect the ADAS subsystem with a metal housing from radiation impacts may be effective, but to comprehensively trade out the cost and weight. On the other hand, it has shown that spread spectrum modulation can effectively inhibit EMI.
EMI standard car-level PMIC
While meeting ADAS performance and power requirements, it is necessary to meet EMI standards, which requires professional automotive-level power management integrated circuit (PMIC). High integration of these devices can effectively reduce overall solution size. The addition of the spreading oscillator can alleviate the impact of EMI. It has high output precision throughout the temperature and operating voltage to ensure that the device meets strict SOC core voltage requirements.
Compliance with Automotive Safety Integrity (ASIL) requirements ensure functional security.
Maxim's rich and diverse automotive PMIC can work with any microprocessor or microcontroller, which also makes up for efficient and small-sized demand while meeting the power requirements. The latest members of the low-voltage PMIC family (where many devices provide pin-compatible ASIL-C versions) include:
The MAX20014 is efficient, three output DC-DC converters, with synchronous 3.8V to 8.5VOUT, 750MA BOOST converter, two synchronization 1A to 3A Buck converters, 2.2MHz switching frequency and spread spectrum oscillator, using 24 pins, 4mm x 4mm TQFN-EP package. The device is used to work with the MAX20003 36V, 3A high-voltage Buck converter.
MAX20075 / 76 36V, 600MA / 1.2A Mini BUCK converter, the static current is only 3.5μA, with integrated high and low-side switches, 3mm x 3mm, 12 pin TDFN package.
For cameras in ADAS applications, Maxim also offers three new camera protection PMICs:
The MAX20087 ASIL-B / D level four / dual camera power protector IC has high-side current limiting to protect each camera module.
MAX20019 Dual Synchronous Buck Converter, 2mm x 3mm package is the smallest 3.2 MHz dual-channel buckstall power supply in the industry.
Figure 3. Maxim power management solution can be integrated into a variety of automotive systems
Summarize
Camera, sensors, microprocessors, and other underlying components for ADAS applications will become more popular in next-generation vehicles, and the requirements for accurately manage power supply power will be more stringent. The automotive-level PMIC integrated balanced power supply requirements and power constraints, while meeting the requirements of small size solutions, and play an important role in ensuring normal work.
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