To achieve a safer and more comfortable experience, how can on-board power management products help?
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To achieve a safer and more comfortable experience, how can on-board power management products help?

Posted Date: 2024-02-02

For consumers, cars are undoubtedly a "big" consumer product, so various factors need to be carefully weighed before purchasing. Among many factors, in addition to hard indicators such as power and appearance, safety and comfort now have increasing weight in people's purchasing decisions.

This is because today’s cars are no longer a simple means of transportation, but have evolved into a “third space” outside of home and office in people’s daily lives. Therefore, how do people spend their time on the wheels and in the cockpit? However, there will be more expectations. In order to meet the endless needs of consumers, developers are constantly launching new in-vehicle products to provide different user experiences. For example, the following new concept products and applications:

ADAS and autonomous driving

Allowing cars to drive safely and autonomously, and completely liberating humans from boring and tiring driving operations, can be said to be people's "ultimate imagination" for car evolution. Whether it is ADAS today or true autonomous driving tomorrow, it is a new function that combines safety and comfort.

Vehicle LED lighting

Exterior lighting (that is, car lights) can enhance the driver's visual ability and is also a common communication "language" between cars. Its importance in safety is self-evident; while interior lighting has It is conducive to creating a comfortable driving atmosphere and providing users with a more comfortable experience. Whether it is exterior or interior lighting, the migration from traditional light sources to LEDs has become a general trend. The resulting improvements in service life, reliability and flexibility of automotive lighting products have been verified by the market.

Smart cockpit

This covers a variety of components, such as central control, electronic instrument panel, vehicle engine, as well as relatively new HUD, gesture/voice recognition, fatigue driving detection and other functions. However, a core element of their design is to become an efficient and safe human-machine interaction interface (HMI), ensuring that drivers can obtain information quickly, intuitively, and accurately, and make timely and correct decisions. This is naturally a key part of improving driving safety and comfort.

There are many similar automotive products and solutions, and new and eye-catching species are constantly emerging on the market. However, all these products and solutions have one characteristic in common - they are all increasingly intelligent automotive electronic products. This also represents a major trend: the degree of electronics in automobiles is constantly increasing. According to a Deloitte research report, electronic products will account for 45% of the total vehicle cost by 2030.

Automotive power management design challenges

The increase in on-board electronic systems also means that the number of electrical loads in the vehicle has increased significantly, and this pressure will be directly passed on to the automotive power management devices.
The task of the automotive power management device is to convert the electric energy from the vehicle battery through multi-level conversion and finally output it to different automotive electronic loads. Whether it can work stably and reliably is related to the status of each vehicle electronic component, which can be described as "responsibility" major".


Figure 1: Simplified diagram of automotive power management system
(Source: ROHM Semiconductor)

And it is worth noting that if automotive power management devices want to meet system design requirements, they do not simply complete power conversion, but must be specially optimized according to the special requirements of the automotive application environment. These design requirements that require special consideration include:

01 Conversion efficiency

This is a very critical indicator in power management design. In the context of the increasing number of electrical loads and total energy consumption in the vehicle, it is very meaningful to compare efficiency at every power conversion node. This requires continuous optimization and improvement of automotive power management devices in terms of improving power conversion efficiency and reducing quiescent current.

02 Reliability

The working environment of automobiles is complex, but the requirements for reliability are higher. It is particularly critical whether power management devices can maintain consistent and stable operation despite voltage fluctuations or transient large energy impacts. Therefore, more reliable circuit protection functions such as overvoltage, overcurrent, and overtemperature are often integrated into automotive power management devices.

03 Thermal Management

Excessively high temperatures will affect the reliability and life of components, and the heat generated by the power management devices themselves and the small and harsh application environment of automobiles will also exacerbate this challenge. Improving the efficiency of power management, adopting heat dissipation-friendly packaging, and optimizing PCB design are all helpful in meeting thermal management challenges, thereby avoiding the use of bulky and expensive heat sinks in designs.

04 Electromagnetic compatibility

EMI electromagnetic interference is a major problem faced by the design of automotive electronic products. It will interfere with the operation of electronic equipment and bring danger to the safety of vehicles and drivers and passengers. Specific to power management, the commonly used DC-DC switching regulator itself is a noise source, and the increase in the number of regulators, the increase in switching frequency, and the requirement for design miniaturization will increase the electromagnetic compatibility (EMC) design requirements. Difficulty. To this end, automotive power management devices need to use some special technologies to ensure that the final system design complies with EMC specifications such as CISPR 25 Class 5.

05 Miniaturization

In the face of limited space in cars, miniaturization of power devices is also a key feature. It is effective to use smaller packages to reduce the floor area, or to integrate more functions on a single chip to simplify the system BOM. measures. The simplification of the power management system can also provide more space for other components and bring greater flexibility to the design of the vehicle's electronic system.

06 Cost-Effectiveness

Although not as "volume" as in the consumer electronics field, cost is still a key factor in the design of automotive products. Moreover, this cost optimization consideration is comprehensive. In addition to the cost of the power management device itself, whether it is conducive to simplifying system design, shortening the development cycle, or facilitating expansion in different markets will affect the final cost-effectiveness. This is also the key to power management. The value that the device can provide to users.

In short, power management devices used for automotive safety and comfort design will have more constraints than general-purpose products. Of course, this also sets up an invisible barrier to competition. Manufacturers who want to enter this field must show some hard power and real skills.
In the field of automotive power management, ROHM Semiconductor (hereinafter referred to as ROHM) is such a manufacturer with outstanding strength and outstanding skills. The products they provide are not only comprehensive, covering various subcategories such as DC-DC converters, LDO linear regulators, LED drivers, PMICs, battery management ICs, etc., but each power management IC is designed around the requirements of automotive applications. Carefully optimized and built, it can well support developers' various design ideas in the fields of safety and comfort.

Efficient and high-speed automotive DC-DC converter

In the field of automotive power management, automotive DC-DC converters (switching regulators) are widely used due to their high efficiency, flexible voltage conversion (can support buck, boost and buck-boost), and wide applicable power range. However, the DC-DC converter generates a lot of noise during the switching action, and the output voltage of the car battery or generator fluctuates greatly, which will pose considerable challenges to the design and application of the vehicle-mounted DC-DC converter.
The BD9P series of primary DC-DC converters launched by ROHM can easily resolve these challenges. It uses ROHM’s unique Nano Pulse Control technology, as well as new control technology, achieve high-speed response characteristics while still maintaining high efficiency - the conversion efficiency is as high as 92% at high load (output current 1A), and also reaches 92% at light load (output current 1mA) 85%, which is very suitable for ADAS-related sensors, cameras, radars, automotive infotainment systems, instrument panels and other applications.


Figure 2: BD9P Series Primary DC-DC Converter
(Source: ROHM Semiconductor)

Compared with similar products, the outstanding advantages of the BD9P series DC-DC converters include:

Achieve high efficiency over an extremely wide load current range. In order to ensure high-speed response performance, conventional power supply ICs require a large drive current, which makes it difficult to achieve high efficiency at light loads. The BD9P series products are equipped with a circuit using a new control method, which achieves excellent high efficiency from light load to high load, which means that the power consumption of the application product can be reduced whether the car engine is stopped or running.


Figure 3: BD9P series has high efficiency performance under different loads.
(Source: ROHM Semiconductor)

It can also work stably when the battery voltage fluctuates. Generally, DC-DC converters may cause the load current to decrease when the input voltage fluctuates, resulting in output voltage overshoot. However, the voltage overshoot of the BD9P series DC-DC converters is only 1/1 of that of ordinary DC-DC converters. 10. This enables vehicle electronic equipment to work stably even when the battery voltage fluctuates due to engine starting and stopping; it also eliminates the need for output capacitors used in the past to deal with overshoot problems, which also helps simplify the system and save costs. .


Figure 4: The BD9P series can operate stably even when the battery voltage fluctuates (Source: ROHM Semiconductor)

Has excellent noise suppression performance. Thanks to Nano Pulse Control With ultra-high-speed pulse control technology, the BD9P series IC can always operate at 2.2MHz without interfering with the AM broadcast band (up to 1.84MHz). In addition, due to the built-in spread spectrum function, which can effectively reduce the noise peak and further suppress noise, this DC-DC converter is very suitable for EMI-sensitive automotive applications.

<About Nano Pulse Control

An ultra-high-speed pulse control technology. The nanosecond (ns) level switch on-time (control pulse width of the power supply IC) is achieved, making it possible to convert high voltage to low voltage that was previously impossible.
You can learn more about Nano Pulse Control™ technology by asking ROHM for details.

It is particularly worth mentioning that the BD9P series can be used in conjunction with ROHM's BD9S series secondary DC/DC converters to provide a complete high-efficiency, high-speed vehicle power supply solution. ROHM can also provide relevant reference design solutions and free online simulation tools to greatly accelerate the development process of vehicle power systems and save overall costs.


Figure 5: Automotive DC/DC reference design based on BD9P and BD9S (Source: ROHM Semiconductor)

Low power ultra-small LDO

In addition to DC-DC converters, LDO linear regulators are also commonly used devices in automotive power management systems. Due to its low noise, simple structure, and low cost, it is often used in noise- and cost-sensitive applications.

In terms of LDO, ROHM also has a rich product portfolio, and for safety and comfort applications, ROHM has also specially developed some unique products, such as the following one developed for ADAS, automotive radar, automotive instrumentation and other applications The BUxxJA2MNVX-C series LDO can meet the design requirements of small form factor, low power consumption and fast response in related applications.


Figure 6: BUxxJA2MNVX-C Series LDO
(Source: ROHM Semiconductor)

In terms of appearance, the BUxxJA2MNVX-C series LDO adopts a 1.0mm × 1.0mm ultra-small package. Compared with the common 1.5mm × 1.5mm packaged LDO, the mounting area is reduced by 55%! In addition, in order to solve the problem of output voltage fluctuation and oscillation when the input voltage changes, it is usually necessary to use an external capacitor. Compared with the 1.0μF capacitor used in previous LDO products, the BUxxJA2MNVX-C series LDO only requires a 0.22μF capacitor to achieve stable output. voltage requirements, which further reduces the footprint of the entire circuit system.


Figure 7: BUxxJA2MNVX-C series LDO adopts ultra-small package (Source: ROHM Semiconductor)

In terms of power consumption and response characteristics, the BUxxJA2MNVX-C series uses unique circuit technologies such as reference voltage circuits and amplifier circuits, making the device consume only 35μA, which is only half of previous products. Moreover, the reduction in current consumption does not affect the response characteristics of the LDO, and the load variation is as low as 65mV.
It is conceivable that when engineers are faced with the design challenge of miniaturization, low power consumption, and high reliability of automotive power systems, they will inevitably not be tempted by such an LDO in front of them.

High efficiency and low EMI PMIC

If you want to design a power system with higher integration and smaller footprint within limited vehicle space, PMIC (power management IC) is a good choice. The so-called PMIC is an IC that integrates multiple power management circuits, timing control and other functions in a single chip. Compared with power systems built with independent DC-DC, LDO and discrete components, PMIC reduces space and shortens the time. There are obvious advantages in terms of development cycle. These features will naturally be favored by many automotive applications.


Figure 8: BD86852MUF-C PMIC
(Source: ROHM Semiconductor)

ROHM's BD86852MUF-C is a PMIC specially built for ADAS automotive camera applications. It integrates three primary and secondary step-down DC-DC converters, an external linear regulator control module, and a CMOS sensor and image transmission The power-on reset function of the sensor power supply enables voltage setting and timing control through only a single IC, so the system board area can be reduced by about 41%, which is very conducive to the miniaturization design of automotive camera modules.


Figure 9: Using BD86852MUF-C PMIC
Significantly reduces the power system footprint (Source: ROHM Semiconductor)

In addition to miniaturization, the BD86852MUF-C PMIC is also optimized to improve power conversion efficiency and reduce power consumption of vehicle camera modules. Since BD86852MUF-C supplies power to the CMOS image sensor through an external LDO, it is beneficial to disperse the heat concentrated in the IC. By suppressing the heat generation of the entire circuit, it can achieve a conversion efficiency of up to 78.6%, which is higher than ordinary products. About 4%.


Figure 10: BD86852MUF-C PMIC application diagram
(Source: ROHM Semiconductor)

Moreover, this circuit design also has the advantage that since the distance between the CMOS image sensor and the LDO is shortened, it can reduce the interference noise to the power line and provide stable power supply for the CMOS image sensor. At the same time, BD86852MUF-C also has countermeasures to further reduce EMI - it is equipped with a spread spectrum function in the built-in DC-DC converter, which can reduce the peak EMI noise caused by the switch by about 10dB. This is undoubtedly good news for vehicle-mounted applications with limited space and complex electromagnetic environment.
In addition, BD86852MUF-C also integrates various protection functions and a Power Good function to monitor voltage status to ensure reliable and stable operation. Moreover, the above-mentioned performance advantages of BD86852MUF-C PMIC have been verified in system-level applications and have become a key part of ROHM's miniaturized, high-efficiency, low-EMI automotive camera module solution (see Figure 4).


Figure 11: ROHM automotive camera module solution
(Source: ROHM Semiconductor)

Low-cost and space-saving LED driver

The increasingly widespread application of LED lighting in automobiles has been promoting the development of automotive LED drivers. ROHM naturally will not miss this market opportunity and has launched a series of automotive LED driver ICs that meet the AEC-Q100 standard, including a full range of product types such as boost, buck, buck-boost, charge pump, and constant current LED drivers. Covering various applications such as automotive exterior lighting (tail lights, turn signals, DRL/positioning lights and fog lights), interior lighting, camera flash, instrument panel backlight and LED status indicators.

These LED drivers are optimized for target applications. For example, the 4-channel LED driver BD183x7EFV-M with built-in MOSFET introduced below has unique advantages in reducing space and saving costs. The reason for these advantages is that the LED driver adopts two new technologies, ROHM's unique heat dissipation circuit and LED individual control function.

In the past, in the design of multi-channel LED drive circuits, each output channel required different heat dissipation circuit pins, but BD183x7EFV-M uses a unique heat dissipation circuit to simplify multiple pins into one pin, through a small The 16-pin package achieves 4-channel higher output (150mA/ch). At the same time, the LED independent control function also makes it possible to drive LEDs of different specifications using two LED drivers in the past. Now it can be achieved with just one driver, greatly reducing the footprint of the final design solution.


Figure 12: Designed with BD183x7EFV-M
The LED driver solution occupies a significant reduction in board area
(Source: ROHM Semiconductor)

The value of the BD183x7EFV-M in terms of cost savings is achieved by simplifying the design process. In the past, multi-channel LED driver products required the design of corresponding heat dissipation circuits for each channel, and the electrical characteristic deviation of the heat dissipation resistor of each channel LED needed to be considered for trade-off adjustments, which was time-consuming and labor-intensive. The BD183x7EFV-M, which uses a unique thermal dispersion circuit, has only one thermal dispersion circuit pin, requiring only one thermal design, saving time and effort.

The LED individual control function also helps simplify system design and shorten the design cycle. BD183x7EFV-M has built-in flexible LED individual control function. When an abnormality occurs in the LED, you can choose to turn off all channels or only a single channel. Since countries around the world have different safety standards for vehicle lighting when abnormalities occur, this flexible function helps to use the same device and solution to cope with the laws and regulations of different countries and regions, so that the same model does not need to be redesigned when expanding to different markets around the world. Or greatly reduce R&D man-hours.


Figure 13: BD183x7EFV-M’s flexibility to support
Rapid expansion of design solutions in different markets
(Source: ROHM Semiconductor)

In addition, BD183x7EFV-M is also equipped with a sequential lighting function that can improve design flexibility. It only needs to add external components such as resistors to realize the expansion design of different models; it also has rich protection functions to prevent abnormality when an abnormality occurs. The LED driver and peripheral circuits are damaged.
The above characteristics make BD183x7EFV-M very suitable for use in automotive lighting systems such as tail lights (brake lights, rear tail lights), fog lights, and turn signals of cars and emerging two-wheeled motor vehicles, making the driving experience safer and more comfortable.

Summary of this article

The expansion of automotive safety and comfort functions and the upgrade of user experience are indispensable with the help of on-board power management ICs. High efficiency, high reliability, miniaturization, low EMI, compliance with EMC requirements, cost-effective... Many design requirements are placed in front of us, which will inevitably make engineers scratch their heads.
However, if you enter ROHM's rich library of automotive power management products and solutions, you will find that no matter what design needs you have, there is always a specially optimized product or solution that suits you and provides assistance for the development of related automotive electronic products! This article only takes you to the door of this technology "treasure house". From here on, let's explore more of its treasure resources in depth.

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