Next-generation door zone system ICs will significantly improve energy efficiency and advance vehicle electrification

In recent years, automobile electrification has been a general trend. Automobile electrification is not only the introduction of pure electric vehicles, but also the continuous replacement of traditional mechanical components and mechanical relays with electronic control technology, or the introduction of new functions in some cases.

The large-scale electrification of cars is driving autonomous driving to a higher level, and in the medium and long term, many vehicles may be considered "driverless taxis". According to this new car driving concept, all functions in the car door will be automated, such as intelligent automatic door opening and collision avoidance detection. These automated systems will be able to detect pedestrians or cyclists approaching the car and automatically control the door opening operation to avoid the risk of collision. In the future, advanced sensors will also be installed in the car door to detect obstacles outside the door to prevent the door from being damaged.

The emergence of this megatrend is inseparable from the paving of dedicated semiconductor chips. These chips need to follow advanced power management concepts to drive loads ranging from milliwatts such as LEDs to high-power DC motors that can easily dissipate 200W of power in an instant. In addition, automotive electronic modules also need to be equipped with highly standardized communication interfaces, such as CAN and LIN physical layers.

How to determine a correct system architecture to implement new features at a reasonable cost without compromising quality and performance is a major challenge facing automakers. As the cost and complexity of hardware and software development continue to increase, it is becoming increasingly difficult to keep up with the performance and functional requirements of OEMs. In addition, OEMs also require the deployment of cost-effective and scalable solutions that can be expanded from low-end models to high-end vehicles, and the development costs can be spread across different platforms and models.

The door zone electronic control module (Figure 1) is a familiar automotive system that benefits from a scalable drive approach. The concept is to use one IC to drive multiple loads in the door zone (door lock motors, adjustable and foldable mirrors, defrosters, window lift motors, and lighting functions such as LEDs and incandescent lamps). Scalable drivers, packaging and software compatibility, and adaptability to the diverse requirements of the door electronic control module are typical features of door zone actuators.

Figure 1:

Over the past 10 years, automotive semiconductor manufacturers have developed several door actuator driver chips, and as the number of automotive electrical loads continues to increase, new features have been added to these products, and packaging, chip manufacturing technology and IP cores have been optimized. In the door area electronic components, in addition to the driver chip (Figure 2), there is also a power management IC to provide a stronger system power supply for the electronic control unit, including various standby modes and communication layers (mainly LIN and/or HS CAN). The power management chip usually integrates two low-dropout regulators to power the system microcontroller and peripheral loads (peripherals such as sensors), and also includes an enhanced system standby function, as well as configurable local and remote wake-up functions.

Figure 2:

Both the door actuator driver and power management ICs are manufactured using ST’s BCD (Bipolar, CMOS and DMOS) semiconductor technology, which is optimized for this application. The door actuator driver IC uses 0.7μm BCD technology, while the power management IC uses 0.57μm BCD technology.

To adapt to new automotive technology development trends, automotive semiconductor devices must efficiently and safely control more electrical loads, minimize quiescent current, and adopt highly integrated solutions to reduce the number of components, reduce circuit board space, and reduce product weight, thereby greatly simplifying the design.

STMicroelectronics' proprietary advanced 0.16μm BCD8S is the key technology to achieve a unique high-integration monolithic solution on the market (Figure 3), which meets the technical requirements of applications such as power management, fault protection and door load drive. This technology can also improve energy efficiency and computing power, increase the chip's junction temperature to 175°C, reaching the standard junction temperature strictly specified by automotive OEM manufacturers, and solve the challenging thermal management problems brought by monolithic integrated power management and actuator drivers.

Figure 3:

STMicroelectronics’ innovative L99DZ100G/GP front door controller and L99DZ120 rear door controller ICs help designers save space while improving reliability and energy efficiency of door-control modules.

The previous door zone ASSP (Application Specific Standard Product) solution required two chips: a 12mm×12mm (TQFP64) door actuator driver and a 10mm x 10mm (PowerSSO-36) power management chip, while STMicroelectronics' door zone control monolithic solution only requires an LQFP64 package area the same as TQFP64 (Figure 4), which is very important for PCB miniaturization and can adapt to more stringent space requirements. In addition to reducing the die size using the new BCD technology, the package area is also reduced through a new innovative package structure, while reducing the door system IC while increasing the output current peak and power density.

Figure 4:

The software compatibility of all products also helps simplify development and shorten product market time.

ST's proprietary BCD8S advanced automotive technology plays a key role in realizing this single-chip solution. The solution has multiple features, including a built-in half-bridge and a high-side driver up to 7.5A, to meet the new requirements of door zone applications. The solution also integrates high-speed CAN (HS-CAN) and LIN 2.2a interfaces (SAE J 2602), control modules, and protection circuits. In addition to standard features, the L99DZ100GP also supports selective wake-up of the ISO 11898-6 HS-CAN standard, allowing ECUs that are not used frequently to enter sleep mode while maintaining connection to the CAN bus to maximize energy saving.

Both front door controllers integrate a MOSFET half-bridge that can drive up to five DC motors and an external H-bridge. In addition, the two chips have eight LED drivers and two incandescent lamp drivers, a mirror heater gate driver and a window electrochromic glass control module. Other features include external circuit (microcontroller, sensor, etc.) regulators, as well as related timers, watchdogs, reset generators and protection functions. The rear door controller L99DZ120 also has similar functions, for example, electric window lift motor drivers.

Equipping vehicles with more electronic systems and features helps increase the selling points of cars, but more electronic configurations also increase power requirements. Therefore, it is necessary to accurately analyze the power consumption of each system under various working conditions, especially for pure electric vehicles, where wasting electricity means shortening the driving range; the more electrical components, the greater the leakage current, which is inevitable. Therefore, all automakers attach great importance to products and/or technologies with low quiescent current and standby current. Most ECUs have a maximum standby current budget of 100μA, so customers often say: "Every microampere is important."

Therefore, STMicroelectronics has integrated an advanced power management module with multiple low quiescent current modes (standby/sleep, periodic monitoring, dedicated low-current mode LDO regulator, timer, contact device power supply) on the new door zone controller chip. In VBAT standby mode, the quiescent current drops to less than 10μA, in the 7μA-8μA range, which is half of the dual-chip IC (door zone driver IC + power management IC) topology. For door applications, the controller does not power the microcontroller (MCU) until the regulator is woken up by external contact device monitoring or the physical layer of the communication interface (LIN, HS-CAN or HS-CAN with selective wake-up support).

STMicroelectronics' new door zone controller not only integrates the previous door zone actuator driver chip and power management chip in one package, but also adds some new functions to better serve the new automotive development trends.

To support the automatic LED duty cycle compensation function, STMicroelectronics' new car door zone controller implements a new IP module. The internal compensation algorithm uses the power supply voltage measurement value to correct the duty cycle of the LED driver power stage to ensure that the LED maintains uniform brightness even when the ECU power supply voltage fluctuates. Developers can flexibly set the duty cycle compensation function according to different loads, use different LEDs and connect LEDs in series, thereby saving the load of the external microprocessor and minimizing the data traffic of the SPI.

The thermal cluster concept is another new feature of the new controller. When an event such as a short circuit occurs, this feature can disable the short-circuited output channel individually while the other output channels remain in normal operation.

To comply with the requirements for safe operation of the power windows, the new controller also implements a dedicated IP core that can put the window into a safe state in the event of a system error, preventing uncontrolled window lifting and lowering. In accordance with safety requirements, this IP core has a deep trench isolation layer between it and the rest of the chip, which is another valuable feature of BCD8s technology. A self-biasing method allows the IP module to continue to operate normally when the battery is dead.