Today, the automotive industry is undergoing an unprecedented wave of transformation. From electrification and intelligence to connectivity and the rise of software-defined vehicles, the entire industry's technical architecture and supply chain system are being reshaped. Against this backdrop, the traditional function-centric centralized electrical/electronic (E/E) architecture is increasingly struggling to meet the demands of next-generation vehicles for computing performance, modular design, and rapid upgrades. It is being replaced by the "Zonal Architecture" design philosophy centered around zone control. This article explores the development trends of zonal architecture in response to the rapid changes in the automotive industry and introduces corresponding solutions launched by onsemi.
Zonal architecture reduces automotive manufacturing complexity and cost
The emergence of zonal architecture aims to address the rapid evolution of the automotive sector, particularly against the backdrop of rising electric vehicles. Significant progress has been made in low-voltage power distribution and in-vehicle networking technologies. Distributed zonal power distribution simplifies wiring harnesses, thereby reducing weight, manufacturing complexity, and costs.
The shift towards software-defined vehicles (SDVs) is driving automakers to continuously innovate, integrating protected semiconductor switches into zonal controllers. Electronic fuses (eFuses) and Smart Field-Effect Transistors (SmartFETs) enhance functional safety and fail-functional situations by safeguarding loads, sensors, and actuators. Unlike traditional domain architectures, zonal architecture centralizes control and computing, moving software from individual Electronic Control Units (ECUs) to a powerful central computer. This provides greater flexibility for downstream electronic control and power distribution.
Automotive Ethernet is crucial for software-defined vehicles, as it can handle the massive amounts of data from sensors like cameras and LiDAR. It ensures real-time data transfer between zonal controllers and the central computer, which is responsible for processing sensor data and making decisions. As computational demands continue to grow, this infrastructure is vital for the future of autonomous vehicles.
The transition from legacy to zonal architecture in modern vehicles
As modern vehicles become increasingly complex, two major trends in power distribution (PD) and in-vehicle networking are shaping zonal architecture. Changes in power distribution are aimed at simplifying the design of current automotive electrical architectures. Power distribution is evolving from centralized PD to zonal (decentralized) PD, which relies on new semiconductor protection devices like eFuses and SmartFETs to enhance functional safety. Due to the enormous volume of data, vehicle networks are increasingly dependent on an Automotive Ethernet backbone.
In the legacy architecture of the 1990s, vehicles used centralized power distribution, where power was delivered directly to individual Electronic Control Units (ECUs), and distributed control and software resided within the ECUs. By the 2010s, domain architecture became widespread, featuring semi-distributed power distribution with domain controllers.
The increasing electronic complexity of vehicles has become critical. Power is no longer delivered directly to ECUs but to domain controllers. Domain controllers are grouped by function, such as power, chassis, and infotainment. To maintain this structure and add more ECUs, the wiring harness connecting all components becomes excessively long and heavy. Protection relies on one or more fuse boxes and potentially domain-specific local fuses.
As the number of electronic components in vehicles grows, power distribution becomes more complex, and the challenges in wiring harness design increase significantly. The traditional cabling approach, which connects similar functions like power, chassis, infotainment, body and comfort, is no longer efficient or flexible enough. The automotive industry is shifting from centralized power distribution to a more distributed zonal approach. Many ECUs, traditionally scattered throughout the vehicle, can be replaced by Zonal Control Units (ZCUs).
A single Power Distribution Unit (PDU) serves as the primary level of the power distribution tree. The PDU connects to the vehicle's low-voltage (LV) battery or to the output of a High-Voltage to Low-Voltage (HV-LV) DC-DC converter, which steps down the voltage from the high-voltage (HV) battery. The PDU provides primary protection via high-current fuses and intelligently distributes power to each zone within the vehicle, ensuring efficient and reliable power management. The ZCUs further distribute power and manage electrical components within its respective zone, significantly reducing the weight and complexity of the wiring harness.
The ZCUs can also act as the vehicle's data and network gateway, relying on Automotive Ethernet. They communicate upstream with the central computer via a 100/1000BASE-T1 Ethernet backbone. Downstream communication with edge nodes like cameras, sensors, and LiDAR is based on 10BASE-T1S Ethernet. Legacy ECUs can remain connected to the ZCUs via legacy bus like CAN, LIN, and FlexRay.
Post-2025, the trend is towards zonal architecture. The vehicle is divided into four zones, managed by Zonal Control Units (ZCUs). The Power Distribution Unit (PDU) distributes power to each zone, and the ZCU further manages the secondary level of the power distribution tree. This distributed model adds redundancy. Each ZCU distributes power and manages electrical components grouped by location. Protected semiconductor switches, such as eFuses and SmartFETs, enhance functional safety and fail-functional situations by safeguarding loads, sensors, and actuators.
Zonal architecture drives the development of software-defined vehicles
In traditional vehicle architecture, software primarily resided within individual Electronic Control Units (ECUs). However, zonal architecture changes this by pulling the software out of the ECUs and centralizing control and computing within a powerful central computer. This shift is crucial for Advanced Driver-Assistance Systems (ADAS) and autonomous driving, as they need to process vast amounts of data from cameras, radar, and LiDAR sensors, which can generate several megabits of data per second. Automotive Ethernet becomes the network backbone within the software-defined vehicle hardware infrastructure, efficiently transmitting real-time data between Zonal Control Units (ZCUs) and the central computer.
Over-the-Air Software (OAS) updates represent another significant advancement for software-defined vehicles. In the past, vehicle software updates were rare and required visits to dealerships. Typically, ECU software was never updated after the vehicle left the factory. However, in the era of smartphones and instant downloads, regularly visiting a dealership for updates is no longer acceptable. Today, vehicles can connect to the cloud and update automatically, often overnight, allowing drivers to enjoy new features and improvements the next morning without inconvenience. The zonal approach, with its centralized computing advantage, simplifies this update process.
The 10BASE-T1S is one of the latest developments in single twisted-pair Ethernet, designed specifically for automotive applications. 10BASE-T1S (compliant with IEEE 802.3cg standard) addresses the automotive industry's need for high-speed, high-bandwidth, and deterministic real-time communication networks. Multidrop topology is a key innovation for automotive applications, as it allows multiple nodes to connect to a host controller over a single unshielded twisted pair. Furthermore, the scalability and flexibility of Automotive Ethernet enable easy integration of new features and technologies. These complex and data-intensive applications include Advanced Driver-Assistance Systems (ADAS), infotainment systems, real-time diagnostics, and other critical components.
Comprehensive semiconductor portfolio supporting zonal architecture
onsemi offers a comprehensive semiconductor portfolio to support the transition to zonal architecture. Key components include Low/Medium Voltage MOSFETs and onsemi's new PowerTrench T10 MOSFETs. onsemi's advanced SmartFET and eFuse protected power switches replace traditional fuses, providing resettable protection and enhanced safety. 10BASE-T1S Ethernet transceivers support innovative features like multidrop topology and PLCA, enabling vehicle networking.
The Zonal Controller (ZCU) is a fundamental element in the zonal vehicle architecture, responsible for managing power distribution within its designated zone. The ZCU can integrate several key components, such as SmartFETs, eFuses, and discrete MOSFETs. Additionally, the ZCU supports high-speed communication networks and can utilize 10BASE-T1S Ethernet transceivers like the NCV7410 and T30HM1TS2500. These transceivers enable efficient data communication between the ZCU and the central computer or other vehicle systems.
The NCV7410 Ethernet transceiver is a 10BASE-T1S compliant transceiver as per the IEEE 802.3cg standard, featuring an integrated Media Access Controller (MAC-PHY). It supports operation over a shared medium (multidrop) network with a single twisted-pair (UTP/STP) connection length of up to 25 meters. The NCV7410 provides an SPI interface in slave mode, enabling low pin-count connection to standard host MCUs or SoCs. It can communicate with multiple nodes connected to a shared medium (UTP) at 10 Mbps.
Multidrop topology is perhaps the most transformative technology in Automotive Ethernet, offering a cost-effective, scalable, and efficient solution for modern vehicle networks within zonal architecture. Multiple devices (nodes) are connected to the same twisted pair cable, forming a bus-like structure. This is similar to older technologies like CAN but possesses Ethernet capabilities. The new zonal architecture simplifies complex domain-based wiring, making it easier to manage and maintain.
The standard supports at least eight nodes, but depending on the implementation and cable length, more can be connected. Modern vehicles require high flexibility, and 10BASE-T1S allows for easy addition of new nodes without extensive rewiring. Furthermore, the Physical Layer Collision Avoidance (PLCA) mechanism ensures data collisions are avoided by assigning each node a specific time slot for data transmission.
The NCV7410 implements a unique feature - PLCA Precedence Mode. Lower PLCA IDs take precedence over higher ones, providing an arbitration mechanism similar to CAN: once any station transmits, the Coordinator (i.e., the head node) sends a new beacon.
The T30HM1TS2500 (T2500) is an advanced 10BASE-T1S Ethernet transceiver with an integrated Media Access Controller (MAC-PHY). It is a next-generation 10BASE-T1S device designed on the new Treo platform (BCD65). It is capable of communicating with multiple nodes connected to a shared medium (UTP) at 10 Mbps.
The T2500 incorporates CSMA/CD MAC and PHY with Physical Layer Collision Avoidance (PLCA) functionality. PLCA prevents collisions at the physical layer, thereby improving CSMA/CD throughput. The T2500 uses SPI (with a clock frequency up to 25 MHz) as the interface to higher layers.
Compared to the NCV7410, the T2500 supports additional features, such as Topology Discovery (compliant with TC14 standard), which measures distances between nodes. It also features Sleep/Wake-up (compliant with TC10 standard) configuration capability with very low current consumption in sleep mode (35 µA). Additionally, Time Stamping (compliant with TC6 standard) enables precise time synchronization, and it supports direct battery connection (VBAT pin) up to 48 V. More features are integrated into a smaller, more compact 4 x 4 mm QFNW20 package.
For ESD protection of 10/100/1000BASE-T1S Ethernet, onsemi's SZESD9901 and SZESD9902 are designed to protect sensitive automotive electronic components from Electrostatic Discharge (ESD), surge, and other harmful transient events. These devices comply with OPEN Alliance 10/100/1000 BASE-T1 Ethernet and other high-speed data network standards. They are suitable for bidirectional ESD protection on the transceiver PHY connector side. They support a high trigger voltage function of ≥ 100 V, where a higher trigger voltage eliminates differential signal distortion clamping.
Conclusion
Facing the accelerated transformation of the automotive industry, zonal architecture has become a core direction for the evolution of future vehicle electrical/electronic systems. By integrating traditionally dispersed control units into zonal controllers, it significantly reduces wiring harness weight and cost while enhancing system scalability and maintenance efficiency. Combined with high-speed Ethernet, centralized computing platforms, and intelligent software architecture, automakers can more flexibly address the challenges of electrification, autonomous driving, and vehicle connectivity. The onsemi solutions introduced in this article can assist automakers in realizing zonal architecture designs, serving as a key enabler for the automotive industry's transition into a new era of intelligence and low-carbon mobility.