Under the trend of automotive regional controller architecture, the typical circuit designs of these three categories are changing

The automotive market is turning to the trend of regional controller architecture, and the automotive regional controller architecture is developing in the direction of distribution, integration and intelligence to achieve more efficient data processing, functional integration and autonomous driving support. There are many design opportunities and challenges based on the regional controller architecture. For example, SmartFET is increasingly replacing traditional MOSFET devices.

SmartFET is a power MOSFET device that integrates intelligent control and protection functions, and has been widely used in electric vehicles today. On the basis of traditional power switching elements, SmartFET adds functions such as overcurrent, overheating, overvoltage protection, and real-time monitoring and diagnosis. By integrating current detection, temperature compensation and adaptive switching control technology, SmartFET can automatically adjust its behavior according to actual working conditions to prevent potential failures, and simplifies circuit design and reduces external component requirements.

For example, in the field of automotive electronics, the high-side SmartFET provided by Onsemi can not only efficiently switch loads such as LED lighting, starters, door modules, HVAC and other actuators, but also has active inrush current management, over-temperature shutdown and automatic restart, and active overvoltage clamping, which greatly improves the stability and service life of the entire system.

From high-side drive to low-side drive, SmartFET's multi-effect "benefits" are usually used when using MOSFET. First, there must be a suitable driver, such as a suitable gate resistor. At the same time, in order to prevent damage to the field effect tube, we also need various protection measures, such as overcurrent, overtemperature and overvoltage protection circuits, to ensure its long-term reliable operation without damage. Usually these protection circuits are achieved by discrete devices, which not only increases system cost, but also occupies a large PCB space.

SmartFET products integrate these drive and monitoring protection circuits into the package of standard MOSFET, so a SmartFET consists of two main components: first, it has a power stage based on standard MOSFET responsible for providing current to the load; the second is the control stage, which mainly refers to the MOSFET drive and monitoring protection circuit. With this control stage, the MOSFET can be switched correctly and prevented from being damaged. This can not only increase the reliability of MOSFET use, but also save system cost and reduce the space occupied by PCB. These advantages make SmartFET widely used in automotive electronics.


High and low side drives are two basic methods for controlling the on and off of loads in circuits. They are widely used in power management, motor control and automotive electronics. Specifically:

Low Side Driver (LSD): In a DC power supply circuit, low side driver refers to the control of the switch element connected to the load ground (or ground terminal) to achieve the on and off of the load current. When this "switch" (usually MOSFET or transistor) is turned on, the load can form a loop and draw current from the power supply; when the switch is turned off, the path between the load and the ground is cut off, thereby stopping the current flow.

High Side Driver (HSD): High side driver refers to controlling the load current by controlling the switch element connected to the positive side of the load power supply. High side driver is relatively complex because it needs to deal with issues including ensuring that the gate drive voltage is higher than the power supply voltage to ensure that the MOSFET is effectively turned on, and a charge pump or bootstrap circuit must be considered to provide sufficient gate drive voltage. When the high side switch is turned on, a path is formed between the load and the power supply to start working; when the switch is turned off, the load loses the upper power supply and the current no longer flows through the load.

In summary, between a power supply and a load, if the load is controlled by controlling the switch on the lower side (near the ground line), it is a low-side drive; if the load is controlled by controlling the switch on the upper side (near the positive pole of the power supply), it is a high-side drive. Both methods have their own advantages and disadvantages and applicable scenarios. When designing, choose the appropriate method based on system requirements, efficiency, safety and other factors.

Three major typical applications of high-side SmartFETs Since various detection and protection circuits are integrated, high-side SmartFETs can actually handle a variety of loads. Common ones can be divided into three categories of applications.



The first category is light bulbs and capacitive loads. The characteristic of this type of load is that they will have a surge voltage when they are first turned on. For example, when a light bulb is cold, its resistance is relatively small. The current when it is first turned on will be much greater than its rated current. This is even more true for capacitors, which have a charging current when they are first turned on. At this time, the high-side SmartFET is required to handle this surge current. These typical loads include lighting inside and outside the car, or various DCDC power modules commonly seen in ECUs, etc.

The second type of load is the inductive load. Loads such as various motors and relays have a common feature. When the coil with energy is disconnected, there must be a freewheeling circuit, and an induced voltage (also called flyback voltage) may be generated in the primary coil. These flyback voltages will generate overvoltage on the power device, and this overvoltage must be clamped to a reasonable range to ensure that it does not cause damage to the MOSFET power switch. Such loads include motors and relays such as wipers, starters, door modules, heating, ventilation and air conditioning (HVAC), fuel injectors, electric power steering, and throttle control. The third type

is resistive loads. Resistive loads themselves have neither surge current nor overvoltage, but in order to know the changes in loads in a timely manner, accurate current detection capabilities are required. For example, in LED applications, if one of the LEDs in a string of LED lamp beads is damaged, the current of the string of LED lamps will change. This change may not be large, but it needs to be detected in a timely and accurate manner. In addition to LED lighting, this type of application also includes heating units, transmissions, and engine management systems.

SmartFET applications under the trend of regional controller architecture An important trend in the current automotive market is that the automotive electronic and electrical architecture has begun to shift to the regional controller architecture. The regional controller architecture is used to replace the widely used domain controller architecture. The so-called regional controller architecture means that the electronic control units are organized and divided according to the physical location of a specific area, rather than according to function. For example, the left body, right body, front body, etc., organize it according to the physical location according to the corresponding required functions to form a regional controller. These regional controllers are connected through high-speed Ethernet. These Ethernets not only transmit and process data, but also transmit and distribute power, thereby greatly reducing the complexity and weight of the wiring harness (it is worth mentioning that the wiring harness is currently the third heaviest and third most expensive component on electric vehicles).

It can be simply attributed to the fact that the regional controller architecture is replacing the wiring harness with the network, that is, the wiring harness in the domain controller has now become a network. This network is not only a data network, but also a power network. Since the regional controller architecture is a ring network composed of Ethernet, it is easy to expand and can add or subtract corresponding regional controls according to the configuration of low, medium and high gears. In this way, it is easy to achieve rapid product market launch.

Based on the regional controller architecture, not only data is transmitted and processed through the network, but also power is distributed in levels through the network. Therefore, SmartFET will be of great use: it is used as the efuse fuse of the entire regional controller to protect the circuit from damage due to surge current or high voltage; at the same time, it can also control the on and off of the power supply of the entire regional controller architecture; SmartFET can also be used to decide when to connect the load to the power supply and when to disconnect the load from the power supply.

These features of ON Semiconductor SmartFET make it easier to apply SmartFET is an advanced semiconductor switch solution designed to provide efficient and reliable power management for automotive and industrial applications. Its structure combines vertical power MOSFET and intelligent control logic to achieve compact packaging and optimized performance. The design concept focuses on providing highly integrated protection features such as over-temperature protection, overload protection, and short-circuit protection to ensure safe operation of the system under various fault conditions. SmartFET also has analog current detection output to support accurate load monitoring.

As the main supplier of SmartFET product technology, ON Semiconductor considers compatibility with controllers in product design, making it easier to switch between SmartFETs of different sizes and different RDS(ON), providing greater flexibility for applications. The entire ON Semiconductor series, from 1 milliohm to 60 milliohm, from 1 amp to 20 amps, has the same package, the same silk screen, the same instruction structure and the same high reliability. Therefore, when designing and making regional controller architecture PCB boards, it has considerable versatility and flexibility, and does not need to remake the PCB board due to changes in external loads, which is a very big advantage.