Vehicle Power Distribution Architecture Must Replace Electronic Fuses

Internal combustion engine standard E/E architecture → Centralized E/E architecture trend
STi2Fuse, Real-time Output Channel Load Monitoring, Fault Protection, and Automatic Recovery

[Editor's Note] As automotive industry trends shift toward electric and autonomous vehicles and the evolution toward SDVs accelerates, the number of Electronic Control Units (ECUs) is surging. Amid these changes, global automakers are considering centralized architectures to address the problem of increasingly complex wiring between ECUs. ST has stepped forward to satisfy the requirements arising from this, such as individual output control and condition diagnosis. On October 26, we will host the 'Smart Fuse for Automotive Power Distribution (STi2Fuse) Webinar,' where you can learn about electronic fuses that incorporate the i2t algorithm and CCM (Capacitive Charging Mode) functionality based on ST's existing HSD products. Ahead of the webinar, we listened to the story of ST Senior Manager Choi Young-min, who will be participating as a speaker.

▲ Choi Young-min, ST Senior Manager

■ What will be presented at the webinar on the upcoming 26th?

We plan to introduce the upcoming STi2Fuse product family.

STi2Fuse products are available in monolithic, hybrid, and controller types depending on the load current size.

The monolithic product family is designed based on VIPower M0-9 SPI technology in a QFN 6x6 package and is intended for Zonal Boxes for low current (1.5A to 15A), while the hybrid product family is designed with VIPower M0-9 SPI + M0-S11 technology in a PowerQFN 7x8.5 package and is intended for Power Distribution Boxes for medium current (6A to 45A).

Finally, the controller type product family is a product with BCD9 technology applied in a QFN 5x5 package, designed for main switches of high-current (40A to 450A) power sources.

In addition, a companion product supporting an active standby function is also scheduled to be released to prepare for cases where each output needs to be kept turned on at all times, just like a standard fuse, such as in the KL30 application.

This product can be used with the hybrid product family, and when the hybrid device is in standby mode, the companion device operates to keep each output in a turned-on state at all times with a low driving current, and when the load current reaches a current threshold value set by the user, the companion device switches to standby mode and automatically switches the hybrid device, which is the main switch, to normal mode.

■ Please introduce STi²Fuse for Automotive Power Distribution and explain why STi²Fuse is attracting attention.

In the future, as various functions such as electrification, connectivity, and autonomous driving are installed in vehicles, the automotive industry will have to process a vast amount of computation and data, and wiring is also expected to become increasingly complex.

In addition, to increase driving range, a key evaluation factor for electric vehicles, it is required to simplify and optimize the wire harness, which accounts for a large portion of the vehicle's weight.

Therefore, as an alternative, global automakers are preparing Zonal Architecture, a centralized E/E architecture, moving away from the framework of existing internal combustion engine-based automotive E/E architectures.

Zonal Architecture refers to a configuration where each ECU is connected to a Zonal Gateway located physically close by, and an architecture in which the MPU, acting as the Central Brain, is connected to the Zonal Gateway to manage and supervise all ECUs within the vehicle.

While existing domain architectures grouped ECUs by function to form domains and processed them in the DCU (Domain Control Unit), Zonal Architecture groups ECUs based on physical location.all.

Configuring this architecture simplifies the wiring harness and significantly reduces its length and weight because all ECUs receive power from a Zonal Gateway located in a physically close proximity. Additionally, since all ECUs can be managed and monitored centrally, system maintenance and repair through software updates are facilitated.

However, the automotive power distribution architecture consisting of mechanical fuses and relays that has been used until now can no longer handle this, so it is necessary to replace them all with electronic fuses.

STi2Fuse products can monitor and control the load status of all output channels in real time, and provide protection and automatic recovery in the event of a failure.

In addition, it incorporates an I2t algorithm identical to the interruption principle of conventional melting fuses, enabling interruption operation based on an I2t interruption curve set by the user. Therefore, if the wire is optimized by setting it to match the actual load current, the wire weight can be reduced by nearly 20%, and the circuit design can be made about 25% lighter and smaller compared to the configuration of conventional relay fuses, contributing to improved fuel efficiency.

■ What are the major application applications?

It can be used as a switch and fuse to distribute power for vehicles and supply power to various ECUs.

STi2Fuse products not only provide on/off control, overcurrent protection, and fault diagnosis for power supply to various loads, but also have a built-in i2t algorithm identical to the fuse tripping operation. When used as a switch for vehicle power distribution, users can set the tripping curve to match the actual load current, thereby optimizing the wire diameter.

■ What are the key requirements of the market/industry?

The requirements for electronic fuse products include the ability to stably supply power without protection operation under normal conditions regardless of whether R, L, or C loads are applied during power supply, and a fast interruption speed of within 100 µs is required so that the power line does not waver under conditions where a large current may flow, such as a hard short.

Regarding wire protection, wire protection using the i2t algorithm, which is identical to the fuse tripping algorithm, is required, and even in fail-safe mode where communication with the MCU is impossible, the output of each channel must be output normally.

ASIL B requirements necessitate status diagnostics and wire protection capable of verifying whether each output is damaged in the on or off state; regarding status diagnostics, a function capable of real-time monitoring of the voltage and current of each output, as well as the chip temperature, is required.

Finally, an active standby function is required that, just like a standard fuse, maintains the turn-on state of each output at all times with a low driving current even in standby mode, and automatically switches to normal mode when the load current increases.

■ What are the main benefits of the product being introduced?

First, the biggest advantage is that the wire can be automatically protected under overcurrent conditions through the user-configurable i2t algorithm, and the wire diameter can be optimized to match the load current.

In addition, it can quickly shut off within 100us even under overcurrent conditions such as hard shorts, ensuring the 12V power line remains stable without fluctuation, and supports LV124.It can operate normally even under micro-cut conditions of the battery.

In addition, by utilizing the CCM (Capacitor Charging Mode) function, the inrush current generated when starting a large-capacity capacitor load can be effectively limited, enabling the device to reach a normal output voltage level.

In addition to this, regarding condition diagnosis, it is possible to monitor not only the chip temperature but also the voltage and current of all output channels in real time, allowing for the prediction and management of risks in advance.

Regarding functional safety, to support ASIL applications, the current sensing blocks support the Built-in Self-Test (BIST) function and a redundancy configuration with duplicate ADC blocks for each channel.

■ What is the difference compared to competitor products (or existing products)?

Regarding the I2t wire protection function settings, all products allow for setting the normal current (=INOM) and normal time (=tNOM) in 8 steps each via SPI communication, creating a total of 64 combinations. Monolithic products support a parallel mode function that can double the driving current by linking output channels in parallel.

These features allow for a wider range of i2t cutoff curve settings compared to competitors, making it effective for wire optimization.

In addition, for low/medium current products, we have dual and quad channel product lines as well as single channel products, and various products capable of covering low currents from 1.5A to high currents up to 450A are scheduled to be released.

■ Please share a few words with the e4ds readers regarding the content introduced today.It is

Thank you for participating in the STi2Fuse seminar. We look forward to your continued interest. If you have any questions, please contact ST Korea or an ST distributor, and we will be happy to answer them.