“Vehicle power distribution architecture must replace electronic fuses”

Internal combustion engine-based E/E architecture → Centralized E/E architecture trend
STi2Fuse, real-time monitoring of output channel load, protection in case of failure, and automatic recovery

[Editor's Note] As the automotive industry trend shifts to electric and autonomous vehicles, and the development of SDVs is rapidly taking place, the number of ECUs (Electronic Control Units) is rapidly increasing. In order to solve the problem of complex and increasing wiring between ECUs amidst these changes, global automakers are considering a centralized architecture. ST has stepped forward to meet the requirements for individual output control and status diagnosis that arise here. On October 26, our magazine will hold a 'Smart Fuse for Automotive Power Distribution (STi2Fuse) Webinar' to discuss ST's electronic fuse with the addition of the i2t algorithm and CCM (Capacitive Charging Mode) function based on its existing HSD product. Before the webinar, we heard from ST Vice President Choi Young-min, who is participating as a speaker.

▲ST Vice President Choi Young-min

■ What will be presented in the webinar on the 26th?

We will be introducing the upcoming STi2Fuse family of products.

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

The monolithic product line is designed based on VIPower M0-9 SPI technology in the QFN 6x6 package and is targeted at small current (1.5A to 15A) zonal boxes, while the hybrid product line is designed using VIPower M0-9 SPI + M0-S11 technology in the PowerQFN 7x8.5 package and is targeted at medium current (6A to 45A) power distribution boxes.

Lastly, the controller type product line is a product that uses BCD9 technology in a QFN 5x5 package and is targeted at the main switch of high-current (40 A to 450 A) power sources.

In addition, a companion product supporting the Active Standby function is also planned to be released for cases where each output must be kept turned on at all times, even in standby mode, just like a general fuse, such as the KL30 application.

This product is available as a hybrid product line, HiveWhen the lead device is in standby mode, the companion device operates to keep each output turned on 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, the automobile industry will have to process a huge amount of calculations and data as various functions such as electrification, connectivity, and autonomous driving are installed in vehicles, and wiring is also expected to become more complex.

In addition, in order to increase the driving range, which is an important evaluation factor for electric vehicles, it is required to simplify and optimize the wiring harness, which accounts for a large proportion of the vehicle weight.

Therefore, global automakers are preparing a centralized E/E architecture called Zonal Architecture as an alternative to the existing internal combustion engine vehicle-based E/E architecture framework.

Zonal Architecture is a configuration in which each ECU is connected to a Zonal Gateway located physically nearby, and the MPU, which is the central brain, is connected to the Zonal Gateway to manage/supervise all ECUs in the vehicle.

While the existing domain architecture groups ECUs by function to form a domain and processes it in the DCU (Domain Control Unit), Zonal Architecture groups ECUs by physical location.

To construct this architecture In this case, since all ECUs receive power from a Zonal Gateway that is physically close to them, the wiring harness can be simplified and its length and weight can be significantly reduced. In addition, since all ECUs can be managed/supervised centrally, system maintenance and repair through SW updates are easy.

However, the automotive power distribution architecture consisting of mechanical fuses and relays that have been used so far is no longer feasible, so it must all be replaced with electronic fuses.

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

And since it has the same I2t algorithm as the blocking principle of the existing melting fuse, it is possible to perform a blocking operation according to the I2t blocking curve set by the user, so if the wire is optimized by setting it according to the actual load current, not only can the wire weight be reduced by about 20%, but the circuit design is about 25% lighter and smaller than the existing relay fuse configuration, contributing to improved automobile fuel efficiency.

■ What are the main application areas?

It can be used as a switch and fuse for vehicle power distribution and power supply 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 that is identical to the fuse blocking operation, allowing users to set the blocking curve according to the actual load current when used as a vehicle power distribution switch, thereby optimizing the wire diameter.

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

The requirements for electronic fuse products include that power must be supplied stably under normal conditions without any protective operation regardless of the R, L, or C load when power is supplied, and that a fast breaking speed of less than 100us is required to prevent the power line from shaking under conditions where a large current may flow, such as a hard short.

In terms of wire protection, wire protection through the same i2t algorithm as the fuse blocking algorithm is required, and even in fail safe mode where communication with the MCU is not possible, the output of each channel must be output normally.

ASIL B requirements require status diagnostics and wire protection to determine whether each output is broken in the on or off state. For status diagnostics, the ability to monitor the voltage and current of each output, including the chip temperature, in real time is required.

Lastly, an active standby function is required that can always keep each output turned on with low operating current even in standby mode like a general fuse, and automatically switch to normal mode when the load current increases.

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

First, the biggest advantage is that it can automatically protect the wire under overcurrent conditions through a user-configurable i2t algorithm, as well as optimize the wire diameter to suit the load current.

And even in overcurrent conditions such as hard shorts, it can be quickly shut off within 100us, so the 12V power line can be maintained in a stable state without shaking, and it supports LV124, so it can operate normally even under micro-cut conditions of the battery.nbsp;

Additionally, the CCM (Capacitor Charging Mode) function effectively limits the inrush current that occurs when starting a large-capacity capacitor load, allowing the normal output voltage level to be reached.

In addition to this, in terms of status diagnosis, it is possible to monitor the voltage and current for all output channels as well as the chip temperature in real time, allowing for predicting and managing risks in advance.

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

■ What are the differences compared to competitors’ products (or existing products)?

In relation to the I2t wire protection function settings, all products can set the normal current (=INOM) and normal time (=tNOM) in 8 steps each via SPI communication, allowing a total of 64 combinations to be created, and in the case of monolithic products, the output channels can be connected in parallel to support the parallel mode function that can double the driving current.

These features provide a wide range of i2t blocking curve settings compared to third parties, making them effective for wire optimization.

In addition, for low/medium current products, we have not only single channel but also dual and quad channel product groups, and various products that can cover low current of 1.5A to high current of 450A are scheduled to be released.

■ Please give a word to e4ds readers regarding the content introduced today.
> Thank you for attending the STi2Fuse seminar. We ask for your continued interest. If you have any questions, please contact ST Korea or your ST distributor. We will do our best to answer them.