ST’s “Stellar” MCUs Aim to Push Forward E/E Architectures for Next-gen EVs

February 23, 2022 by Jake Hertz

A new microcontroller unit (MCU) from STMicroelectronics (ST) seeks to optimize centralized electric vehicle (EV) electronic and electrical (E/E) architectures.

The electrification of vehicles is creating a demand for new, more specialized MCUs that are optimized for the needs of EVs.This challenge is becoming increasingly hard as the field evolves and new electronic architectures gain popularity.


Overview of the evolution of E/E architecture. Image used courtesy of Renesas


This week, STMicroelectronics released new MCUs within its Arm-based Stellar family, specifically designed for EVs using centralized architectures.

In this article, we’ll discuss popular EV electronic architectures and dive deeper into the new offerings from ST.


Historical Automotive Architectures

Historically, vehicles have tended to employ multiple electronic control units (ECUs), which are embedded systems to control electrical subsystems, mostly independently of each other. 

These types of systems were known as flat architecture.


A flat architecture.

A flat architecture. Image used courtesy of GuardKnox


As vehicles became more intelligent, with sensors and increased electrification, the flat architecture was no longer feasible. 

Not only did engineers need greater computing resources to handle the sensor data, but to make a smarter vehicle, engineers also needed the disparate electrical subsystems to become more interconnected. 

The most popular approach to this was the domain architecture.

The domain architecture works to consolidate ECUs that share the same function under one domain controller or gateway. 

For example, the domain architecture will consolidate ECUs for applications like the powertrain separately from applications like the advanced driver assistance systems (ADAS). 


A domain architecture.

A domain architecture. Image used courtesy of GuardKnox


While this architecture works well for systems where sensors and compute are spatially local, it is not feasible when they are far from one another, as has become the case in today’s automobiles with advanced ADAS systems.

This leads to the next architecture type: zonal.


Zonal Architecture

Engineers created the zonal architecture to address the challenges with cabling and system complexity for automobiles employing the domain architecture.


An example of zonal architecture.

An example of zonal architecture. Image used courtesy of Texas Instruments


In a zonal architecture, ECUs that are spatially local are consolidated under a shared domain controller. This kind of architecture is beneficial by significantly reducing cabling, weight, and wiring complexity. 

On the other hand, this has to be made up for by increased software complexity. The controllers must be able to manage and differentiate traffic for different applications’ ECUs. For this reason, zonal architectures are sometimes called “software-defined EVs.”

Overall, zonal architectures have proven more scalable for future EVs, ADAS, and AVs developments.


New Stellar MCUs from ST

Aiming to keep the momentum going for zonal architecture-related solutions, ST released its new Stellar E MCUs, a new offering optimized specifically for software-defined EVs.

Built around 32-bit, 300 MHz Arm Cortex-M7 cores, the new MCUs feature up to 2 MB of on-chip Flash and up to 16 Kbyte of cache per core. 

The new MCUs, which are an extension of the Stellar family, are meant to be powerful, centralized domain and zone controllers to simplify design and scalability for a zonal architecture automobile.

As such, the MCUs include interfaces for CAN, UART, SPI, I2C, as well as several low-power sleep modes.

On top of this, the new MCUs aims to allow for easy control of wide-bandgap power electronics, such as silicon carbide, which have become a mainstay for efficient power conversion in EVs. 

To do this, the Stellar E MCUs integrate high-speed control-loop processing on-chip, which allows for a single MCU to control entire power modules.

Altogether, the MCUs, which have achieved an ASIL-D rating, can control multiple power converters while also serving as a domain or zone controller for a software-defined EV.



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