At a recent virtual media event hosted by STMicroelectronics, Davide Santo, Senior Director of the Automotive MCU BU and Division Strategic Office Member at STMicroelectronics, unveiled xMemory — a new architectural concept integrated into ST’s Stellar automotive microcontrollers. Built on Phase Change Memory (PCM) technology, the xMemory concept aims to address the evolving demands of electrification, autonomous driving, and software-defined vehicles by offering unmatched flexibility, efficiency, and scalability.
In this exclusive conversation, Davide Santo shares insights into how xMemory—powered by Phase Change Memory (PCM)—is redefining embedded memory architecture, streamlining logistics, and enabling scalable intelligence across next-generation automotive platforms.
Can you explain what xMemory is and how it’s set to transform automotive microcontrollers?
Davide Santo: xMemory is a transformative concept built into our Stellar family of automotive microcontrollers. It redefines the way memory is utilized in embedded systems by introducing the idea of extensibility, rather than traditional scalability.
While scalability involves increasing the overall size and cost of a device, extensibility allows us to expand memory capacity during development, production, or even while the product is in use—without changing the silicon die or requalifying the part. This means our customers can deploy a single qualified part and adapt it to evolving software requirements over time—something that’s increasingly critical in the era of software-defined vehicles.
What specific technological innovation enables this level of memory flexibility?
Davide Santo: The foundation of xMemory lies in our Phase Change Memory (PCM) technology, which is a form of embedded non-volatile memory (eNVM). PCM stands out in the industry for having the smallest memory cell footprint, which allows us to pack more functional storage into the same physical space.
Beyond density, PCM offers remarkable endurance and thermal resilience, supporting junction temperatures of up to 165°C—a key requirement in automotive environments. It’s also radiation tolerant and highly power-efficient, and it delivers 25 years of data retention. In short, PCM is not only compact but robust and production-ready for automotive-grade reliability.
Regarding the above question, why is this high memory density so significant in practical terms?
Davide Santo: High density is vital because the true value of a microcontroller in a vehicle is defined by the amount and complexity of the software it can run. With PCM, we can integrate over twice the memory content compared to conventional Flash in the same process node.
This gives our automotive customers the ability to embed more intelligent functions—whether it’s for powertrain control, ADAS, connectivity, or AI—without increasing the size or cost of the silicon. And critically, with xMemory, they can expand this capability as new needs arise, without redesigning the ECU or creating a new part number.
How does this concept of extensible memory benefit the supply chain and production logistics?
Davide Santo: That’s a very important point. The extensibility built into xMemory significantly simplifies logistics and inventory management. Traditionally, different memory sizes mean multiple part numbers, more inventory complexity, and higher supply chain risk.
With xMemory, we provide a single part number that can support multiple memory configurations. This:
• Reduces warehouse SKUs
• Simplifies procurement
• Enables easier project reuse
• And reduces risk during supply shortages, such as those we experienced during the pandemic.
It’s a strategic shift from a fragmented to a unified supply chain model.
Automotive platforms are evolving rapidly. How does xMemory help OEMs adapt to faster development timelines?
Davide Santo: That’s a critical challenge, especially in regions like China, where development timelines are incredibly compressed. For example, new vehicle platforms can go from concept to production in as little as 18 months, sometimes even less.
xMemory helps meet this speed by enabling software-driven feature updates without hardware redesigns. OEMs can reuse existing hardware platforms and incrementally add functionality through software, thanks to the flexible and expandable memory model. This not only keeps pace with rapid market demands but also aligns with the vision of future-proof, upgradable automotive systems.
Can you share some specific use cases where extensible memory provides a distinct advantage?
Davide Santo: Certainly. A good example is in AI-enabled ECUs, where memory requirements evolve as models are retrained or expanded. Another use case is cryptographic applications, where security algorithms may need to be updated post-deployment to stay ahead of threats.
But even beyond that, in markets like China, we often see frequent updates to core vehicle functions—say, adding a Battery Management System (BMS) to an existing ECU managing traction or energy regeneration. xMemory enables this kind of multi-functionality integration within the same hardware unit, without any physical redesign.
Why did ST choose PCM over Flash or other memory technologies for this architecture?
Davide Santo: PCM was a strategic choice. While Flash has been the traditional go-to, it simply doesn’t offer the same combination of density, endurance, and temperature robustness. PCM has matured over the past two decades and now fully meets automotive-grade reliability standards.
It provides a cost-effective and scalable solution for our customers because it supports higher integration levels without increasing the silicon area. That directly translates into lower BOM costs and better performance margins—something OEMs are constantly striving for.
When can we expect xMemory-enabled products to hit the market?
Davide Santo: We’re excited to announce that xMemory will be available on all upcoming Stellar P and G series microcontrollers, with production scheduled to begin in the latter part of this year (2024). These devices will carry forward our vision of enabling flexible, future-proof MCUs that align with the evolving needs of electrification, autonomous driving, and software-defined vehicles.
To conclude, what should automotive engineers and designers take away from this innovation?
Davide Santo: In summary, xMemory introduces three pivotal advantages:
1. Innovation in technology – leveraging PCM to offer high-density memory that fits within the same budget and physical footprint.
2. Operational efficiency – unifying product part numbers to streamline logistics, reduce cost, and improve flexibility across programs.
3. Acceleration of time-to-market – enabling rapid development, seamless software updates, and continuous feature evolution without hardware changes.
With xMemory, we are not just launching a new feature—we’re enabling a new design philosophy for automotive microcontrollers.
