Dual-MCU Industrial Power Supply: STM32G4 + U5/H5 for IEC 62443 Compliance

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I am a firmware engineer working on industrial power supply products. Our device needs to comply with IEC 62443 industrial cybersecurity standards (target SL2/SL3).

We plan to adopt a dual-MCU architecture for this project:

• STM32G4: Responsible for real-time power control, protection logic and analog front-end processing. This series fully meets our requirements for power-related functions, but lacks sufficient native security features to satisfy IEC 62443 independently.
• STM32U5 or STM32H5: Dedicated to network communication, secure boot, TLS/IPSec encryption, secure data storage, firmware encryption and remote update, undertaking all cybersecurity functions required by IEC 62443.

Both STM32U5 and STM32H5 are based on Cortex-M33 core. There are clear positioning differences between them. I would appreciate your advice on the following questions:

1. For industrial power supply applications with network access and long-term firmware maintenance, which series is more recommended for IEC 62443 (especially IEC 62443-4-2) compliance, STM32U5 or STM32H5? Could you also recommend specific part numbers?
2. What are the common communication interfaces (SPI / UART / I2C) for inter-MCU communication between STM32G4 and the security MCU? Are there any official reference designs or examples from ST?
3. Regarding IEC 62443 compliant development, what toolchains and security frameworks (such as STM32Trust, TF-M, SBSFU) does ST officially recommend?

Besides, are there any other alternative solutions? For instance, a single MCU that can fulfill both power control and cybersecurity requirements.

Thank you very much for your support.

[Bubbles]

Hi .,

implementing the SBSFU is possible with STM32G4: X-CUBE-SBSFU | Product - STMicroelectronics

with enough care, it's suitable for fair degree of security in applications, where TrustZone isolation is not mandatory (single-tenant applications).

My suggestion would be to try meeting the requirements with G4, and going for U5 or H5 only when there's some limitation found with the STM32G4 SBSFU.

The U5 is an ultra low power platform with strong secure elements, while the H5 is primarily designed with security in mind, tuned to higher performance without much regard for the low power modes. 

This Introduction to security for STM32 MCUs - Application note is intended for basic orientation in STM32 security features.

BR

J