STMicroelectronics’ Ultra-Low Power STM32L5 MCU For IoT Data Security

  • Arm TrustZone technology is the basis of proprietary security features including secure boot, full hardware isolation and encryption algorithm accelerator
  • Has excellent power management performance for energy-sensitive applications

Trusted computing technology was originally developed and designed for devices such as desktops, mobile devices and communications infrastructure, capable of legitimising connected devices and safe implementation for data protection functions and sensitive codes (encryption modules and key storage) to prevent any attempt to damage the device or software.

On this basis, STMicroelectronics has introduced the STM32L5x2 series of ultra-low-power microcontrollers (MCUs) that has an enhanced security feature for IoT applications. The company has introduced the ability to add or delete each I/O pin, peripheral or flash or SRAM storage area at will in the TrustZone isolation and protection area to completely isolate sensitive work tasks to the maximum extent for ensuring equipment safety.

The MCU series has a clock frequency of up to 110MHz and is based on the Arm Cortex-M33 32-bit RISC processor core with built-in Arm TrustZone hardware security technology.


The STM32L5x2 MCU is equipped with a 512 KB dual-zone flash memory, allowing simultaneous read and write operations, convenient device management and supports error correction code (ECC) diagnostics to improve data security. It is also equipped with 256KB SRAM to support high-speed external memory, including single-line, dual-line, four- or eight-wire SPI and Hyperbus flash or SRAM and an interface for SRAM, PSRAM, NOR, NAND, or FRAM.

Consistent power supply

The digital peripherals of STM32L5x2 include a USB Full Speed ​​controller with a dedicated power supply. Even if the system power is 1.8V, customers can still use USB to transfer data. It also includes UCPD control that complies with USB Type-C version 1.2 and USB Power Delivery version 3.0 specifications. Intelligent analogue functions include state-of-the-art analogue-to-digital converters (ADCs), two power-gated digital-to-analogue converters (DACs), two ultra-low-power comparators and two operational amplifiers, which have external or internal voltage follower circuit and programmable gain amplifier (PGA) function.

Improved Debug, Programming Probe for MCUs

Secure assistance

Also, the TrustZone supports secure boot, dedicated read and write protection of internal SRAM and flash memory and encryption algorithm acceleration technologies, including AES 128/256-bit key hardware acceleration and public key acceleration (PKA) and protection of external storage AES-128 Instant Decryption of Code or Data (OTFDEC). STM32L5 also supports active tamper detection and secure firmware installation. Due to security concerns, the STM32L5 has passed PSA Level 2 certification.

Thomas Ensergueix, senior director of the Automotive and IoT business line at Arm, said, “As IoT and embedded devices continue to improve intelligence and functionality, security must be built from scratch. The STM32L5 family makes it easier for developers to develop Arm Cortex-M33-based processors PSA-certified trusted devices provide a reliable and secure platform for the development of consumer, industrial and other devices.”

Low-power consumption

STMicroelectronics has also added its proprietary ultra-low-power technologies, such as adaptive voltage regulation, real-time acceleration, power gating and a variety of low-power operating modes that enable microcontrollers to be powered from either a coin cell battery or energy harvesting for high performance and long battery life.

In addition, when the VDD voltage is high enough, the high-efficiency switching buck regulator can be turned on or off in real-time to improve low-power performance.

ULPMark is a key indicator of energy efficiency of ultra-low-power microcontrollers developed by the Embedded Microprocessor Benchmark Consortium (EEMBC). The device’s final ULPMark test results were very good: 370 ULPMark-CoreProfile and 54 ULPMark-PeripheralProfile (1.8V operating voltage).

Ricardo De Sa Earp, General Manager of STMicroelectronics’ Microcontroller Division, said, “ST is a leader in the MCU market, placing smart cities, smart buildings and smart industries as the company’s strategic priorities. We recognize that a series of Best-in-class ultra-low-power and industry-leading data security MCUs are important for protecting mission-critical applications and edge computing data. Inheriting ST’s expertise in ultra-low-power design and manufacturing processes, it is solid in Arm TrustZone Based on this, join our data security protection technology and rely on the industry-leading STM32 development ecosystem. STM32L5x2 MCUs are industrial IoT applications that require reliability and security, such as metering, health (human or machine) monitoring, and mobile sales terminals.”

Solutions Simplify Cellular-to-Cloud Connectivity For IoT Developers

Software combination

The STM32L5 series belongs to the market-leading STM32 MCU product family that fully supports the development ecosystem of STM32. It has its STM32CubeL5 software package, which includes the hardware abstraction layer and underlying drivers, FreeRTOS, Trusted Firmware-M (TF-M ), Secure Boot and Secure Firmware Update (SBSFU), USB-PD device drivers, MbedTLS and MbedCrypto, FatFS file system and touch-sensing drivers.

Additionally, the STM32CubeL5 has more than 300 project examples that can run on the STM32L552E-EV evaluation board, the STM32L562E-DK discovery kit, and the NUCLEO-L552ZE-Q development board. These projects can be compiled using ArmKeil development tools, IAR or STM32CubeIDE toolkits. Project output includes a STM32CubeMX configuration file, allowing users to easily customize settings and update code.


STM32L5x2 MCUs are now in full production. There are currently two versions of the product on sale: consumer and commercial standard temperature versions (-40 degrees Celsius to +85 degrees Celsius) and extreme environment high-temperature versions (-40 degrees Celsius to + 125 degrees Celsius).



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