Ultra Low Power Microcontrollers: STM32L5 Series

STM32L5 security ultra low power

The ST Microelectronics introduced new ultra-low-power microcontroller series in February, 2020. The STM32L5 series of microcontrollers that hold one of the first the PSA Certified Level 2 accreditation from Arm®, and now it is available for mass production.

Platform Security Architecture (PSA) is a framework designed to increase the security of Internet of Things (IoT) systems. However, It revolves around the analysis of threats and potential breaches, precise architectural specifications, the implementation of various APIs and features, as well as a certification process that guarantees the compliance of components, operating systems, or boards.

The STM32L5 series of microcontrollers are shows its excellence in main challenges for embedded design. These main challenges are:

  • Security
    -Increase the robustness against attacks
  • Low Power Consumption
    -Long life time, small battery size
  • Integration, Performance, Ecosystem
    -Best fit versus the application requirement

STM32L5 Development Boards

Now, STM32L5x2 microcontrollers are available for Internet of Things (IoT) and embedded systems developers. The STM32L552E-EV evaluation board, the STM32L562E-DK Discovery kit, and the NUCLEO-L552ZE-Q development boards may be used for different level of application developments.

You can visit STM32L5x2 development board official pages for detailed information:

STM32L5 Security

STM32L5 series of microcontrollers provide high granularity of isolation in Internet of Things (IoT) and embedded devices with TrustZone feature.  On STM32L5, each General Purpose Input Output (GPIO) or peripheral, Direct Memory Address (DMA) channel clock configuration register Adaptive Real-Time (ART) accelerator  or small part of Flash or Static Random Access Memory (SRAM) can be configured by developer as Trusted or un-Trusted.

For instance, If we have an example of Internet of Things application implementation which have Radio Frequency (RF) Module and sensors like humidity and temperature sensors. The RF module can be assigned as un-trusted application and sensors can be assigned to trusted application. STM32L5 will have full isolation between two application with TrustZone.

The microcontroller series (STM32L5) security features in fields of encryption, decryption, authentication, memory and IP protection:

Encryption, decryption and authentication:

• AES-128/256 Encryption • SHA-256 Authentication
• Public Key Acceleration (PKA): for RSA, Diffie-Hellmann or ECC (Elliptic Curve Cryptography)
• Certified Crypto library
• True Random Number Generator
• Unique ID
• OTP Zone

Memory and IP protection:

• Active and static Anti-tamper detection
• Memory Protection Unit (MPU)
• Secure Boot • Read and Write Protection
• HDP (Hide Protect)
• Unique Boot Entry
• OTFDEC (On-the-fly decryption) on Octo SPI to protect external memory
• JTAG fuse
• TrustZone
• SFI (Secure Firmware Installation)

STM32L5 Power Efficiency

STM32L5 series of microcontrollers reuse the STM32L4 series of microcontrollers technology which achieved best-in-class power consumption features. The new series microcontrollers integrate an optional Switched-Mode Power Supply (SMPS) as known as DC/DC buck voltage regulator which can be enabled or disabled on the fly to avoid external noice for external RF or data acquisition on Internet of things applications.

Most importantly, the STM32L5 power consumption behaviours proved by the Embedded Microprocessor Benchmark Consortium (EEMBC). Therefore, the benchmark test results are scored as 370 ULPMark-CP (Core Profile) and 54 UMPMark-PP (Peripheral Profile).

STM32L5 Performance

Low-power consumption flagship microcontroller series STM32L5 provides %20 better responsiveness if we compare with Arm® Cortex®-M4 on the internet of things application with Arm® Cortex®-M33. The new designed ST ART Accelerator™ working both internal and external Flash memory with 8Kbytes of instruction cache.

These new microcontrollers comes with up to 512-Kbyte Flash memory, 256-Kbyte RAM, USB Type-C™ with power delivery controller and Controller Area Networking with Flexible Data-rate (CAN FD).

Also, The STM32L5 produced with 7 different packages types like LQFP48, QFN48, LQFP64, WLCSP81, LQFP100, UFBGA132 and LQFP144. The microcontrollers have HW crypto feature options.