Ultra-low-power MCUs deliver security for IoT applications

By Alex Pluemer, contributing writer

STMicroelectronics recently introduced the STM32L5 microcontroller (MCU) series featuring the Arm Cortex-M33 core with Arm’s TrustZone hardware-based security. The MCUs provide an ultra-low-power, highly secure solution for connected devices from industrial sensors and controls and home automation devices to smartwatches and fitness trackers. While Arm’s TrustZone security enhances protection for IoT devices, the STM23L5 series also supports secure boot, key storage, hardware cryptographic accelerators, and flexible software isolation.

The new MCU series leverages STMicroelectronics’ know-how in low-power technology by implementing methods like power gating, real-time acceleration, adaptive voltage scaling, and reduced-power operating modes to reduce power consumption to as low as 33 nA in shutdown mode. The devices achieved 402 (non-certified) ULPMark-CP in the Embedded Microcontroller Benchmarking Consortium’s (EEMBC) ULPBench.

The STM23L5 MCUs provide consumer and industrial interfaces such as USB Type-C, USB Power Delivery, and CAN FD as well as a variety of analog and integrated digital peripherals.

Smart analog features include an analog-to-digital converter, two power-gated digital-to-analog converters, two ultra-low-power comparators, and two operational amplifiers with programmable-gain amplifier (PGA) functionality and external or internal follower routing.

Digital peripherals include USB Full Speed with dedicated supply and a UCPD controller compliant with USB Type-C Rev. 1.2 and USB Power Delivery Rev. 3.0 specifications.

Implementing the ST ART accelerator at 110 MHz allows STM32L5 series MCUs to provide up to 165 DMIPS/427 CoreMark. The ST ART accelerator now supports internal flash memory and external memory with an 8-Kbyte instruction cache for greater efficiency in case the software runs out of external memory, said ST.

Other features include 512-Kbyte dual-bank flash memory, which enables read-while-write operations and provides a highly secure environment by implementing error correction code (ECC) with diagnostics; a 256-Kbyte SRAM; and support for high-speed external memory including single, dual, quad, or octal SPI and HyperBus flash or SRAM and an interface for SRAM, PSRAM, NOR, NAND, or FRAM.

The STM32L5 MCUs are available in standard temperature grade for conventional applications or high temperature grade (–40°C to 125°C) for harsher environments. Samples are available. Volume production is scheduled to begin in Q2 2019.