ST has used near-threshold logic to create an MCU series that will run at 117Coremark/mW and has a <2µA stop mode.

STM32U3 block
“The STM32U3 series offers greater power efficiency in run mode compared to previous product generations. It is the first STM32 near-threshold design, which drastically reduces dynamic consumption,” said the company, which is aiming them at IoT devices which operate for extended periods without maintenance and with energy from coin cell, ambient solar or a thermoelectric source.

Based around a 96MHz Arm Cortex-M33 core there is 256kbyte of ram and 1Mbyte of dual bank flash, or 512kbyte of flash.

Operation is over -40 to +105°C (or 85°C), and 1.71 to 3.6V.

For security, hardware is included to confine secret keys in secure memory “to eliminate vulnerable CPU fetching processes”, said ST. It has Arm’s TrustZone code isolation, a random generator, and its cryptographic accelerators are SESIP3 and PSA Level3 certifiable “offering customers reassurance that they can comply with upcoming EU RED and CRA regulations”, continued the company, adding: “Newly, secret keys are loaded in-factory by ST on the MCUs and are protected by a coupling and chaining bridge, representing the first use of this technology in the STM32 MCU family.”

ST also announced a 2.4GHz wireless MCU with similar security, but without near-threshold power saving

STM32U385xx parts will have all of the above, and STM32U375xx parts are available for those not wanting the hardware cryptographic accelerator.

Typical applications include utility meters, healthcare devices and industrial sensors