ST claims peak energy efficiency for Cortex-M4 MCUs

February 12, 2016 // By Graham Prophet
STMicroelectronics says it achieves highest-yet microcontroller power savings and performance with its latest STM32L4 series devices. The microcontrollers also introduce peripheral and package configurations that simplify design and increase flexibility.

Measured using the EEMBC ULPBench tests for low-power microcontrollers, STM32L4 devices achieve 176.70 ULPMark-CP, without the help of a buck converter that adds external components such as a coil and capacitor. The EEMBC CoreMark score of 273.55 at 80 MHz shows that the STM32L4 series delivers a combination of high peak performance and energy efficiency.

The performance and efficiency advantages come from smart architectural features such as independently adjustable peripheral supply voltages and a programmable multi-speed internal clock, as well as Batch Acquisition Mode (BAM) and ST’s Adaptive Real-Time Accelerator (ART Accelerator). Multiple power-management modes, including ultra-low-power 8 nA shutdown, help maximise energy savings.

Designers can now access these advantages in six added STM32L4 lines that offer economy, a range of application-targeted features, and extra package choices. The STM32L471 combines up to 1 MB Flash with rich analogue and audio features for projects that require no LCD controller or USB connectivity. The STM32L475 has a USB OTG Full Speed controller, and both devices have multiple timers, clock sources, and communication interfaces including CAN, SDMMC, USART, SPI, and I²C. The analogue peripherals include 12-bit ADCs with 5 MSPS capability and power-saving modes, as well as two 12-bit DACs, two op-amps with built-in Programmable-Gain Amplifier (PGA), and two ultra-low-power comparators.

The STM32L432 and STM32L433 bring 100DMIPS ARM Cortex-M4 core performance to lightweight applications that require up to 256 kB Flash. Analogue and audio features combine with a crystal-less USB controller in the STM32L432. The STM32L433 additionally features an LCD controller. Both lines support extra package options, from 7 x 7 mm UFBGA100 to 3.14 x 3.13 mm WLCSP49, including the small-footprint UFQPN32 for customers without WLCSP-assembly capability.

STM32L442 and STM32L443 lines offer designers the same feature sets and flexibility as the STM32L432/433, with the addition of a cryptographic accelerator in each device.