STM32 L4 microcontroller MCU

In a world that is competing for better performance at lower and lower power consumption, the new STM32L4 is the latest microcontroller released by STMicroelectronics. What is special about this small integrated circuit (IC) is the fact that it is optimised for ultra-low-power consumption, to a level unprecedented till today. This article discusses how this fits into electronics today.


Making wearables smarter…

Wearable devices, particularly fitness bands, are one among the kind of devices that the STM32L4 focuses on. The following features make the IC suitable to be the processor for IoT products in the wearable market such as fitness bands, smart watches, and smart glasses.

  • Low battery usage: The device uses ultra-low power (ULP) for operation; this is one of the most advantageous features for battery powered wearable devices, as they cannot be charged quite often.

At an active power consumption as low as 100µA/MHz, this IC can achieve a performance of up to 100DMIPS (Dhrystone Million Instructions per Second – a measure of computer performance).

The FlexPowerControl platform of STM32L4 offers dynamic voltage scaling to balance power consumption with processing demands. It can also run on seven modes (including Run, Standby, Stop, Sleep and Shutdown) with sub-modes. The current consumption during inactive age can go as low as 30nm.

  • Fast wake-up: Smart architecture and smart peripherals (communication peripherals, timers, other analogue circuits etc) can detect even the slightest movements and any of these peripherals can wake up the microcontroller unit (MCU) from its inactive mode, in a very short time. STM32L4 can go from 0 to 48MHz frequency in less than 5µs.

This means, the wearable device will immediately be active on even the slightest body movement, thereby giving better precision.

  • Integration: This small IC supports interfacing with different kinds of sensors (accelerometer, gyroscope etc), thin-film-transistor (TFT) display, Bluetooth, subscriber identity module (SIM) card, universal serial bus on-the-go (USB OTG), audio accessories and more. These are the major modules found in wearable devices.


Smart Metering

Smart meters are slowly replacing the traditional meters to accurately measure, log and bill electricity, cooking gas and water usage. Discussed below are the major factors to be considered while selecting a processor for smart meters and how STM32L4 fits into this.

  • Connectivity: The smart meters should be connected to the grid so that the product consumption details are continuously communicated to the server and details updated or actions performed in real time. STM32L4 supports two-way wireless communication protocols including low power radio frequency (RF) mesh solutions, and cellular wireless wide area network (WAN) technologies such as General Packet Radio Service (GPRS) and satellite navigation systems.
  • Safety and security: It is important to ensure that the application and data inside the smart meters are safe and that the meter does not malfunction or get lost due to crystal jerks and other issues. Features such as brown-out in all modes, Flash with error correction code (ECC), clock security system, static random access memory (SRAM) parity check, supply monitoring, backup byte register and dual watchdog keep the data safe. Moreover, it has a 128/256 bit Advanced Encryption Standard (AES) specification hardware accelerator for encrypting the data, thereby securing information.
  • Others: Some of the features that make STM32L4 suitable for smart metering solution are the ability to integrate with liquid crystal display (LCD), VBAT mode with real-time clock (RTC) for battery backup, digital filter for sigma delta modulators, external memory interface, and up to 114 fast input/output (I/O) interfaces for buttons and relays.


The industrial side of things

With a lot of focus shifting to Industry 4.0 (industrial IoT), a wide variety of sensors are being used for industrial applications including automation and energy management. The following features of STM32L4 make it suitable as the processor for such sensors.

  • Ruggedness: Industrial sensors must be able to withstand sudden variations and drastic changes. Not just withstand, but these should functioning correctly even when put to test In the most extreme cases. The STM32L4 is designed to function over a range of temperatures, right from -40 degrees up to 125 degree celsius.
  • Compatibility: Once a solution is arrived at, to modify a device entirely owing to a simple component change is a huge hassle to industrial production. So much so that, it might be easier to release a whole new product than to upgrade the product. With pin-to-pin compatibility with different STM32 series, the STM32L4 eases migration within the STM32 ecosystem.
  • Control: STM32L4 has a motor control system that has 2×16-bit advanced timers and 3×12-bit analogue-to-digital converters with five megasamples per second (MSPS) and up to 16-bit hardware oversampling. This ensures a seamless process with the motor efficiently controlling the machine’s operation.


Equipped for medical application

Advances in technology have led to miracles being created in the field of medical electronics and the result is seen in a number of medical electronic devices performing complex analysis with ease. Here is why the STM32L4 processor could help equipment get more equipped.

  • Interface: A feature that is trivial, yet important is the single wire protocol master interface (SWPMI) that aids equipment collecting information, while at the same time control it according to need.
  • Data acquisition: It is necessary that equipment for monitoring can collect data repeatedly and accurately each time, while also continuously over a period of time. STM32L4 can function in batch acquisition mode (BAM), efficiently exchanging data with its peripherals. What makes this stand out is the efficiency with which this mode performs data acquisition even in the low power mode.
  • Computation: The ST ART accelerator unleashes ARM Cortex-M4 to show a linear performance over all temperatures and frequencies. With features like hardware oversampling for enhanced resolution, low voltage (1.71V to 3.6V) operation, advanced digital signal processing (DSP) instructions and a floating point unit (FPU) to perform arithmetic of floating point integers, computation sounds promising.


Automate your home

The field that is working towards enhancing the quality of life most prominently is home automation. With comfort and luxury being targeted, cutting-edge technology that is customer-friendly and efficient at the same time is the focus. STM32L4 aims at fitting into this bracket.

  • Connection: A device for home automation has to communicate with devices all around at the same time. STM32L4 is built to support smart peripherals that will also consume low power, even with multiple devices connected at the same time.
  • Think and act: Advanced and low power analogue packages as small as 3.7mm x 4.2mm is one way of referring to this IC. With up to 1MB of dual—bank flash memory and 128KB of SRAM, this fits in very well with efforts to make home automation devices compact and fast.
  • Communication: The entire home automation system is built around a network that aids communication between devices. STM32L4 supports 1xCAN (controlled area network), inter-integrated circuit (I2C) and serial peripheral interface (SPI) that promise a robust communication network. With advanced support to universal serial bus (USB), this IC suits the purpose it was designed for.


A product that balances aggressive low power consumption and performance at the same time, this IC looks to be the new efficient solution for developers. Let us wait and watch how the STM32L4 stands the test of time.


Please enter your comment!
Please enter your name here