ST Announces “First LoRa SoC,” Including Advanced Semtech Radio

January 08, 2020 by Gary Elinoff

The new SoC expedites the design of smart devices with LoRa and other types of LPWAN IoT connectivity.

ST Microelectronics describes its new STM32L3—the STM32WLE5—as the world’s first LoRa SoC. The device is capable of (G)FSK, (G)MSK, and BPSK modulation, as well as other protocols, including some that are proprietary.



The STM32WL. Image from ST Microelectronics 

ST explains that the device operates with low power requirements and also incorporates extensive security capabilities.


Fundamental Architecture

The (PDF) STM32WLE5 consists of a sub-GHz radio subsystem that interfaces with a microcontroller subsystem based on an Arm Cortex-M4.


block diagram of STM32WLE5

Block diagram for the STM32WLEJ9/JB/JC. Image used courtesy of (PDF) ST Microelectronics

Communication between the radio and the CPU is handled over an SPI interface.


Computational Power

The computational portion of the microcontroller, running at 48MHz, is based on ST’s STM32L4 ultra-low-power architecture, which itself features the Arm Cortex-M4 core.

The Arm Cortex-M4 was designed with low-power embedded systems in mind, including low power requirements and low pin count. Because of its deployment within the STM32WLE, the device is compatible with the ever-expanding ecosystem of Arm tools and software.


Wireless Connectivity

The integrated radio portion of the STM32WLE5 is based on Semtech’s SX126x IP. It covers a frequency range from 150MHz to 960MHz, assuring compatibility with the various LoRa networks in international jurisdictions. These include: ETSI EN 300 220; FCC CFR 47 Part 15; Japan’s ARIB T-108; and China’s regulatory requirements.


sub-GHz radio system block diagram

STM32WLE’s sub-GHz radio system block diagram. Image used courtesy of (PDF) ST Microelectronics 

There are high power and low power transmitters with up to 22 dBm and 15 dBm maximum transmit power, respectively. Receiver sensitivity is as low as -148 dBm.


Boot Modes

The device can boot from the flash memory or the SRAM. There is also an option to boot from the boot system memory.


System Peripherals

The STM32WLE5 line features 43 GPIOs. The unit includes a 12-bit ADC (that can operate at 2.5 Msps) and a 12-bit DAC. There is also an integrated SMPS for power consumption optimization with multiple low-power modes for maximum battery life.



Security features include:

  • 128- / 256-bit AES hardware encryption
  • Sector protection for read and write operations include PCROP, RDP, and WRP 
  • Public-key cryptography with an elliptic curve encryption engine
  • A true random number generator
  • Support for RSA and other cryptographic algorithms
  • A 64-bit unique devices identifier that complies with IEEE 802-2001


Memory Options

There are currently three announced versions of the STM32WLE5—each with its own memory specifications.


Memory of STM32WLE5


The devices also include a 20- by 32-bit backup register.


Power Requirements

The unit will work with a power supply ranging from 1.8V to 3.6V. 

With a 3V power supply, Shutdown Mode and Standby (+ Real Time Clock) Mode draw 31nA and 360nA, respectively.

Active mode for the receiver draws 5.4mA. For LoRa at 125kHz, Active Mode for transmitting draws 15mA at 10 dBm and 84mA at 20 dBm.


Physical Considerations

The STM32WLE is available in 5mm x 5mm UFBGA73 package and operates over a -40°C to +85°C temperature range.