Introduction

The STM32WL5x/Ex microcontrollers are long-range wireless and ultra-low-power devices and embed a powerful and ultra-low-

power LPWAN-compliant radio solution. These devices are designed to be extremely low-power and are based on the high-

performance Arm

Cortex

‑M4 32-bit RISC core that operates at a frequency of up to 48 MHz. It is complemented by an Arm

Cortex

‑M0+.

The STM32WL5x/Ex devices feature a flexible management of the power modes, allowing the overall application consumption

to be reduced.

A large number of smart and high-performance peripherals, a large set of advanced and low-power analog features, and several

peripherals tuned for low-power modes are embedded. By using the batch acquisition mode (BAM), these peripherals optimize

the power consumption when data is transferred using the communication peripherals, while the rest of the device is kept in low-

power mode.

The STM32WL5x/Ex devices enable an easy migration from a dual-chip solution (such as STM32L4 Series MCU

+ LoRa

/ sub‑GHz module), to a single chip, with a better power budget.

An embedded SMPS improves the power consumption in the applications, as well as the overall consumption for the

sub‑GHz radio communications.

Thanks to the built-in internal voltage regulator and voltage scaling, the device consumption in active modes is kept at a

minimum, whatever the external supply voltage. This makes the STM32WL5x/Ex devices particularly suited for hand-held

battery‑powered products, down to 1.8 V. In addition, multi-voltage domains supply the devices at low voltage (further reducing

consumption), while the analog-to-digital converters operate with a higher supply and reference voltage, up to 3.6 V.

The STM32WL5x/Ex devices support a battery Backup domain to keep the RTC running, and a set of 20 registers (32-bit wide),

that can be retained in case of power loss. This optional backup battery can be charged when the main supply is present.

The various supported low-power modes allow the user to achieve the best compromise between low-power consumption,

shorter start-up time, available set of peripherals and maximum number of wakeup sources.

Ultra-low-power features of STM32WL5x/Ex microcontrollers

AN5568

Application note

AN5568 - Rev 3 - January 2025

For further information, contact your local STMicroelectronics sales office.

www.st.com

1 Energy-efficient processing

The high-processing performance in Run mode (in DMIPS/MHz) is achieved thanks to the Arm

Cortex

‑M4 core

and its associated memory interfaces used in the STM32WL5x/Ex devices.

Note: Arm is a registered trademark of Arm Limited (or its subsidiaries) in the US and/or elsewhere.

The embedded ART Accelerator ensures full operating performance up to 48 MHz, by masking the Flash memory

access wait‑state. 1.25 DMIPS/MHz can be achieved, whatever the system clock frequency.

The "undervolting" method (adapt dynamically the internal supply voltage to the operating frequency) is used to

reach a high-energy efficiency (in mA/DMIPS). STM32WL5x/Ex devices offer the following dynamically selectable

voltage and frequency ranges:

• Range 1 for a system frequency up to 48 MHz

• Range 2 for a system frequency up to 16 MHz, with improved efficiency by 20% at 16 MHz versus Range 1

Thanks to the dedicated LPRun (low-power run) mode, the core can operate at 2 MHz and lower, with improved

efficiency by 60% at 2 MHz versus Range 2, mainly due to the sub-GHz radio going into Deep-Sleep in LPRun

mode.

Section 1 shows the typical current consumption of the STM32WL5x/Ex devices, from LDO and SMPS, versus

system frequency and power modes (reminder: CPU1 = Cortex-M4 and CPU2 = Cortex-M0+, only available on

the STM32WL5x devices).

AN5568

Energy-efficient processing

AN5568 - Rev 3

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