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Ultra-low-power Arm Cortex-M0+ MCU with 64 Kbytes of Flash memory, 56 MHz CPU

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Product overview

Key Benefits

Energy savings

  • Best-in-class static consumption.
  • Many ultra-low-power modes for greater flexibility

High compatibility

  • Benefitting from the STM32 development ecosystem
  • Pin-to-pin compatible with several STM32 products

Cost effectiveness

  • Lower BOM costs thanks to high integration.
  • Attractive price point.


The STM32U031x4/6/8 devices are ultra-low-power microcontrollers based on the high-performance Arm® Cortex®-M0+ 32-bit RISC core operating at a frequency of up to 56 MHz.

The STM32U031x4/6/8 devices embed high-speed memories (up to 64-Kbyte flash memory and 12-Kbyte SRAM with hardware parity check), and an extensive range of enhanced I/Os and peripherals connected to APB and AHB buses, and a 32-bit multi-AHB bus matrix.

They also embed protection mechanisms for embedded flash memory and SRAM, such as readout protection and write protection.

The STM32U031x4/6/8 devices offer a 12-bit ADC, a 12-bit DAC, an embedded rail-to-rail analog comparator, one operational amplifier, a low-power RTC, one general-purpose 32-bit timer, one 16-bit PWM timer dedicated to motor control, three general-purpose 16-bit timers, and two 16-bit low-power timers

The devices also embed up to 21 capacitive sensing channels.

They also feature standard and advanced communication interfaces, namely three I2Cs, two SPIs, four USARTs and two low-power UARTs.

The STM32U031x4/6/8 operate in the -40 to +85 °C (+105 °C junction) and -40 to +125 °C (+130 °C junction) temperature ranges from a 1.71 to 3.6 V VDD power supply using an internal LDO regulator. A comprehensive set of power-saving modes makes possible the design of low-power applications.

Independent power supplies are supported: analog independent supply input for ADC, DAC, OPAMP and comparator, as well as VBAT input allowing the backup of the RTC and backup registers.

The STM32U031x4/6/8 offer eight packages from 20 to 64 pins.

  • All features

    • Includes ST state-of-the-art patented technology.
    • Ultra-low-power features (ultra-low-power devices)
      • 1.71 V to 3.6 V power supply
      • -40 °C to 85/125 °C temperature range
      • VBAT mode: 130 nA (with RTC and 9 x 32-bit backup registers)
      • Shutdown mode (4 wake-up pins): 16 nA
      • Standby mode (4 wake-up pins): 160 nA with RTC, 30 nA without RTC
      • Stop 2 mode: 630 nA with RTC, 515 nA without RTC
      • Run mode (LDO mode): 52 μA/MHz
      • Batch acquisition mode (BAM)
      • 4 μs wake-up from Stop mode
      • Brownout reset (BOR)
    • Core
      • 32-bit Arm® Cortex®-M0+ CPU, frequency up to 56 MHz
    • ART Accelerator
      • 1-Kbyte instruction cache allowing 0-wait-state execution from flash memory
    • Benchmarks
      • 1.13 DMIPS/MHz (Drystone 2.1)
      • 134 CoreMark® (2.4 CoreMark/MHz at 56 MHz)
      • 430 ULPMark™-CP
      • 167 ULPMark™-PP
      • 20.3 ULPMark™-CM
    • Memories
      • Up to 64-Kbyte single bank flash memory, proprietary code readout protection
      • 12-Kbyte SRAM with hardware parity check
    • Rich analog peripherals (independent supply)
      • 1x 12-bit ADC (0.4 µs conversion time), up to 16-bit with hardware oversampling
      • 1x 12-bit DAC output channel, low-power sample and hold
      • 1x general-purpose operational amplifier with built-in PGA (variable gain up to 16)
      • 1x ultra-low-power comparator
    • General-purpose inputs/outputs
      • Up to 53 fast I/Os, most of them 5 V‑tolerant
    • 16 communication interfaces
      • 6x USARTs/LPUARTs (SPI, ISO 7816, LIN, IrDA, modem)
      • 3x I2C interfaces supporting Fast-mode and Fast-mode Plus (up to 1 Mbit/s)
      • 2x SPIs, plus 4x USARTs in SPI mode
      • IRTIM (Infrared interface)
    • Security
      • Customer code protection
      • Robust read out protection (RDP): 3 protection level states and password-based regression (128-bit PSWD)
      • Hardware protection feature (HDP)
      • Secure boot
      • True random number generation, candidate for NIST SP 800-90B certification
      • Candidate for Arm® PSA level 1 and SESIP level 3 certifications
      • 5 passive anti-tamper pins
      • 96-bit unique ID
    • Clock management
      • 4 to 48 MHz crystal oscillator
      • 32 kHz crystal oscillator for RTC (LSE)
      • Internal 16 MHz factory-trimmed RC (±1%)
      • Internal low-power 32 kHz RC (±5%)
      • Internal multispeed 100 kHz to 48 MHz oscillator, auto-trimmed by LSE (better than ±0.25 % accuracy)
      • PLL for system clock, ADC
    • 9 timers, RTC, and 2 watchdogs
      • 1x 16-bit advanced motor-control, 1x 32-bit and 3x 16-bit general purpose, 2x 16-bit basic, 2x low-power 16-bit timers (available in Stop mode), 2x watchdogs, SysTick timer
      • RTC with hardware calendar, alarms and calibration
    • CRC calculation unit
    • Up to 18 capacitive sensing channels
      • Supporting touchkey, linear and rotary touch sensors
    • 7-channel DMA controller
      • Flexible mapping (DMAMUX)
    • Debug
      • Development support: serial wire debug (SWD)
    • All packages are ECOPACK2 compliant.

Circuit Diagram

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STMicroelectronics - STM32U031G8

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Quality and Reliability

Part Number Marketing Status Package SMPS Grade RoHS Compliance Grade Material Declaration**
WLCSP 27 2.55x2.34x0.55 P 0.4 mm - Industrial Ecopack2



WLCSP 27 2.55x2.34x0.55 P 0.4 mm

Material Declaration**:


Marketing Status



WLCSP 27 2.55x2.34x0.55 P 0.4 mm





(**) The Material Declaration forms available on may be generic documents based on the most commonly used package within a package family. For this reason, they may not be 100% accurate for a specific device. Please contact our sales support for information on specific devices.

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