STMicroelectronics STM32L431KBU3

Overview

STM32L431KBU3 from STMicroelectronics is an ultra-low-power Arm® Cortex®-M4 32-bit MCU with FPU, 80 MHz max frequency, 128 KB Flash, 40 KB SRAM, and integrated analog peripherals including 12-bit ADC (5 Msps), dual 12-bit DACs, op-amp with PGA, and two ultra-low-power comparators. It targets battery-powered IoT sensor nodes requiring long runtime, secure firmware execution, and mixed-signal processing in compact WLCSP64 packaging.

For engineers reviewing the STM32L431KBU3 datasheet, STM32L431KBU3 pinout, STM32L431KBU3 application, or STM32L431KBU3 equivalent, key selection criteria include its 28 nA Standby mode (with RTC), 4 µs wakeup from Stop mode, 176.7 ULPBench® score, and support for capacitive touch sensing across 21 channels - critical for wearable and portable edge-node designs.

Technical Context

The STM32L431KBU3 implements an Adaptive Real-time Accelerator (ART Accelerator™) enabling zero-wait-state execution from Flash at 80 MHz, paired with a Memory Protection Unit (MPU) for secure task isolation. Its FlexPowerControl architecture integrates multiple low-power modes - Shutdown (8 nA), Standby (28 nA), Stop 2 (1.0 µA), and Run (84 µA/MHz) - managed via hardware-controlled voltage scaling and dynamic clock gating.

It features dual PLLs (system and audio), a dedicated LPUART for Stop 2 wake-up, SAI for stereo audio streaming, and a 32-bit interconnect matrix enabling concurrent peripheral access without bus contention. The embedded 32-bit RTC includes hardware calendar, alarm, and calibration - all retained in VBAT mode with 200 nA supply current.

Key Specifications

Pinout & Package

STM32L431KBU3 is housed in a 64-ball WLCSP (Wafer-Level Chip-Scale Package) with 0.4 mm ball pitch and 3.19 × 3.19 mm footprint. This package supports automated assembly and provides optimal thermal performance for thermally sensitive portable applications.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar ultra-low-power Cortex-M4 MCU applications.

Compared with STM32L432KBU3, the STM32L431KBU3 provides CAN 2.0B and SAI at the expense of USB - making it superior for industrial fieldbus and audio-enabled edge nodes. Against STM32L412KBU3, it delivers full analog subsystem capability and higher peripheral concurrency, justifying its use in multi-sensor, real-time control systems.

Availability

STM32L431KBU3 is available at Aetrix Electronics and suitable for wearable health monitors, smart utility meters, industrial predictive maintenance sensors, and portable medical diagnostic devices requiring stable component supply across multi-year production cycles.

Supply support for STM32L431KBU3 includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

STMicroelectronics is a global semiconductor leader headquartered in Geneva, Switzerland, designing and manufacturing microcontrollers, power ICs, sensors, and analog components for industrial, automotive, and consumer markets.

The STM32L4 series targets ultra-low-power embedded applications demanding high performance-per-milliwatt, security, and rich analog integration - optimized for battery-operated edge intelligence and energy-harvesting systems.

FAQ

What is the maximum operating temperature range for STM32L431KBU3?

The STM32L431KBU3 is qualified for industrial operation from –40 °C to +85 °C. This rating is confirmed in DS11453 Rev 3 Section 6.3.1 and applies to all WLCSP64 variants. No extended temperature grade (e.g., 105 °C or 125 °C) is offered for this specific part number.

Does STM32L431KBU3 support hardware encryption acceleration?

No, the STM32L431KBU3 does not integrate a dedicated cryptographic accelerator (e.g., AES, PKA, or HASH). It relies on software libraries (STM32CubeL4) for encryption; secure key storage is enabled via proprietary readout protection (RDP) and firewall features, but no hardware crypto engine is present.

Can the internal op-amp be used in standalone mode without ADC/DAC involvement?

Yes, the integrated op-amp (OPAMP1) operates independently of ADC/DAC peripherals. It supports non-inverting, inverting, and follower configurations using external resistors, with rail-to-rail output and programmable gain (1× to 40×) - verified in Section 3.19 of DS11453 Rev 3.

Is the WLCSP64 package of STM32L431KBU3 compatible with standard reflow profiles?

Yes, the WLCSP64 package complies with JEDEC J-STD-020D moisture sensitivity level 3 and supports standard Pb-free reflow profiles (peak 260 °C, 10–30 sec above 217 °C). Thermal characteristics and soldering recommendations are specified in Section 7.5 of DS11453 Rev 3.