STM32L4S9AII6 - 120MHz Cortex-M4 MCU | STMicroelectronics
MPN: STM32L4S9AII6 ✓ ActiveSTM32L4S9AII6 Overview
An ultra-low-power microcontroller is a semiconductor controller designed to execute firmware efficiently while limiting energy consumption during active processing, sleep, and standby operation. The STM32L4 family occupies the middle ground between conventional high-performance microcontrollers and highly constrained low-power devices. Its Cortex-M4 architecture supports real-time control, communications, data acquisition, and human-machine-interface tasks without requiring a separate processor for each function.
The STM32L4S9AII6 provides 136 I/O, USB OTG, DFSD capability, 2 MB of Flash, and 640 KB of SRAM. Its 120 MHz operating frequency supports computationally demanding control loops, while the substantial SRAM reduces the need for external memory in graphics, connectivity, and protocol-intensive designs. The STM32L4S9AI family is specifically identified as part of the STM32L4+ ultra-low-power product family.
The Cortex-M4 core uses a 32-bit RISC architecture and includes floating-point-oriented processing capability within the STM32L4+ platform. Integrated communication and storage features allow the MCU to connect to USB-based systems, transfer data through digital interfaces, and work with file-oriented storage peripherals. These capabilities make the device suitable for consolidating peripheral functions around one low-power controller.
Typical uses include industrial control and automation, connected sensor nodes, medical monitoring equipment, USB data-acquisition systems, secure access terminals, consumer electronics, and compact portable products. The combination of 120 MHz processing, 2 MB of Flash, 640 KB of SRAM, and a 7 x 7 mm UFBGA package supports sophisticated functions in space-constrained boards.
Board design should pay particular attention to the 169-ball BGA escape routing, power integrity, decoupling, and exposed-pad thermal management. Confirm the complete pin assignment, programming interface, decoupling network, clock requirements, and unused-ball treatment against the manufacturer datasheet before layout release. The high pin count also makes assembly inspection and prototype rework more demanding than with a leaded or small-outline package.
This product page combines manufacturer-family information with a practical engineering comparison of related STM32 devices, memory characteristics, package constraints, design considerations, sourcing questions, and the important limits imposed by exact MPN, firmware, and footprint matching. It is designed to help engineers identify when the STM32L4S9AII6 is appropriate and when a different device requires an intentional redesign rather than a simple substitution.
Drop-in alternatives for STM32L4S9AII6 — same package, pin-to-pin compatible. Different-package parts requiring PCB rework are excluded.
Variants in this series
Same-series models that are drop-in compatible with STM32L4S9AII6 (same form factor and footprint) — differing in Architecture, Flash Memory, Maximum CPU Frequency.
No drop-in alternatives available for this product.
Request AlternativesSTM32L4S9AII6 Maximum Ratings & Electrical Characteristics
| Product Type | 32-bit ultra-low-power microcontroller |
| Processor Core | Arm Cortex-M4 |
| Architecture | 32-bit RISC |
| Maximum CPU Frequency | 120 MHz |
| Flash Memory | 2 MB (2M x 8 bits) |
| SRAM | 640 KB |
| General-Purpose I/O | 136 I/O |
| USB Interface | USB OTG |
| Digital Flash Storage Support | DFSD |
| Package | 169-UFBGA, 7 x 7 mm |
| Package Ball Pitch | 0.6 mm |
| Package Height | 0.6 mm maximum package designation |
| Mounting Type | Surface mount |
| Packaging Format | Tray |
| Product Series | STM32L4+ Series |
| Core Variant | STM32L4S9xx |
STM32L4S9AII6 0.6 mm maximum package designation Pin Configuration Guide
Pin configuration for STM32L4S9AII6 (0.6 mm maximum package designation package). This digital IC includes GPIO, communication interfaces (UART, SPI, I2C), and power pins. Refer to the manufacturer datasheet for alternate pin functions and configuration options. Essential for embedded system design and PCB layout.
No detailed pinout data available for STM32L4S9AII6.
Refer to the datasheet for full pin configuration.
Typical Applications
STM32L4S9AII6 is suitable for 6 applications: Industrial Automation Controllers, USB Data-Acquisition Systems, Medical Monitoring Equipment, Connected Sensor and IoT Nodes, Secure Access and Payment Terminals, Portable Consumer Electronics.
Industrial Automation Controllers
The STM32L4S9AII6 fits industrial automation controllers that combine deterministic control with connectivity and local data handling. Its Arm Cortex-M4 processor operates up to 120 MHz, while 2 MB of Flash stores application firmware and 640 KB of SRAM supports control loops, diagnostics, and communication buffers. The 136 I/O available in the device give a design room for sensors, actuators, status indicators, and service interfaces. USB OTG can support configuration transfer and field-service access, while DFSD provides a path to removable or local digital flash storage. Engineers should verify industrial temperature requirements and isolation provisions before deployment.
Recommended
USB Data-Acquisition Systems
The STM32L4S9AII6 is suitable for compact USB data-acquisition systems that must collect and process measurements while remaining connected to a host. The 120 MHz Cortex-M4 core provides processing capacity for signal conditioning logic, filtering, and protocol handling, while 640 KB of SRAM reduces pressure on external memory during burst acquisition. Its integrated USB OTG interface reduces the need for a separate USB controller. The 169-UFBGA package supports dense integration, but designers must plan careful USB routing, decoupling, and differential-pair return paths while confirming that the selected connector and protection strategy satisfy the required USB signaling environment.
Recommended
Medical Monitoring Equipment
The STM32L4S9AII6 can support compact medical monitoring equipment in which sensor processing, user-interface control, and local data management must coexist. Its 120 MHz Cortex-M4 core supports responsive signal processing, 2 MB of Flash accommodates larger firmware modules, and 640 KB of SRAM can hold acquisition buffers and intermediate results. The 136 I/O allows connection to sensor inputs, displays, controls, and communications peripherals. Because this is an ultra-low-power MCU family, it is also relevant to portable monitoring devices. Medical use still requires application-specific validation of electrical isolation, accuracy, reliability, regulatory quality procedures, and the complete operating-temperature range.
Recommended
Connected Sensor and IoT Nodes
The STM32L4S9AII6 suits connected sensor nodes that must interpret local measurements, manage communication tasks, and maintain a compact board footprint. The Cortex-M4 core can execute protocol stacks and application logic at up to 120 MHz, while the 640 KB of SRAM supports networking buffers and sensor data processing. USB OTG offers a service or configuration path, and DFSD can support local data logging where appropriate. The large number of I/O permits integration of multiple sensors and status signals. Low-power behavior still depends on the selected clock configuration, peripheral state, and firmware, so active and sleep-mode consumption must be evaluated under the actual workload.
Recommended
Secure Access and Payment Terminals
The STM32L4S9AII6 is suitable for secure access terminals, payment peripherals, and compact user-interface controllers that need substantial firmware and memory capacity. Its 2 MB of Flash can support encrypted firmware, communication stacks, and application layers, while 640 KB of SRAM assists with protocol buffers and display handling. USB OTG provides a useful service or peripheral connection, and 136 I/O leaves room for keyboards, displays, card interfaces, and status controls. Security-sensitive designs must enable and validate the appropriate cryptographic functions, secure boot, key protection, debug access controls, and peripheral lifecycle requirements specified by STMicroelectronics.
Recommended
Portable Consumer Electronics
The STM32L4S9AII6 fits portable consumer products that combine responsive control, USB connectivity, and a need for more memory than a small entry-level MCU. Its 120 MHz Cortex-M4 core can coordinate displays, buttons, sensors, and communication tasks, while 2 MB of Flash and 640 KB of SRAM support richer applications. The 169-UFBGA package helps limit board area in space-constrained products, although its 0.6 mm ball pitch requires fine-pitch assembly and careful escape routing. Product developers should verify battery-life objectives in the manufacturer’s power modes, check thermal requirements for the intended enclosure, and confirm whether tray packaging aligns with the production assembly process.
Recommended
Recommended Products Summary
Engineering reference data for STM32L4S9AII6 — comparison, design guidance, and compliance information.
Selection Guide
Comparison with Alternatives
| Parameter | This Product | STM32L4R9AI | STM32L4P5AI | STM32L4A6AGI6 |
|---|---|---|---|---|
| Brand | STMicroelectronics | STMicroelectronics | STMicroelectronics | STMicroelectronics |
| Processor Core | Arm Cortex-M4, 32-bit | Arm Cortex-M4 family | Arm Cortex-M4 family | Arm Cortex-M4, 32-bit |
Key Differentiators
- Substantially integrated memory for a low-power Cortex-M4 device (vs STM32L4A6AGI6)
- Higher integration on the exact device (vs STM32L4R9AI)
- Exact 169-UFBGA configuration identified for manufacturing (vs STM32L4P5AI)
Design Notes
Treat the 169-UFBGA footprint as a fine-pitch BGA escape-routing problem. Use the manufacturer’s package drawing and land-pattern data for pad dimensions, solder-mask definition, and ball numbering, then route each required signal from the ball array through the escape area. Check drill and via spacing against the PCB fabricator’s capabilities before committing to the stack-up. The 7 x 7 mm body saves area but does not eliminate routing congestion beneath the device.
Build the power tree from the manufacturer’s recommended decoupling and pin requirements rather than generic capacitor values. Place bulk and high-frequency bypass capacitance close to the relevant power balls, provide a low-impedance ground reference, and isolate sensitive analog or communication supply paths from switching-node currents. The available device information does not state operating or decoupling values, so the exact capacitor network and supply limits must be taken from the official STM32L4S9AI datasheet.
Evaluate PCB heat spreading under the maximum intended ambient temperature and workload. Because the available information does not specify junction-temperature limits, power dissipation, or package thermal resistance, use the manufacturer’s electrical characteristics and application guidance for the final thermal calculation. Preserve exposed-pad connections and copper area where required by the package design, while avoiding thermal coupling to precision analog or temperature-sensitive sections of the board.
Route USB signals as a controlled-impedance pair with a continuous reference plane, minimal stubs, and carefully placed protection devices. DFSD data and clock lines also require short paths and clean return references. Review alternate-function conflicts because 136 I/O does not mean every peripheral can be assigned arbitrarily: several pins may support multiple functions, and board planning must reserve boot, debug, clock, and programming signals before finalizing placement.
Do not assume that a device from the STM32L4 or STM32L4+ range is a drop-in replacement merely because it uses a similar processor core. Exact suffix selection controls package, pinout, temperature range, flash size, SRAM, peripheral availability, and qualification. Verify the full ordering information, ball map, electrical limits, startup behavior, bootloader compatibility, and peripheral assignments before changing an approved STM32L4S9AII6 design.
Compliance Information
The available product information does not state the required compliance status. AEC-Q100 applicability must be confirmed from the exact ordering information and manufacturer qualification documentation.