STMicroelectronics AEK-MOT-SM81M1

Overview

AEK-MOT-SM81M1 from STMicroelectronics is an AutoDevKit™ evaluation board built around the automotive-grade L99SM81V programmable stepper motor driver IC, supporting micro-stepping (4–64 steps), BEMF-based stall detection, SPI-configurable operation, and integrated 5 V linear regulator output. It targets adaptive front lighting systems and HUD projectors requiring precise bipolar stepper control under 6–28 V supply.

For engineers reviewing the AEK-MOT-SM81M1 datasheet, AEK-MOT-SM81M1 pinout, AEK-MOT-SM81M1 application, or AEK-MOT-SM81M1 equivalent, this board provides validated hardware for evaluating L99SM81V's coil voltage monitoring, RUN/HOLD profile switching, SPI register access, and reverse-battery-protected power delivery in automotive ECU environments.

Technical Context

The board implements the L99SM81V's full functional stack: dual H-bridge outputs with embedded MOSFETs drive bipolar stepper coils; internal timers and mode registers enable configurable step resolution and current profiles; BEMF sensing on phase terminals enables real-time stall flagging without external ADCs. SPI interface (CSN, SCLK, MOSI, MISO) supports read/write access to status, configuration, and diagnostic registers.

Reverse battery protection uses STD95N4F3 N-channel MOSFET in high-side configuration, with jumper-selectable diode substitution (two 1N4007-equivalent diodes). The 5 V regulator (V5V) powers external logic and is accessible via board connector; V3V rail supports MCU I/O level translation.

Key Specifications

Availability

AEK-MOT-SM81M1 is available at Aetrix Electronics and suitable for adaptive front lighting systems, head-up display (HUD) projectors, and automotive HVAC damper control requiring stable component supply, automotive qualification traceability, and rapid prototyping support.

Supply support for AEK-MOT-SM81M1 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, specializing in automotive, industrial, and power management solutions with AEC-Q100 qualified components across its portfolio.

The AEK-MOT-SM81M1 belongs to the AutoDevKit™ initiative - a modular, interoperable evaluation platform designed specifically for rapid development of automotive subsystems using ST's automotive-grade ICs and reference firmware.

FAQ

Does AEK-MOT-SM81M1 support closed-loop stall detection without external sensors?

Yes. The board leverages the L99SM81V's integrated BEMF monitoring circuitry to detect coil voltage anomalies during motion, enabling real-time stall flagging via SPI status register (STALL bit) without external current shunts or position encoders. This is validated per DB3986 section 4.3 and confirmed in AutoDevKit firmware examples.

Can the 5 V regulator output power an external SPC5 MCU directly?

Yes. The V5V rail delivers up to 150 mA at 5 V (±2%) and is routed to the 12-pin male connector and JP1 test points. It meets SPC56ELxx and SPC572Lxx MCU core I/O supply requirements when used with appropriate local decoupling (C20, C16 on board).

What SPI interface voltage levels does AEK-MOT-SM81M1 use for MCU communication?

The board uses 3.3 V logic-level SPI (CSN, SCLK, MOSI, MISO) referenced to the V3V rail. Level-shifting is handled internally by the L99SM81V; no external translators are needed when interfacing with 3.3 V automotive MCUs like the SPC5 family.

Is reverse battery protection active by default, and can it be disabled?

Yes. Reverse polarity protection is enabled by default via the STD95N4F3 MOSFET. It can be disabled by removing the MOSFET and installing two diodes (D1/D2 positions) with JP2 jumper set to "DIODE" mode - as documented in DB3986 schematic page 3 and layout notes.