STMicroelectronics L99SM81VQ6TR

Overview

L99SM81VQ6TR from STMicroelectronics is an AEC-Q100 qualified bipolar 2-phase stepper motor driver IC for automotive applications, supporting micro-stepping up to 1/16 resolution, 1.35 A output current, integrated 5 V LDO regulator, stall detection via ADC-based coil voltage measurement, and ST SPI 4.1 interface. It is deployed in adaptive front-lighting systems (AFS) and head-up display (HUD) projectors.

For engineers reviewing the L99SM81VQ6TR datasheet, L99SM81VQ6TR pinout, L99SM81VQ6TR application, or L99SM81VQ6TR equivalent, key selection criteria include programmable decay modes, dual full-scale current settings (RUN/HOLD), 10-bit-equivalent current regulation precision, thermal warning/shutdown behavior, and SPI register-mapped diagnostics for functional safety compliance.

Technical Context

The L99SM81VQ6TR implements a fully integrated PWM-controlled current regulation loop with two independent 4-bit full-scale amplitude registers (RUN/HOLD) and a 6-bit DAC for reference current generation-achieving effective 10-bit resolution. Its stall detection relies on synchronized ADC sampling of motor coil voltages at four electrical angles (0°, 90°, 180°, 270°), processed against programmable upper/lower limits.

It features four selectable MOSFET switching speed options for EMC/power trade-off optimization, wobbled PWM frequency to reduce conducted EMI, and ST SPI 4.1 protocol with built-in clock polarity/phase validation, CSN timeout, and data-stuck detection-enabling robust diagnostics in ASIL-B–capable architectures.

Key Specifications

Pinout & Package

Package: PowerSSO-36 (exposed pad, thermally enhanced, RoHS-compliant). Pin count: 36 terminals. Mounting: surface-mount, lead-free reflow compatible.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar stepper motor driver applications.

Compared with TMC2130-LA and DRV8889-Q1, the L99SM81VQ6TR uniquely integrates stall detection ADC, 5 V LDO, and ST SPI 4.1 with hardware-level protocol validation-making it the only option qualified for ASIL-B–aligned optical actuation where sensor integration, EMI resilience, and diagnostic completeness are mandatory.

Availability

L99SM81VQ6TR is available at Aetrix Electronics and suitable for adaptive front-lighting systems, head-up display projectors, and electronic parking brake actuators requiring stable component supply, AEC-Q100 compliance, and long-term automotive lifecycle support.

Supply support for L99SM81VQ6TR 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 automotive-grade analog devices for industrial, automotive, and consumer markets.

The L99SM81V belongs to ST's automotive smart power driver product line, engineered specifically for precision electromechanical actuation in safety-critical optical and braking systems-emphasizing integrated diagnostics, EMC robustness, and functional safety readiness.

FAQ

What is the maximum motor supply voltage supported by the L99SM81VQ6TR?

The L99SM81VQ6TR supports VS supply from 5.5 V to 28 V DC, compliant with automotive 12 V and 24 V battery systems including cold-crank (down to 4.5 V) and load-dump (up to 40 V) transients when used with appropriate external protection. Absolute maximum rating is 41 V, but operation above 28 V requires derating per thermal data in Section 4.4 of the datasheet.

Does the L99SM81VQ6TR require external current sense resistors?

No. The L99SM81VQ6TR implements fully integrated current sensing using on-die MOSFET R_DS(on) monitoring, eliminating external sense resistors and associated PCB area, power loss, and layout sensitivity. Current regulation precision remains stable across temperature due to matched internal sensing paths.

How does stall detection work without external components?

Stall detection uses the integrated 10-bit ADC to sample motor coil voltages at four precisely timed electrical angles (0°, 90°, 180°, 270°) during each micro-step. Measured values are compared against programmable upper/lower limits stored in MCVUL, MCVLLA, and MCVLLB registers. A match triggers the STALL bit in MSR (0x02), readable via SPI without firmware intervention.

Can the L99SM81VQ6TR operate in standalone mode without SPI communication?

Yes. STEP, DIR, and SMODE pins allow direct hardware control of stepping, direction, and micro-step mode (full/half/mini/1/8/1/16) without SPI. HOLD mode, current amplitude, and decay mode must be pre-configured via SPI during initialization-but once set, the device runs autonomously with only GPIO-level inputs.