STMicroelectronics L9951

Overview

L9951 from STMicroelectronics is an automotive-grade, SPI-controlled rear door actuator driver IC integrating three half-bridge outputs (OUT1–OUT3) and two high-side drivers (OUT4–OUT5) for driving DC motors and resistive loads in vehicle door modules. It delivers 7.4 A (OUT1), 5 A (OUT2/OUT3), and 1.25 A (OUT4/OUT5) with on-resistances of 150 mΩ, 200 mΩ, and 800 mΩ respectively, and supports programmable softstart, current monitoring, and comprehensive diagnostics including open-load, overload, and overtemperature detection - deployed in rear door lock and lighting control systems.

For engineers reviewing the L9951 datasheet, L9951 pinout, L9951 application, or L9951 equivalent, this page provides verified technical context, validated pin functions, real-world automotive use cases, and confirmed alternative parts with documented functional differences - all grounded in ST's official documentation (Doc ID 14173 Rev 9).

Technical Context

The L9951 implements a microcontroller-driven architecture with a standard 16-bit SPI interface (CSN, CLK, DI, DO) enabling full control of output states (forward/reverse/brake/high-Z) and real-time access to diagnostic status registers. All five outputs feature integrated protection: short-circuit, open-load, overload, and thermal shutdown (TjSD ON = 170 °C), with temperature warning (TjTW ON = 150 °C) and hysteresis.

It operates from dual supplies: VS (7–28 V) powers the power stage and CP charge pump (outputting 6–13 V for external reverse-polarity MOSFET gate drive), while VCC (4.5–5.3 V) supplies logic. Standby mode draws <3 µA (typ., Tj ≤ 85 °C), and the CM/PWM pin serves bidirectionally as current monitor (1:10,000 ratio) or PWM input for all outputs.

Key Specifications

Pinout & Package

Package: PowerSO-36 (L9951) and PowerSSO-36 (L9951XP), thermally enhanced exposed-pad surface-mount packages rated for automotive under-hood environments (Tj = –40 to 150 °C).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar rear door actuator driver applications.

Compared with BD37100GUL and TLE9201SG, the L9951 uniquely integrates three half-bridges, two high-side drivers, current monitoring, softstart, and reverse-polarity support in one package - making it the only single-chip solution for full rear door module actuation, lighting, and protection.

Availability

L9951 is available at Aetrix Electronics and suitable for automotive body control modules, rear door electronic latching systems, and vehicle interior lighting subsystems requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for L9951 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 ICs with broad AEC-Q100 qualification coverage.

The L9951 belongs to ST's automotive smart-power driver product line, engineered specifically for intelligent, diagnostic-rich control of electromechanical actuators in vehicle door, seat, and mirror modules.

FAQ

What is the maximum junction temperature and thermal shutdown behavior of the L9951?

The L9951 specifies an operating junction temperature range of –40 °C to 150 °C, with thermal shutdown triggered at 170 °C (TjSD ON) and released at 150 °C (TjSD OFF), providing 20 °C hysteresis. Temperature warning activates at 150 °C (TjTW ON) and deactivates at 130 °C (TjTW OFF), allowing host MCU time to reduce load before shutdown. These thresholds are factory-trimmed and guaranteed across process/voltage corners.

How does the programmable softstart function work, and what parameters can be configured?

The softstart function is configured via SPI register bits to set ramp duration and slew rate for each output independently. It limits inrush current during turn-on by gradually increasing gate drive to power transistors - critical for driving high-inductance door lock solenoids or cold-filament bulbs. Ramp time is adjustable in discrete steps up to several milliseconds, preventing voltage droop and electromagnetic interference during actuation.

Can the L9951 drive both motors and lamps simultaneously, and how are they isolated electrically?

Yes - OUT1–OUT3 (half-bridges) drive bidirectional DC motors, while OUT4–OUT5 (high-side-only) drive grounded resistive lamps. Electrical isolation is maintained by separate output stages: half-bridges include complementary DMOS switches with bulk diodes, whereas high-side drivers omit low-side diodes and rely on external grounding. All outputs share common VS/GND rails but have independent protection and diagnostic circuits.

What is the role of the CP (charge pump) pin, and what external component is required?

The CP pin delivers a regulated 6–13 V output (depending on VS) to drive the gate of an external N-channel power MOSFET used for reverse-polarity battery protection. An external MOSFET (e.g., STP16NF06L) is required between battery input and VS, with its source tied to battery, drain to VS, and gate to CP. This configuration achieves <0.1 V forward drop versus >0.7 V with a series diode, improving efficiency and thermal performance.