STMicroelectronics L4989MD

Overview

L4989MD from STMicroelectronics is an AEC-Q100 qualified automotive 5 V low-dropout linear voltage regulator with integrated reset and watchdog functions, delivering up to 150 mA output current, 180 mV typical dropout at 150 mA, ±3% output voltage accuracy, and operation across 5.6 V–31 V input range - used to power microcontroller subsystems in engine control units.

For engineers reviewing the L4989MD datasheet, L4989MD pinout, L4989MD application, or L4989MD equivalent, this device is selected for automotive MCU supply supervision where low quiescent current (69 µA typ. with watchdog disabled), programmable reset delay, and watchdog timeout via external capacitor are critical design requirements.

Technical Context

The L4989MD implements a p-channel MOSFET pass element enabling regulation independent of input transients up to 40 V, with precision achieved via pre-trimmed internal reference. Its reset circuit monitors Vo down to 1 V and triggers within 100–700 µs when Vo falls below 6–10% below nominal.

The watchdog function operates only when WEn is high, using Wi as pulse input and Vcw as timing capacitor node; its sawtooth oscillator generates a 20–80 ms period (with 47 nF) and asserts Reset if Wi pulses cease, ensuring fail-safe MCU supervision in safety-critical vehicle systems.

Key Specifications

Pinout & Package

Package: SO-20 narrow-body surface-mount package with 4 dedicated ground pins (pins 4, 15, 16, and GND pad) for thermal dissipation and noise immunity in automotive PCB layouts.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar automotive voltage regulator with supervision applications.

Compared with TL49412GSXUMA1 and MAX6723SKA+T, the L4989MD uniquely combines AEC-Q100 Grade 0 rating, programmable reset/watchdog timing via capacitors, and ultra-low quiescent current - making it optimal for cost-sensitive, thermally demanding, and safety-aware MCU power domains.

Availability

L4989MD is available at Aetrix Electronics and suitable for engine control units, body control modules, transmission control units, and ADAS camera ECUs requiring stable component supply across automotive production lifecycles.

Supply support for L4989MD 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 silicon solutions for automotive, industrial, and consumer markets since 1987.

The L4989MD belongs to ST's automotive analog power management portfolio, engineered specifically for robust, integrated power-supervision in engine, transmission, and chassis control systems where reliability under extreme thermal and electrical stress is mandatory.

FAQ

What is the minimum input voltage required for regulation at full 150 mA load?

The L4989MD maintains regulation down to 5.6 V input at 150 mA output, enabled by its 180 mV typical dropout voltage. At lower loads, regulation extends further - e.g., at 10 mA, dropout drops to ~100 mV, allowing stable operation even below 5.2 V input. This meets ISO 16750-2 cold-crank requirements for 12 V systems.

How does the reset output behave when the output voltage falls below 1 V?

When Vo drops below 1 V, the L4989MD guarantees sub-2 µs reset reaction time - significantly faster than the standard 100–700 µs window - ensuring immediate MCU reset during catastrophic supply collapse. The Res pin remains low until Vo recovers above the threshold and the programmed delay (set by Vcr capacitor) expires.

Can the watchdog be disabled independently of the voltage regulator?

Yes. Driving WEn low disables only the watchdog function while preserving full voltage regulation and reset supervision. The regulator remains active regardless of WEn state, and the Res pin continues to monitor Vo for brown-out events. This allows selective watchdog deactivation during debug or low-power sleep modes without compromising power integrity.

Is the SO-20 package thermally enhanced compared to SO-8?

Yes. The SO-20 package features four dedicated ground pins (4, 15, 16, and internal thermal pad) and achieves 50°C/W junction-to-ambient thermal resistance with a 6 cm² PCB copper pour - versus 130–180°C/W for SO-8. This enables continuous 150 mA operation at +125°C ambient, critical for under-hood placement without forced cooling.