STMicroelectronics L4988D

Overview

L4988D from STMicroelectronics is an AEC-Q100 qualified automotive 5V low-dropout linear voltage regulator with integrated reset and watchdog functions, delivering up to 200mA output current, 500mV max dropout at 200mA, ±2% output voltage tolerance, and operation across 5.6V–31V input range. It supplies microprocessor core logic in engine control units (ECUs) where transient immunity to 40V load-dump events is required.

For engineers reviewing the L4988D datasheet, L4988D pinout, L4988D application, or L4988D equivalent, key selection criteria include its programmable reset delay (via external capacitor on Vcr), adjustable watchdog timeout (via Vcw), enable-controlled watchdog activation, thermal shutdown at 150°C, and SO-8 package compatibility with automotive PCB thermal constraints.

Technical Context

The L4988D implements a p-channel MOSFET pass element enabling regulation down to 500mV dropout at full 200mA load while maintaining stable 5.0V ±2% output across -40°C to +150°C junction temperature. Its internal pre-trimmed reference ensures line/load regulation ≤25mV under specified conditions.

Reset and watchdog circuits operate independently: reset triggers when Vo drops below 8% of nominal (Vo_th), with reaction time as fast as 2µs below 4V; watchdog monitors Wi input frequency and asserts Res low if pulses exceed Twop (25–90ms, set by Ctw), both functions enabled only when WEn is high.

Key Specifications

Pinout & Package

Package: SO-8 (Small Outline, 8-pin, surface-mount, ECOPACK® compliant). Thermal resistance R_th-jamb = 130°C/W with 2 cm² copper area per JEDEC standard.

Key Features

Applications

Equivalent & Alternatives

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

Compared with TL7705ACDR and MAX6803US29D3+, the L4988D uniquely integrates regulation, reset, and watchdog in one SO-8 package - reducing component count, improving timing correlation between supervision signals and supply rail, and eliminating inter-device propagation delays critical for ASIL-B diagnostics.

Availability

L4988D is available at Aetrix Electronics and suitable for engine control units, body control modules, ADAS camera ECUs, and transmission control units requiring stable component supply with automotive-grade reliability and long-term lifecycle support.

Supply support for L4988D 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 L4988D belongs to ST's automotive power management portfolio, engineered specifically for robust, integrated voltage regulation and functional safety supervision in harsh-temperature vehicle subsystems.

FAQ

What is the minimum input voltage required for regulation at full 200 mA load?

The L4988D maintains 5.0V output regulation down to 5.6V input at 200mA load, as confirmed by DS5334 Rev 8 Table 5 (Vdp = 500mV max). Below 5.6V, dropout occurs - output follows input minus Vdp. This enables reliable operation during automotive cold-crank conditions where battery voltage may dip to 6V.

How does the watchdog function interact with the reset output?

Both watchdog timeout and output undervoltage assert the same open-drain Res pin low. The Res output is not multiplexed - it reflects OR logic of either fault condition. When WEn is low, watchdog is disabled and only Vo-related reset remains active. No internal arbitration or priority logic exists between the two triggers.

Can the L4988D be used in non-automotive applications?

Yes - while AEC-Q100 qualified and optimized for automotive thermal/electrical stress, the L4988D functions identically in industrial or medical systems requiring 5V regulation, reset supervision, and watchdog monitoring. Its 150°C junction rating and 40V transient tolerance remain valid outside automotive contexts.

What is the recommended output capacitor value and type for stability?

ST specifies ≥100 nF ceramic capacitor directly between Vo and Gnd for basic loop stability (Figure 24). For high-current transient suppression, add ≥10 µF electrolytic or polymer capacitor in parallel. Total effective capacitance must maintain ESR < 1 Ω across 10 Hz–100 kHz to prevent oscillation per Section 3.1.