STMicroelectronics L4979DTR-E

Overview

L4979DTR-E from STMicroelectronics is an AEC-Q100 qualified automotive low-dropout linear voltage regulator with integrated reset and watchdog functions, delivering 5.0 V ±2% output at up to 150 mA, featuring 0.4 V typical dropout at 150 mA, 6 µA quiescent current in disable mode, and operation across 5.6 V–31 V input range for engine control unit (ECU) power rail conditioning.

For engineers reviewing the L4979DTR-E datasheet, L4979DTR-E pinout, L4979DTR-E application, or L4979DTR-E equivalent, key selection criteria include its programmable reset delay (via external capacitor on Vcr), watchdog timeout adjustability (via Vcw), thermal shutdown at 150 °C, automotive-grade -40 °C to 150 °C junction temperature range, and SO-8 package compatibility with high-reliability vehicle subsystems.

Technical Context

The L4979DTR-E integrates a p-channel MOSFET pass element enabling low dropout (≤400 mV at 150 mA) while maintaining regulation under transient input voltages up to 40 V. Its internal bandgap reference and on-chip trimming ensure ±2% output accuracy over line, load, and temperature (-40 °C to 150 °C).

Reset functionality monitors Vo with threshold set at 6–10% below nominal output; delay time (trd) is programmable via external capacitor on Vcr (e.g., 150 ms with 1 nF). Watchdog operation relies on Wi pulse detection and Vcw-based timing, where capacitor discharge/charge between Vwlth (0.5–0.8 V) and Vwhth (2.2–2.5 V) defines timeout period (25–90 ms with 47 nF).

Key Specifications

Pinout & Package

Package: SO-8 (ECOPACK®, RoHS-compliant, 1.27 mm pitch, 5.0 × 4.0 × 1.75 mm body height).

Key Features

Applications

Equivalent & Alternatives

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

Compared with TLV70750PDRVR and MAX6720TTUT+T, the L4979DTR-E uniquely combines AEC-Q100 qualification, programmable reset delay, and independent watchdog in a single SO-8 package-reducing BOM count and PCB footprint while meeting ASIL-B diagnostic requirements without external components.

Availability

L4979DTR-E is available at Aetrix Electronics and suitable for engine control units, ADAS sensor modules, body control modules, and electric power steering systems requiring stable component supply with automotive-grade reliability and long-term lifecycle support.

Supply support for L4979DTR-E 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 L4979DTR-E belongs to ST's automotive power management portfolio, engineered specifically for functional safety-critical vehicle subsystems requiring integrated voltage regulation, reset supervision, and watchdog monitoring in a single monolithic device.

FAQ

What is the maximum allowable input voltage for continuous operation?

The L4979DTR-E operates continuously within 5.6 V to 31 V DC input range. Its absolute maximum rating is 40 V, but sustained operation above 31 V may trigger thermal shutdown or reduce lifetime reliability due to increased power dissipation in the p-channel pass transistor.

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

The RES pin remains asserted low even when Vo falls below 1 V, as specified in the datasheet. The reset circuit guarantees valid low-state operation down to Vo = 1 V, and the reaction time accelerates to 2 µs below 4 V to ensure rapid fault signaling during deep brown-out events.

Can the watchdog function operate independently of the voltage regulator?

No-the watchdog circuit is powered internally from the VO rail and disabled when EN is low. It requires the regulator to be enabled and Vo ≥ 4.9 V to function; there is no separate watchdog supply pin or independent enable control.

Is the SO-8 package thermally enhanced compared to standard variants?

Yes-the SO-8 package uses exposed thermal pad pins (5 and 6) connected to internal GND and designed for soldering to large PCB copper areas. With 2 cm² heatsink, R_{th j-amb} drops to 130 °C/W, enabling 150 mA output at T_j ≤ 150 °C in free-air conditions per Figure 6.