STMicroelectronics L4979D-E

Overview

L4979D-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 6 µA quiescent current in enable-low mode, <400 mV dropout at 150 mA, and operation across 5.6 V–31 V input range for engine control unit (ECU) power management.

For engineers reviewing the L4979D-E datasheet, L4979D-E pinout, L4979D-E application, or L4979D-E equivalent, key selection criteria include its automotive-grade thermal shutdown (150 °C), programmable reset delay via external capacitor, watchdog timer adjustability, and SO-8 package compatibility with space-constrained vehicle electronics designs.

Technical Context

The L4979D-E integrates a p-channel MOSFET pass element enabling low dropout (<400 mV at 150 mA) and high line/load regulation (25 mV each). Its internal bandgap reference is laser-trimmed for ±2% output accuracy over −40 °C to +150 °C junction temperature and full input/output load range.

Reset functionality monitors Vo with threshold set at 6–10% below nominal output; delay is generated by a 512-cycle oscillator whose period depends on external C_tr and internal charge/discharge currents (8–30 µA). Watchdog timing uses a sawtooth waveform on C_tw, triggered by Wi edges and bounded by V_whth/V_wlth thresholds.

Key Specifications

Pinout & Package

Package: SO-8 (ECOPACK®, 5.0 mm × 4.0 mm × 1.65 mm body, 1.27 mm pitch).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar automotive LDO-with-supervision applications.

Compared with TLV70750PDRVR and MAX6326LT31D3+T, the L4979D-E uniquely combines AEC-Q100-compliant 5 V regulation, programmable reset, and watchdog in one SO-8 device - eliminating external components, reducing failure points, and meeting ISO 26262 ASIL-B support requirements for functional safety systems.

Availability

L4979D-E is available at Aetrix Electronics and suitable for engine control units, body control modules, ADAS camera ECUs, and infotainment head units requiring stable component supply across automotive production lifecycles.

Supply support for L4979D-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 power applications.

The L4979D-E belongs to ST's automotive power management portfolio, engineered specifically for single-chip power supervision in safety-critical vehicle subsystems where integration, reliability, and AEC-Q100 compliance are mandatory.

FAQ

What is the maximum allowable input voltage for continuous operation?

The L4979D-E supports continuous DC input from 5.6 V to 31 V. Its absolute maximum rating is 40 V, allowing it to survive automotive load-dump transients without latch-up or damage, though sustained operation above 31 V is not specified for regulation performance.

How does the reset delay time scale with external capacitor value?

Reset pulse delay (t_rd) is calculated as 512 × T_OSC, where T_OSC = [(V_rhth − V_rlth) × C_tr] / I_cr + [(V_rhth − V_rlth) × C_tr] / I_dr. With typical I_cr/I_dr ≈ 12 µA and V_rhth−V_rlth ≈ 1.5 V, t_rd ≈ 125 ms per nanofarad - e.g., 1 nF yields ~150 ms.

Can the watchdog timer be disabled while retaining voltage regulation?

No - the En pin controls all functions simultaneously. When En is low, the regulator, reset circuit, and watchdog are all disabled, drawing only 6 µA. There is no independent watchdog disable mode; disabling watchdog requires external gating of the Wi signal or removal of the watchdog stimulus.

What thermal derating applies when using the SO-8 package on a 2 cm² copper pour?

With 2 cm² PCB copper area, the SO-8 package achieves R_{th j-amb} ≈ 130 °C/W. At T_j(max) = 150 °C and T_a = 85 °C, maximum allowable power dissipation is (150 − 85) / 130 ≈ 0.5 W. For V_in = 13.5 V and V_out = 5 V, this limits output current to ~590 mA - well above the 150 mA rated limit, confirming thermal adequacy in typical automotive ambient conditions.