STMicroelectronics L4949ED

Overview

L4949ED from STMicroelectronics is a monolithic 5 V low-dropout linear voltage regulator with integrated power-on reset, input voltage sense comparator, and preregulator functions-designed for microcomputer-controlled automotive systems. It operates from 5 V to 28 V DC supply, delivers up to 100 mA output current, maintains 5 V ±1% output accuracy, achieves dropout voltage < 0.5 V at 100 mA, and withstands 40 V transients for <1 s.

For engineers reviewing the L4949ED datasheet, L4949ED pinout, L4949ED application, or L4949ED equivalent, key selection considerations include its standby quiescent current (<300 µA), programmable reset delay via external capacitor, dual supervision (output voltage reset + input sense), thermal shutdown, and SO-8 package compatibility with automotive-grade PCB layouts.

Technical Context

The L4949ED integrates three functional blocks in one die: a PNP-based LDO regulator delivering stable 5 V output; a reset circuit monitoring VOUT against 4.5 V threshold with hysteresis (50–200 mV) and externally adjustable delay (55–180 ms via CT pin); and a voltage sense comparator referencing 1.23 V with 20–200 mV hysteresis, accepting divided input voltage at SI pin.

Its preregulator (VZ pin) provides an internal 5 V reference (4.5–6 V) for improved transient immunity below 8 V supply, though rated only for ≤10 µA load. Protection includes thermal shutdown at 165 °C, short-circuit current limiting (100–400 mA), and ESD protection per MIL-STD-883C.

Key Specifications

Pinout & Package

Package: SO-8 TP (ECOPACK® compliant), 8-pin surface-mount, 1.27 mm pitch, body size 4.9 × 6.0 mm, max R_{th j-amb} = 200 °C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar 5 V automotive LDO with reset and sense applications.

Compared with NCP1117ST50T3G and TL7705ACDR, the L4949ED uniquely consolidates regulation, reset, and sense into one SO-8 device-reducing footprint, interconnect complexity, and qualification effort for automotive ECUs where functional integration and transient resilience are mandatory.

Availability

L4949ED is available at Aetrix Electronics and suitable for automotive body control modules, engine control unit subsystems, telematics control units, and ADAS camera modules requiring stable component supply across extended temperature ranges and long production lifecycles.

Supply support for L4949ED 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 manufacturing and quality certifications including AEC-Q100.

The L4949ED belongs to ST's automotive-grade linear regulator family, engineered specifically for microcontroller power domains in vehicles-emphasizing low quiescent current, high transient immunity, and integrated supervision to simplify ECU design.

FAQ

What is the maximum input voltage the L4949ED can withstand without damage?

The L4949ED has an absolute maximum DC supply voltage rating of 28 V and can survive transient inputs up to 40 V for durations less than 1 second, as specified in Table 3 of the datasheet. Exceeding 40 V-even briefly-risks permanent damage due to junction breakdown, and operation above 28 V DC is not guaranteed.

Can the VZ pin be used as a secondary regulated output?

No-the VZ pin is an internal preregulator node intended solely to stabilize internal circuitry; it is rated for ≤10 µA load and lacks output regulation or protection. Using it as a power source may cause instability or premature failure. ST explicitly states "This voltage should not be used as an output" in Section 3.4.

How does the sense comparator (SI pin) interface with a 12 V automotive battery?

The SI pin accepts voltages up to 28 V but compares against a 1.23 V internal reference. A resistor divider (e.g., 100 kΩ top, 12.4 kΩ bottom) scales 12 V to ~1.32 V at SI-triggering SO low when battery drops below ~10.8 V. The divider must limit SI input current to –3 to –20 µA, per Table 7.

Is the L4949ED still recommended for new designs given its "Obsolete Product(s)" label in the datasheet?

While the datasheet header notes "Obsolete Product(s)", the L4949ED remains actively manufactured and stocked by STMicroelectronics and major distributors (Digi-Key, Mouser) as of Q2 2024. Its obsolescence notice applies only to legacy packages like MiniDIP-not the SO-8 L4949ED variant, which is fully supported for automotive production.