STMicroelectronics L4949EP

Overview

L4949EP 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 transient supply voltages up to 40 V.

For engineers reviewing the L4949EP datasheet, L4949EP pinout, L4949EP application, or L4949EP equivalent, this device is selected for robustness in automotive ECU power management where precise reset timing, input supervision, and ultra-low quiescent current (<300 µA) under standby are critical design requirements.

Technical Context

The L4949EP integrates three functional blocks: a PNP-based LDO regulator delivering stable 5 V output; a voltage-sense comparator (threshold 1.23 V, hysteresis 20–200 mV) configurable via external divider on SI pin; and a reset circuit with programmable delay (via CT capacitor) and 4.5 V threshold (VRT = VO − 0.5 V) with 50–200 mV hysteresis.

Its SO-20W package supports thermal dissipation (R_{th j-amb} = 50 °C/W), enabling operation up to +150 °C junction temperature. The preregulator output (VZ pin) provides internal 5 V stabilization but is limited to ≤10 µA sourcing-intended only for noise suppression, not load driving.

Key Specifications

Pinout & Package

Package: SO-20W (20-pin Small Outline Wide-body, ECOPACK® compliant, body width 7.4–7.6 mm, pitch 1.27 mm).

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar multifunction automotive LDO regulator applications.

Compared with NCP109x and TLE4275, the L4949EP offers tighter 5 V ±1% regulation, integrated sense comparator for flexible input monitoring, and user-adjustable reset delay-making it uniquely suited for safety-critical automotive subsystems requiring coordinated power-up supervision.

Availability

L4949EP is available at Aetrix Electronics and suitable for engine control units, body control modules, ADAS sensor hubs, and telematics control units requiring stable component supply, long-term automotive qualification, and legacy design continuity.

Supply support for L4949EP 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 certification coverage.

The L4949EP belongs to ST's automotive-grade linear regulator family, engineered specifically for microcontroller power domains in harsh environments-emphasizing transient resilience, precise reset behavior, and extended temperature operation (−40 °C to +150 °C).

FAQ

What is the maximum allowable input voltage for continuous operation of the L4949EP?

The L4949EP supports continuous DC input voltage from 5 V to 28 V. It can withstand transient overvoltages up to 40 V for durations less than 1 second without damage or functional interruption, as specified in Table 3 (Absolute Maximum Ratings). Operation beyond 28 V DC is not permitted for sustained use.

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

No-the VZ pin is not intended as a functional output. It provides an internally stabilized ~5 V rail for noise reduction and internal biasing, with a maximum sourcing capability of only 10 µA. Attempting to draw load current from VZ will degrade regulation, compromise transient immunity, and may cause malfunction. The datasheet explicitly states "This voltage should not be used as an output."

How does the sense comparator (SI/SO pins) function in a typical automotive application?

The SI pin accepts a divided version of the main supply (e.g., VS through resistor divider), and the internal 1.23 V comparator triggers SO (open-collector) when SI falls below threshold. In practice, this enables early low-battery warning-e.g., configuring the divider to assert SO at ~9 V battery voltage-allowing the MCU to initiate controlled shutdown before VOUT collapses.

Is the L4949EP still recommended for new designs given its obsolete status in ST's documentation?

While ST labels L4949EP as "Obsolete Product(s)" in its revision history, the part remains actively stocked and supported by major authorized distributors (Digi-Key, Mouser) and is widely deployed in fielded automotive systems. Aetrix Electronics confirms full traceability, guaranteed minimum 5-year supply continuity, and access to legacy qualification data for new designs requiring proven reliability and drop-in compatibility.