STMicroelectronics L4949ED-E

Overview

L4949ED-E from STMicroelectronics is an AEC-Q100 qualified automotive 5 V very low dropout linear voltage regulator with integrated power-on reset, input voltage sense comparator, and preregulator output (VZ). It delivers up to 100 mA output current with dropout voltage < 0.5 V at 100 mA, quiescent current ≤ 300 µA, and standby output accuracy of 5 V ±1%. It is used to supply microcontroller subsystems in engine control units and body electronics.

For engineers reviewing the L4949ED-E datasheet, L4949ED-E pinout, L4949ED-E application, or L4949ED-E equivalent, key selection criteria include its 40 V transient tolerance, programmable reset delay via external capacitor, sense comparator with 1.23 V threshold, and SO-8 package compatibility with automotive thermal and reliability requirements.

Technical Context

The device integrates a PNP-based low-dropout regulator core with a dedicated reset circuit that monitors VOUT against a 4.5 V threshold (VRT = VO − 0.5 V) and provides adjustable delay (55–180 ms with 100 nF CT). Its sense comparator operates independently with a 1.23 V internal reference and supports external voltage divider supervision of VS or upstream rails.

A built-in preregulator (VZ pin) stabilizes internal bias at ~5 V for improved transient immunity below 8 V input, while thermal shutdown (165 °C) and short-circuit foldback protection ensure robust operation across −40 °C to +125 °C junction temperature range.

Key Specifications

Pinout & Package

Package: SO-8 TP (ECOPACK®, RoHS-compliant, lead-free), 1.27 mm pitch, 5.0 × 6.2 mm body size, R_{th j-amb} = 200 °C/W.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar automotive 5 V LDO regulator applications.

Compared with TLV73350PDBVR and NCP1117ST50T3G, the L4949ED-E trades raw current capacity for automotive-grade integration-delivering reset, sense, and transient resilience in a single SO-8 footprint, reducing total system BOM and validation effort for ECU designs.

Availability

L4949ED-E is available at Aetrix Electronics and suitable for engine control units, body control modules, ADAS camera ECUs, and automotive gateway modules requiring stable component supply under AEC-Q100 compliance and long-term automotive lifecycle support.

Supply support for L4949ED-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 L4949ED-E belongs to ST's automotive-grade analog power management portfolio, engineered specifically to replace discrete reset + LDO + supervisor combinations in microcontroller power domains for ASIL-B–aligned systems.

FAQ

What is the maximum allowable input voltage for continuous operation?

The L4949ED-E supports continuous DC input voltage from 5 V to 28 V. Transient input voltage up to 40 V is allowed for durations less than 1 second, per ISO 7637-2 Pulse 5a specifications. Operation above 28 V beyond transient limits risks permanent damage due to exceeding absolute maximum ratings.

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

No. The VZ pin delivers only ≤10 µA and is intended solely to stabilize internal circuitry. It is not rated for external load driving. Connecting any load will degrade transient immunity and may cause regulation instability. ST explicitly states "This output may be used as an option when a better transient behaviour… is required" - not as a power source.

How is the reset delay time calculated from the CT capacitor value?

The nominal reset delay t_RD is calculated as t_RD = CT × 2 V / 2 µA. For example, a 100 nF capacitor yields t_RD ≈ 100 ns × 2 V / 2 µA = 100 ms. This relationship is confirmed in Section 3.5 and Figure 7 of the datasheet, where CT charges linearly at 2 µA from a 2 V reference.

Is the SO pin compatible with 3.3 V microcontroller inputs?

Yes. The SO pin is an open-collector output with V_SL ≤ 0.4 V at I_SO = 10 kΩ to V_OUT, and leakage < 1 µA when high. When pulled up to 3.3 V (not V_OUT), it safely interfaces with 3.3 V logic inputs, provided the external pull-up resistor is sized to limit current within SO's 5 mA rating.