Send an Inquiry

To receive a quote for your project, please fill in the following information, and we’ll get back to you promptly.

Submit Inventory List

Please fill in the following information, and we’ll get back to you promptly.

Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Voltage Regulators - Linear, Low Drop Out (LDO) Regulators

STMicroelectronics L4949E

Name: L4949E
Brand: STMicroelectronics
SKU: L4949E
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: L4949E

Manufacturer:: STMicroelectronics

Category:: Voltage Regulators - Linear, Low Drop Out (LDO) Regulators

Package:: 8-DIP (0.300", 7.62mm)

Datasheet:: L4949E.pdf

Description:: IC REG LINEAR 5V 100MA 8DIP

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:2,584

Please send an inquiry. Send us your inquiry, and we will respond immediately.

Product details

Overview

L4949E from STMicroelectronics is a monolithic 5V low-dropout linear voltage regulator with integrated power-on reset, input voltage sense comparator, and preregulator output. It delivers up to 100mA output current with dropout voltage <0.5V at 100mA, standby output accuracy of 5V±1%, and supports DC supply from 5V–28V (transient up to 40V). Designed for microcomputer-controlled automotive systems requiring robust reset supervision and low-quiescent-current operation.

For engineers reviewing the L4949E datasheet, L4949E pinout, L4949E application, or L4949E equivalent, key selection criteria include its programmable reset delay via external capacitor, 1.23V internal sense reference, thermal shutdown, short-circuit protection, and dual-package availability (Minidip/SO-8).

Technical Context

The L4949E integrates three functional blocks: a PNP-based LDO regulator with foldback current limiting, a voltage-sense comparator referenced to 1.23V for flexible undervoltage detection, and a dedicated reset circuit with 4.5V threshold and externally adjustable delay (t_RD = C_T × 2V / 2µA). Its isolated-collector vertical PNP pass element enables stable regulation down to 3V input while maintaining 5V output.

Internal 5V preregulator (pin VZ) stabilizes bias rails against transients-usable as auxiliary reference only (≤10µA load). Reset immunity exceeds 100V/µs above 8V supply but requires CT filtering below 8V. All protections-including thermal shutdown at 165°C and short-circuit foldback-are fully integrated without external components.

Key Specifications

Parameter	Value and Actual Design Meaning
Output Voltage	5V ±1% (4.95–5.05V at 25°C, 4.90–5.10V over full load/temp)
Dropout Voltage	<0.5V at 100mA (enables operation down to 3V input while regulating 5V)
Quiescent Current	200–300µA (standby), 5mA (full load; enables ultra-low-power sleep modes)
Reset Threshold	4.5V with 50–200mV hysteresis (ensures noise-immune brownout detection)
Reset Delay	55–180ms (programmable via external CT capacitor, e.g., 100nF)
Sense Reference	1.23V ±100mV (supports configurable input monitoring via external divider)
Transient Tolerance	40V for <1s (prevents functional interruption during automotive load-dump events)

Pinout & Package

Available in Minidip (8-pin) and SO-8 packages. Pin functions are identical across variants; Minidip uses through-hole mounting while SO-8 supports surface-mount assembly.

Pin/Terminal	Circuit Role	Design Meaning
VS	Input Supply	Main DC input (5–28V); withstands 40V transients for <1s
SI	Sense Input	Connects to external voltage divider for undervoltage warning or pre-diode monitoring
VZ	Preregulator Output	Stabilized 5V internal rail (≤10µA drive); optional transient filter node
CT	Reset Delay Capacitor	Controls reset pulse width (t_RD = C_T × 2V / 2µA)
GND	Ground Reference	Common return for regulator, reset, and sense circuits
RES	Reset Output	Open-drain active-low reset signal (V_OL ≤ 0.4V @ 10kΩ)
SO	Sense Output	Open-drain comparator output (low when SI < 1.16V)
VOUT	Regulated Output	5V ±1% main supply rail (100mA max, <0.5V dropout)

Key Features

Feature	Design Value
Programmable Reset Delay	External capacitor (CT) sets delay from 55ms to 180ms-enables precise timing alignment with MCU boot sequence
Integrated Sense Comparator	1.23V reference allows flexible input monitoring before/after protection diodes-supports early low-voltage warnings
Low-Dropout Operation	<0.5V dropout at 100mA ensures stable 5V output even at 5.5V input-critical for battery-powered automotive modules
Transient-Robust Preregulator	VZ pin provides filtered 5V bias rail-improves reset immunity below 8V supply when decoupled with 100nF–1µF capacitor
Foldback Current Limiting	Current limit drops from 120mA to 400mA under short-circuit-reduces power dissipation and thermal stress during fault

Applications

Engine Control Unit (ECU)

Body Control Module (BCM)

Use Scenario: Powering 5V microcontrollers and CAN transceivers in engine bay environments subject to load dump and cold cranking.

IC Role / Device Role / Timing Role: Primary 5V LDO regulator with synchronized reset assertion during undervoltage events.

Use Value: Maintains regulation down to 3V input and survives 40V/1s transients-eliminates need for external TVS or reset IC.

Use Scenario: Supplying door module MCUs where space-constrained PCBs require minimal external components.

IC Role / Device Role / Timing Role: Single-chip solution combining regulated 5V output, reset generation, and battery voltage monitoring.

Use Value: Reduces BOM count by integrating sense comparator and programmable reset-no discrete comparators or RC timers required.

Instrument Cluster Display

Telematics Control Unit (TCU)

Use Scenario: Providing clean 5V rail to LCD drivers and touch controllers with strict EMI and noise requirements.

IC Role / Device Role / Timing Role: Low-noise LDO with CT-filtered reset and VZ-decoupled bias for analog subsystem stability.

Use Value: External capacitor on CT and VZ pins suppresses output noise and improves transient immunity-meets automotive display EMC specs.

Use Scenario: Enabling safe firmware update sequences in cellular-connected vehicle gateways.

IC Role / Device Role / Timing Role: Reset supervisor ensuring MCU remains held until post-update 5V rail stabilizes.

Use Value: Adjustable reset delay (via CT) aligns with modem power-up timing-prevents race conditions during OTA updates.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
TL7705ACDR	Fixed 5V output, no sense comparator, no preregulator output, higher quiescent current (2mA typical)	Lacks voltage monitoring capability; requires external components for undervoltage detection	Select when only basic reset + LDO is needed and board space permits added discretes
NCP1117ST50T3G	No reset or sense functions; 1.2V reference not available; dropout ~1.1V at 100mA	Requires separate reset IC and comparator for automotive brownout handling	Choose for cost-sensitive non-automotive applications where extended features are unnecessary

Compared with TL7705ACDR and NCP1117ST50T3G, the L4949E uniquely integrates reset, sense, and preregulator functions in one package-reducing component count, improving transient immunity, and enabling compact, ASIL-ready designs without external timing or monitoring circuitry.

Availability

L4949E is available at Aetrix Electronics and suitable for engine control units, body control modules, instrument clusters, and telematics control units requiring stable component supply under automotive temperature and transient stress conditions.

Supply support for L4949E 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.

The L4949E belongs to ST's automotive-grade linear regulator family, engineered specifically for microcontroller power and supervision in harsh environments-emphasizing transient resilience, integrated diagnostics, and AEC-Q100 compliance readiness.

FAQ

What is the maximum allowable input voltage for continuous operation?

The L4949E supports continuous DC input from 5V to 28V. Transient voltages up to 40V are permitted for durations less than 1 second-this rating is validated per absolute maximum ratings and enables compatibility with ISO 7637-2 Pulse 5a load-dump waveforms in automotive systems.

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

No-the VZ pin delivers a stabilized 5V internal bias rail with ≤10µA output capability. It is intended solely for improving transient immunity of internal circuitry. Connecting external loads risks degrading reset behavior and violating thermal limits; ST explicitly advises leaving VZ open unless used with a 100nF–1µF bypass capacitor.

How does the sense comparator function in a typical application?

The SI pin accepts a divided version of the main supply (e.g., via resistor network), comparing it to an internal 1.23V reference. When SI falls below 1.16V, SO asserts low-enabling early warning of battery sag before the main 5V rail collapses. This allows the MCU to initiate graceful shutdown or alert drivers prior to reset activation.

Is the L4949E pin-compatible across Minidip and SO-8 packages?

Yes-both Minidip and SO-8 variants share identical pin numbering and electrical functionality. The pinout (VS, SI, VZ, CT, GND, RES, SO, VOUT) is electrically and logically identical; only mechanical dimensions and mounting method differ. Layout migration between packages requires only footprint adjustment-not schematic changes.

L4949E Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 8-DIP (0.300", 7.62mm)

Packaging:: Tube

Product Status:: Obsolete

Output Configuration:: Positive

Output Type:: Fixed

Number of Regulators:: 1

Voltage - Input (Max):: 28V

Voltage - Output (Min/Fixed):: 5V

Voltage - Output (Max):: -

Voltage Dropout (Max):: 0.5V @ 100mA

Current - Output:: 100mA

Current - Quiescent (Iq):: 300 µA

Current - Supply (Max):: 5 mA

PSRR:: -

Control Features:: Reset Output

Protection Features:: Over Temperature, Short Circuit

Operating Temperature:: -40°C ~ 125°C

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: -

L4949E FAQ

1.How can I place an order for L4949E through Aetrix?

Please submit a Request for Quotation (RFQ) for L4949E on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for L4949E reliable?

The price and inventory of L4949E are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L4949E is usually 5 days.

3.What payment methods are accepted for L4949E?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L4949E transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for L4949E?

L4949E orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your L4949E order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for L4949E?

For technical support, including L4949E datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L4949E requirements.

6.How does Aetrix verify that L4949E is sourced from the original manufacturer or authorized distributors?

All L4949E products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that L4949E meets industry standards.

7.What is the process for return or replacement of L4949E?

All L4949E units undergo pre-shipment inspection (PSI). If there is an issue with L4949E, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The L4949E part is unused and in its original packaging.

Return procedure for L4949E:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

Tech Hub

2026-09-03 Logic Level Shifter: How to Connect 3.3V and 5V Logic Safely

A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.

2026-09-03 74HC595 vs TPIC6B595: Output Drive, Pinout, Current, and Load Selection

The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…

2026-09-01 74HC595 Pinout, Timing, Output Current, and Applications

The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…

2026-09-01 Latch vs Flip-Flop: Timing, Differences and Design Choices

A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…

2026-08-30 D Latch Circuit: Truth Table, Timing, ICs and Applications

A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …

2026-08-28 SR Latch Explained: NOR and NAND Circuits, Truth Tables, and Applications

An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…

2026-08-27 Latch Circuit: SR and D Latches, Truth Tables, Timing, and Applications

Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…

2026-08-21 What Is an LED Driver? Types, Circuits, Dimming, and Selection

An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…

2026-08-18 Operational Amplifier (Op Amp): Basics, Configurations, Feedback and Applications

Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…

2026-08-14 Jumper Cables: How to Use, Connect and Choose Them Safely

Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…