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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > Voltage Regulators - DC DC Switching Regulators

STMicroelectronics L6981N50DR

Name: L6981N50DR
Brand: STMicroelectronics
SKU: L6981N50DR
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: L6981N50DR

Manufacturer:: STMicroelectronics

Category:: Voltage Regulators - DC DC Switching Regulators

Package:: 8-SOIC (0.154", 3.90mm Width)

Datasheet:: L6981N50DR.pdf

Description:: IC REG BUCK 5V 1.5A 8SO

Quantity:: RFQ Add To RFQ list

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Product details

Overview

L6981N50DR from STMicroelectronics is a synchronous monolithic step-down DC-DC converter delivering up to 1.5 A output current with 3.5–38 V input range, fixed 5.0 V output, and 550 µA typical quiescent current in low-noise mode (LNM). It features internal compensation, 400 kHz nominal switching frequency, output overvoltage protection, and EN/CLKIN pin supporting external clock synchronization-designed for smart meters and robot cleaners requiring stable, low-noise 5 V rail from 24 V bus or battery.

For engineers reviewing the L6981N50DR datasheet, L6981N50DR pinout, L6981N50DR application, or L6981N50DR equivalent, key selection criteria include its LNM-mode constant-frequency operation, VIN-compatible enable threshold (1.2 V), 0.85 V internal feedback reference, thermal shutdown at 165 °C, and SO8 package compatibility with standard PCB layout practices for industrial power conversion.

Technical Context

The L6981N50DR implements peak current mode control with integrated high-side and low-side MOSFETs (R_DS(on) = 0.175 Ω / 0.125 Ω), slope compensation to prevent subharmonic oscillation, and a transconductance error amplifier with internal compensation network. Its LNM variant enforces constant 400 kHz switching across all loads to minimize conducted EMI.

It supports output voltage sequencing via soft-start (1.3 ms typical), enables external clock synchronization (200–500 kHz) on the EN/CLKIN pin, and delivers valley-current sinking capability (1.25–1.75 A) during overvoltage events to actively discharge the output capacitor-critical for safety-critical sensor nodes and always-on applications.

Key Specifications

Parameter	Value and Actual Design Meaning
Input Voltage Range	3.5 V to 38 V - supports direct connection to 24 V industrial buses and wide-range battery inputs without pre-regulation.
Output Voltage	Fixed 5.0 V ±1% - eliminates external resistor divider; meets USB-powered peripheral and microcontroller I/O rail requirements.
Max Output Current	1.5 A DC - sufficient for powering MCU cores, sensors, and communication ICs in decentralized intelligent nodes.
Quiescent Current (LNM)	550 µA typical from VIN - enables multi-year battery life in always-on sensor applications with minimal standby loss.
Switching Frequency	400 kHz nominal - balances EMI filtering size and efficiency; synchronizable to external clock for system-level noise coordination.
OVP Threshold	120% of V_OUT (6.0 V) with 2% hysteresis - triggers active low-side sinking to clamp overvoltage within safe limits during load dump or transient faults.
Thermal Shutdown	165 °C with 30 °C hysteresis - protects against sustained overload or poor heatsinking in enclosed industrial enclosures.

Pinout & Package

Package: SO8 (SOIC-8, 150 mil width), surface-mount, RoHS-compliant, with exposed thermal pad (PGND-connected).

Pin/Terminal	Circuit Role	Design Meaning
1 SW	Switching node	Connects to inductor and bootstrap capacitor; carries high di/dt; requires tight layout to minimize ringing and EMI.
2 BOOT	Bootstrap supply	Drives high-side MOSFET gate; requires 100 nF ceramic capacitor between BOOT and SW for reliable gate charge replenishment.
3 VCC	Analog supply rail	Powers internal reference and error amplifier; requires ≥1 µF ceramic bypass capacitor to stabilize bandgap reference.
4 VOUT/FB	Output sense / feedback	In fixed-VOUT versions like L6981N50DR, functions as regulated 5.0 V output pin-not feedback node; no external divider needed.
5 EN/CLKIN	Enable & sync input	VIN-compatible digital enable (1.2 V threshold); in LNM variants, accepts 200–500 kHz external clock for EMI reduction and timing coordination.
6 AGND	Analog ground	Reference for error amplifier and internal circuits; must be separated from PGND and connected at single point near VCC capacitor.
7 VIN	Main input supply	Accepts 3.5–38 V DC; requires 10 µF low-ESR input capacitor close to VIN and PGND pins to suppress ripple and transients.
8 PGND	Power ground	Return path for high-current switches and inductor; connects to thermal pad; must be low-impedance copper pour under device.

Key Features

Feature	Design Value
Low-Noise Mode (LNM)	Forced PWM operation with constant 400 kHz frequency ensures predictable spectral content and minimal output voltage ripple at light loads-ideal for analog sensor front-ends.
Internal Soft-Start	1.3 ms monotonic ramp prevents inrush current and output overshoot during power-up, sequencing, or recovery from UVLO/thermal shutdown.
Output Overvoltage Protection	Active sinking via low-side MOSFET discharges output capacitor when V_OUT exceeds 6.0 V, limiting fault energy and protecting downstream 5 V logic.
VIN-Compatible Enable	EN pin operates up to 38 V, eliminating need for level-shifting circuitry when enabling from 24 V system rails or microcontroller GPIOs.
Integrated Compensation	No external compensation components required-reduces BOM count, board area, and design validation effort for standard 5 V/1.5 A applications.

Applications

Smart Meters

Robot Cleaners

Use Scenario: Powering metrology ICs, RF modules, and real-time clocks in Class 0.2 electricity meters operating continuously from 24 V auxiliary supply.

IC Role / Device Role / Timing Role: Primary 5 V regulator supplying precision analog and low-power digital subsystems with strict ripple and stability requirements.

Use Value: LNM mode ensures <10 mV_PP output ripple at 10 mA load, preventing measurement errors in ADC references and enabling Class 0.2 accuracy compliance.

Use Scenario: Providing clean 5 V rail to motor control MCU, Li-ion fuel gauge, and obstacle-detection sensors in compact vacuum robots with 24 V battery input.

IC Role / Device Role / Timing Role: Main system regulator managing dynamic load steps (e.g., brush motor startup) while maintaining stable 5 V for navigation processors.

Use Value: 1.5 A current capability and 165 °C thermal shutdown allow sustained operation during cleaning cycles; soft-start prevents brownout during motor commutation spikes.

Industrial Sensors

Decentralized I/O Nodes

Use Scenario: Powering MEMS accelerometers, temperature transmitters, and IO-Link PHYs in hazardous-area field devices powered by 24 V loop or local battery.

IC Role / Device Role / Timing Role: Always-on power source with ultra-low quiescent current and robust OVP/UVLO for unattended remote monitoring.

Use Value: 550 µA LNM quiescent current extends 2× AA battery life beyond 5 years in sleep-wake cycles; EN pin enables firmware-controlled power gating.

Use Scenario: Supplying 5 V to ARM Cortex-M7-based edge controllers in modular PLC backplanes with distributed 24 V bus architecture.

IC Role / Device Role / Timing Role: Local point-of-load regulator per module, synchronized via EN/CLKIN to avoid beat frequencies in multi-channel systems.

Use Value: External clock synchronization (200–500 kHz) eliminates inter-module EMI coupling and simplifies EMC filter design across 16-slot chassis.

Equivalent & Alternatives

The following parts are listed as comparable options for similar synchronous buck regulator applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
LM61480RGER	4.5–36 V input, 5 V fixed, 8 A output, 15 µA IQ, 2.1 MHz switching - higher current, higher frequency, lower IQ but larger solution size.	Targets high-power industrial HMIs and servo drives where 1.5 A is insufficient; not suitable for space-constrained robot cleaner PCBs.	Select LM61480RGER only if >3 A output or <10 µA IQ is mandatory; L6981N50DR offers better EMI control at 400 kHz and smaller SO8 footprint.
TPS54202HDDCR	4.5–28 V input, adjustable VOUT, 2 A output, 26 µA IQ, 500 kHz–2.2 MHz sync-capable - no fixed 5 V option; requires external feedback resistors.	Suited for designs needing programmable output or tighter load regulation; lacks integrated OVP and LNM-specific noise optimization.	Choose TPS54202HDDCR only when adjustable output or dual-rail generation is required; L6981N50DR provides plug-and-play 5 V with superior light-load noise performance.

Compared with LM61480RGER and TPS54202HDDCR, the L6981N50DR delivers optimal balance of fixed 5 V simplicity, LNM-mode EMI control, SO8 compactness, and industrial-grade protection-making it the preferred choice for cost-sensitive, noise-sensitive 1.5 A applications.

Availability

L6981N50DR is available at Aetrix Electronics and suitable for smart meter deployments, robot cleaner production, and industrial sensor node manufacturing requiring stable component supply, long-term lifecycle support, and traceable sourcing.

Supply support for L6981N50DR 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, specializing in power management, microcontrollers, and automotive ICs with strong industrial and IoT focus.

The L6981 series targets industrial and battery-powered applications demanding high efficiency at light loads, low EMI, and robust protection-designed specifically for decentralized nodes, smart meters, and robotics where reliability and noise immunity are critical.

FAQ

What is the function of the EN/CLKIN pin on the L6981N50DR?

The EN/CLKIN pin serves dual roles: as a digital enable input with 1.2 V rising threshold for VIN-compatible on/off control, and-as exclusive to LNM variants-as a synchronization input accepting 200–500 kHz external clock signals to align switching edges with system timing domains and reduce beat-frequency EMI.

Does the L6981N50DR require external compensation components?

No. The L6981N50DR integrates a complete compensation network optimized for standard 5 V output configurations. No external Type-II or Type-III compensation components are needed-only the required input, output, bootstrap, and VCC capacitors per the datasheet's typical application circuit.

How does overvoltage protection operate in the L6981N50DR?

When V_OUT exceeds 120% of nominal (6.0 V), the device activates low-side MOSFET sinking to discharge the output capacitor. It maintains this state until negative current reaches 1.25–1.75 A, clamping voltage safely without relying on external TVS diodes or crowbar circuits.

Can the L6981N50DR be used with a 24 V battery input in automotive environments?

Yes-the 3.5–38 V input range covers cold-crank (6.5 V) to load-dump (36 V) conditions. However, for full AEC-Q100 compliance, ST recommends the automotive-grade L6981A variant; the L6981N50DR is qualified for industrial temperature range (–40 °C to 125 °C) and widely deployed in off-road and commercial vehicle auxiliary systems.

L6981N50DR Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 8-SOIC (0.154", 3.90mm Width)

Packaging:: Tape & Reel (TR)

Product Status:: Active

Function:: Step-Down

Output Configuration:: Positive

Topology:: Buck

Output Type:: Fixed

Number of Outputs:: 1

Voltage - Input (Min):: 3.5V

Voltage - Input (Max):: 38V

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

Voltage - Output (Max):: -

Current - Output:: 1.5A

Frequency - Switching:: 400kHz

Synchronous Rectifier:: Yes

Operating Temperature:: -40°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 8-SO

L6981N50DR FAQ

1.How can I place an order for L6981N50DR through Aetrix?

Please submit a Request for Quotation (RFQ) for L6981N50DR 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 L6981N50DR reliable?

The price and inventory of L6981N50DR are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L6981N50DR is usually 5 days.

3.What payment methods are accepted for L6981N50DR?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L6981N50DR transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for L6981N50DR?

L6981N50DR orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your L6981N50DR 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 L6981N50DR?

For technical support, including L6981N50DR datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L6981N50DR requirements.

6.How does Aetrix verify that L6981N50DR is sourced from the original manufacturer or authorized distributors?

All L6981N50DR 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 L6981N50DR meets industry standards.

7.What is the process for return or replacement of L6981N50DR?

All L6981N50DR units undergo pre-shipment inspection (PSI). If there is an issue with L6981N50DR, 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 L6981N50DR part is unused and in its original packaging.

Return procedure for L6981N50DR:

1.Submit a request within 90 days.

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

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