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) > PFC (Power Factor Correction)

STMicroelectronics L4981B

Name: L4981B
Brand: STMicroelectronics
SKU: L4981B
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: L4981B

Manufacturer:: STMicroelectronics

Category:: PFC (Power Factor Correction)

Package:: 20-DIP (0.300", 7.62mm)

Datasheet:: L4981B.pdf

Description:: IC PFC CTR AV CURR 100KHZ 20DIP

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:3,947

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

Product details

Overview

L4981B from STMicroelectronics is a fixed- or frequency-modulated average-current-mode PWM controller IC for active power factor correction (PFC) pre-regulators in universal-input AC/DC supplies. It achieves up to 0.99 power factor, limits line current THD to <5%, supports 85–265V_AC input without switching, and integrates bipolar/DMOS totem-pole gate driver delivering >1A peak output for MOSFET/IGBT drive.

For engineers reviewing the L4981B datasheet, L4981B pinout, L4981B application, or L4981B equivalent, this device is selected for high-efficiency PFC stages requiring precise line/load regulation, programmable UVLO, soft-start control, and robust overvoltage/overcurrent protection in industrial and telecom power supplies.

Technical Context

The L4981B implements an analog multiplier-based average current mode control architecture with RMS line voltage feedforward (Pin 7), load feedforward (Pin 6), and external frequency modulation via Pin 16. Its internal 5.1V ±2% reference (Pin 11) enables accurate error amplifier (Pin 13/14) and current amplifier (Pin 5/9) operation without external trimming.

Unlike the L4981A, the L4981B uses a dedicated FREQ-MOD input (Pin 16) to dynamically adjust switching frequency between 74–115 kHz based on rectified line voltage and external resistor programming-reducing EMI and optimizing input filter size while maintaining sinusoidal line current without slope compensation.

Key Specifications

Parameter	Value and Actual Design Meaning
Power Factor	Up to 0.99 - enables compliance with IEC 61000-3-2 Class D harmonic limits.
THD Limit	<5% line current distortion - ensures low harmonic injection into mains infrastructure.
Switching Frequency	74–115 kHz (modulated) - reduces EMI and allows smaller input EMI filter vs. fixed-frequency designs.
Reference Voltage	5.1 V ±2% - provides stable, externally accessible precision reference for feedback loops.
Gate Driver Output	1 A sink / 1.5 A source peak - directly drives power MOSFETs or IGBTs without external buffers.
Startup Current	0.3 mA typical - minimizes auxiliary supply losses during initial power-up.
UVLO Threshold	Programmable 10.6–13.4 V turn-on - supports flexible brown-out recovery design with external resistor divider.

Pinout & Package

Available in DIP20 (25.4 mm × 8.5 mm) and SO20 (13.0 mm × 7.6 mm) packages using MultiPower BCD 60II technology. Thermal resistance: 80°C/W (DIP20), 120°C/W (SO20).

Pin/Terminal	Circuit Role	Design Meaning
1	P-GND	Power ground return for gate driver and high-current paths.
2	IPK	Peak current limit sense input - accepts precision two-resistor network for accurate overcurrent threshold setting.
3	OVP	Overvoltage protection comparator input - monitors boost output via resistive divider against internal 5.1V reference.
4	IAC	AC current sensing input - receives proportional signal from rectified mains for multiplier-based current reference generation.
5	CA-OUT	Current amplifier output - drives external RC compensation network to stabilize inner current loop.
6	LFF	Load feedforward input - improves transient response by scaling multiplier output with load level (1.6–5.3V range).
7	VRMS	RMS line voltage input - enables line-voltage feedforward for consistent current shaping across 85–265V_AC.
8	MULT-OUT	Multiplier output node - high-impedance junction of multiplier and current amplifier inputs; must not go below –0.5V.
9	ISENSE	Inverting input of current amplifier - connects to shunt resistor for sensed inductor current feedback.
10	S-GND	Signal ground - isolated reference for analog circuitry to minimize noise coupling.
11	VREF	5.1V ±2% reference output - powers external circuits and serves as precision bias for comparators and amplifiers.
12	SS	Soft-start capacitor connection - 100 µA internal current charges external cap to ramp up duty cycle gradually.
13	VA-OUT	Error amplifier output - drives outer voltage loop compensation network to regulate boost output voltage.
14	VFEED	Voltage feedback input - connects to resistive divider from boost output for closed-loop voltage regulation.
15	P-UVLO	Programmable UVLO threshold input - sets turn-on voltage via resistor divider between VCC and GND.
16	FREQ-MOD	Frequency modulation current sink - accepts line-synchronized current to vary oscillator frequency (L4981B only).
17	ROSC	Oscillator timing resistor - sets constant charging current for COSC capacitor to define base frequency.
18	COSC	Oscillator timing capacitor - determines switching period in conjunction with ROSC; modulated by FREQ-MOD current.
19	VCC	Supply input - operates from 12–19.5 V; includes internal zener clamp (20–30 V) for transient protection.
20	GDRV	Gate driver output - totem-pole stage delivers >1A peak current to switch external MOSFET/IGBT efficiently.

Key Features

Feature	Design Value
Average current mode PWM	Eliminates need for slope compensation and enables stable, low-noise current control across full line/load range.
Line and load feedforward	VRMS (Pin 7) and LFF (Pin 6) inputs enable fast dynamic response and consistent sinusoidal line current at all operating points.
Integrated protections	Programmable UVLO, overvoltage (OVP), overcurrent (OCP), and soft-start discharge ensure safe startup and fault recovery.
High-precision reference	5.1 V ±2% reference (Pin 11) with 10 mA drive capability enables accurate, self-contained feedback without external references.
Frequency modulation	FREQ-MOD input (Pin 16) allows line-synchronized frequency sweep (74–115 kHz), reducing EMI peaks and easing filter design.

Applications

Industrial AC/DC Power Supplies

Telecom Rectifier Modules

Use Scenario: 360W universal-input PFC front-end powering telecom shelf systems with strict harmonic and efficiency requirements.

IC Role / Device Role / Timing Role: Primary PFC controller implementing average current mode boost topology with line-synchronized frequency modulation.

Use Value: Achieves 0.993 PF and 96.4% efficiency at 220V_AC, meeting GR-902 and EN 61000-3-2 Class A limits without external compensation.

Use Scenario: 200W PFC stage in distributed power architecture (DPA) for base station remote radio units (RRUs).

IC Role / Device Role / Timing Role: Fixed- or modulated-frequency PWM controller regulating boost output to 400V DC with fast load transient response.

Use Value: Load feedforward (Pin 6) reduces output voltage dip to <1.2% during 50–100% load steps, improving system stability.

Medical Equipment Power Systems

LED Driver Front-Ends

Use Scenario: PFC pre-regulator in Class II medical AC/DC adapter (IEC 60601-1 compliant) powering imaging subsystems.

IC Role / Device Role / Timing Role: Safety-critical PFC controller with programmable UVLO, OVP, and precise 2% reference for reliable regulation.

Use Value: Under-voltage lockout with 1.5V hysteresis prevents erratic operation during brownouts, ensuring controlled shutdown.

Use Scenario: High-power LED streetlight driver with universal input and integrated PFC stage driving 100W+ LED arrays.

IC Role / Device Role / Timing Role: PFC controller managing boost converter to deliver stable 400V bus for downstream constant-current LED drivers.

Use Value: RMS line feedforward (Pin 7) maintains THD <4.7% across 88–264V_AC, enabling single-design global deployment.

Equivalent & Alternatives

The following parts are listed as comparable options for similar power factor correction controller applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
UCC28019	Fixed-frequency CCM PFC controller with internal 7.5V reference; no frequency modulation capability.	Lacks line-synchronized frequency sweep - requires larger EMI filter for same THD performance.	Select when fixed-frequency operation and TI ecosystem compatibility are prioritized over EMI optimization.
ICE2PCS01	Continuous conduction mode (CCM) PFC controller with integrated 600V startup circuit; no external FREQ-MOD pin.	Higher integration but less flexibility in frequency tuning - limited to fixed or voltage-controlled frequency.	Choose for simplified BOM count in cost-sensitive consumer power supplies where modulated frequency is not required.

Compared with UCC28019 and ICE2PCS01, the L4981B uniquely supports line-synchronized frequency modulation (74–115 kHz), enabling smaller passive EMI filters and lower THD across universal input ranges without sacrificing control loop stability.

Availability

L4981B is available at Aetrix Electronics and suitable for industrial AC/DC power supplies, telecom rectifier modules, and medical equipment power systems requiring stable component supply, long-term lifecycle support, and guaranteed traceability.

Supply support for L4981B 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 specializing in power management, analog, and microcontroller solutions for industrial, automotive, and consumer markets.

The L4981B belongs to ST's legacy MultiPower BCD analog power controller family, designed specifically for high-efficiency, continuous-conduction-mode (CCM) active PFC pre-regulators in universal-input offline power supplies.

FAQ

What is the key functional difference between L4981A and L4981B?

The L4981B features a dedicated FREQ-MOD input (Pin 16) that enables line-synchronized frequency modulation (74–115 kHz), whereas the L4981A uses a SYNC pin for fixed-frequency operation or external clock synchronization. This modulation reduces EMI peaks and allows smaller input filters while maintaining high power factor and low THD.

How is overcurrent protection implemented in the L4981B?

The L4981B implements overcurrent protection using a precision current-sense amplifier with IPK (Pin 2) configured via a two-resistor network tied to VREF (Pin 11) and the current-sense shunt. This achieves better accuracy than the single-resistor method used in the L4981A, with propagation delay under 0.9 µs and ±30 mV threshold tolerance.

Can the L4981B operate without external frequency-setting components?

No - the L4981B requires both ROSC (Pin 17) and COSC (Pin 18) to define its base oscillator frequency. Unlike some controllers with internal timing, it relies on external R/C for accuracy and temperature stability. The FREQ-MOD function (Pin 16) further requires an external resistor to the rectified line to enable modulation.

What is the maximum allowable voltage on the GDRV (Pin 20) output?

The GDRV output has an internal voltage clamp rated at 13–19 V (typical 16 V), allowing safe direct drive of standard 12 V or 15 V gate-rated MOSFETs. Exceeding 19 V risks latch-up or damage; external gate resistors and Zener clamps are recommended for 20 V+ logic-level devices.

L4981B Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 20-DIP (0.300", 7.62mm)

Packaging:: Tube

Product Status:: Obsolete

Mode:: Average Current

Frequency - Switching:: 100kHz

Current - Startup:: 100 µA

Voltage - Supply:: 14.5V ~ 19.5V

Operating Temperature:: -40°C ~ 125°C

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: 20-DIP

L4981B FAQ

1.How can I place an order for L4981B through Aetrix?

Please submit a Request for Quotation (RFQ) for L4981B 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 L4981B reliable?

The price and inventory of L4981B are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L4981B is usually 5 days.

3.What payment methods are accepted for L4981B?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L4981B transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for L4981B?

L4981B orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your L4981B 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 L4981B?

For technical support, including L4981B datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L4981B requirements.

6.How does Aetrix verify that L4981B is sourced from the original manufacturer or authorized distributors?

All L4981B 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 L4981B meets industry standards.

7.What is the process for return or replacement of L4981B?

All L4981B units undergo pre-shipment inspection (PSI). If there is an issue with L4981B, 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 L4981B part is unused and in its original packaging.

Return procedure for L4981B:

1.Submit a request within 90 days.

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

Tech Hub

2026-09-08 Obsolete Electronic Components: How to Source and Evaluate Replacements

A practical engineering and sourcing framework covering lifecycle verification, lifetime-buy calculations, replacement qualification, supplier checks and counterfeit-risk controls.

2026-09-07 TTL vs CMOS Logic Levels: 74HC and 74HCT Compatibility Explained

TTL and CMOS logic families differ in thresholds, loading, output drive, power and timing. This engineering guide compares 74HC and 74HCT, calculates noise margins and checks 3.3 V/5 V compatibility.

2026-09-04 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…

2026-09-02 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…