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Home > Products > Integrated Circuits (ICs) > Power Management (PMIC) > PFC (Power Factor Correction)

STMicroelectronics L4981AD

Name: L4981AD
Brand: STMicroelectronics
SKU: L4981AD
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: L4981AD

Manufacturer:: STMicroelectronics

Category:: PFC (Power Factor Correction)

Package:: 20-SOIC (0.295", 7.50mm Width)

Datasheet:: L4981AD.pdf

Description:: IC PFC CTR AVER CURR 100KHZ 20SO

Quantity:: RFQ Add To RFQ list

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Product details

Overview

L4981AD from STMicroelectronics is a fixed-frequency average-current-mode Power Factor Correction (PFC) controller IC designed for boost pre-regulator topologies in universal-input AC/DC power supplies. It delivers up to 0.99 power factor, limits line current THD to <5%, integrates a ±2% precision 5.1 V reference, supports 85–265 V_AC mains without switching, and features a 1 A totem-pole gate driver for MOSFET/IGBT stages.

For engineers reviewing the L4981AD datasheet, L4981AD pinout, L4981AD application, or L4981AD equivalent, key selection criteria include its fixed-frequency operation (L4981A variant), programmable UVLO threshold, average-current-mode control architecture, integrated OVP/OCP protection, and SO-20 package compatibility with industrial PFC designs requiring stable high-voltage DC bus generation.

Technical Context

The L4981AD implements an analog multiplier-based average-current-mode PWM controller that generates a sinusoidal reference current proportional to rectified line voltage (via VRMS pin) and load condition (via LFF pin), eliminating slope compensation. Its internal error amplifier regulates output voltage via a voltage divider on VFEED, while the CA-OUT loop shapes current-loop bandwidth using external RC components.

It uses a constant-frequency oscillator (100 kHz typ.) set by ROSC/COSC, with dedicated pins for soft-start (SS), peak-current limiting (IPK), and programmable under-voltage lockout (P-UVLO). The device operates in continuous conduction mode (CCM), supports universal input, and embeds protections including overvoltage (OVP), overcurrent (OCP), and thermal-safe gate drive with 1 A sink/source capability.

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 for >75 W equipment.
THD Limit	<5% - ensures low line current distortion across full input range (85–265 V_AC).
Reference Voltage	5.1 V ±2% - provides stable, externally accessible feedback reference for voltage loop accuracy.
Oscillator Frequency	100 kHz typ. - fixed switching frequency simplifies EMI filter design and magnetics selection.
Gate Driver Output	1 A sink / 1.5 A source - directly drives power MOSFET gates without external buffers in 200–400 W PFC stages.
Start-up Current	0.3 mA typ. - minimizes auxiliary supply burden during initial power-up sequence.
UVLO Threshold	Programmable 10.6–13.4 V - allows precise turn-on control based on bulk capacitor voltage.

Pinout & Package

Package: SO-20 (Small Outline, 20-pin, 0.5 mm pitch, body width 7.5 mm), compliant with JEDEC MS-013, thermal resistance R_{th j-amb} = 120 °C/W.

Pin	Circuit Role	Design Meaning
1	P-GND	Power ground return for gate driver and high-current paths; separate from signal ground (Pin 10) to minimize noise coupling.
2	IPK	Peak current limit sense input; sets current threshold via resistor network between Pin 2, sense resistor, and VREF (Pin 11).
3	OVP	Overvoltage protection comparator input; monitors boosted DC bus via resistive divider to clamp output at 442 V (typ.) in fault condition.
4	IAC	AC current sensing input; receives scaled rectified line current to generate sinusoidal reference for multiplier stage.
5	CA-OUT	Current amplifier output; connects to external RC network to set current-loop gain and phase margin for stability.
12	SS	Soft-start timing node; 100 µA internal current charges external capacitor to ramp up duty cycle gradually and prevent inrush.
13	VA-OUT	Error amplifier output; interfaces with external RC to define voltage-loop compensation (e.g., Type II or III).
14	VFEED	Voltage feedback input; connected to resistive divider from boost output to close outer voltage regulation loop.
15	P-UVLO	Programmable UVLO threshold input; voltage divider from VCC to GND sets precise turn-on/off hysteresis (e.g., 12 V ON / 10.1 V OFF).
16	SYNC	Synchronization I/O; functions as CMOS-compatible clock output (for multi-phase sync) or external clock input (for master-slave coordination).
17	ROSC	Oscillator timing resistor connection; sets constant charging current for COSC (Pin 18) to fix switching frequency.
18	COSC	Oscillator timing capacitor connection; together with ROSC defines 100 kHz nominal switching frequency.
19	VCC	Supply input (19.5 V max); powers internal circuitry and gate driver; includes internal zener clamp (25 V typ.) for transient protection.
20	GDRV	Gate driver output; totem-pole bipolar/DMOS stage delivers 1 A sink / 1.5 A source to drive N-channel MOSFET gates directly.

Key Features

Feature	Design Value
Average-current-mode PWM	Eliminates need for slope compensation, improves noise immunity, and maintains sinusoidal line current across line/load variations.
Integrated 5.1 V ±2% reference	Externally accessible reference enables accurate voltage feedback scaling and reduces external component count.
Programmable UVLO with hysteresis	Allows system-level brown-out recovery tuning (e.g., 12 V turn-on / 10.1 V turn-off) to avoid oscillatory start-up near low-line conditions.
Dedicated LFF and VRMS inputs	Enables fast load transient response and line-voltage feedforward for improved regulation without digital control.
On-chip OVP and OCP protection	Reduces external protection circuitry; OVP triggers at 5.1 V threshold (±20 mV), OCP uses IPK pin with resistor-programmable trip level.

Applications

Server PSU Pre-regulator

Industrial Motor Drive Input Stage

Use Scenario: 360 W universal-input front-end in 1U server power supply operating from 88–264 V_AC.

IC Role / Device Role / Timing Role: PFC controller managing boost converter to generate regulated 400 V DC bus with <2.2% THD at 110 V_AC.

Use Value: Enables 94% efficiency and 0.999 PF per IEC 61000-3-2, reducing upstream transformer and fuse sizing.

Use Scenario: Input stage of 3 kW variable-frequency drive accepting 3-phase 380–480 V_AC via rectification.

IC Role / Device Role / Timing Role: Single-phase PFC controller regulating DC link voltage to 650 V with dynamic load feedforward (LFF) for torque step response.

Use Value: Maintains PF >0.98 under 50% load steps, minimizing reactive current draw from utility grid.

Medical Imaging Power Supply

LED Streetlight Driver

Use Scenario: High-reliability 500 W X-ray generator power supply requiring low EMI and strict harmonic compliance.

IC Role / Device Role / Timing Role: Fixed-frequency (100 kHz) PFC controller driving 1200 V SiC MOSFET in CCM boost stage.

Use Value: Average-current-mode control ensures stable operation with minimal current-sense noise susceptibility in noisy diagnostic environments.

Use Scenario: Outdoor-rated 150 W LED streetlight operating 24/7 across -40°C to +85°C ambient.

IC Role / Device Role / Timing Role: Universal-input PFC controller generating 400 V DC bus for downstream LLC resonant converter.

Use Value: Low 0.3 mA start-up current extends hold-up time during brief AC dips; SO-20 package supports conformal coating for moisture resistance.

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
UC3854BDW	Peak-current-mode control; requires external slope compensation; no integrated LFF/VRMS feedforward.	Higher THD at low line; less robust against line transients; needs more external compensation components.	Choose when legacy UC3854 footprint compatibility is required and average-current-mode is not mandatory.
TDA16888	Fixed-frequency average-current-mode like L4981AD but lacks programmable UVLO and has lower gate drive (0.5 A).	Lower power capability (<150 W typical); limited OVP/OCP flexibility; no SYNC pin for multi-phase sync.	Prefer for cost-sensitive <200 W consumer applications where full L4981AD feature set is unnecessary.

Compared with UC3854BDW and TDA16888, the L4981AD offers superior line/load regulation via dual feedforward (LFF + VRMS), higher gate drive strength for faster switching, and fully programmable UVLO-making it optimal for industrial and medical PFC designs demanding high PF, low THD, and robust protection.

Availability

L4981AD is available at Aetrix Electronics and suitable for server PSUs, industrial motor drives, medical imaging power supplies, and outdoor LED lighting systems requiring stable component supply, long-lifecycle support, and RoHS-compliant packaging.

Supply support for L4981AD 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 power management, analog, microcontrollers, and automotive ICs with vertical manufacturing capabilities.

The L4981AD belongs to ST's MultiPower BCD technology family, engineered specifically for high-voltage, high-efficiency AC/DC power conversion in industrial and computing applications requiring integrated PFC control and robust gate drive.

FAQ

What is the maximum recommended output power for L4981AD-based PFC designs?

L4981AD is validated for continuous operation up to 400 W in reference designs (e.g., Figure 19 demo board at 360 W). With proper heatsinking and MOSFET selection, reliable operation at 500 W is achievable in forced-air-cooled industrial enclosures. Thermal derating above 70°C ambient must follow R_{th j-amb} = 120 °C/W and maximum junction temperature of 125°C.

Can L4981AD operate in discontinuous conduction mode (DCM)?

No-L4981AD is designed exclusively for continuous conduction mode (CCM) boost PFC operation. Its average-current-mode architecture, internal multiplier, and CA-OUT compensation network assume CCM waveforms. Attempting DCM operation results in unstable current loop behavior and loss of PF correction capability.

How is the OVP threshold set, and what happens when triggered?

OVP threshold is set by a resistive divider from the boost output to Pin 3 (OVP), comparing against an internal 5.1 V reference. When exceeded, the controller immediately disables GDRV (Pin 20), halts switching, and holds soft-start capacitor discharged. Recovery requires cycling VCC or clearing UVLO condition-no automatic restart is provided.

Is the L4981AD pin-compatible with L4981A or L4981B variants?

Yes-L4981AD shares identical pinout, electrical characteristics, and SO-20 package with L4981A (fixed-frequency) and L4981B (frequency-modulated). The "D" suffix denotes SO-20 packaging; functional differences are limited to oscillator configuration (Pin 16: SYNC vs. FREQ-MOD), not pin assignment or DC parameters.

L4981AD Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 20-SOIC (0.295", 7.50mm Width)

Packaging:: Tube

Product Status:: Active

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:: Surface Mount

Supplier Device Package:: 20-SO

L4981AD FAQ

1.How can I place an order for L4981AD through Aetrix?

Please submit a Request for Quotation (RFQ) for L4981AD 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 L4981AD reliable?

The price and inventory of L4981AD are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L4981AD is usually 5 days.

3.What payment methods are accepted for L4981AD?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L4981AD transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for L4981AD?

L4981AD orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your L4981AD 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 L4981AD?

For technical support, including L4981AD datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L4981AD requirements.

6.How does Aetrix verify that L4981AD is sourced from the original manufacturer or authorized distributors?

All L4981AD 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 L4981AD meets industry standards.

7.What is the process for return or replacement of L4981AD?

All L4981AD units undergo pre-shipment inspection (PSI). If there is an issue with L4981AD, 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 L4981AD part is unused and in its original packaging.

Return procedure for L4981AD:

1.Submit a request within 90 days.

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

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