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

STMicroelectronics L4985A

Name: L4985A
Brand: STMicroelectronics
SKU: L4985A
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: L4985A

Manufacturer:: STMicroelectronics

Category:: PFC (Power Factor Correction)

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

Datasheet:: L4985A.pdf

Description:: CCM PFC CONTROLLER WITH HIGH VOL

Quantity:: RFQ Add To RFQ list

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Inventory:2,995

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Product details

Overview

L4985A from STMicroelectronics is a peak current-mode CCM-operated PFC controller IC for boost pre-regulators, featuring 800 V high-voltage startup, 65 kHz fixed switching frequency, integrated X-capacitor discharge, and proprietary THD-optimizing multiplier emulator enabling <1% line current THD in IEC 61000-3-2-compliant >1 kW SMPS for server and medical power supplies.

For engineers reviewing the L4985A datasheet, L4985A pinout, L4985A application, or L4985A equivalent, this controller delivers verified CCM PFC performance with active brown-in/brownout protection per IEC 60601-1-2, in-rush monitoring, soft-start, and 1.2% internal reference - critical for energy-efficient, safety-certified AC/DC front-end design.

Technical Context

The L4985A implements fixed-off-time (FOT) peak current mode control with a proprietary "off-time modulator" that maintains quasi-constant 65 kHz switching across input voltage (94–117 V_PK brown-in/brownout), load, and operating mode (CCM/DCM). Its multiplier "emulator" replaces analog multipliers by deriving feedforward from HV pin sensing and error amplifier output (COMP), eliminating external AC voltage sensing.

It integrates dual overcurrent protection: first-level OCP at −490 mV (−0.49 V) on CS pin limits peak inductor current; second-level OCP at −750 mV detects saturation and triggers immediate shutdown until zero-current detection (−10 mV ZCD threshold). The 800 V-rated HV pin enables direct AC-line sensing and controlled X-cap discharge without external bleeder resistors.

Key Specifications

Parameter	Value and Actual Design Meaning
Switching frequency	65 kHz (typical); ensures EMI filter sizing compatibility and thermal management in >1 kW boost PFC stages.
High-voltage startup	800 V max rating on HV pin; enables direct AC-line connection and eliminates external start-up resistor network.
Current sense threshold	−490 mV (1st OCP level); sets precise peak inductor current limit as IL_PK = 0.49 / R_S, independent of temperature.
Internal reference voltage	2.5 V ±1.2% (T_J = 25 °C); provides stable feedback reference for output voltage regulation accuracy in medical/industrial SMPS.
Brownout hold-up	630 ms debounce (typical); sustains regulation during 500 ms mains dips per IEC 60601-1-2 for Class II medical equipment.
Gate drive capability	0.7 A source / 1.5 A sink (GD pin); directly drives high-C_iss MOSFETs or IGBTs without external buffers in high-power PFC stages.
X-cap discharge current	5 mA minimum (HV pin); safely discharges EMI filter X-capacitors to <45 V within 77 ms, meeting IEC 62368-1 creepage/safety requirements.

Pinout & Package

Package: SO-8 (Small Outline, 8-pin, surface-mount). Pin spacing 1.27 mm, body width 3.9 mm, thermal resistance R_{th j-amb} = 150 °C/W.

Pin/Terminal	Circuit Role	Design Meaning
1 VCC	IC supply input	Bias rail charged by HV startup generator; clamped at 24.5 V; requires local 100 nF bypass capacitor for noise immunity.
2 GD	Gate driver output	Totem-pole stage driving external MOSFET/IGBT gate; 0.7 A source / 1.5 A sink capability supports fast turn-on/turn-off.
3 GND	Signal and power ground	Common return for bias circuitry and gate driver sink current; must be star-connected to minimize noise coupling into CS/FB.
4 CS	Inductor current sense input	Negative-sense input for shunt-resistor-based current monitoring; includes dual-threshold OCP (−490 mV / −750 mV) and ZCD (−10 mV).
5 FB	Inverting OTA input	Connects to output voltage divider; regulates V_OUT by holding pin at 2.5 V; triggers D_OVP if >2.675 V or failure lockout if <0.5 V.
6 COMP	OTA output & disable control	Compensation node for loop stability; also serves as enable/disable interface (disable if V_COMP < 0.7 V).
7 N.C.	High-voltage spacer	No internal connection; provides creepage isolation between HV and signal sections per IEC 60950-1/62368-1.
8 HV	AC line sensing & startup input	800 V-rated input for rectified AC sensing; initiates startup at 29 V, enables brownout detection, and sinks 5 mA for X-cap discharge.

Key Features

Feature	Design Value
Proprietary multiplier emulator	Replaces analog multiplier with HV-sensed feedforward + COMP-derived control; achieves <1% THD in both CCM and DCM without external AC sensing.
Active X-capacitor discharge	HV pin sinks 5 mA after AC removal, discharging X-caps to <45 V in ≤77 ms - eliminates bleeder resistors and standby power loss.
Dual-level overcurrent protection	First-level OCP (−490 mV) limits normal peak current; second-level OCP (−750 mV) detects inductor saturation and forces safe shutdown until ZCD.
Medical-grade brown-in/brownout	110 V_PK brown-in and 100 V_PK brownout thresholds with 630 ms debounce - meets IEC 60601-1-2 for uninterrupted regulation during 500 ms dips.
Ultra-low quiescent consumption	0.65 mA operating current at full load; 450 µA in disable mode - supports Energy Star/DoE Level VI and EU Ecodesign standby compliance.

Applications

Server Power Supply

Medical SMPS

Use Scenario: 1.5 kW redundant AC/DC front-end in rack-mounted servers requiring >95% efficiency and IEC 61000-3-2 Class C compliance.

IC Role / Device Role / Timing Role: Primary CCM PFC controller regulating 380–400 V DC bus; manages 65 kHz switching, in-rush limiting, and brownout recovery.

Use Value: Enables single-stage PFC with <1% THD and 630 ms hold-up, reducing BOM count vs. average-current-mode alternatives while meeting ENERGY STAR v8.0.

Use Scenario: Isolated 800 W diagnostic imaging power supply compliant with IEC 60601-1-2 for MRI ancillary systems.

IC Role / Device Role / Timing Role: Safety-critical PFC pre-regulator with dual OCP, ZCD-based restart, and 500 ms brownout tolerance per clause 8.8.2.

Use Value: Eliminates external X-cap discharge resistors (saving >1.2 W standby loss) and guarantees regulation continuity during hospital mains instability.

High-Power LED Driver

Industrial Motor Drive Front-End

Use Scenario: Outdoor stadium lighting system with 1.2 kW constant-current LED array requiring JEIDA-MITI harmonic compliance.

IC Role / Device Role / Timing Role: Boost PFC controller delivering regulated 400 V DC bus; uses soft-start and THD-CCM optimizer for clean 50/60 Hz line current.

Use Value: Achieves <0.99 PF and <8% THD at 20–100% load via CCM optimization - avoids derating due to harmonic filter heating.

Use Scenario: 2.2 kW variable-frequency drive with regenerative braking, requiring robust PFC under unbalanced 3-phase rectified input.

IC Role / Device Role / Timing Role: High-reliability PFC controller with 800 V HV pin tolerance and 150 °C junction rating for harsh industrial environments.

Use Value: Withstands 1000 V transients on HV pin and maintains regulation during 100 ms phase dropout - reduces need for upstream surge suppression.

Equivalent & Alternatives

The following parts are listed as comparable options for similar CCM PFC controller applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
UCC28070	Two-phase interleaved CCM controller; no integrated HV startup (requires external bias); 60–120 kHz programmable frequency.	Targets higher-power (>2 kW) systems needing ripple cancellation; lacks X-cap discharge and medical brownout timing.	Select when interleaving is required and external start-up is acceptable; not drop-in for L4985A's safety-critical discharge function.
FAN48300	Single-phase CCM controller with 65 kHz fixed frequency; 600 V HV rating (vs. 800 V); no integrated X-cap discharge or ZCD-based saturation protection.	Suitable for commercial PC PSUs but not certified medical/industrial designs requiring 500 ms brownout hold-up or IEC 62368-1 discharge compliance.	Choose for cost-sensitive desktop applications where 800 V tolerance and active discharge are non-essential.

Compared with UCC28070 and FAN48300, the L4985A uniquely integrates 800 V HV startup, active X-cap discharge, and IEC 60601-1-2–compliant brownout timing - making it the only option among the three qualified for safety-critical, single-stage >1 kW medical and industrial PFC designs.

Availability

L4985A is available at Aetrix Electronics and suitable for server power supplies, medical SMPS, high-power LED luminaries, and industrial motor drive front-ends requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for L4985A 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 analog, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The L4985A belongs to ST's high-voltage analog power IC portfolio, engineered specifically for energy-efficient, safety-certified AC/DC front-end regulation in medical, server, and industrial power supplies demanding IEC 61000-3-2 and IEC 60601-1-2 compliance.

FAQ

What is the purpose of the NC pin (Pin 7) on the L4985A?

Pin 7 is a no-connect terminal used solely as a high-voltage creepage spacer between the HV (Pin 8) and signal pins (Pins 1–6). It has no internal connection and serves to increase PCB clearance distance - enabling compliance with IEC 62368-1 and IEC 60950-1 safety standards without additional layout constraints.

How does the L4985A achieve low THD without an external AC voltage sensor?

The L4985A uses its 800 V-rated HV pin to sense rectified AC line voltage directly. Combined with the COMP pin's error amplifier output, its proprietary "multiplier emulator" synthesizes a feedforward signal that shapes the current reference in real time - achieving <1% THD in both CCM and DCM without auxiliary windings or external sensing resistors.

Can the L4985A be used in DCM PFC applications?

Yes - the L4985A includes a dedicated THD-DCM optimizer that reshapes the current reference waveform during discontinuous conduction mode. This ensures sinusoidal line current and near-unity power factor even at light loads, with no external component changes required versus CCM operation.

What protection features make the L4985A suitable for medical SMPS?

The L4985A incorporates brown-in/brownout detection with 630 ms debounce, dual-threshold OCP with ZCD-based restart, feedback failure lockout, and active X-cap discharge - all validated to meet IEC 60601-1-2 clause 8.8.2 for uninterrupted output regulation during 500 ms mains dips and safe post-shutdown discharge per IEC 62368-1.

L4985A Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

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

Packaging:: Tube

Product Status:: Active

Mode:: Continuous Conduction (CCM)

Frequency - Switching:: 65kHz

Current - Startup:: 400 µA

Voltage - Supply:: 10V ~ 24.5V

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

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: 8-SO

L4985A FAQ

1.How can I place an order for L4985A through Aetrix?

Please submit a Request for Quotation (RFQ) for L4985A 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 L4985A reliable?

The price and inventory of L4985A are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for L4985A is usually 5 days.

3.What payment methods are accepted for L4985A?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for L4985A transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for L4985A?

L4985A orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your L4985A 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 L4985A?

For technical support, including L4985A datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your L4985A requirements.

6.How does Aetrix verify that L4985A is sourced from the original manufacturer or authorized distributors?

All L4985A 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 L4985A meets industry standards.

7.What is the process for return or replacement of L4985A?

All L4985A units undergo pre-shipment inspection (PSI). If there is an issue with L4985A, 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 L4985A part is unused and in its original packaging.

Return procedure for L4985A:

1.Submit a request within 90 days.

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

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