STMicroelectronics L4986A

Overview

L4986A from STMicroelectronics is a peak current-mode CCM-operated PFC controller for boost converters, featuring 800 V high-voltage startup, integrated AC voltage sensing, and a proprietary multiplier "emulator" delivering ≤1% THD in all operating conditions. It provides active X-capacitor discharge, 65 kHz fixed-frequency operation, and supports medical-grade SMPS per IEC 60601-1-2 with brown-in/brownout protection up to 500 ms dips - deployed in >1 kW desktop/server PSUs and high-power LED luminaries.

For engineers reviewing the L4986A datasheet, L4986A pinout, L4986A application, or L4986A equivalent, this controller delivers verified quasi-fixed-frequency CCM PFC control with ultra-low external component count, precise 1.2% internal reference (2.5 V @ 25 °C), totem-pole gate drive (0.7 A source / 1.5 A sink), and safety-compliant HV startup/discharge functionality - critical for EN61000-3-2/IEC61000-3-2 Class D and JEIDA-MITI compliance.

Technical Context

The L4986A implements fixed-off-time (FOT) peak current-mode control with a proprietary "Vin & multiplier emulator" that replaces analog multipliers by generating a sinusoidal current reference using only V_OUT, V_IN peak detection (via HV pin), and error amplifier output (COMP), eliminating need for dedicated line-sensing circuitry. Its THD-CCM optimizer injects programmable current into the CS pin to shape inductor current waveform, achieving <1% THD in continuous conduction mode.

It integrates an 800 V-rated HV pin for direct AC sensing and controlled X-capacitor discharge (5 mA sink, 45 V residual), enabling compliance with IEC 62368-1 without external bleed resistors. The device features dual OCP thresholds (−490 mV and −750 mV), zero-current detection (−10 mV), and burst-mode entry at V_COMP < 1.0 V - all coordinated via internal logic to ensure safe restart after mains dips or saturation events.

Key Specifications

Pinout & Package

SSOP10 package: 4.4 mm × 3 mm body, 0.65 mm pitch, exposed pad optional; designed for high-voltage isolation (HV pin creepage spacing) and thermal performance in compact PFC layouts.

Key Features

Applications

Equivalent & Alternatives

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

Compared with UCC28070 and FAN9612, the L4986A uniquely integrates 800 V HV sensing, active X-cap discharge, and IEC 60601-1-2–compliant brownout response - reducing external component count by ≥40% and eliminating safety-critical discrete parts in certified medical/industrial designs.

Availability

L4986A is available at Aetrix Electronics and suitable for desktop/server PSUs, high-power LED luminaries, industrial motor drives, and medical diagnostic equipment requiring stable component supply, long-term lifecycle support, and full traceability under IEC 62474 compliance.

Supply support for L4986A 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, designing and manufacturing silicon solutions for automotive, industrial, and power management applications with emphasis on energy efficiency and functional safety.

The L4986A belongs to ST's high-voltage analog PFC controller product line, engineered specifically for EN61000-3-2/IEC61000-3-2 Class D and medical-grade SMPS - prioritizing integration, safety compliance, and THD optimization in single-chip CCM boost topologies.

FAQ

What is the purpose of the NC pin (Pin 9) on the L4986A?

Pin 9 is an unconnected high-voltage spacer pin. It provides mandatory creepage distance between the HV (Pin 10) and signal pins (e.g., FB, COMP) on the PCB to meet IEC 62368-1 and IEC 61010-1 safety standards. It must remain unconnected and routed with adequate clearance - no trace or copper pour should approach it within 4.5 mm.

How does the L4986A achieve THD <1% without a traditional analog multiplier?

The L4986A uses a proprietary "multiplier emulator" that combines the HV pin's AC peak voltage detection with the COMP pin's error amplifier output to synthesize a sinusoidal current reference. Combined with the THD-CCM optimizer injecting current into the CS pin, it shapes the inductor current waveform to match line voltage phase and amplitude - eliminating multiplier ICs and associated precision resistors.

Can the L4986A operate in discontinuous conduction mode (DCM)?

No - the L4986A is explicitly designed for continuous conduction mode (CCM) operation only. Its THD-CCM optimizer, fixed-off-time modulator, and current-sense architecture assume CCM waveforms. Attempting DCM operation results in unstable regulation, increased THD, and potential OCP false triggering due to uncontrolled zero-crossing behavior.

What is the maximum allowable voltage on the HV pin during normal operation?

The HV pin is rated for 800 V absolute maximum, but recommended operating voltage is ≤600 V (per Table 3). During normal operation, peak AC line voltage (e.g., 310 V_RMS × √2 ≈ 438 V_PK) appears at HV via diode clamp - well within rating. Transient spikes up to 600 V are acceptable; sustained >600 V risks permanent damage and voids IEC 62368-1 certification.