STMicroelectronics EVAL4981A

Overview

EVAL4981A from STMicroelectronics is an evaluation board for the L4981A fixed-frequency power factor correction (PFC) controller IC, designed to implement continuous-conduction-mode (CCM) boost pre-regulators. It supports universal AC input (85–265 VAC), delivers up to 381 W output at 412 VDC, achieves >0.99 power factor, limits THD to <6.4%, and integrates gate drive for external MOSFETs/IGBTs in high-efficiency offline SMPS.

For engineers reviewing the EVAL4981A datasheet, EVAL4981A pinout, EVAL4981A application, or EVAL4981A equivalent, this board enables rapid validation of L4981A-based PFC stages in industrial power supplies, LED drivers, and server front-ends-particularly where line current distortion, soft-start behavior, and programmable UVLO threshold tuning are critical design parameters.

Technical Context

The EVAL4981A implements a complete CCM boost PFC stage using the L4981A's average-current-mode PWM control architecture, with external ROSC/COSC setting fixed 80 kHz switching frequency and integrated multiplier + current amplifier enabling sinusoidal line current shaping without slope compensation. It uses a 0.9 mH boost inductor, 400 V bulk capacitor, and STW15NB50 MOSFET pair driven by the L4981A's totem-pole gate driver (1 A peak sink/source).

Board-level features include programmable overvoltage protection (442 V), adjustable under-voltage lockout via resistor divider on Pin 15, soft-start timing set by 1 µF capacitor on Pin 12, and feedforward compensation via VRMS (Pin 7) and LFF (Pin 6) inputs to maintain regulation across wide load and line variations.

Key Specifications

Availability

EVAL4981A is available at Aetrix Electronics and suitable for industrial power supply development, LED driver qualification, and server PSU pre-regulator validation requiring stable component supply, traceable reference designs, and fast-turn prototyping support.

Supply support for EVAL4981A 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 and broad industrial certification coverage.

The EVAL4981A belongs to ST's Power Factor Correction Evaluation Kit product line, developed specifically to accelerate design-in of high-efficiency, low-THD CCM boost PFC stages for universal-input AC/DC converters targeting IEC 61000-3-2 Class D compliance.

FAQ

What is the primary function of the EVAL4981A board?

The EVAL4981A is a fully assembled and tested evaluation platform for the L4981A power factor correction controller. It implements a continuous-conduction-mode boost pre-regulator that shapes input current to match the AC voltage waveform, achieving >0.99 power factor and THD below 6.4% across 85–265 VAC input. It is not a standalone power supply but a reference design for validating L4981A integration.

Can EVAL4981A be used with the L4981B controller?

No-EVAL4981A is hardware-optimized for the L4981A's fixed-frequency operation and SYNC pin functionality (Pin 16). The L4981B requires frequency modulation via Pin 16 (FREQ-MOD), different ROSC/COSC interaction, and distinct current-sense calibration. ST provides separate EVAL4981B hardware; substituting L4981B into EVAL4981A will not yield correct frequency modulation or protection behavior.

What external components must be modified to adjust output voltage or THD performance?

To adjust output voltage, modify the resistive divider on L4981A Pin 14 (VFEED) and Pin 3 (OVP). To optimize THD, tune the VRMS filter network (Pin 7), LFF feedforward resistor (Pin 6), and current-sense gain (Pin 2 and sense resistor). The board includes test points and footprint options for all these adjustments per AN628 design guidelines.

Does EVAL4981A include safety certifications or isolation barriers?

No-EVAL4981A is a development tool without UL/EN62368-1 certification. It lacks reinforced isolation between AC input and DC output sections; the boost stage shares common ground topology. Users must implement full safety isolation, EMI filtering, and enclosure compliance separately when integrating into end products.