L4984D

Overview

The L4984D is a current-mode Power Factor Correction (PFC) controller designed for Continuous Conduction Mode (CCM) boost converters. It utilizes a proprietary Line-Modulated Fixed-Off-Time (LM-FOT) modulator to maintain fixed-frequency operation in CCM applications. The device integrates a highly linear multiplier with a crossover distortion reduction circuit, enabling wide-range mains operation and low Total Harmonic Distortion (THD). Key electrical specifications include an accurate internal voltage reference with 1% tolerance at 25°C junction temperature and a totem-pole output stage capable of sourcing 600 mA and sinking 800 mA. It operates within a power range spanning from a few hundred watts to over 1 kW.

Feature Summary

• Proprietary LM-FOT modulator enables nearly fixed-frequency operation for boost PFC converters in continuous conduction mode.
• Integrated THD optimizer circuit reduces AC input current crossover distortion for improved power quality across large load ranges.
• Fast bidirectional voltage feedforward function optimizes loop stability and significantly improves line transient response during mains drops or surges.
• Comprehensive embedded protection suite includes feedback loop failure detection, overvoltage protection, inductor saturation handling, and AC brownout prevention.

Applications

• High-end game consoles
• Desktop computers and workstations
• High-end servers
• EV battery chargers
• Solar inverters

Procurement Notes

Verify the specific package variant when ordering, as the L4984D is available in different tape-and-reel configurations such as the L4984DTR. Confirm that the application design strictly adheres to the component's continuous conduction mode requirements, as the fixed-frequency modulation relies on this operating state. Ensure the PCB layout supports the high-current drive capabilities of the totem-pole output stage for reliable MOSFET or IGBT switching.

Selection Notes

Select the L4984D for designs requiring a cost-effective solution for CCM boost PFC pre-regulators in the hundreds of watts to 1 kW range. It is particularly suitable for applications demanding compliance with EN61000-3-2 and JEIDA-MITI standards without complex control loops. Choose this controller if the design benefits from simplified BOMs due to integrated protections and if the target applications include consumer electronics or industrial equipment requiring robust line transient rejection.

Part Context

The L4984D belongs to STMicroelectronics' portfolio of active PFC controllers, positioned alongside models like the L4983 and L4985. It is specifically engineered to address the needs of middle-to-high power SMPS where high performance and compact form factors are critical. The device leverages ST's proprietary SSOP10 package to achieve higher power density compared to traditional SO-8 footprints while maintaining ten pins for enhanced functionality.

Replacement Considerations

For direct pin-compatible replacements within the same family, consider the L4983, which also targets CCM PFC applications. Verify that any substitute maintains compatibility with the required line-modulated fixed-off-time control scheme and meets the necessary electromagnetic interference standards for the specific end-use environment.

FAQ

How does the L4984D maintain fixed-frequency operation?

It uses a proprietary Line-Modulated Fixed-Off-Time (LM-FOT) modulator that allows the boost PFC converter to operate at a fixed frequency as long as it remains in Continuous Conduction Mode (CCM).

What protection features are embedded in the L4984D?

The IC includes protection against feedback loop failures, overvoltage conditions, boost inductor saturation, and AC brownout events to ensure safe operation under various fault conditions.

Can the L4984D drive large power switches?

Yes, the totem-pole output stage provides high drive capability, sourcing 600 mA and sinking 800 mA, making it suitable for driving large MOSFETs or IGBTs.