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L4984D：CCM PFC CONTROLLER

The L4984D is a current-mode PFC controller operating with line-modulated fixed-off-time (LM-FOT) control. A proprietary LM-FOT modulator allows fixed-frequency operation for boost PFC converters as long as they are operated in CCM (continuous conduction mode).

The chip comes in a 10-pin SO package and offers a low-cost solution for CCM-operated boost PFC pre-regulators in EN61000-3-2 and JEIDA-MITI compliant applications, in a power range that spans from few hundred W to 1 KW and above.

The highly linear multiplier includes a special circuit, able to reduce the crossover distortion of the AC input current, that allows wide-range-mains operation with a reasonably low THD, even over a large load range.

The output voltage is controlled by means of a voltage-mode error amplifier and an accurate (1% at Tj = 25 °C) internal voltage reference. Loop stability is optimized by the voltage feedforward function (1/V²correction), which in this IC uses a proprietary technique that also significantly improves line transient response in the case of mains drops and surges (“bi-directional”).

The device features low consumption and includes a disable function suitable for IC remote on/off. These features allow use in applications which also comply with the latest energy saving requirements (Blue Angel, ENERGY STAR , Energy 2000, etc.).

In addition to overvoltage protection able to keep the output voltage under control during transient conditions, the IC is also provided with protection against feedback loop failures or erroneous settings. Other onboard protection functions allow that brownout conditions and boost inductor saturation can be safely handled. Soft-start limits peak current and extends off-time to prevent flux runaway in the initial cycles.

The totem pole output stage, capable of 600 mA source and 800 mA sink current, is suitable for big MOSFETs or IGBT drive.

Key Features

• Line-modulated fixed-off-time (LM-FOT) control of CCM-operated PFC pre-regulators
• Proprietary LM-FOT modulator for nearly fixed-frequency operation
• Proprietary multiplier design for minimum THD of AC input current
• Fast “bi-directional” input voltage feedforward (1/V2 correction)
• Accurate adjustable output overvoltage protection
• Protection against feedback loop failure (latched shutdown)
• Inductor saturation protection
• AC brownout detection
• Digital leading-edge blanking on current sense
• Soft-start
• 1% (at Tj = 25 °C) internal reference voltage
• - 600 / + 800 mA totem pole gate driver with active pull-down during UVLO and voltage clamp
• SSOP10 package

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